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CN102055335B - Buck-boost power converter and control method thereof - Google Patents

️Wed Aug 12 2015

CN102055335B - Buck-boost power converter and control method thereof - Google Patents

Buck-boost power converter and control method thereof Download PDF

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Publication number

CN102055335B

CN102055335B CN200910212078.9A CN200910212078A CN102055335B CN 102055335 B CN102055335 B CN 102055335B CN 200910212078 A CN200910212078 A CN 200910212078A CN 102055335 B CN102055335 B CN 102055335B Authority

China

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signal

power converter

buck

switch

mode

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2009-11-03

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CN102055335A (en

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陈科宏

吴纬权

何心欣

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Richtek Technology Corp

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Richtek Technology Corp

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2009-11-03

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2015-08-12

2009-11-03 Application filed by Richtek Technology Corp filed Critical Richtek Technology Corp

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2011-05-11 Publication of CN102055335A publication Critical patent/CN102055335A/en

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2015-08-12 Publication of CN102055335B publication Critical patent/CN102055335B/en

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Abstract

一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一第二开关连接在所述电感的第一端及一接地端之间，一第三开关连接在所述电感的第二端及所述接地端之间，以及一第四开关连接在所述电感的第二端及所述电源转换器的输出端之间，其特征在于所述控制方法包括下列步骤：检测所述输入端及输出端上的电压以及在所述输出端上的负载电流以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；在所述第一及第二升降压模式时，控制所述第一、第二、第三及第四开关。

A control method for a buck-boost power converter, wherein the power converter includes an inductor, a first switch connected between the input terminal of the power converter and the first terminal of the inductor, a second switch connected between the first terminal of the inductor and a ground terminal, a third switch connected between the second terminal of the inductor and the ground terminal, and a fourth switch connected between the second terminal of the inductor and the output terminal of the power converter, characterized in that the control method includes the following steps: detecting the voltages on the input terminal and the output terminal and the load current on the output terminal to determine whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode; and controlling the first, second, third and fourth switches in the first and second buck-boost modes.

Description

升降压式电源转换器及其控制方法Buck-boost power converter and its control method

技术领域 technical field

本发明涉及一种电源转换器，具体地说，是一种改善切换损失以及正确切换模式的升降压式电源转换器及其控制方法。The invention relates to a power converter, in particular to a buck-boost power converter with improved switching loss and correct switching mode and its control method.

背景技术 Background technique

图1显示已知的升降压式电源转换器10，其包括功率级1 2及控制电路1 4。在功率级12中，开关SW1连接在输入电压Vin及电感L之间，开关SW2连接在电感L及接地端GND之间，开关SW3连接在电感L及接地端GND之间，开关SW4连接在电感L及输出电压Vout之间。电阻R1及R2分压输出电压Vout产生回授信号VFB，在控制电路14中，误差放大器24根据回授信号VFB及参考电压Vref产生误差信号VEA，锯齿波产生器22提供两个锯齿波信号SAW1及SAW2，比较器18比较误差信号VEA及锯齿波信号SAW1产生信号PWM1，比较器20比较误差信号VEA及锯齿波信号SAW2产生信号PWM2，控制逻辑电路16根据信号PWM1及PWM2产生信号VA、VB、VC及VD分别切换开关SW1、SW2、SW3及SW4以将输入电压Vin转为输出电压Vout。当误差信号VEA只切到锯齿波信号SAW1或SAW2时，电源转换器10操作在降压模式或升压模式，当误差信号VEA切到两个锯齿波信号SAW1或SAW2时，电源转换器10操作在升降压模式。然而，事实上，锯齿波信号SAW1及SAW2的波形在峰值与谷值并非理想线性，因此，在输入电压Vin接近输出电压Vout时，也就是信号PWM1或PWM2的责任周期比(duty ratio)接近100％时，将因非线性问题使得输出电压Vout的涟波变大。FIG. 1 shows a known buck-boost power converter 10, which includes a power stage 12 and a control circuit 14. In the power stage 12, the switch SW1 is connected between the input voltage Vin and the inductor L, the switch SW2 is connected between the inductor L and the ground terminal GND, the switch SW3 is connected between the inductor L and the ground terminal GND, and the switch SW4 is connected between the inductor L and the ground terminal GND. Between L and the output voltage Vout. Resistors R1 and R2 divide the output voltage Vout to generate a feedback signal VFB. In the control circuit 14, the error amplifier 24 generates an error signal VEA according to the feedback signal VFB and the reference voltage Vref. The sawtooth wave generator 22 provides two sawtooth wave signals SAW1 and SAW2, the comparator 18 compares the error signal VEA and the sawtooth signal SAW1 to generate the signal PWM1, the comparator 20 compares the error signal VEA and the sawtooth signal SAW2 to generate the signal PWM2, and the control logic circuit 16 generates the signals VA, VB, VC and VD respectively switch switches SW1 , SW2 , SW3 and SW4 to convert the input voltage Vin to the output voltage Vout. When the error signal VEA only cuts to the sawtooth signal SAW1 or SAW2, the power converter 10 operates in the step-down mode or the boost mode, and when the error signal VEA cuts to the two sawtooth signals SAW1 or SAW2, the power converter 10 operates in buck-boost mode. However, in fact, the waveforms of the sawtooth signals SAW1 and SAW2 are not ideally linear at peak and valley values. Therefore, when the input voltage Vin is close to the output voltage Vout, that is, the duty ratio of the signal PWM1 or PWM2 is close to 100. %, the ripple of the output voltage Vout will become larger due to nonlinear problems.

Chen等人在美国专利号第7,176,667号中提出一种升降压式电源转换器，其在升降压模式时，利用一个锯齿波信号及误差信号切出所需要的降压或升压的责任周期，并在所述责任周期之内插入一个固定的升压或降压责任周期。然而，不论是图1或Chen等人所提出的电源转换器，在升降压模式时，开关的切换循环为(1)打开(turn on)开关SW2及SW4并关闭(turn off)开关SW1及SW3，(2)打开开关SW1及SW4并关闭开关SW2及SW3，(3)打开开关SW1及SW3并关闭开关SW2及SW4，(4)打开开关SW1及SW4并关闭开关SW2及SW3，由于在每一周期中开关切换的次数较多，故切换损失(switching loss)也较大。Chen et al. proposed a buck-boost power converter in U.S. Patent No. 7,176,667. In the buck-boost mode, a sawtooth signal and an error signal are used to cut out the required buck or boost duty cycle. , and insert a fixed boost or buck duty cycle within the duty cycle. However, regardless of the power converter proposed by FIG. 1 or Chen et al., in the buck-boost mode, the switch switching cycle is (1) turn on (turn on) switches SW2 and SW4 and turn off (turn off) switches SW1 and SW3, (2) open switches SW1 and SW4 and close switches SW2 and SW3, (3) open switches SW1 and SW3 and close switches SW2 and SW4, (4) open switches SW1 and SW4 and close switches SW2 and SW3, because in each The number of switch switching in one cycle is more, so the switching loss (switching loss) is also larger.

因此已知的升降压式电源转换器存在着上述种种不便和问题。Therefore, the known buck-boost power converters have the above-mentioned inconveniences and problems.

发明内容 Contents of the invention

本发明的目的，在于提出一种在输入电压接近输出电压时使用新的开关顺序，降低切换损失及导通损失的升降压式电源转换器及其控制方法。The object of the present invention is to propose a buck-boost power converter and a control method thereof that use a new switching sequence when the input voltage is close to the output voltage to reduce switching loss and conduction loss.

本发明的另一目的，在于提出一种在输入电压接近输出电压时延长开关的切换周期以降低切换损失的升降压式电源转换器及其控制方法。Another object of the present invention is to provide a buck-boost power converter and a control method thereof that extend the switching period of the switch to reduce switching loss when the input voltage is close to the output voltage.

本发明的再一目的，在于提出一种考虑负载电流对升降压责任周期的影响使其可在正确点切换模式，因此输出电压不会因为改变模式而受影响的升降压式电源转换器及其控制方法。Another object of the present invention is to propose a buck-boost power converter that considers the influence of the load current on the duty cycle of the buck-boost so that it can switch modes at the correct point, so the output voltage will not be affected by changing the mode and its control methods.

为实现上述目的，本发明的技术解决方案是：For realizing the above object, technical solution of the present invention is:

一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一第二开关连接在所述电感的第一端及一接地端之间，一第三开关连接在所述电感的第二端及所述接地端之间，以及一第四开关连接在所述电感的第二端及所述电源转换器的输出端之间，其特征在于所述控制方法包括下列步骤：A control method for a buck-boost power converter, the power converter includes an inductor, a first switch is connected between the input end of the power converter and the first end of the inductor, and a second A switch is connected between the first terminal of the inductor and a ground terminal, a third switch is connected between the second terminal of the inductor and the ground terminal, and a fourth switch is connected between the first terminal of the inductor Between the two terminals and the output terminal of the power converter, it is characterized in that the control method includes the following steps:

第一步骤：检测所述输入端及输出端上的电压以及在所述输出端上的负载电流以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；The first step: detecting the voltage on the input terminal and the output terminal and the load current on the output terminal to determine the operation of the power converter in the buck mode, the first buck-boost mode, and the second buck-boost mode mode or boost mode;

第二步骤：在所述第一及第二升降压模式时，所述第一、第二、第三及第四开关的控制包含：The second step: in the first and second buck-boost modes, the control of the first, second, third and fourth switches includes:

(a)关闭所述第一开关，打开所述第二开关，关闭所述第三开关，打开所述第四开关；(a) closing the first switch, opening the second switch, closing the third switch, and opening the fourth switch;

(b)打开所述第一开关，关闭所述第二开关，维持所述第三开关关闭，维持所述第四开关打开；(b) opening the first switch, closing the second switch, keeping the third switch closed, and keeping the fourth switch open;

(c)维持所述第一开关打开，维持所述第二开关关闭，打开所述第三开关，关闭所述第四开关。(c) keeping the first switch open, keeping the second switch closed, opening the third switch, and closing the fourth switch.

本发明的升降压式电源转换器的控制方法还可以采用以下的技术措施来进一步实现。The control method of the buck-boost power converter of the present invention can also be further realized by adopting the following technical measures.

前述的控制方法，其中所述决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式的步骤包括下列步骤：In the aforementioned control method, the step of determining whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode includes the following steps:

第一步骤：当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值小于一第一临界值，决定所述电源转换器操作在降压模式；Step 1: When the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current is smaller than a first critical value, determine that the power converter operates in a step-down mode;

第二步骤：当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值，决定所述电源转换器操作在所述第一升降压模式；Step two: determine the power converter when the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current is greater than the first critical value and smaller than a second critical value operating in said first buck-boost mode;

第三步骤：当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值，决定所述电源转换器操作在所述第二升降压模式；Step 3: determine the power converter when the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current is less than a third critical value and greater than the second critical value operating in said second buck-boost mode;

第四步骤：当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。Step 4: When the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current is greater than the third critical value, determine that the power converter operates at the boost voltage model.

前述的控制方法，其中更包括：The aforementioned control method, which further includes:

放大一第一信和及一参考电压之间的差值产生一第二信号，所述第一信号为所述输出端上电压的函数；amplifying a difference between a first signal sum and a reference voltage to generate a second signal, said first signal being a function of the voltage at said output terminal;

提供一第一频率及一第二频率；providing a first frequency and a second frequency;

根据所述电源转换器的操作模式及所述第一频率产生一第三信号及一第四信号；generating a third signal and a fourth signal according to the operation mode of the power converter and the first frequency;

比较所述第二信号及第三信号产生一第五信号；comparing the second signal and the third signal to generate a fifth signal;

比较所述第二信号及第四信号产生一第六信号；comparing the second signal and the fourth signal to generate a sixth signal;

根据所述电源转换器的操作模式、所述第五及第六信号、第一频率及第二频率控制所述第一、第二、第三及第四开关。The first, second, third and fourth switches are controlled according to the operating mode of the power converter, the fifth and sixth signals, the first frequency and the second frequency.

前述的控制方法，其中在所述降压模式时，所述第一及第二开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二、第三及第四开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二、第三及第四开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第三及第四开关的切换周期为一小于所述第二及第三周期的第四周期。The aforementioned control method, wherein in the step-down mode, the switching period of the first and second switches is a first period; in the first buck-boost mode, the first, second, second The switching period of the third and fourth switches is a second period greater than the first period; in the second buck-boost mode, the switching periods of the first, second, third and fourth switches are one A third period longer than the first period; in the boost mode, the switching period of the third and fourth switches is a fourth period shorter than the second and third periods.

前述的控制方法，其中在所述第一升降压模式时，所述第三及第四开关的责任周期固定。In the aforementioned control method, in the first buck-boost mode, the duty periods of the third and fourth switches are fixed.

前述的控制方法，其中在所述第二升降压模式时，所述第一及第二开关的责任周期固定。In the aforementioned control method, in the second buck-boost mode, the duty cycles of the first and second switches are fixed.

一种升降压式电源转换器，其特征在于，包括：A buck-boost power converter, characterized in that it comprises:

一电感；an inductance;

一第一开关，连接在所述电源转换器的输入端及所述电感的第一端之间；a first switch connected between the input terminal of the power converter and the first terminal of the inductor;

一第二开关，连接在所述电感的第一端及一接地端之间；a second switch connected between the first terminal of the inductor and a ground terminal;

一第三开关，连接在所述电感的第二端及所述接地端之间；a third switch connected between the second terminal of the inductor and the ground terminal;

一第四开关，连接在所述电感的第二端及所述电源转换器的输出端之间；a fourth switch connected between the second end of the inductor and the output end of the power converter;

一控制电路，控制所述第一、第二、第三及第四开关的切换，并根据所述输入端及输出端上的电压以及所述输出端上的负载电流决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；a control circuit, controlling switching of the first, second, third and fourth switches, and determining the operation of the power converter according to the voltage on the input terminal and the output terminal and the load current on the output terminal In buck mode, first buck-boost mode, second buck-boost mode or boost mode;

其中，在所述第一及第二升降压模式时，所述第一、第二、第三及第四开关的控制包含(a)关闭所述第一开关、打开所述第二开关、关闭所述第三开关及打开所述第四开关，(b)打开所述第一开关、关闭所述第二开关、维持所述第三开关关闭及维持所述第四开关打开，以及(c)维持所述第一开关打开、维持所述第二开关关闭、打开所述第三开关及关闭所述第四开关。Wherein, in the first and second buck-boost modes, the control of the first, second, third and fourth switches includes (a) closing the first switch, opening the second switch, closing the third switch and opening the fourth switch, (b) opening the first switch, closing the second switch, keeping the third switch closed and keeping the fourth switch open, and (c ) maintain the first switch open, maintain the second switch closed, open the third switch, and close the fourth switch.

前述的电源转换器，其中所述控制电路在所述输入端及输出端上的电压与所述负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在所述降压模式；在所述输入端及输出端上的电压与所述负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；在所述输入端及输出端上的电压与所述负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；在所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。The aforementioned power converter, wherein the control circuit determines the power supply when the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current is less than a first critical value The converter operates in the step-down mode; the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current is greater than the first critical value and less than a second critical value value, it is determined that the power converter operates in the first buck-boost mode; the voltage on the input terminal and the output terminal and the load current determine the value of the multiplying factor at both ends of the inductance is less than a first When three critical values are greater than the second critical value, it is determined that the power converter operates in the second buck-boost mode; the voltage on the input terminal and the output terminal and the load current determined by the When the multiplier value at both ends of the inductor is greater than the third critical value, it is determined that the power converter operates in the boost mode.

前述的电源转换器，其中所述控制电路包括：The aforementioned power converter, wherein the control circuit includes:

一误差放大器，根据一第一信号及一参考电压产生一第二信号，所述第一信号为所述电源转换器输出端上电压的函数；an error amplifier generating a second signal based on a first signal and a reference voltage, the first signal being a function of the voltage at the output of the power converter;

一频率产生器，提供一第一频率及一第二频率；a frequency generator providing a first frequency and a second frequency;

一模式检测器，检测所述电源转换器的输入端及输出端上的电压产生一第三信号以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；A mode detector, detecting the voltage on the input end and the output end of the power converter to generate a third signal to determine whether the power converter is operating in the buck mode, the first buck-boost mode, the second buck-boost mode mode or boost mode;

一锯齿波产生器，根据所述第三信号及第一频率提供一第四信号或一第五信号；a sawtooth wave generator, providing a fourth signal or a fifth signal according to the third signal and the first frequency;

一第一比较器，比较所述第二信号及所述第四信号产生一第六信号；a first comparator, comparing the second signal and the fourth signal to generate a sixth signal;

一第二比较器，比较所述第二信号及所述第五信号产生一第七信号；a second comparator, comparing the second signal and the fifth signal to generate a seventh signal;

一控制逻辑电路，根据所述第三、第六及第七信号以及第一及第二频率控制所述第一、第二、第三及第四开关的切换。A control logic circuit controls switching of the first, second, third and fourth switches according to the third, sixth and seventh signals and the first and second frequencies.

