CN103166442B - Prevent device, converter and power supply that step-down buck circuital current is reverse - Google Patents

The invention provides a kind of device, converter and power supply that prevents that step-down buck circuital current is reverse, method comprises: the work dutycycle D of rectifier switch pipe in the input voltage vin of the described buck circuit of sampling and described buck circuit, and utilize described Vin and described D, obtain theoretical output voltage V in × D; The actual output voltage of described theoretical output voltage and described buck circuit is compared, in the time that described theoretical output voltage is less than described actual output voltage, the continued flow switch pipe of controlling in described buck circuit turn-offs, in the time that described theoretical output voltage is more than or equal to described actual output voltage, control the continued flow switch pipe conducting in described buck circuit. Controlled exactly the switch shape of the continued flow switch pipe of buck circuit, realized at output and having existed in prebias situation, continued flow switch pipe normal switch state open time, in output inductor without reverse irrigated current.

Prevent device, converter and power supply that step-down buck