前述的电源转换器，其中所述控制逻辑电路包括：The aforementioned power converter, wherein the control logic circuit includes:

一除频器，对所述第一频率除频产生一第三频率；a frequency divider that divides the first frequency to generate a third frequency;

一第一逻辑电路，根据所述第六信号、第一频率、第二频率、第三频率及一第二参考电压产生一第一控制信号、第二控制信号、第三控制信号及第四控制信号；A first logic circuit, generating a first control signal, a second control signal, a third control signal and a fourth control signal according to the sixth signal, the first frequency, the second frequency, the third frequency and a second reference voltage Signal;

一第一多任务器，根据所述三信号从所述第一、第二、第三及第四控制信号中选取其中之一来控制所述第一及第二开关的切换；A first multiplexer, selecting one of the first, second, third and fourth control signals according to the three signals to control switching of the first and second switches;

一第二逻辑电路，根据所述第七信号、第一频率、第三频率及一第三参考电压产生一第五控制信号、第六控制信号、第七控制信号及第八控制信号；A second logic circuit, generating a fifth control signal, a sixth control signal, a seventh control signal and an eighth control signal according to the seventh signal, the first frequency, the third frequency and a third reference voltage;

一第二多任务器，根据所述第三信号从所述第五、第六、第七及第八控制信号中选取其中之一来控制所述第三及第四开关的切换。A second multiplexer, selecting one of the fifth, sixth, seventh and eighth control signals according to the third signal to control switching of the third and fourth switches.

前述的电源转换器，其中所述除频器包括D型正反器。In the aforementioned power converter, the frequency divider includes a D-type flip-flop.

前述的电源转换器，其中在所述降压模式时，所述第一及第二开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二、第三及第四开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二、第三及第四开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第三及第四开关的切换周期为一小于所述第二及第三周期的第四周期。The aforementioned power converter, wherein in the step-down mode, the switching cycle of the first and second switches is a first cycle; in the first buck-boost mode, the first, second, and The switching period of the third and fourth switches is a second period greater than the first period; in the second buck-boost mode, the switching periods of the first, second, third and fourth switches are a third period longer than the first period; and a switching period of the third and fourth switches in the boost mode is a fourth period shorter than the second and third periods.

前述的电源转换器，其中在所述第一升降压模式时，所述第三及第四开关的责任周期固定。In the aforementioned power converter, in the first buck-boost mode, duty periods of the third and fourth switches are fixed.

前述的电源转换器，其中在所述第二升降压模式时，所述第一及第二开关的责任周期固定。In the aforementioned power converter, in the second buck-boost mode, the duty cycles of the first and second switches are fixed.

一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一第二开关连接在所述电感的第一端及一接地端之间，一第三开关连接在所述电感的第二端及所述接地端之间，以及一二极管具有一阳极连接所述电感的第二端及一阴极连接所述电源转换器的输出端，其特征在于所述控制方法包括下列步骤：A control method for a buck-boost power converter, the power converter includes an inductor, a first switch is connected between the input end of the power converter and the first end of the inductor, and a second A switch is connected between the first terminal of the inductor and a ground terminal, a third switch is connected between the second terminal of the inductor and the ground terminal, and a diode has an anode connected to the first terminal of the inductor. Two terminals and a cathode are connected to the output terminal of the power converter, wherein the control method includes the following steps:

第一步骤：检测所述输入端及输出端上的电压以及所述输出端上的负载电流以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；The first step: detecting the voltage on the input terminal and the output terminal and the load current on the output terminal to determine whether the power converter is operating in a buck mode, a first buck-boost mode, or a second buck-boost mode or boost mode;

第二步骤：在所述第一及第二升降压模式时，所述第一、第二及第三开关的控制包含：The second step: in the first and second buck-boost modes, the control of the first, second and third switches includes:

(a)关闭所述第一开关，打开所述第二开关，关闭所述第三开关；(a) closing the first switch, opening the second switch, and closing the third switch;

(b)打开所述第一开关，关闭所述第二开关，维持所述第三开关关闭；(b) opening the first switch, closing the second switch, and keeping the third switch closed;

(c)维持所述第一开关打开，维持所述第二开关关闭，打开所述第三开关。(c) keeping the first switch on, keeping the second switch off, and turning on the third switch.

前述的控制方法，其中所述决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式的步骤包括：The aforementioned control method, wherein the step of determining whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode comprises:

当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在降压模式；When the multiplier value of both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a first critical value, it is determined that the power converter operates in a step-down mode. ;

当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the first critical value and less than a second critical value, determine the the power converter operates in the first buck-boost mode;

当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a third critical value and greater than the second critical value, determine the the power converter operates in the second buck-boost mode;

当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the third critical value, it is determined that the power converter operates at the boost mode.

前述的控制方法，其中更包括：The aforementioned control method, which further includes:

放大一第一信号及一参考电压之间的差值产生一第二信号，所述第一信号为所述输出端上电压的函数；amplifying a difference between a first signal and a reference voltage to generate a second signal, the first signal being a function of the voltage at the output;

提供一第一频率及一第二频率；providing a first frequency and a second frequency;

比较所述第二信号及第三信号产生一第五信号；comparing the second signal and the third signal to generate a fifth signal;

比较所述第二信号及第四信号产生一第六信号；comparing the second signal and the fourth signal to generate a sixth signal;

根据所述电源转换器的操作模式、所述第五及第六信号、第一频率及第二频率控制所述第一、第二及第三开关。The first, second and third switches are controlled according to the operating mode of the power converter, the fifth and sixth signals, the first frequency and the second frequency.

前述的控制方法，其中在所述降压模式时，所述第一及第二开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第三开关的切换周期为一小于所述第二及第三周期的第四周期。The aforementioned control method, wherein in the step-down mode, the switching cycle of the first and second switches is a first cycle; in the first buck-boost mode, the first, second and second The switching period of the three switches is a second period greater than the first period; in the second buck-boost mode, the switching period of the first, second and third switches is a period greater than the first period the third cycle; in the boost mode, the switching cycle of the third switch is a fourth cycle shorter than the second and third cycles.

前述的控制方法，其中在所述第一升降压模式时，所述第三开关的责任周期固定。In the aforementioned control method, in the first buck-boost mode, the duty cycle of the third switch is fixed.

一种升降压式电源转换器，其特征在于，包括：A buck-boost power converter, characterized in that it comprises:

一电感；an inductance;

一第二开关，连接在所述电感的第一端及一接地端之间；a second switch connected between the first terminal of the inductor and a ground terminal;

一第三开关，连接在所述电感的第二端及所述接地端之间；a third switch connected between the second terminal of the inductor and the ground terminal;

一二极管，具有一阳极连接所述电感的第二端及一阴极连接所述电源转换器的输出端；a diode having an anode connected to the second end of the inductor and a cathode connected to the output end of the power converter;

其中，在所述第一及第二升降压模式时，所述第一、第二及第三开关的控制包含(a)关闭所述第一开关、打开所述第二开关及关闭所述第三开关，(b)打开所述第一开关、关闭所述第二开关及维持所述第三开关关闭，以及(c)维持所述第一开关打开、维持所述第二开关关闭及打开所述第三开关。Wherein, in the first and second buck-boost modes, the control of the first, second and third switches includes (a) closing the first switch, opening the second switch and closing the a third switch, (b) opening the first switch, closing the second switch and keeping the third switch closed, and (c) keeping the first switch open, keeping the second switch closed and opening the third switch.

前述的电源转换器，其中所述控制电路在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在所述降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。In the above-mentioned power converter, when the control circuit determines the voltage at the input terminal and the output terminal and the load current at the output terminal, when the magnification value at both ends of the inductance is less than a first critical value, It is determined that the power converter operates in the step-down mode; the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the first When the critical value is less than a second critical value, it is determined that the power converter operates in the first buck-boost mode; the voltage on the input terminal and the output terminal is determined by the load current on the output terminal When the obtained multiplier value at both ends of the inductance is less than a third critical value and greater than the second critical value, it is determined that the power converter operates in the second buck-boost mode; at the input terminal and the output terminal When the multiplier value of both ends of the inductor determined by the voltage on the output terminal and the load current on the output terminal is greater than the third critical value, it is determined that the power converter operates in the boost mode.

前述的电源转换器，其中所述控制电路包括：The aforementioned power converter, wherein the control circuit includes:

一频率产生器，提供一第一频率及一第二频率；a frequency generator providing a first frequency and a second frequency;

一第一比较器，比较所述第二信号及所述第四信号产生一第六信号；a first comparator, comparing the second signal and the fourth signal to generate a sixth signal;

一第二比较器，比较所述第二信号及所述第五信号产生一第七信号；a second comparator, comparing the second signal and the fifth signal to generate a seventh signal;

一控制逻辑电路，根据所述第三、第六及第七信号以及第一及第二频率控制所述第一、第二及第三开关的切换。A control logic circuit controls switching of the first, second and third switches according to the third, sixth and seventh signals and the first and second frequencies.

前述的电源转换器，其中所述控制逻辑电路包括：The aforementioned power converter, wherein the control logic circuit includes:

一除频器，对所述第一频率除频产生一第三频率；a frequency divider that divides the first frequency to generate a third frequency;

一第一逻辑电路，根据所述第六信号、第一频率、第二频率、第三频率及一第二参考电压产生一第一控制信号、第二控制信号及第三控制信号及第四控制信号；A first logic circuit, generating a first control signal, a second control signal, a third control signal and a fourth control signal according to the sixth signal, the first frequency, the second frequency, the third frequency and a second reference voltage Signal;

一第二多任务器，根据所述第三信号从所述第五、第六、第七及第八控制信号中选取其中之一来控制所述第三开关的切换。A second multiplexer, selecting one of the fifth, sixth, seventh and eighth control signals according to the third signal to control switching of the third switch.

前述的电源转换器，其中所述除频器包括D型正反器。In the aforementioned power converter, the frequency divider includes a D-type flip-flop.

前述的电源转换器，其中在所述降压模式时，所述第一及第二开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第三开关的切换周期为一小于所述第二及第三周期的第四周期。The aforementioned power converter, wherein in the step-down mode, the switching cycle of the first and second switches is a first cycle; in the first buck-boost mode, the first, second and The switching period of the third switch is a second period greater than the first period; in the second buck-boost mode, the switching period of the first, second and third switches is a period greater than the first period A third period of the period; in the boost mode, the switching period of the third switch is a fourth period shorter than the second and third periods.

前述的电源转换器，其中在所述第一升降压模式时，所述第三开关的责任周期固定。In the aforementioned power converter, in the first buck-boost mode, the duty cycle of the third switch is fixed.

一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一二极管具有一阳极连接一接地端及一阴极连接所述电感的第一端，一第二开关连接在所述电感的第二端及所述接地端之间，以及一第三开关连接在所述电感的第二端及所述电源转换器的输出端之间，其特征在于所述控制方法包括下列步骤：A control method for a buck-boost power converter, the power converter includes an inductor, a first switch is connected between the input end of the power converter and the first end of the inductor, and a diode has An anode is connected to a ground terminal and a cathode is connected to the first terminal of the inductor, a second switch is connected between the second terminal of the inductor and the ground terminal, and a third switch is connected to the inductor Between the second end and the output end of the power converter, it is characterized in that the control method includes the following steps:

(a)关闭所述第一开关，关闭所述第二开关，打开所述第三开关；(a) closing the first switch, closing the second switch, and opening the third switch;

(b)打开所述第一开关，维持所述第二开关关闭，维持所述第三开关打开；(b) opening the first switch, keeping the second switch closed, and keeping the third switch open;

(c)维持所述第一开关打开，打开所述第二开关，关闭所述第三开关。(c) Keep the first switch open, open the second switch, and close the third switch.

当所述输入端及输出端上的与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；When the multiplication value at both ends of the inductance determined by the load current on the input terminal and the output terminal and the output terminal is greater than the first critical value and smaller than a second critical value, the power supply is determined the converter operates in said first buck-boost mode;

前述的控制方法，其中更包括：The aforementioned control method, which further includes:

提供一第一频率及一第二频率；providing a first frequency and a second frequency;

比较所述第二信号及第三信号产生一第五信号；comparing the second signal and the third signal to generate a fifth signal;

比较所述第二信号及第四信号产生一第六信号；comparing the second signal and the fourth signal to generate a sixth signal;

前述的控制方法，其中在所述降压模式时，所述第一开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第二及第三开关的切换周期为一小于所述第二及第三周期的第四周期。The aforementioned control method, wherein in the buck mode, the switching period of the first switch is a first period; in the first buck-boost mode, the switching period of the first, second and third switches The switching period is a second period greater than the first period; in the second buck-boost mode, the switching period of the first, second and third switches is a third period greater than the first period. Period; in the boost mode, the switching period of the second and third switches is a fourth period shorter than the second and third periods.

前述的控制方法，其中在所述第一升降压模式时，所述第二及第三开关的责任周期固定。In the aforementioned control method, in the first buck-boost mode, the duty cycles of the second and third switches are fixed.

前述的控制方法，其中在所述第二升降压模式时，所述第一开关的责任周期固定。In the aforementioned control method, in the second buck-boost mode, the duty cycle of the first switch is fixed.

一种升降压式电源转换器，其特征在于，包括：A buck-boost power converter, characterized in that it comprises:

一电感；an inductance;

一二极管，具有一阳极连接一接地端及一阴极连接所述电感的第一端；a diode having an anode connected to a ground terminal and a cathode connected to the first end of the inductor;

一第二开关，连接在所述电感的第二端及所述接地端之间；a second switch connected between the second terminal of the inductor and the ground terminal;

一第三开关，连接在所述电感的第二端及所述电源转换器的输出端之间；a third switch connected between the second end of the inductor and the output end of the power converter;

一控制电路，控制所述第一、第二及第三开关的切换，并根据所述输入端及输出端上的电压以及所述输出端上的负载电流决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；a control circuit, controlling switching of the first, second and third switches, and determining the step-down operation of the power converter according to the voltage on the input terminal and the output terminal and the load current on the output terminal mode, the first buck-boost mode, the second buck-boost mode or the boost mode;

其中，在所述第一及第二升降压模式时，所述第一、第二及第三开关的控制包含(a)关闭所述第一开关、关闭所述第二开关及打开所述第三开关，(b)打开所述第一开关、维持所述第二开关关闭及维持所述第三开关打开，以及(c)维持所述第一开关打开、打开所述第二开关及关闭所述第三开关。Wherein, in the first and second buck-boost modes, the control of the first, second and third switches includes (a) closing the first switch, closing the second switch and opening the For a third switch, (b) open the first switch, keep the second switch closed and keep the third switch open, and (c) keep the first switch open, open the second switch and close the third switch.

前述的电源转换器，其中所述控制电路在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在所述降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于一第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。In the above-mentioned power converter, when the control circuit determines the voltage at the input terminal and the output terminal and the load current at the output terminal, when the magnification value at both ends of the inductance is less than a first critical value, It is determined that the power converter operates in the step-down mode; the multiplier value of both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than a first threshold When the value is less than a second critical value, it is determined that the power converter operates in the first buck-boost mode; the voltage on the input terminal and the output terminal is determined by the load current on the output terminal. When the multiplier value at both ends of the inductance is less than a third critical value and greater than the second critical value, it is determined that the power converter operates in the second buck-boost mode; on the input terminal and the output terminal When the multiplier value at both ends of the inductance determined by the voltage at the output terminal and the load current at the output terminal is greater than the third critical value, it is determined that the power converter operates in the boost mode.

前述的电源转换器，其中所述控制电路包括：The aforementioned power converter, wherein the control circuit includes:

一频率产生器，提供一第一频率及一第二频率；a frequency generator providing a first frequency and a second frequency;

一第一比较器，比较所述第二信号及所述第四信号产生一第六信号；a first comparator, comparing the second signal and the fourth signal to generate a sixth signal;

一第二比较器，比较所述第二信号及所述第五信号产生一第七信号；a second comparator, comparing the second signal and the fifth signal to generate a seventh signal;

前述的电源转换器，其中所述控制逻辑电路包括：The aforementioned power converter, wherein the control logic circuit includes:

一除频器，对所述第一频率除频产生一第三频率；a frequency divider that divides the first frequency to generate a third frequency;

一第一多任务器，根据所述三信号从所述第一、第二、第三及第四控制信号中选取其中之一来控制所述第一开关的切换；A first multiplexer, selecting one of the first, second, third and fourth control signals according to the three signals to control switching of the first switch;

一第二多任务器，根据所述第三信号从所述第五、第六、第七及第八控制信号中选取其中之一来控制所述第二及第三开关的切换。A second multiplexer, selecting one of the fifth, sixth, seventh and eighth control signals according to the third signal to control switching of the second and third switches.

前述的电源转换器，其中所述除频器包括D型正反器。In the aforementioned power converter, the frequency divider includes a D-type flip-flop.

前述的电源转换器，其中在所述降压模式时，所述第一开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第二及第三开关的切换周期为一小于所述第二及第三周期的第四周期。The aforementioned power converter, wherein in the buck mode, the switching cycle of the first switch is a first cycle; in the first buck-boost mode, the first, second and third switches The switching period is a second period greater than the first period; in the second buck-boost mode, the switching period of the first, second and third switches is a second period greater than the first period Three periods; in the boost mode, the switching period of the second and third switches is a fourth period shorter than the second and third periods.

前述的电源转换器，其中在所述第一升降压模式时，所述第二及第三开关的责任周期固定。In the aforementioned power converter, in the first buck-boost mode, duty cycles of the second and third switches are fixed.

42、如权利要求35所述的电源转换器，其特征在于，在所述第二升降压模式时，所述第一开关的责任周期固定。42. The power converter of claim 35, wherein in the second buck-boost mode, the duty cycle of the first switch is fixed.

一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一第一二极管具有一阳极连接一接地端及一阴极连接所述电感的第一端，一第二开关连接在所述电感的第二端及所述接地端之间，以及一第二二极管具有一阳极连接所述电感的第二端及一阴极连接所述电源转换器的输出端，其特征在于所述控制方法包括下列步骤：A control method for a buck-boost power converter, the power converter includes an inductor, a first switch is connected between the input end of the power converter and the first end of the inductor, and a first The diode has an anode connected to a ground terminal and a cathode connected to the first terminal of the inductor, a second switch connected between the second terminal of the inductor and the ground terminal, and a second diode It has an anode connected to the second end of the inductor and a cathode connected to the output end of the power converter, characterized in that the control method includes the following steps:

第二步骤：在所述第一及第二升降压模式时，所述第一及第二开关的控制包含：The second step: in the first and second buck-boost modes, the control of the first and second switches includes:

(a)关闭所述第一开关，关闭所述第二开关；(a) closing the first switch and closing the second switch;

(b)打开所述第一开关，维持所述第二开关关闭；(b) opening the first switch and keeping the second switch closed;

(c)维持所述第一开关打开，打开所述第二开关。(c) Keeping the first switch open and turning on the second switch.

当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。When the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current is greater than the third critical value, it is determined that the power converter operates in the boost mode.

前述的控制方法，其中更包括：The aforementioned control method, which further includes:

提供一第一频率及一第二频率；providing a first frequency and a second frequency;

比较所述第二信号及第三信号产生一第五信号；comparing the second signal and the third signal to generate a fifth signal;

比较所述第二信号及第四信号产生一第六信号；comparing the second signal and the fourth signal to generate a sixth signal;

根据所述电源转换器的操作模式、所述第五及第六信号、第一频率及第二频率控制所述第一及第二开关。The first and second switches are controlled according to the operating mode of the power converter, the fifth and sixth signals, the first frequency and the second frequency.

前述的控制方法，其中在所述降压模式时，所述第一开关的切换周期为一第一周期；在所述第一升降压模式时所述第一及第二开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一及第二开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第二开关的切换周期为一小于所述第二及第三周期的第四周期。The aforementioned control method, wherein in the step-down mode, the switching cycle of the first switch is a first cycle; in the first buck-boost mode, the switching cycles of the first and second switches are A second period greater than the first period; in the second buck-boost mode, the switching period of the first and second switches is a third period greater than the first period; in the boost In voltage mode, the switching period of the second switch is a fourth period shorter than the second and third periods.

前述的控制方法，其中在所述第一升降压模式时，所述第二开关的责任周期固定。In the aforementioned control method, in the first buck-boost mode, the duty cycle of the second switch is fixed.

一种升降压式电源转换器，其特征在于，包括：A buck-boost power converter, characterized in that it comprises:

一电感；an inductance;

一第一二极管，具有一阳极连接一接地端及一阴极连接所述电感的第一端；a first diode having an anode connected to a ground terminal and a cathode connected to the first end of the inductor;

一第二开关，连接在所述电感的第二端及所述接地端之间；a second switch connected between the second terminal of the inductor and the ground terminal;

一第二二极管，具有一阳极连接所述电感的第二端及一阴极连接所述电源转换器的输出端；A second diode, having an anode connected to the second end of the inductor and a cathode connected to the output end of the power converter;

一控制电路，控制所述第一及第二开关的切换，并根据所述输入端及输出端上的电压以及所述输出端上的负载电流决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；A control circuit, controlling switching of the first and second switches, and determining the power converter to operate in step-down mode, the second A buck-boost mode, a second buck-boost mode or a boost mode;

其中，在所述第一及第二升降压模式时，所述第一及第二开关的控制包含(a)关闭所述第一开关及关闭所述第二开关，(b)打开所述第一开关及维持所述第二开关关闭，以及(c)维持所述第一开关打开及打开所述第二开关。Wherein, in the first and second buck-boost modes, the control of the first and second switches includes (a) closing the first switch and closing the second switch, (b) opening the first switch and maintaining said second switch closed, and (c) maintaining said first switch open and opening said second switch.

前述的电源转换器，其中所述控制电路在当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在所述降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。The aforementioned power converter, wherein the control circuit is when the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a first critical value , it is determined that the power converter operates in the step-down mode; the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the first When a critical value is less than a second critical value, it is determined that the power converter operates in the first buck-boost mode; the voltage on the input terminal and the output terminal is determined by the load current on the output terminal When the determined multiplier value at both ends of the inductance is less than a third critical value and greater than the second critical value, it is determined that the power converter operates in the second buck-boost mode; at the input and output When the multiplier value at both ends of the inductor determined by the voltage at the terminal and the load current at the output terminal is greater than the third critical value, it is determined that the power converter operates in the boost mode.

前述的电源转换器，其中所述控制电路包括：The aforementioned power converter, wherein the control circuit includes:

一频率产生器，提供一第一频率及一第二频率；a frequency generator providing a first frequency and a second frequency;

一第一比较器，比较所述第二信号及所述第四信号产生一第六信号；a first comparator, comparing the second signal and the fourth signal to generate a sixth signal;

一第二比较器，比较所述第二信号及所述第五信号产生一第七信号；a second comparator, comparing the second signal and the fifth signal to generate a seventh signal;

一控制逻辑电路，根据所述第三、第六及第七信号以及第一及第二频率控制所述第一及第二开关的切换。A control logic circuit controls switching of the first and second switches according to the third, sixth and seventh signals and the first and second frequencies.

前述的电源转换器，其中所述控制逻辑电路包括：The aforementioned power converter, wherein the control logic circuit includes:

一除频器，对所述第一频率除频产生一第三频率；a frequency divider that divides the first frequency to generate a third frequency;

一第二多任务器，根据所述第三信号从所述第五、第六、第七及第八控制信号中选取其中之一来控制所述第二开关的切换。A second multiplexer, selecting one of the fifth, sixth, seventh and eighth control signals according to the third signal to control switching of the second switch.

前述的电源转换器，其中所述除频器包括D型正反器。In the aforementioned power converter, the frequency divider includes a D-type flip-flop.

前述的电源转换器，其中在所述降压模式时，所述第一开关的切换周期为一第一周期；在所述第一升降压模式时所述第一及第二开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一及第二开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第二开关的切换周期为一小于所述第二及第三周期的第四周期。The aforementioned power converter, wherein in the step-down mode, the switching period of the first switch is a first period; in the first buck-boost mode, the switching periods of the first and second switches are is a second period greater than the first period; in the second buck-boost mode, the switching period of the first and second switches is a third period greater than the first period; in the In the boost mode, the switching period of the second switch is a fourth period shorter than the second and third periods.

前述的电源转换器，其中在所述第一升降压模式时，所述第二开关的责任周期固定。In the aforementioned power converter, in the first buck-boost mode, the duty cycle of the second switch is fixed.

前述的电源转换器，其中在所述第二升降压模式时，所述第一开关的责任周期固定。In the aforementioned power converter, in the second buck-boost mode, the duty cycle of the first switch is fixed.

采用上述技术方案后，本发明的升降压式电源转换器及其控制方法具有以下优点：After adopting the above technical solution, the buck-boost power converter and its control method of the present invention have the following advantages:

1.电源转换器操作在升降压模式时，以新的切换顺序控制所述至少二开关，进而减少切换损失及导通损失。1. When the power converter operates in the buck-boost mode, the at least two switches are controlled in a new switching sequence, thereby reducing switching loss and conduction loss.

2.电源转换器由降压模式或升压模式进入升降压模式时，将所述至少二开关的切换周期延长，以进一步减少切换损失，且考虑负载电流对升降压责任周期的影响使其可在正确点切换模式，因此输出电压不会因为改变模式而受影响。2. When the power converter enters the buck-boost mode from the buck mode or the boost mode, the switching period of the at least two switches is extended to further reduce the switching loss, and the influence of the load current on the buck-boost duty cycle is considered so that It switches modes at the correct point, so the output voltage is not affected by changing modes.

附图说明 Description of drawings

图1为已知的升降压式电源转换器示意图；FIG. 1 is a schematic diagram of a known buck-boost power converter;

图2为本发明的第一实施例示意图；Fig. 2 is a schematic diagram of the first embodiment of the present invention;

图3为图2中电源转换器操作在第一模式时的信号波形；FIG. 3 is a signal waveform when the power converter in FIG. 2 operates in a first mode;

图4为图2中电源转换器操作在第一模式时电感L上电感电流IL与开关顺序；FIG. 4 shows the inductor current IL on the inductor L and the switching sequence when the power converter in FIG. 2 operates in the first mode;

图5为图2中电源转换器操作在第二模式时的信号波形；FIG. 5 is a signal waveform when the power converter in FIG. 2 operates in a second mode;

图6为图2中电源转换器操作在第二模式时电感L上电感电流IL与开关顺序；FIG. 6 shows the inductor current IL on the inductor L and the switching sequence when the power converter in FIG. 2 operates in the second mode;

图7为图2中电源转换器操作在第三模式时的信号波形；FIG. 7 is a signal waveform when the power converter in FIG. 2 operates in a third mode;

图8为图2中电源转换器操作在第三模式时电感L上电感电流IL与开关顺序；FIG. 8 shows the inductor current IL on the inductor L and the switching sequence when the power converter in FIG. 2 operates in the third mode;

图9为图2中电源转换器操作在第四模式时的信号波形；FIG. 9 is a signal waveform when the power converter in FIG. 2 operates in a fourth mode;

图10为图2中电源转换器操作在第四模式时电感L上电感电流IL与开关顺序；FIG. 10 shows the inductor current IL on the inductor L and the switching sequence when the power converter in FIG. 2 operates in the fourth mode;

图11为图2中电源转换器的模式转换图；Fig. 11 is a mode conversion diagram of the power converter in Fig. 2;

图12为图2中控制逻辑电路的实施例示意图；Fig. 12 is a schematic diagram of an embodiment of the control logic circuit in Fig. 2;

图13为本发明的第二实施例示意图；Fig. 13 is a schematic diagram of the second embodiment of the present invention;

图14为本发明的第三实施例示意图；Fig. 14 is a schematic diagram of a third embodiment of the present invention;

图15为本发明的第四实施例示意图；Fig. 15 is a schematic diagram of a fourth embodiment of the present invention;

图16为模式检测器的实施例示意图。Figure 16 is a schematic diagram of an embodiment of a pattern detector.

图中，10、电源转换器 12、功率级 14、控制电路 16、控制逻辑电路 18、比较器20、比较器 22、锯齿波产生器 24、误差放大器 30、电源转换器 32、功率级 34、控制电路 36、控制逻辑电路 3602、D型正反器 3604、逻辑电路 3606、多任务器 3608、逻辑电路 3610、多任务器 38、模式检测器 3802、电流源 3804、运算放大器 3806、电流源 3808、比较器 3810、比较器 3812、比较器 40、比较器 42、比较器 44、锯齿波产生器 46、误差放大器 48、频率产生器 50、锯齿波信号SAW12的波形 52、误差信号VEA的波形 54、信号PWM1的波形 56、频率Clk_buck的波形 58、频率Clk_boost的波形 60、控制信号VA的波形 62、控制信号VB的波形 64、控制信号VC的波形66、控制信号VD的波形 68、锯齿波信号SAW12的波形 70、误差信号VEA的波形 72、信号PWM1的波形 74、频率Clk_buck的波形 76、频率Clk_boost的波形 78、控制信号VA的波形 80、控制信号VB的波形 82、控制信号VC的波形 84、控制信号VD的波形 86、锯齿波信号SAW34的波形 88、误差信号VEA的波形 90、信号PWM2的波形92、频率Clk_buck的波形 94、频率Clk_boost的波形 96、控制信号VA的波形98、控制信号VB的波形 100、控制信号VC的波形 102、控制信号VD的波形 104、锯齿波信号SAW34的波形 106、误差信号VEA的波形 108、信号PWM2的波形 110、频率Clk_buck的波形 112、频率Clk_boost的波形 114、控制信号VA的波形 116、控制信号VB的波形 118、控制信号VC的波形 120、控制信号VD的波形 130、电源转换器 132、功率级 140、电源转换器 142、功率级 150、电源转换器 152、功率级。In the figure, 10, power converter 12, power stage 14, control circuit 16, control logic circuit 18, comparator 20, comparator 22, sawtooth wave generator 24, error amplifier 30, power converter 32, power stage 34, Control circuit 36, control logic circuit 3602, D-type flip-flop 3604, logic circuit 3606, multiplexer 3608, logic circuit 3610, multiplexer 38, mode detector 3802, current source 3804, operational amplifier 3806, current source 3808 , comparator 3810, comparator 3812, comparator 40, comparator 42, comparator 44, sawtooth wave generator 46, error amplifier 48, frequency generator 50, waveform of sawtooth wave signal SAW12 52, waveform of error signal VEA 54 , waveform of signal PWM1 56, waveform of frequency Clk_buck 58, waveform of frequency Clk_boost 60, waveform of control signal VA 62, waveform of control signal VB 64, waveform of control signal VC 66, waveform of control signal VD 68, sawtooth wave signal Waveform of SAW12 70, waveform of error signal VEA 72, waveform of signal PWM1 74, waveform of frequency Clk_buck 76, waveform of frequency Clk_boost 78, waveform of control signal VA 80, waveform of control signal VB 82, waveform of control signal VC 84 , the waveform of the control signal VD 86, the waveform of the sawtooth signal SAW34 88, the waveform of the error signal VEA 90, the waveform of the signal PWM2 92, the waveform of the frequency Clk_buck 94, the waveform of the frequency Clk_boost 96, the waveform of the control signal VA 98, the control signal Waveform of VB 100, waveform of control signal VC 102, waveform of control signal VD 104, waveform of sawtooth signal SAW34 106, waveform of error signal VEA 108, waveform of signal PWM2 110, waveform of frequency Clk_buck 112, waveform of frequency Clk_boost 114. Waveform of control signal VA 116. Waveform of control signal VB 118. Waveform of control signal VC 120. Waveform of control signal VD 130. Power converter 132. Power stage 140. Power converter 142. Power stage 150. Power conversion Device 152, power stage.

具体实施方式 Detailed ways

以下结合实施例及其附图对本发明作更进一步说明。The present invention will be further described below in conjunction with embodiment and accompanying drawing.

现请参阅图2，图2显示本发明的第一实施例。如图所示，所述在升降压式电源转换器30中，控制电路34输出控制信号VA、VB、VC及VD驱动功率级32，以将输入电压Vin转换为输出电压Vout，电阻R1及R2分压输出电压Vout产生回授信号VFB给控制电路34。在功率级32中，开关SW1连接在输入电压Vin及电感L之间，开关SW2连接在电感L及接地端GND之间，开关SW3连接在电感L及接地端GND之间，开关SW4连接在电感L及输出电压Vout之间。由于整个系统的责任周期不仅与输入电压和输出电压有关，负载电流也会影响责任周期的大小，因此模式的切换点也必须将负载电流的因素考虑进去。在控制电路34中，模式检测器38检测输入电压Vin、输出电压Vout以及负载电流Iload产生模式选择信号S[3:0]以决定电源转换器30的操作模式，误差放大器46根据参考电压Vref及回授信号VFB产生误差信号VEA，频率产生器48提供频率Clk_boost及Clk_buck，频率Clk_boost及Clk_buck具有固定的周期Ts以及固定的责任周期，锯齿波产生器44根据频率Clk_boost及模式选择信号S[3:0]提供锯齿波信号SAW12及SAW34，比较器40比较误差信号VEA及锯齿波信号SAW12产生信号PWM1，比较器42比较误差信号VEA及锯齿波信号SAW34产生信号PWM2，控制逻辑电路36根据信号PWM1及PWM2、模式选择信号S[3:0]以及频率Clk_boost及Clk_buck产生控制信号VA、VB、VC及VD切换开关SW1、SW2、SW3及SW4以将输入电压Vin转换为输出电压Vout。Please refer now to FIG. 2, which shows a first embodiment of the present invention. As shown in the figure, in the buck-boost power converter 30, the control circuit 34 outputs control signals VA, VB, VC and VD to drive the power stage 32 to convert the input voltage Vin into the output voltage Vout, and the resistors R1 and R2 divides the output voltage Vout to generate a feedback signal VFB to the control circuit 34 . In the power stage 32, the switch SW1 is connected between the input voltage Vin and the inductor L, the switch SW2 is connected between the inductor L and the ground terminal GND, the switch SW3 is connected between the inductor L and the ground terminal GND, and the switch SW4 is connected between the inductor L and the ground terminal GND. Between L and the output voltage Vout. Since the duty cycle of the entire system is not only related to the input voltage and output voltage, but also the load current will affect the size of the duty cycle, the switching point of the mode must also take the factor of the load current into consideration. In the control circuit 34, the mode detector 38 detects the input voltage Vin, the output voltage Vout and the load current Iload to generate the mode selection signal S[3:0] to determine the operation mode of the power converter 30, and the error amplifier 46 according to the reference voltage Vref and The feedback signal VFB generates an error signal VEA, and the frequency generator 48 provides frequencies Clk_boost and Clk_buck. The frequencies Clk_boost and Clk_buck have a fixed cycle Ts and a fixed duty cycle. The sawtooth wave generator 44 selects the signal S[3: 0] provide sawtooth signal SAW12 and SAW34, comparator 40 compares error signal VEA and sawtooth signal SAW12 to generate signal PWM1, comparator 42 compares error signal VEA and sawtooth signal SAW34 to generate signal PWM2, control logic circuit 36 according to signal PWM1 and PWM2 , mode selection signal S[3:0] and frequencies Clk_boost and Clk_buck generate control signals VA, VB, VC and VD to switch switches SW1 , SW2 , SW3 and SW4 to convert the input voltage Vin to the output voltage Vout.

所述电源转换器30可以操作在四种模式，当输入电压Vin、输出电压Vout与负载电流Iload所决定出的电感两端的倍率值小于第一临界值时，电源转换器30操作在第一模式。图3显示电源转换器30操作在第一模式时的信号波形，其中波形50为锯齿波信号SAW12，波形52为误差信号VEA，波形54为信号PWM1，波形56为频率Clk_buck，波形58为频率Clk_boost，波形60为控制信号VA，波形62为控制信号VB，波形64为控制信号VC，波形66为控制信号VD。图4显示电源转换器30操作在第一模式时电感L上电感电流IL与开关顺序。第一模式为单纯的降压模式，在时间t1至t2，控制信号VA、VB、VC及VD均为低准位，如波形60、62、64及66所示，由于开关SW1及SW4为PMOS而开关SW2及SW3为NMOS，故开关SW1及SW4打开(turn on)而开关SW2及SW3关闭(turn off)，这段时间定义为tAD1，在时间tAD1中，输入电压Vin对电感L充电使得电感电流IL上升，如图4所示。在时间t2至t3，控制信号VA及VB为高准位而控制信号VC及VD为低准位，故开关SW2及SW4打开而开关SW1及SW3关闭，这时间定义为tBD1，在时间tBD1中，电感L放电使得电感电流IL下降。在第一模式中，开关SW1及SW2的切换周期以及电感电流IL的周期均为Ts，降压责任周期比Kbuck1为开关SW1的责任周期比。The power converter 30 can operate in four modes. When the multiplier value at both ends of the inductance determined by the input voltage Vin, the output voltage Vout and the load current Iload is smaller than a first critical value, the power converter 30 operates in the first mode. . 3 shows signal waveforms when the power converter 30 operates in the first mode, wherein the waveform 50 is the sawtooth signal SAW12, the waveform 52 is the error signal VEA, the waveform 54 is the signal PWM1, the waveform 56 is the frequency Clk_buck, and the waveform 58 is the frequency Clk_boost , the waveform 60 is the control signal VA, the waveform 62 is the control signal VB, the waveform 64 is the control signal VC, and the waveform 66 is the control signal VD. FIG. 4 shows the inductor current IL on the inductor L and the switching sequence when the power converter 30 operates in the first mode. The first mode is a simple step-down mode. From time t1 to t2, the control signals VA, VB, VC and VD are all at low level, as shown in waveforms 60, 62, 64 and 66. Since the switches SW1 and SW4 are PMOS The switches SW2 and SW3 are NMOS, so the switches SW1 and SW4 are turned on (turn on) and the switches SW2 and SW3 are turned off (turn off). This period of time is defined as tAD1. During the time tAD1, the input voltage Vin charges the inductor L so that the inductor L The current IL rises, as shown in Figure 4. From time t2 to t3, the control signals VA and VB are at the high level and the control signals VC and VD are at the low level, so the switches SW2 and SW4 are turned on and the switches SW1 and SW3 are turned off. This time is defined as tBD1. In the time tBD1, The discharge of the inductor L causes the inductor current IL to drop. In the first mode, the switching period of the switches SW1 and SW2 and the period of the inductor current IL are both Ts, and the buck duty cycle ratio Kbuck1 is the duty cycle ratio of the switch SW1.

当输入电压Vin、输出电压Vout与负载电流Iload所决定出的电感两端的倍率值大于第一临界值且小于1时，电源转换器30操作在第二模式。图5显示电源转换器30操作在第二模式时的信号波形，其中波形68为锯齿波信号SAW12，波形70为误差信号VEA，波形72为信号PWM1，波形74为频率Clk_buck，波形76为频率Clk_boost，波形78为控制信号VA，波形80为控制信号VB，波形82为控制信号VC，波形84为控制信号VD。图6显示电源转换器30操作在第二模式时电感电流IL与开关顺序。第二模式为升降压模式，在时间t4至t5，控制信号VA及VB为高准位而控制信号VC及VD为低准位，故开关SW1及SW3关闭而开关SW2及SW4打开，这段时间定义为tBD2，在时间t5至t6，控制信号VA、VB、VC及VD均为低准位，故开关SW1及SW4打开而开关SW2及SW3关闭，这段时间定义为tAD2，在时间t6至t7，控制信号A及B为低准位而控制信号C及D为高准位，故开关SW1及SW3打开而开关SW2及SW4关闭，这段时间定义为tAC1。在第二模式中，开关SW1、SW2、SW3及SW4的切换周期以及电感电流IL的周期均为2Ts。参照图6，电感电流IL的每一周期包括降压及升压操作，在第二模式中，开关SW3及SW4的责任周期由频率Clk_boost决定，故开关SW3及SW4具有固定的责任周期，因此，在升压操作期间的升压责任周期比Kboost1固定，藉由调整在降压操作期间的降压责任周期比Kbuck2可以让输出电压Vout稳定。When the multiplier value at both ends of the inductor determined by the input voltage Vin, the output voltage Vout and the load current Iload is greater than the first critical value and less than 1, the power converter 30 operates in the second mode. 5 shows signal waveforms when the power converter 30 operates in the second mode, wherein the waveform 68 is the sawtooth signal SAW12, the waveform 70 is the error signal VEA, the waveform 72 is the signal PWM1, the waveform 74 is the frequency Clk_buck, and the waveform 76 is the frequency Clk_boost , the waveform 78 is the control signal VA, the waveform 80 is the control signal VB, the waveform 82 is the control signal VC, and the waveform 84 is the control signal VD. FIG. 6 shows the inductor current IL and the switching sequence when the power converter 30 operates in the second mode. The second mode is the buck-boost mode. From time t4 to t5, the control signals VA and VB are high level and the control signals VC and VD are low level, so the switches SW1 and SW3 are closed and the switches SW2 and SW4 are open. The time is defined as tBD2. From time t5 to t6, the control signals VA, VB, VC and VD are all at low level, so the switches SW1 and SW4 are turned on and the switches SW2 and SW3 are turned off. This time is defined as tAD2. From time t6 to t7, the control signals A and B are at low level and the control signals C and D are at high level, so the switches SW1 and SW3 are turned on and the switches SW2 and SW4 are turned off. This period is defined as tAC1. In the second mode, the switching period of the switches SW1 , SW2 , SW3 and SW4 and the period of the inductor current IL are both 2Ts. Referring to FIG. 6, each cycle of the inductor current IL includes step-down and boost operations. In the second mode, the duty cycle of the switches SW3 and SW4 is determined by the frequency Clk_boost, so the switches SW3 and SW4 have a fixed duty cycle. Therefore, The boost duty cycle ratio Kboost1 during the boost operation is fixed, and the output voltage Vout can be stabilized by adjusting the buck duty cycle ratio Kbuck2 during the buck operation.

当输入电压Vin、输出电压Vout与负载电流Iload所决定出的电感两端的倍率值小于第二临界值且大于1时，电源转换器30操作在第三模式。图7显示电源转换器30操作在第三模式时的信号波形，其中波形86为锯齿波信号SAW34，波形88为误差信号VEA，波形90为信号PWM2，波形92为频率Clk_buck，波形94为频率Clk_boost，波形96为控制信号VA，波形98为控制信号VB，波形100为控制信号VC，波形102为控制信号VD。图8显示电源转换器30操作在第三模式时电感电流IL与开关顺序。第三模式为升降压模式，在时间t8至t9，控制信号VA及VB为高准位而控制信号VC及VD为低准位，故开关SW1及SW3关闭而开关SW2及SW4打开，这段时间定义为tBD3，在时间t9至t10，控制信号VA、VB、VC及VD均为低准位，故开关SW1及SW4打开而开关SW2及SW3关闭，这段时间定义为tAD3，在时间t10至t11，控制信号A及B为低准位而控制信号C及D为高准位，故开关SW1及SW3打开而开关SW2及SW4关闭，这段时间定义为tAC2。在第三模式中，开关SW1、SW2、SW3及SW4的切换周期以及电感电流IL的周期均为2Ts。参照图8，电感电流IL的每一周期包括降压及升压操作，在第三模式中，开关SW1及SW2的责任周期由频率Clk_buck决定，故开关SW1及SW2的责任周期固定，因此，在降压操作期间的降压责任周期比Kbuck3固定，藉由调整在升压操作期间的升压责任周期比Kboost2可以让输出电压Vout稳定。When the multiplier value at both ends of the inductance determined by the input voltage Vin, the output voltage Vout and the load current Iload is smaller than the second critical value and larger than 1, the power converter 30 operates in the third mode. 7 shows signal waveforms when the power converter 30 operates in the third mode, wherein the waveform 86 is the sawtooth signal SAW34, the waveform 88 is the error signal VEA, the waveform 90 is the signal PWM2, the waveform 92 is the frequency Clk_buck, and the waveform 94 is the frequency Clk_boost , the waveform 96 is the control signal VA, the waveform 98 is the control signal VB, the waveform 100 is the control signal VC, and the waveform 102 is the control signal VD. FIG. 8 shows the inductor current IL and the switching sequence when the power converter 30 operates in the third mode. The third mode is the buck-boost mode. From time t8 to t9, the control signals VA and VB are at the high level and the control signals VC and VD are at the low level, so the switches SW1 and SW3 are closed and the switches SW2 and SW4 are open. The time is defined as tBD3. From time t9 to t10, the control signals VA, VB, VC and VD are all at low level, so the switches SW1 and SW4 are turned on and the switches SW2 and SW3 are turned off. This time is defined as tAD3. From time t10 to t11, the control signals A and B are at low level and the control signals C and D are at high level, so the switches SW1 and SW3 are turned on and the switches SW2 and SW4 are turned off. This period of time is defined as tAC2. In the third mode, the switching period of the switches SW1 , SW2 , SW3 and SW4 and the period of the inductor current IL are both 2Ts. Referring to FIG. 8, each cycle of the inductor current IL includes step-down and step-up operations. In the third mode, the duty cycles of the switches SW1 and SW2 are determined by the frequency Clk_buck, so the duty cycles of the switches SW1 and SW2 are fixed. Therefore, in The buck duty cycle ratio Kbuck3 during the buck operation is fixed, and the output voltage Vout can be stabilized by adjusting the boost duty cycle ratio Kboost2 during the boost operation.

当输入电压Vin、输出电压Vou与负载电流Iload所决定出的电感两端的倍率值大于第二临界值，电源转换器30操作在第四模式。图9显示电源转换器30操件在第四模式时的信号波形，其中波形104为锯齿波信号SAW34，波形106为误差信号VEA，波形108为信号PWM2，波形110为频率Clk_buck，波形112为频率Clk_boost，波形114为控制信号VA，波形116为控制信号VB，波形118为控制信号VC，波形120为控制信号VD。图10显示电源转换器30操作在第四模式时电感电流IL与开关顺序。第四模式为单纯的升压模式，在时间t12至t13，控制信号VA及VB为低准位而控制信号VC及VD为高准位，故开关SW1及SW3打开而开关SW2及SW4关闭，这段时间定义为tAC3，在时间t13至t14，控制信号VA、VB、VC及VD均为低准位，故开关SW1及SW4打开而开关SW2及SW3关闭，这段时间定义为tAD4。在第四模式中，开关SW3及SW4的切换周期以及电感电流IL的周期均为Ts，升压责任周期比Kboost3为开关SW3的责任周期比。When the multiplier value at both ends of the inductance determined by the input voltage Vin, the output voltage Vou and the load current Iload is greater than the second critical value, the power converter 30 operates in the fourth mode. 9 shows signal waveforms when the power converter 30 operates in the fourth mode, wherein the waveform 104 is the sawtooth signal SAW34, the waveform 106 is the error signal VEA, the waveform 108 is the signal PWM2, the waveform 110 is the frequency Clk_buck, and the waveform 112 is the frequency Clk_boost, the waveform 114 is the control signal VA, the waveform 116 is the control signal VB, the waveform 118 is the control signal VC, and the waveform 120 is the control signal VD. FIG. 10 shows the inductor current IL and the switching sequence when the power converter 30 operates in the fourth mode. The fourth mode is a simple boost mode. From time t12 to t13, the control signals VA and VB are at low level and the control signals VC and VD are at high level, so the switches SW1 and SW3 are turned on and the switches SW2 and SW4 are turned off. A period of time is defined as tAC3. From time t13 to t14, the control signals VA, VB, VC, and VD are all at low levels, so switches SW1 and SW4 are turned on and switches SW2 and SW3 are turned off. This period is defined as tAD4. In the fourth mode, the switching period of the switches SW3 and SW4 and the period of the inductor current IL are both Ts, and the boost duty cycle ratio Kboost3 is the duty cycle ratio of the switch SW3.

当电源转换器30操作在升降压模式时，开关的切换顺序为(1)打开开关SW2及SW4并关闭开关SW1及SW3，(2)打开开关SW1及SW4并关闭开关SW2及SW3，(3)打开开关SW1及SW3并关闭开关SW2及SW4，与习知技术相比，在相同时间的循环中，电源转换器30的开关切换次数较少，而且当电源转换器30的操作模式由降压模式或升压模式进入升降压模式时，开关的切换周期将由Ts延长为2Ts，故能降低切换损失。再者，此新的开关顺序可以让电感L与电源转换器30的输出端Vout连接的持续时间延长，故能减小导通损失。When the power converter 30 operates in the buck-boost mode, the switching sequence of the switches is (1) turn on the switches SW2 and SW4 and turn off the switches SW1 and SW3, (2) turn on the switches SW1 and SW4 and turn off the switches SW2 and SW3, (3) ) Turn on the switches SW1 and SW3 and close the switches SW2 and SW4. Compared with the prior art, in the cycle of the same time, the switching times of the power converter 30 are less, and when the operation mode of the power converter 30 is changed from step-down When the mode or boost mode enters the buck-boost mode, the switching period of the switch will be extended from Ts to 2Ts, so the switching loss can be reduced. Furthermore, the new switching sequence can extend the duration of the connection between the inductor L and the output terminal Vout of the power converter 30 , thereby reducing the conduction loss.

利用伏秒平衡(voltage second balance)原理可以推导出在四种模式下电源转换器30的输入电压Vin、输出电压Vout与负载电流Iload之间的关系。参照图4，假设每一开关SW1、SW2、SW3及SW4上的跨压都为Vsw，当转换器操作在第一模式时，输入电压Vin、输出电压Vout以及开关之跨压Vsw之间的关系为The relationship between the input voltage Vin, the output voltage Vout and the load current Iload of the power converter 30 in the four modes can be deduced by using the principle of voltage second balance. Referring to FIG. 4 , assuming that the voltage across each switch SW1, SW2, SW3 and SW4 is Vsw, when the converter operates in the first mode, the relationship between the input voltage Vin, the output voltage Vout and the voltage across the switch Vsw for

Vin-2Vsw/(tAD1/Ts)＝Vout/(tAD1/Ts) 公式1Vin-2Vsw/(tAD1/Ts)＝Vout/(tAD1/Ts) Formula 1

参照图6，在第二模式时，输入电压Vin、输出电压Vout以及开关之跨压Vsw之间的关系为Referring to FIG. 6, in the second mode, the relationship between the input voltage Vin, the output voltage Vout and the switch voltage Vsw is

Vin-4Vsw/(Ts+tAD2_1)Vin-4Vsw/(Ts+tAD2_1)

＝Vout[(Ts+tAD2_2)/(Ts+tAD2_1)]=Vout[(Ts+tAD2_2)/(Ts+tAD2_1)]

＝Vout[(2-Kboost1)Ts/(Ts+tAD2_1)] 公式2＝Vout[(2-Kboost1)Ts/(Ts+tAD2_1)] Formula 2

参照图8，在第三模式时，输入电压Vin、输出电压Vout以及开关之跨压Vsw之间的关系为Referring to FIG. 8, in the third mode, the relationship between the input voltage Vin, the output voltage Vout and the switch voltage Vsw is

Vin-4Vsw/(Ts+tAD3_1)Vin-4Vsw/(Ts+tAD3_1)

＝Vout[(Ts+tAD3_2)/(Ts+tAD3_1)]=Vout[(Ts+tAD3_2)/(Ts+tAD3_1)]

＝Vout[(Ts+tAD3_2)/(1+Kbuck3)Ts] 公式3＝Vout[(Ts+tAD3_2)/(1+Kbuck3)Ts] Formula 3

参照图10，在第四模式时，输入电压Vin、输出电压Vout以及开关之跨压Vsw之间的关系为Referring to FIG. 10 , in the fourth mode, the relationship between the input voltage Vin, the output voltage Vout and the switch voltage Vsw is

Vin-2Vsw＝Vout(1-tAC3/Ts) 公式4Vin-2Vsw＝Vout(1-tAC3/Ts) Formula 4

为了防止锯齿波信号SAW12及SAW34的非线性问题使得输出电压Vout无法稳定，故限定降压的最大责任周期及升压的最小责任周期分别为K1及K2，以使输入电压Vin在接近或等于输出电压Vout时，能让输出电压Vout稳定。图11显示电源转换器30的模式转换图，从公式1至公式4及所设定的临界值K1及K2可以得到电源转换器30的模式转换。当电源转换器30操作在第一模式时，参照图11，若输入电压Vin持续下降使得电感L两端的倍率值等于临界值A1时，电源转换器30切换至第二模式。当电源转换器30操作在第二模式时，参照图11，若输入电压Vin持续下降使得电感L两端的倍率值等于临界值A2时，电源转换器30切换至第三模式。当电源转换器30操作在第三模式时，参照图11，若输入电压Vin持续下降使得电感L两端的倍率值等于临界值A3时，电源转换器30切换至第四模式。当电源转换器30操作在第四模式时，参照图11及公式4，若输入电压Vin持续上升使得电感L两端的倍率值等于临界值A3时，电源转换器30切换至第三模式。当电源转换器30操作在第三模式时，若输入电压Vin持续上升使得电感L两端的倍率值等于临界值A2时，电源转换器30切换至第二模式。当电源转换器30操作在第二模式时，若输入电压Vin持续上升，使得电感两端L的倍率值等于临界值A1时电源转换器30切换至第一模式。In order to prevent the non-linear problem of the sawtooth signal SAW12 and SAW34 from causing the output voltage Vout to be unstable, the maximum duty cycle of the step-down and the minimum duty cycle of the boost are limited to K1 and K2 respectively, so that the input voltage Vin is close to or equal to the output voltage. When the voltage Vout is lower, the output voltage Vout can be stabilized. FIG. 11 shows a mode conversion diagram of the power converter 30 . The mode conversion of the power converter 30 can be obtained from Equation 1 to Equation 4 and the set critical values K1 and K2 . When the power converter 30 operates in the first mode, referring to FIG. 11 , if the input voltage Vin continues to drop such that the multiplication value across the inductor L equals the threshold value A1, the power converter 30 switches to the second mode. When the power converter 30 is operating in the second mode, referring to FIG. 11 , if the input voltage Vin continues to drop such that the multiplier value across the inductor L is equal to the threshold value A2, the power converter 30 switches to the third mode. When the power converter 30 is operating in the third mode, referring to FIG. 11 , if the input voltage Vin continues to drop such that the multiplication value across the inductor L is equal to the critical value A3, the power converter 30 switches to the fourth mode. When the power converter 30 operates in the fourth mode, referring to FIG. 11 and Equation 4, if the input voltage Vin continues to rise such that the multiplication value across the inductor L equals the threshold value A3, the power converter 30 switches to the third mode. When the power converter 30 is operating in the third mode, if the input voltage Vin continues to rise such that the multiplier value across the inductor L equals the critical value A2, the power converter 30 switches to the second mode. When the power converter 30 is operating in the second mode, if the input voltage Vin continues to rise such that the multiplier value of both ends of the inductor L is equal to the critical value A1, the power converter 30 switches to the first mode.

图12显示图2中控制逻辑电路36的实施例，其中D型正反器3602作为除频器用以对频率Clk_boost除频产生频率CLK2及CLK2B，逻辑电路3604根据信号PWM1、频率Clk_boost、CLK2及Clk_buck以及接地端GND的电位产生控制信号S1、S2、S3及S4，多任务器3606根据模式选择信号S[3:0]从控制信号S4、S3、S2及S1中选取其中之一做为控制信号VA及VB，逻辑电路3608根据接地端GND的电位、频率CLK2B及Clk_boost以及信号PWM2产生控制信号S5、S6、S7及S8，多任务器3610根据模式选择信号S[3:0]从控制信号S8、S7、S6及S5中选取其中之一做为控制信号VC及VD。FIG. 12 shows an embodiment of the control logic circuit 36 in FIG. 2, wherein the D-type flip-flop 3602 is used as a frequency divider to divide the frequency Clk_boost to generate frequencies CLK2 and CLK2B, and the logic circuit 3604 generates frequencies CLK2 and CLK2B according to the signal PWM1, the frequencies Clk_boost, CLK2 and Clk_buck And the potential of the ground terminal GND generates control signals S1, S2, S3 and S4, and the multiplexer 3606 selects one of the control signals S4, S3, S2 and S1 as the control signal according to the mode selection signal S[3:0] VA and VB, the logic circuit 3608 generates the control signals S5, S6, S7 and S8 according to the potential of the ground terminal GND, the frequencies CLK2B and Clk_boost and the signal PWM2, and the multiplexer 3610 generates the control signals S8 according to the mode selection signal S[3:0] One of , S7 , S6 and S5 is selected as the control signal VC and VD.

图13显示本发明的第二实施例，在升降压式电源转换器130中，控制电路34驱动功率级132以将输入电压Vin转换为输出电压Vout，电阻R1及R2分压输出电压Vout产生回授信号VFB给控制电路34。在功率级132中，开关SW1连接在输入电压Vin及电感L之间，开关SW2连接在电感L及接地端GND之间，开关SW3连接在电感L及接地端GND之间，二极管D1连接在电感L及输出电压Vout之间。控制电路34同样包括控制逻辑电路36、模式检测器38、比较器40及42、锯齿波产生器44、误差放大器46及频率产生器48，控制逻辑电路36根据信号PWM1及PWM2、模式选择信号S[3:0]以及频率Clk_boost及Clk_buck产生控制信号VA、VB及VC切换开关SW1、SW2及SW3以将输入电压Vin转换为输出电压Vout。FIG. 13 shows the second embodiment of the present invention. In the buck-boost power converter 130, the control circuit 34 drives the power stage 132 to convert the input voltage Vin to the output voltage Vout, and the resistors R1 and R2 divide the voltage to generate the output voltage Vout. The feedback signal VFB is sent to the control circuit 34 . In the power stage 132, the switch SW1 is connected between the input voltage Vin and the inductor L, the switch SW2 is connected between the inductor L and the ground terminal GND, the switch SW3 is connected between the inductor L and the ground terminal GND, and the diode D1 is connected between the inductor L and the ground terminal GND. Between L and the output voltage Vout. The control circuit 34 also includes a control logic circuit 36, a mode detector 38, comparators 40 and 42, a sawtooth wave generator 44, an error amplifier 46, and a frequency generator 48. The control logic circuit 36 is based on the signals PWM1 and PWM2, the mode selection signal S [3:0] and frequencies Clk_boost and Clk_buck generate control signals VA, VB and VC to switch switches SW1 , SW2 and SW3 to convert the input voltage Vin to the output voltage Vout.

当电源转换器130操作在升降压模式时，其开关的切换顺序为(1)打开开关SW2并关闭开关SW1及SW3，(2)打开开关SW1并关闭开关SW2及SW3，(3)打开开关SW1及SW3并关闭开关SW2，之后重复步骤(1)至(3)，其中，当输入电压Vin、输出电压Vout与负载电流Iload所决定出的责任周期大于第一临界值且小于1，开关SW3的责任周期固定，当输入电压Vin、输出电压Vout与负载电流Iload所决定出的责任周期小于第二临界值且大于1，开关SW1及SW2的责任周期固定，而且当电源转换器130的操作模式由降压模式或升压模式进入升降压模式时，开关的切换周期将由Ts延长为2Ts。When the power converter 130 operates in the buck-boost mode, the switching sequence of the switches is (1) turn on the switch SW2 and turn off the switches SW1 and SW3, (2) turn on the switch SW1 and turn off the switches SW2 and SW3, (3) turn on the switches SW1 and SW3 close the switch SW2, and then repeat steps (1) to (3), wherein, when the duty cycle determined by the input voltage Vin, the output voltage Vout and the load current Iload is greater than the first critical value and less than 1, the switch SW3 The duty cycle of the switches SW1 and SW2 is fixed, and when the duty cycle determined by the input voltage Vin, the output voltage Vout and the load current Iload is less than the second critical value and greater than 1, the duty cycle of the switches SW1 and SW2 is fixed, and when the operation mode of the power converter 130 is When entering buck-boost mode from buck mode or boost mode, the switching period of the switch will be extended from Ts to 2Ts.

图14显示本发明的第三实施例，在升降压式电源转换器140中，控制电路34驱动功率级142以将输入电压Vin转换为输出电压Vout，电阻R1及R2分压输出电压Vout产生回授信号VFB给控制电路34。在功率级142中，开关SW1连接在输入电压Vin及电感L之间，二极管D2连接在电感L及接地端GND之间，开关SW3连接在电感L及接地端GND之间，开关SW4连接在电感L及输出电压Vout之间。控制电路34同模包括控制逻辑电路36、模式检测器38、比较器40及42、锯齿波产生器44、误差放大器46及频率产生器48，控制逻辑电路36根据信号PWM1及PWM2、模式选择信号S[3:0]以及频率Clk_boost及Clk_buck产生控制信号VA、VC及VD切换开关SW1、SW3及SW4以将输入电压Vin转换为输出电压Vout。FIG. 14 shows the third embodiment of the present invention. In the buck-boost power converter 140, the control circuit 34 drives the power stage 142 to convert the input voltage Vin into the output voltage Vout, and the resistors R1 and R2 divide the voltage to generate the output voltage Vout. The feedback signal VFB is sent to the control circuit 34 . In the power stage 142, the switch SW1 is connected between the input voltage Vin and the inductor L, the diode D2 is connected between the inductor L and the ground terminal GND, the switch SW3 is connected between the inductor L and the ground terminal GND, and the switch SW4 is connected between the inductor L and the ground terminal GND. Between L and the output voltage Vout. The control circuit 34 includes a control logic circuit 36, a mode detector 38, comparators 40 and 42, a sawtooth wave generator 44, an error amplifier 46, and a frequency generator 48. The control logic circuit 36 is based on the signals PWM1 and PWM2 and the mode selection signal. S[3:0] and the frequencies Clk_boost and Clk_buck generate control signals VA, VC and VD to switch the switches SW1 , SW3 and SW4 to convert the input voltage Vin to the output voltage Vout.

当电源转换器140操作在升降压模式时，其开关的切换顺序为(1)打开开关SW4并关闭开关SW1及SW3，(2)打开开关SW1及SW4并关闭开关SW3，(3)打开开关SW1及SW3并关闭开关SW4，之后重复步骤(1)至(3)，其中，当输入电压Vin、输出电压Vout与负载电流Iload所决定出的责任周期大于第一临界值且小于1，开关SW3及SW4的责任周期固定，当输入电压Vin、输出电压Vout与负载电流Iload所决定出的责任周期小于第二临界值且大于1，开关SW1的责任周期固定，而且当电源转换器140的操作模式由降压模式或升压模式进入升降压模式时，开关的切换周期将由Ts延长为2Ts。When the power converter 140 operates in the buck-boost mode, the switching sequence of its switches is (1) turn on the switch SW4 and turn off the switches SW1 and SW3, (2) turn on the switches SW1 and SW4 and turn off the switch SW3, (3) turn on the switch SW1 and SW3 close the switch SW4, and then repeat steps (1) to (3), wherein, when the duty cycle determined by the input voltage Vin, the output voltage Vout and the load current Iload is greater than the first critical value and less than 1, the switch SW3 and the duty cycle of SW4 is fixed, when the duty cycle determined by the input voltage Vin, the output voltage Vout and the load current Iload is less than the second critical value and greater than 1, the duty cycle of the switch SW1 is fixed, and when the operation mode of the power converter 140 When entering buck-boost mode from buck mode or boost mode, the switching period of the switch will be extended from Ts to 2Ts.

图15显示本发明的第四实施例，在升降压式电源转换器150中，控制电路34驱动功率级152以将输入电压Vin转换为输出电压Vout，电阻R1及R2分压输出电压Vout产生回授信号VFB给控制电路34。在功率级152中，开关SW1连接在输入电压Vin及电感L之间，二极管D3连接在电感L及接地端GND之间，开关SW3连接在电感L及接地端GND之间，二极管D4连接在电感L及输出电压Vout之间。控制电路34同模包括控制逻辑电路36、模式检测器38、比较器40及42、锯齿波产生器44、误差放大器46及频率产生器48，控制逻辑电路36根据信号PWM1及PWM2、模式选择信号S[3:0]以及频率Clk_boost及Clk_buck产生控制信号VA及VC切换开关SW1及SW3以将输入电压Vin转换为输出电压Vout。FIG. 15 shows the fourth embodiment of the present invention. In the buck-boost power converter 150, the control circuit 34 drives the power stage 152 to convert the input voltage Vin to the output voltage Vout, and the resistors R1 and R2 divide the voltage to generate the output voltage Vout. The feedback signal VFB is sent to the control circuit 34 . In the power stage 152, the switch SW1 is connected between the input voltage Vin and the inductor L, the diode D3 is connected between the inductor L and the ground terminal GND, the switch SW3 is connected between the inductor L and the ground terminal GND, and the diode D4 is connected between the inductor L and the ground terminal GND. Between L and the output voltage Vout. The control circuit 34 includes a control logic circuit 36, a mode detector 38, comparators 40 and 42, a sawtooth wave generator 44, an error amplifier 46, and a frequency generator 48. The control logic circuit 36 is based on the signals PWM1 and PWM2 and the mode selection signal. S[3:0] and the frequencies Clk_boost and Clk_buck generate control signals VA and VC to switch the switches SW1 and SW3 to convert the input voltage Vin to the output voltage Vout.

当电源转换器150操作在升降压模式时，其开关的切换顺序为(1)关闭开关SW1及SW3，(2)打开开关SW1并关闭开关SW3，(3)打开开关SW1及SW3，之后重复步骤(1)至(3)，其中，当输入电压Vin、输出电压Vout与负载电流Iload所决定出的责任周期大于第一临界值且小于1，开关SW3的责任周期固定，当输入电压Vin、输出电压Vout与负载电流Iload所决定出的责任周期小于第二临界值且大于1，开关SW1的责任周期固定，而且当电源转换器150的操作模式由降压模式或升压模式进入升降压模式时，开关的切换周期将由Ts延长为2Ts。When the power converter 150 operates in the buck-boost mode, the switching sequence of the switches is (1) turn off the switches SW1 and SW3, (2) turn on the switch SW1 and turn off the switch SW3, (3) turn on the switches SW1 and SW3, and then repeat Steps (1) to (3), wherein, when the duty cycle determined by the input voltage Vin, the output voltage Vout and the load current Iload is greater than the first critical value and less than 1, the duty cycle of the switch SW3 is fixed. When the input voltage Vin, The duty cycle determined by the output voltage Vout and the load current Iload is less than the second critical value and greater than 1, the duty cycle of the switch SW1 is fixed, and when the operation mode of the power converter 150 changes from the buck mode or the boost mode to the buck-boost mode mode, the switching period of the switch will be extended from Ts to 2Ts.

图16显示模式检测器38的实施例，在模式检测器38中，当开关SW1打开时，开关MP1也同时打开，因此电压Vb为(Vin-Vsw-Ib×R3)，其中电压Vsw与负载电流Iload成正比，运算放大器3804将电压Vb及Va锁在同一准位上，因此流过电阻R4的电流Ia为(Ib+Vsw/R4)，设计电流源3802及3806相等，使得流经电阻R5的电流Ic为(Vsw/R4)，因此可推得电压Figure 16 shows an embodiment of the mode detector 38. In the mode detector 38, when the switch SW1 is opened, the switch MP1 is also opened at the same time, so the voltage Vb is (Vin-Vsw-Ib×R3), where the voltage Vsw is related to the load current Iload is proportional, and the operational amplifier 3804 locks the voltages Vb and Va at the same level, so the current Ia flowing through the resistor R4 is (Ib+Vsw/R4), and the designed current sources 3802 and 3806 are equal, so that the current Ia flowing through the resistor R5 The current Ic is (Vsw/R4), so the voltage can be pushed

VDEC＝Vin-Ia×R4-Ic×R5VDEC＝Vin-Ia×R4-Ic×R5

＝Vin-Ib×R4-Vsw-(R5/R4)×Vsw=Vin-Ib×R4-Vsw-(R5/R4)×Vsw

＝Vin-(1+R5/R4)Vsw-Ib×R4 公式5＝Vin-(1+R5/R4)Vsw-Ib×R4 Formula 5

由于(Ib×R4)可以设计的相对小，因此电压Since (Ib×R4) can be designed relatively small, the voltage

公式6 Formula 6

由公式6可知，藉由调整电阻R5及R4的比值可以调节电压VDEC，接着比较器3808、3810及3812分别比较(M1×Vout)、(M2×Vout)及(M3×Vout)与电压VDEC，逻辑电路3814根据比较器3808、3810及3812的输出产生模式选择信号S[3:0]。It can be seen from formula 6 that the voltage VDEC can be adjusted by adjusting the ratio of the resistors R5 and R4, and then the comparators 3808, 3810 and 3812 respectively compare (M1×Vout), (M2×Vout) and (M3×Vout) with the voltage VDEC, The logic circuit 3814 generates the mode selection signal S[3:0] according to the outputs of the comparators 3808 , 3810 and 3812 .

以上实施例仅供说明本发明之用，而非对本发明的限制，有关技术领域的技术人员，在不脱离本发明的精神和范围的情况下，还可以作出各种变换或变化。因此，所有等同的技术方案也应该属于本发明的范畴，应由各权利要求限定。The above embodiments are only for illustrating the present invention, rather than limiting the present invention. Those skilled in the relevant technical field can also make various transformations or changes without departing from the spirit and scope of the present invention. Therefore, all equivalent technical solutions should also belong to the category of the present invention and should be defined by each claim.

Claims (48)

1.一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一第二开关连接在所述电感的第一端及一接地端之间，一第三开关连接在所述电感的第二端及所述接地端之间，以及一第四开关连接在所述电感的第二端及所述电源转换器的输出端之间，其特征在于所述控制方法包括下列步骤：1. A control method for a buck-boost power converter, the power converter includes an inductor, a first switch is connected between the input end of the power converter and the first end of the inductor, a A second switch is connected between the first terminal of the inductor and a ground terminal, a third switch is connected between the second terminal of the inductor and the ground terminal, and a fourth switch is connected between the inductor Between the second end of the power converter and the output end of the power converter, it is characterized in that the control method includes the following steps: 检测所述输入端及输出端上的电压以及在所述输出端上的负载电流以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；detecting the voltages on the input terminal and the output terminal and the load current on the output terminal to determine whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost model; 放大一第一信号及一参考电压之间的差值产生一第二信号，所述第一信号为所述输出端上电压的函数；amplifying a difference between a first signal and a reference voltage to generate a second signal, the first signal being a function of the voltage at the output; 提供一第一频率及一第二频率；providing a first frequency and a second frequency; 根据所述电源转换器的操作模式及所述第一频率产生一第三信号及一第四信号；generating a third signal and a fourth signal according to the operation mode of the power converter and the first frequency; 比较所述第二信号及第三信号产生一第五信号；comparing the second signal and the third signal to generate a fifth signal; 比较所述第二信号及第四信号产生一第六信号；以及comparing the second signal and the fourth signal to generate a sixth signal; and 根据所述电源转换器的操作模式、所述第五及第六信号、第一频率及第二频率控制所述第一、第二、第三及第四开关；controlling the first, second, third and fourth switches according to an operating mode of the power converter, the fifth and sixth signals, a first frequency and a second frequency; 在所述第一及第二升降压模式时，所述第一、第二、第三及第四开关的控制包含：In the first and second buck-boost modes, the control of the first, second, third and fourth switches includes: a、关闭所述第一开关，打开所述第二开关，关闭所述第三开关，打开所述第四开关；a. Turn off the first switch, turn on the second switch, turn off the third switch, and turn on the fourth switch; b、打开所述第一开关，关闭所述第二开关，维持所述第三开关关闭，维持所述第四开关打开；以及b. Turn on the first switch, turn off the second switch, keep the third switch off, and keep the fourth switch on; and c、维持所述第一开关打开，维持所述第二开关关闭，打开所述第三开关，关闭所述第四开关。c. Keep the first switch on, keep the second switch off, turn on the third switch, and turn off the fourth switch. 2.如权利要求1所述的控制方法，其特征在于，所述决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式的步骤包括下列步骤：2. The control method according to claim 1, wherein the step of determining whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode comprises Follow these steps: 第一步骤：当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值小于一第一临界值，决定所述电源转换器操作在降压模式；Step 1: When the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current is smaller than a first critical value, determine that the power converter operates in a step-down mode; 第二步骤：当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值，决定所述电源转换器操作在所述第一升降压模式；Step two: determine the power converter when the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current is greater than the first critical value and smaller than a second critical value operating in said first buck-boost mode; 第三步骤：当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值，决定所述电源转换器操作在所述第二升降压模式；以及Step 3: determine the power converter when the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current is less than a third critical value and greater than the second critical value operating in said second buck-boost mode; and 第四步骤：当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。Step 4: When the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current is greater than the third critical value, determine that the power converter operates at the boost voltage model. 3.如权利要求1所述的控制方法，其特征在于，在所述降压模式时，所述第一及第二开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二、第三及第四开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二、第三及第四开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第三及第四开关的切换周期为一小于所述第二及第三周期的第四周期。3. The control method according to claim 1, wherein in the buck mode, the switching period of the first and second switches is a first period; in the first buck-boost mode The switching period of the first, second, third and fourth switches is a second period greater than the first period; in the second buck-boost mode, the first, second and fourth switches The switching period of the third and fourth switches is a third period greater than the first period; in the boost mode, the switching period of the third and fourth switches is a period shorter than the second and third period of the fourth cycle. 4.如权利要求1所述的控制方法，其特征在于，在所述第一升降压模式时，所述第三及第四开关的责任周期固定。4. The control method according to claim 1, wherein in the first buck-boost mode, duty cycles of the third and fourth switches are fixed. 5.如权利要求1所述的控制方法，其特征在于，在所述第二升降压模式时，所述第一及第二开关的责任周期固定。5. The control method according to claim 1, wherein in the second buck-boost mode, duty periods of the first and second switches are fixed. 6.一种升降压式电源转换器，其特征在于，包括：6. A buck-boost power converter, characterized in that it comprises: 一电感；an inductance; 一第一开关，连接在所述电源转换器的输入端及所述电感的第一端之间；a first switch connected between the input terminal of the power converter and the first terminal of the inductor; 一第二开关，连接在所述电感的第一端及一接地端之间；a second switch connected between the first terminal of the inductor and a ground terminal; 一第三开关，连接在所述电感的第二端及所述接地端之间；a third switch connected between the second terminal of the inductor and the ground terminal; 一第四开关，连接在所述电感的第二端及所述电源转换器的输出端之间；以及a fourth switch connected between the second terminal of the inductor and the output terminal of the power converter; and 一控制电路，控制所述第一、第二、第三及第四开关的切换，并根据所述输入端及输出端上的电压以及所述输出端上的负载电流决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；a control circuit, controlling switching of the first, second, third and fourth switches, and determining the operation of the power converter according to the voltage on the input terminal and the output terminal and the load current on the output terminal In buck mode, first buck-boost mode, second buck-boost mode or boost mode; 其中，所述控制电路包括：Wherein, the control circuit includes: 一误差放大器，根据一第一信号及一参考电压产生一第二信号，所述第一信号为所述电源转换器输出端上电压的函数；an error amplifier generating a second signal based on a first signal and a reference voltage, the first signal being a function of the voltage at the output of the power converter; 一频率产生器，提供一第一频率及一第二频率；a frequency generator providing a first frequency and a second frequency; 一模式检测器，检测所述电源转换器的输入端及输出端上的电压产生一第三信号以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；A mode detector, detecting the voltage on the input end and the output end of the power converter to generate a third signal to determine whether the power converter is operating in the buck mode, the first buck-boost mode, the second buck-boost mode mode or boost mode; 一锯齿波产生器，根据所述第三信号及第一频率提供一第四信号或一第五信号；a sawtooth wave generator, providing a fourth signal or a fifth signal according to the third signal and the first frequency; 一第一比较器，比较所述第二信号及所述第四信号产生一第六信号；a first comparator, comparing the second signal and the fourth signal to generate a sixth signal; 一第二比较器，比较所述第二信号及所述第五信号产生一第七信号；以及a second comparator, comparing the second signal and the fifth signal to generate a seventh signal; and 一控制逻辑电路，根据所述第三、第六及第七信号以及第一及第二频率控制所述第一、第二、第三及第四开关的切换；a control logic circuit, controlling switching of the first, second, third and fourth switches according to the third, sixth and seventh signals and the first and second frequencies; 其中，在所述第一及第二升降压模式时，所述第一、第二、第三及第四开关的控制包含a、关闭所述第一开关、打开所述第二开关、关闭所述第三开关及打开所述第四开关，b、打开所述第一开关、关闭所述第二开关、维持所述第三开关关闭及维持所述第四开关打开，以及c、维持所述第一开关打开、维持所述第二开关关闭、打开所述第三开关及关闭所述第四开关。Wherein, in the first and second buck-boost modes, the control of the first, second, third and fourth switches includes a, closing the first switch, opening the second switch, closing the third switch and open the fourth switch, b. open the first switch, close the second switch, keep the third switch closed and keep the fourth switch open, and c. keep the The first switch is turned on, the second switch is kept closed, the third switch is turned on, and the fourth switch is turned off. 7.如权利要求6所述的电源转换器，其特征在于，所述控制电路在所述输入端及输出端上的电压与所述负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在所述降压模式；在所述输入端及输出端上的电压与所述负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；在所述输入端及输出端上的电压与所述负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；在所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。7. The power converter according to claim 6, characterized in that, the voltage at the input terminal and the output terminal of the control circuit and the load current determine the multiplier value of both ends of the inductance is less than one When the first critical value is reached, it is determined that the power converter operates in the step-down mode; the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current is greater than the When the first critical value is less than a second critical value, it is determined that the power converter operates in the first buck-boost mode; the voltage on the input terminal and the output terminal is determined by the load current When the multiplier value at both ends of the inductance is less than a third critical value and greater than the second critical value, it is determined that the power converter operates in the second buck-boost mode; When the multiplier value at both ends of the inductor determined by the voltage and the load current is greater than the third critical value, it is determined that the power converter operates in the boost mode. 8.如权利要求6所述的电源转换器，其特征在于，所述控制逻辑电路包括：8. The power converter according to claim 6, wherein the control logic circuit comprises: 一除频器，对所述第一频率除频产生一第三频率；a frequency divider that divides the first frequency to generate a third frequency; 一第一逻辑电路，根据所述第六信号、第一频率、第二频率、第三频率及一第二参考电压产生一第一控制信号、第二控制信号、第三控制信号及第四控制信号；A first logic circuit, generating a first control signal, a second control signal, a third control signal and a fourth control signal according to the sixth signal, the first frequency, the second frequency, the third frequency and a second reference voltage Signal; 一第一多任务器，根据所述三信号从所述第一、第二、第三及第四控制信号中选取其中之一来控制所述第一及第二开关的切换；A first multiplexer, selecting one of the first, second, third and fourth control signals according to the three signals to control switching of the first and second switches; 一第二逻辑电路，根据所述第七信号、第一频率、第三频率及一第三参考电压产生一第五控制信号、第六控制信号、第七控制信号及第八控制信号；以及a second logic circuit for generating a fifth control signal, a sixth control signal, a seventh control signal and an eighth control signal according to the seventh signal, the first frequency, the third frequency and a third reference voltage; and 一第二多任务器，根据所述第三信号从所述第五、第六、第七及第八控制信号中选取其中之一来控制所述第三及第四开关的切换。A second multiplexer, selecting one of the fifth, sixth, seventh and eighth control signals according to the third signal to control switching of the third and fourth switches. 9.如权利要求8所述的电源转换器，其特征在于，所述除频器包括D型正反器。9. The power converter according to claim 8, wherein the frequency divider comprises a D-type flip-flop. 10.如权利要求6所述的电源转换器，其特征在于，在所述降压模式时，所述第一及第二开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二、第三及第四开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二、第三及第四开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第三及第四开关的切换周期为一小于所述第二及第三周期的第四周期。10. The power converter according to claim 6, wherein in the step-down mode, the switching period of the first and second switches is a first period; mode, the switching period of the first, second, third and fourth switches is a second period greater than the first period; in the second buck-boost mode, the first, second, The switching period of the third and fourth switches is a third period greater than the first period; in the boost mode, the switching period of the third and fourth switches is a period shorter than the second and third The fourth cycle of the cycle. 11.如权利要求6所述的电源转换器，其特征在于，在所述第一升降压模式时，所述第三及第四开关的责任周期固定。11. The power converter as claimed in claim 6, wherein in the first buck-boost mode, duty cycles of the third and fourth switches are fixed. 12.如权利要求6所述的电源转换器，其特征在于，在所述第二升降压模式时，所述第一及第二开关的责任周期固定。12. The power converter as claimed in claim 6, wherein in the second buck-boost mode, duty periods of the first and second switches are fixed. 13.一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一第二开关连接在所述电感的第一端及一接地端之间，一第三开关连接在所述电感的第二端及所述接地端之间，以及一二极管具有一阳极连接所述电感的第二端及一阴极连接所述电源转换器的输出端，其特征在于所述控制方法包括下列步骤：13. A control method for a buck-boost power converter, the power converter includes an inductor, a first switch is connected between the input end of the power converter and the first end of the inductor, and a A second switch is connected between the first terminal of the inductor and a ground terminal, a third switch is connected between the second terminal of the inductor and the ground terminal, and a diode has an anode connected to the inductor The second end and a cathode are connected to the output end of the power converter, characterized in that the control method includes the following steps: 检测所述输入端及输出端上的电压以及所述输出端上的负载电流以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；Detecting the voltages on the input terminal and the output terminal and the load current on the output terminal to determine whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode ; 放大一第一信号及一参考电压之间的差值产生一第二信号，所述第一信号为所述输出端上电压的函数；amplifying a difference between a first signal and a reference voltage to generate a second signal, the first signal being a function of the voltage at the output; 提供一第一频率及一第二频率；providing a first frequency and a second frequency; 根据所述电源转换器的操作模式及所述第一频率产生一第三信号及一第四信号；generating a third signal and a fourth signal according to the operation mode of the power converter and the first frequency; 比较所述第二信号及第三信号产生一第五信号；comparing the second signal and the third signal to generate a fifth signal; 比较所述第二信号及第四信号产生一第六信号；以及comparing the second signal and the fourth signal to generate a sixth signal; and 根据所述电源转换器的操作模式、所述第五及第六信号、第一频率及第二频率控制所述第一、第二及第三开关；controlling the first, second and third switches according to an operating mode of the power converter, the fifth and sixth signals, a first frequency and a second frequency; 在所述第一及第二升降压模式时，所述第一、第二及第三开关的控制包含：In the first and second buck-boost modes, the control of the first, second and third switches includes: a、关闭所述第一开关，打开所述第二开关，关闭所述第三开关；a. Turn off the first switch, turn on the second switch, and turn off the third switch; b、打开所述第一开关，关闭所述第二开关，维持所述第三开关关闭；以及b. Turn on the first switch, turn off the second switch, and keep the third switch off; and c、维持所述第一开关打开，维持所述第二开关关闭，打开所述第三开关。c. Keep the first switch on, keep the second switch off, and turn on the third switch. 14.如权利要求13所述的控制方法，其特征在于，所述决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式的步骤包括：14. The control method according to claim 13, wherein the step of determining whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode comprises : 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在降压模式；When the multiplier value of both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a first critical value, it is determined that the power converter operates in a step-down mode. ; 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the first critical value and less than a second critical value, determine the the power converter operates in the first buck-boost mode; 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；以及When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a third critical value and greater than the second critical value, determine the the power converter operates in the second buck-boost mode; and 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the third critical value, it is determined that the power converter operates at the boost mode. 15.如权利要求13所述的控制方法，其特征在于，在所述降压模式时，所述第一及第二开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第三开关的切换周期为一小于所述第二及第三周期的第四周期。15. The control method according to claim 13, wherein in the buck mode, the switching period of the first and second switches is a first period; in the first buck-boost mode When the switching period of the first, second and third switches is a second period greater than the first period; in the second buck-boost mode, the switching periods of the first, second and third switches The switching period is a third period longer than the first period; the switching period of the third switch in the boost mode is a fourth period shorter than the second and third periods. 16.如权利要求13所述的控制方法，其特征在于，在所述第一升降压模式时，所述第三开关的责任周期固定。16. The control method according to claim 13, wherein in the first buck-boost mode, the duty cycle of the third switch is fixed. 17.如权利要求13所述的控制方法，其特征在于，在所述第二升降压模式时，所述第一及第二开关的责任周期固定。17. The control method according to claim 13, wherein in the second buck-boost mode, duty periods of the first and second switches are fixed. 18.一种升降压式电源转换器，其特征在于，包括：18. A buck-boost power converter, characterized in that it comprises: 一电感；an inductance; 一第一开关，连接在所述电源转换器的输入端及所述电感的第一端之间；a first switch connected between the input terminal of the power converter and the first terminal of the inductor; 一第二开关，连接在所述电感的第一端及一接地端之间；a second switch connected between the first terminal of the inductor and a ground terminal; 一第三开关，连接在所述电感的第二端及所述接地端之间；a third switch connected between the second terminal of the inductor and the ground terminal; 一二极管，具有一阳极连接所述电感的第二端及一阴极连接所述电源转换器的输出端；以及a diode having an anode connected to the second end of the inductor and a cathode connected to the output end of the power converter; and 一控制电路，控制所述第一、第二、第三及第四开关的切换，并根据所述输入端及输出端上的电压以及所述输出端上的负载电流决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；a control circuit, controlling switching of the first, second, third and fourth switches, and determining the operation of the power converter according to the voltage on the input terminal and the output terminal and the load current on the output terminal In buck mode, first buck-boost mode, second buck-boost mode or boost mode; 其中，所述控制电路包括：Wherein, the control circuit includes: 一误差放大器，根据一第一信号及一参考电压产生一第二信号，所述第一信号为所述电源转换器输出端上电压的函数；an error amplifier generating a second signal based on a first signal and a reference voltage, the first signal being a function of the voltage at the output of the power converter; 一频率产生器，提供一第一频率及一第二频率；a frequency generator providing a first frequency and a second frequency; 一模式检测器，检测所述电源转换器的输入端及输出端上的电压产生一第三信号以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；A mode detector, detecting the voltage on the input end and the output end of the power converter to generate a third signal to determine whether the power converter is operating in the buck mode, the first buck-boost mode, the second buck-boost mode mode or boost mode; 一锯齿波产生器，根据所述第三信号及第一频率提供一第四信号或一第五信号；a sawtooth wave generator, providing a fourth signal or a fifth signal according to the third signal and the first frequency; 一第一比较器，比较所述第二信号及所述第四信号产生一第六信号；a first comparator, comparing the second signal and the fourth signal to generate a sixth signal; 一第二比较器，比较所述第二信号及所述第五信号产生一第七信号；以及a second comparator, comparing the second signal and the fifth signal to generate a seventh signal; and 一控制逻辑电路，根据所述第三、第六及第七信号以及第一及第二频率控制所述第一、第二及第三开关的切换；a control logic circuit, controlling switching of the first, second and third switches according to the third, sixth and seventh signals and the first and second frequencies; 其中，在所述第一及第二升降压模式时，所述第一、第二及第三开关的控制包含a、关闭所述第一开关、打开所述第二开关及关闭所述第三开关，b、打开所述第一开关、关闭所述第二开关及维持所述第三开关关闭，以及c、维持所述第一开关打开、维持所述第二开关关闭及打开所述第三开关。Wherein, in the first and second buck-boost modes, the control of the first, second and third switches includes a, closing the first switch, opening the second switch and closing the first switch Three switches, b, open the first switch, close the second switch and keep the third switch closed, and c, keep the first switch open, keep the second switch closed and open the third switch Three switches. 19.如权利要求18所述的电源转换器，其特征在于，控制电路在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在所述降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。19. The power converter as claimed in claim 18, characterized in that, the control circuit has a multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal When it is less than a first critical value, it is determined that the power converter operates in the step-down mode; the voltage on the input terminal and the output terminal and the load current on the output terminal determine the inductance When the magnification value of the terminal is greater than the first critical value and smaller than a second critical value, it is determined that the power converter operates in the first buck-boost mode; the voltage on the input terminal and the output terminal is the same as the When the multiplier value at both ends of the inductor determined by the load current on the output terminal is less than a third critical value and greater than the second critical value, it is determined that the power converter operates in the second buck-boost mode; When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the third critical value, it is determined that the power converter operates at the boost mode. 20.如权利要求18所述的电源转换器，其特征在于，所述控制逻辑电路包括：20. The power converter according to claim 18, wherein the control logic circuit comprises: 一除频器，对所述第一频率除频产生一第三频率；a frequency divider that divides the first frequency to generate a third frequency; 一第一逻辑电路，根据所述第六信号、第一频率、第二频率、第三频率及一第二参考电压产生一第一控制信号、第二控制信号及第三控制信号及第四控制信号；A first logic circuit, generating a first control signal, a second control signal, a third control signal and a fourth control signal according to the sixth signal, the first frequency, the second frequency, the third frequency and a second reference voltage Signal; 一第一多任务器，根据所述三信号从所述第一、第二、第三及第四控制信号中选取其中之一来控制所述第一及第二开关的切换；A first multiplexer, selecting one of the first, second, third and fourth control signals according to the three signals to control switching of the first and second switches; 一第二逻辑电路，根据所述第七信号、第一频率、第三频率及一第三参考电压产生一第五控制信号、第六控制信号、第七控制信号及第八控制信号；以及一第二多任务器，根据所述第三信号从所述第五、第六、第七及第八控制信号中选取其中之一来控制所述第三开关的切换。a second logic circuit, generating a fifth control signal, a sixth control signal, a seventh control signal and an eighth control signal according to the seventh signal, the first frequency, the third frequency and a third reference voltage; and a The second multiplexer selects one of the fifth, sixth, seventh and eighth control signals according to the third signal to control switching of the third switch. 21.如权利要求20所述的电源转换器，其特征在于，所述除频器包括D型正反器。21. The power converter according to claim 20, wherein the frequency divider comprises a D-type flip-flop. 22.如权利要求18所述的电源转换器，其特征在于，在所述降压模式时，所述第一及第二开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第三开关的切换周期为一小于所述第二及第三周期的第四周期。22. The power converter according to claim 18, wherein in the step-down mode, the switching period of the first and second switches is a first period; mode, the switching period of the first, second and third switches is a second period greater than the first period; in the second buck-boost mode, the first, second and third switches The switching period of the switch is a third period longer than the first period; the switching period of the third switch in the boost mode is a fourth period shorter than the second and third periods. 23.如权利要求18所述的电源转换器，其特征在于，在所述第一升降压模式时，所述第三开关的责任周期固定。23. The power converter according to claim 18, wherein in the first buck-boost mode, the duty cycle of the third switch is fixed. 24.如权利要求18所述的电源转换器，其特征在于，在所述第二升降压模式时，所述第一及第二开关的责任周期固定。24. The power converter as claimed in claim 18, wherein in the second buck-boost mode, duty periods of the first and second switches are fixed. 25.一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一二极管具有一阳极连接一接地端及一阴极连接所述电感的第一端，一第二开关连接在所述电感的第二端及所述接地端之间，以及一第三开关连接在所述电感的第二端及所述电源转换器的输出端之间，其特征在于所述控制方法包括下列步骤：25. A control method for a buck-boost power converter, the power converter includes an inductor, a first switch is connected between the input end of the power converter and the first end of the inductor, and a The diode has an anode connected to a ground terminal and a cathode connected to the first terminal of the inductor, a second switch connected between the second terminal of the inductor and the ground terminal, and a third switch connected to the Between the second end of the inductor and the output end of the power converter, it is characterized in that the control method includes the following steps: 检测所述输入端及输出端上的电压以及所述输出端上的负载电流以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；Detecting the voltages on the input terminal and the output terminal and the load current on the output terminal to determine whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode ; 放大一第一信号及一参考电压之间的差值产生一第二信号，所述第一信号为所述输出端上电压的函数；amplifying a difference between a first signal and a reference voltage to generate a second signal, the first signal being a function of the voltage at the output; 提供一第一频率及一第二频率；providing a first frequency and a second frequency; 根据所述电源转换器的操作模式及所述第一频率产生一第三信号及一第四信号；generating a third signal and a fourth signal according to the operation mode of the power converter and the first frequency; 比较所述第二信号及第三信号产生一第五信号；comparing the second signal and the third signal to generate a fifth signal; 比较所述第二信号及第四信号产生一第六信号；以及comparing the second signal and the fourth signal to generate a sixth signal; and 根据所述电源转换器的操作模式、所述第五及第六信号、第一频率及第二频率控制所述第一、第二及第三开关；controlling the first, second and third switches according to an operating mode of the power converter, the fifth and sixth signals, a first frequency and a second frequency; 在所述第一及第二升降压模式时，所述第一、第二及第三开关的控制包含：In the first and second buck-boost modes, the control of the first, second and third switches includes: a、关闭所述第一开关，关闭所述第二开关，打开所述第三开关；a. Turn off the first switch, turn off the second switch, and turn on the third switch; b、打开所述第一开关，维持所述第二开关关闭，维持所述第三开关打开；以及b. Open the first switch, keep the second switch closed, and keep the third switch open; and c、维持所述第一开关打开，打开所述第二开关，关闭所述第三开关。c. Keep the first switch open, open the second switch, and close the third switch. 26.如权利要求25所述的控制方法，其特征在于，所述决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式的步骤包括：26. The control method according to claim 25, wherein the step of determining whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode comprises : 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在降压模式；When the multiplier value of both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a first critical value, it is determined that the power converter operates in a step-down mode. ; 当所述输入端及输出端上的与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；When the multiplication value at both ends of the inductance determined by the load current on the input terminal and the output terminal and the output terminal is greater than the first critical value and smaller than a second critical value, the power supply is determined the converter operates in said first buck-boost mode; 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；以及When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a third critical value and greater than the second critical value, determine the the power converter operates in the second buck-boost mode; and 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the third critical value, it is determined that the power converter operates at the boost mode. 27.如权利要求25所述的控制方法，其特征在于，在所述降压模式时，所述第一开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第二及第三开关的切换周期为一小于所述第二及第三周期的第四周期。27. The control method according to claim 25, characterized in that, in the step-down mode, the switching period of the first switch is a first period; in the first buck-boost mode, the The switching period of the first, second and third switches is a second period greater than the first period; in the second buck-boost mode, the switching period of the first, second and third switches is a third period longer than the first period; and a switching period of the second and third switches in the boost mode is a fourth period shorter than the second and third periods. 28.如权利要求25所述的控制方法，其特征在于，在所述第一升降压模式时，所述第二及第三开关的责任周期固定。28. The control method according to claim 25, wherein in the first buck-boost mode, duty periods of the second and third switches are fixed. 29.如权利要求25所述的控制方法，其特征在于，在所述第二升降压模式时，所述第一开关的责任周期固定。29. The control method according to claim 25, wherein in the second buck-boost mode, the duty cycle of the first switch is fixed. 30.一种升降压式电源转换器，其特征在于，包括：30. A buck-boost power converter, characterized in that it comprises: 一电感；an inductance; 一第一开关，连接在所述电源转换器的输入端及所述电感的第一端之间；a first switch connected between the input terminal of the power converter and the first terminal of the inductor; 一二极管，具有一阳极连接一接地端及一阴极连接所述电感的第一端；a diode having an anode connected to a ground terminal and a cathode connected to the first end of the inductor; 一第二开关，连接在所述电感的第二端及所述接地端之间；a second switch connected between the second terminal of the inductor and the ground terminal; 一第三开关，连接在所述电感的第二端及所述电源转换器的输出端之间；以及a third switch connected between the second terminal of the inductor and the output terminal of the power converter; and 一控制电路，控制所述第一、第二及第三开关的切换，并根据所述输入端及输出端上的电压以及所述输出端上的负载电流决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；a control circuit, controlling switching of the first, second and third switches, and determining the step-down operation of the power converter according to the voltage on the input terminal and the output terminal and the load current on the output terminal mode, the first buck-boost mode, the second buck-boost mode or the boost mode; 其中，所述控制电路包括：Wherein, the control circuit includes: 一误差放大器，根据一第一信号及一参考电压产生一第二信号，所述第一信号为所述电源转换器输出端上电压的函数；an error amplifier generating a second signal based on a first signal and a reference voltage, the first signal being a function of the voltage at the output of the power converter; 一频率产生器，提供一第一频率及一第二频率；a frequency generator providing a first frequency and a second frequency; 一模式检测器，检测所述电源转换器的输入端及输出端上的电压产生一第三信号以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；A mode detector, detecting the voltage on the input end and the output end of the power converter to generate a third signal to determine whether the power converter is operating in the buck mode, the first buck-boost mode, the second buck-boost mode mode or boost mode; 一锯齿波产生器，根据所述第三信号及第一频率提供一第四信号或一第五信号；a sawtooth wave generator, providing a fourth signal or a fifth signal according to the third signal and the first frequency; 一第一比较器，比较所述第二信号及所述第四信号产生一第六信号；a first comparator, comparing the second signal and the fourth signal to generate a sixth signal; 一第二比较器，比较所述第二信号及所述第五信号产生一第七信号；以及a second comparator, comparing the second signal and the fifth signal to generate a seventh signal; and 一控制逻辑电路，根据所述第三、第六及第七信号以及第一及第二频率控制所述第一、第二及第三开关的切换；a control logic circuit, controlling switching of the first, second and third switches according to the third, sixth and seventh signals and the first and second frequencies; 其中，在所述第一及第二升降压模式时，所述第一、第二及第三开关的控制包含a、关闭所述第一开关、关闭所述第二开关及打开所述第三开关，b、打开所述第一开关、维持所述第二开关关闭及维持所述第三开关打开，以及c、维持所述第一开关打开、打开所述第二开关及关闭所述第三开关。Wherein, in the first and second buck-boost modes, the control of the first, second and third switches includes a, closing the first switch, closing the second switch and opening the first switch Three switches, b, open the first switch, keep the second switch closed and keep the third switch open, and c, keep the first switch open, open the second switch and close the third switch Three switches. 31.如权利要求30所述的电源转换器，其特征在，所述控制电路在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在所述降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于一第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。31. The power converter according to claim 30, characterized in that, the voltage at the input terminal and the output terminal of the control circuit is determined by the load current at the output terminal. When the magnification value is less than a first critical value, it is determined that the power converter operates in the step-down mode; the voltage on the input terminal and the output terminal and the load current on the output terminal determine the When the multiplier value at both ends of the inductance is greater than a first critical value and smaller than a second critical value, it is determined that the power converter operates in the first buck-boost mode; When the multiplier value at both ends of the inductor determined by the load current at the output terminal is less than a third critical value and greater than the second critical value, it is determined that the power converter operates in the second buck-boost mode ; When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the third critical value, it is determined that the power converter operates at the specified boost mode described above. 32.如权利要求30所述的电源转换器，其特征在于，所述控制逻辑电路包括：32. The power converter of claim 30, wherein the control logic circuit comprises: 一除频器，对所述第一频率除频产生一第三频率；a frequency divider that divides the first frequency to generate a third frequency; 一第一逻辑电路，根据所述第六信号、第一频率、第二频率、第三频率及一第二参考电压产生一第一控制信号、第二控制信号、第三控制信号及第四控制信号；A first logic circuit, generating a first control signal, a second control signal, a third control signal and a fourth control signal according to the sixth signal, the first frequency, the second frequency, the third frequency and a second reference voltage Signal; 一第一多任务器，根据所述三信号从所述第一、第二、第三及第四控制信号中选取其中之一来控制所述第一开关的切换；A first multiplexer, selecting one of the first, second, third and fourth control signals according to the three signals to control switching of the first switch; 一第二逻辑电路，根据所述第七信号、第一频率、第三频率及一第三参考电压产生一第五控制信号、第六控制信号、第七控制信号及第八控制信号；以及a second logic circuit for generating a fifth control signal, a sixth control signal, a seventh control signal and an eighth control signal according to the seventh signal, the first frequency, the third frequency and a third reference voltage; and 一第二多任务器，根据所述第三信号从所述第五、第六、第七及第八控制信号中选取其中之一来控制所述第二及第三开关的切换。A second multiplexer, selecting one of the fifth, sixth, seventh and eighth control signals according to the third signal to control switching of the second and third switches. 33.如权利要求32所述的电源转换器，其特征在于，所述除频器包括D型正反器。33. The power converter of claim 32, wherein the frequency divider comprises a D-type flip-flop. 34.如权利要求30所述的电源转换器，其特征在于，在所述降压模式时，所述第一开关的切换周期为一第一周期；在所述第一升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一、第二及第三开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第二及第三开关的切换周期为一小于所述第二及第三周期的第四周期。34. The power converter according to claim 30, wherein in the buck mode, the switching period of the first switch is a first period; in the first buck-boost mode, the The switching period of the first, second and third switches is a second period greater than the first period; the switching period of the first, second and third switches in the second buck-boost mode is a third period longer than the first period; in the boost mode, the switching period of the second and third switches is a fourth period shorter than the second and third periods. 35.如权利要求30所述的电源转换器，其特征在于，在所述第一升降压模式时，所述第二及第三开关的责任周期固定。35. The power converter as claimed in claim 30, wherein in the first buck-boost mode, duty periods of the second and third switches are fixed. 36.如权利要求30所述的电源转换器，其特征在于，在所述第二升降压模式时，所述第一开关的责任周期固定。36. The power converter of claim 30, wherein in the second buck-boost mode, the duty cycle of the first switch is fixed. 37.一种升降压式电源转换器的控制方法，所述电源转换器包含一电感，一第一开关连接在所述电源转换器的输入端及所述电感的第一端之间，一第一二极管具有一阳极连接一接地端及一阴极连接所述电感的第一端，一第二开关连接在所述电感的第二端及所述接地端之间，以及一第二二极管具有一阳极连接所述电感的第二端及一阴极连接所述电源转换器的输出端，其特征在于所述控制方法包括下列步骤：37. A control method for a buck-boost power converter, the power converter includes an inductor, a first switch is connected between the input end of the power converter and the first end of the inductor, and a The first diode has an anode connected to a ground terminal and a cathode connected to the first terminal of the inductor, a second switch connected between the second terminal of the inductor and the ground terminal, and a second The pole tube has an anode connected to the second end of the inductor and a cathode connected to the output end of the power converter, wherein the control method includes the following steps: 检测所述输入端及输出端上的电压以及所述输出端上的负载电流以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；Detecting the voltages on the input terminal and the output terminal and the load current on the output terminal to determine whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode ; 放大一第一信号及一参考电压之间的差值产生一第二信号，所述第一信号为所述输出端上电压的函数；amplifying a difference between a first signal and a reference voltage to generate a second signal, the first signal being a function of the voltage at the output; 提供一第一频率及一第二频率；providing a first frequency and a second frequency; 根据所述电源转换器的操作模式及所述第一频率产生一第三信号及一第四信号；generating a third signal and a fourth signal according to the operation mode of the power converter and the first frequency; 比较所述第二信号及第三信号产生一第五信号；comparing the second signal and the third signal to generate a fifth signal; 比较所述第二信号及第四信号产生一第六信号；以及comparing the second signal and the fourth signal to generate a sixth signal; and 根据所述电源转换器的操作模式、所述第五及第六信号、第一频率及第二频率控制所述第一及第二开关；controlling the first and second switches based on an operating mode of the power converter, the fifth and sixth signals, a first frequency and a second frequency; 在所述第一及第二升降压模式时，所述第一及第二开关的控制包含：In the first and second buck-boost modes, the control of the first and second switches includes: a、关闭所述第一开关，关闭所述第二开关；a. Turn off the first switch and turn off the second switch; b、打开所述第一开关，维持所述第二开关关闭；以及b. opening the first switch and keeping the second switch closed; and c、维持所述第一开关打开，打开所述第二开关。c. Keep the first switch open, and open the second switch. 38.如权利要求37所述的控制方法，其特征在于，所述决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式的步骤包括：38. The control method according to claim 37, wherein the step of determining whether the power converter operates in a buck mode, a first buck-boost mode, a second buck-boost mode or a boost mode comprises : 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在降压模式；When the multiplier value of both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a first critical value, it is determined that the power converter operates in a step-down mode. ; 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the first critical value and less than a second critical value, determine the the power converter operates in the first buck-boost mode; 当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；以及When the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is less than a third critical value and greater than the second critical value, determine the the power converter operates in the second buck-boost mode; and 当所述输入端及输出端上的电压与负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。When the multiplier value at both ends of the inductor determined by the voltage on the input terminal and the output terminal and the load current is greater than the third critical value, it is determined that the power converter operates in the boost mode. 39.如权利要求37所述的控制方法，其特征在于，在所述降压模式时，所述第一开关的切换周期为一第一周期；在所述第一升降压模式时所述第一及第二开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一及第二开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第二开关的切换周期为一小于所述第二及第三周期的第四周期。39. The control method according to claim 37, characterized in that, in the step-down mode, the switching period of the first switch is a first period; in the first buck-boost mode, the The switching period of the first and second switches is a second period greater than the first period; in the second buck-boost mode, the switching period of the first and second switches is a period greater than the first period A third period of the period; in the boost mode, the switching period of the second switch is a fourth period shorter than the second and third periods. 40.如权利要求37所述的控制方法，其特征在于，在所述第一升降压模式时，所述第二开关的责任周期固定。40. The control method according to claim 37, wherein in the first buck-boost mode, the duty cycle of the second switch is fixed. 41.如权利要求37所述的控制方法，其特征在于，在所述第二升降压模式时，所述第一开关的责任周期固定。41. The control method according to claim 37, wherein in the second buck-boost mode, the duty cycle of the first switch is fixed. 42.一种升降压式电源转换器，其特征在于，包括：42. A buck-boost power converter, characterized by comprising: 一电感；an inductance; 一第一开关，连接在所述电源转换器的输入端及所述电感的第一端之间；a first switch connected between the input terminal of the power converter and the first terminal of the inductor; 一第一二极管，具有一阳极连接一接地端及一阴极连接所述电感的第一端；a first diode having an anode connected to a ground terminal and a cathode connected to the first end of the inductor; 一第二开关，连接在所述电感的第二端及所述接地端之间；a second switch connected between the second terminal of the inductor and the ground terminal; 一第二二极管，具有一阳极连接所述电感的第二端及一阴极连接所述电源转换器的输出端；以及a second diode having an anode connected to the second end of the inductor and a cathode connected to the output end of the power converter; and 一控制电路，控制所述第一及第二开关的切换，并根据所述输入端及输出端上的电压以及所述输出端上的负载电流决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；A control circuit, controlling switching of the first and second switches, and determining the power converter to operate in step-down mode, the second A buck-boost mode, a second buck-boost mode or a boost mode; 其中，所述控制电路包括：Wherein, the control circuit includes: 一误差放大器，根据一第一信号及一参考电压产生一第二信号，所述第一信号为所述电源转换器输出端上电压的函数；an error amplifier generating a second signal based on a first signal and a reference voltage, the first signal being a function of the voltage at the output of the power converter; 一频率产生器，提供一第一频率及一第二频率；a frequency generator providing a first frequency and a second frequency; 一模式检测器，检测所述电源转换器的输入端及输出端上的电压产生一第三信号以决定所述电源转换器操作在降压模式、第一升降压模式、第二升降压模式或升压模式；A mode detector, detecting the voltage on the input end and the output end of the power converter to generate a third signal to determine whether the power converter is operating in the buck mode, the first buck-boost mode, the second buck-boost mode mode or boost mode; 一锯齿波产生器，根据所述第三信号及第一频率提供一第四信号或一第五信号；a sawtooth wave generator, providing a fourth signal or a fifth signal according to the third signal and the first frequency; 一第一比较器，比较所述第二信号及所述第四信号产生一第六信号；a first comparator, comparing the second signal and the fourth signal to generate a sixth signal; 一第二比较器，比较所述第二信号及所述第五信号产生一第七信号；以及a second comparator, comparing the second signal and the fifth signal to generate a seventh signal; and 一控制逻辑电路，根据所述第三、第六及第七信号以及第一及第二频率控制所述第一及第二开关的切换；a control logic circuit, controlling switching of the first and second switches according to the third, sixth and seventh signals and the first and second frequencies; 其中，在所述第一及第二升降压模式时，所述第一及第二开关的控制包含a、关闭所述第一开关及关闭所述第二开关，b、打开所述第一开关及维持所述第二开关关闭，以及c、维持所述第一开关打开及打开所述第二开关。Wherein, in the first and second buck-boost modes, the control of the first and second switches includes a, closing the first switch and closing the second switch, b, opening the first switching and keeping said second switch closed, and c. keeping said first switch open and opening said second switch. 43.如权利要求42所述的电源转换器，其特征在于，所述控制电路在当所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第一临界值时，决定所述电源转换器操作在所述降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第一临界值且小于一第二临界值时，决定所述电源转换器操作在所述第一升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值小于一第三临界值且大于所述第二临界值时，决定所述电源转换器操作在所述第二升降压模式；在所述输入端及输出端上的电压与所述输出端上的负载电流所决定出的所述电感两端的倍率值大于所述第三临界值时，决定所述电源转换器操作在所述升压模式。43. The power converter according to claim 42, wherein the control circuit operates between the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal. When the multiplier value of the terminal is less than a first critical value, it is determined that the power converter operates in the step-down mode; the voltage on the input terminal and the output terminal and the load current on the output terminal are determined by the When the multiplier value at both ends of the inductance is greater than the first critical value and smaller than a second critical value, it is determined that the power converter operates in the first buck-boost mode; the voltage on the input terminal and the output terminal When the multiplier value at both ends of the inductance determined by the load current on the output terminal is less than a third critical value and greater than the second critical value, it is determined that the power converter operates at the second lifting voltage mode; when the multiplier value at both ends of the inductance determined by the voltage on the input terminal and the output terminal and the load current on the output terminal is greater than the third critical value, the operation of the power converter is determined in the boost mode. 44.如权利要求42所述的电源转换器，其特征在于，所述控制逻辑电路包括：44. The power converter of claim 42, wherein the control logic circuit comprises: 一除频器，对所述第一频率除频产生一第三频率；a frequency divider that divides the first frequency to generate a third frequency; 一第一逻辑电路，根据所述第六信号、第一频率、第二频率、第三频率及一第二参考电压产生一第一控制信号、第二控制信号、第三控制信号及第四控制信号；A first logic circuit, generating a first control signal, a second control signal, a third control signal and a fourth control signal according to the sixth signal, the first frequency, the second frequency, the third frequency and a second reference voltage Signal; 一第一多任务器，根据所述三信号从所述第一、第二、第三及第四控制信号中选取其中之一来控制所述第一开关的切换；A first multiplexer, selecting one of the first, second, third and fourth control signals according to the three signals to control switching of the first switch; 一第二逻辑电路，根据所述第七信号、第一频率、第三频率及一第三参考电压产生一第五控制信号、第六控制信号、第七控制信号及第八控制信号；以及a second logic circuit for generating a fifth control signal, a sixth control signal, a seventh control signal and an eighth control signal according to the seventh signal, the first frequency, the third frequency and a third reference voltage; and 一第二多任务器，根据所述第三信号从所述第五、第六、第七及第八控制信号中选取其中之一来控制所述第二开关的切换。A second multiplexer, selecting one of the fifth, sixth, seventh and eighth control signals according to the third signal to control switching of the second switch. 45.如权利要求44所述的电源转换器，其特征在于，所述除频器包括D型正反器。45. The power converter of claim 44, wherein the frequency divider comprises a D-type flip-flop. 46.如权利要求42所述的电源转换器，其特征在于，在所述降压模式时，所述第一开关的切换周期为一第一周期；在所述第一升降压模式时所述第一及第二开关的切换周期为一大于所述第一周期的第二周期；在所述第二升降压模式时所述第一及第二开关的切换周期为一大于所述第一周期的第三周期；在所述升压模式时所述第二开关的切换周期为一小于所述第二及第三周期的第四周期。46. The power converter according to claim 42, wherein in the step-down mode, the switching cycle of the first switch is a first cycle; in the first buck-boost mode, the The switching period of the first and second switches is a second period greater than the first period; in the second buck-boost mode, the switching period of the first and second switches is a period greater than the first period A third period of one period; in the boost mode, the switching period of the second switch is a fourth period shorter than the second and third periods. 47.如权利要求42所述的电源转换器，其特征在于，在所述第一升降压模式时，所述第二开关的责任周期固定。47. The power converter according to claim 42, wherein in the first buck-boost mode, the duty cycle of the second switch is fixed. 48.如权利要求42所述的电源转换器，其特征在于，在所述第二升降压模式时，所述第一开关的责任周期固定。48. The power converter of claim 42, wherein in the second buck-boost mode, the duty cycle of the first switch is fixed.

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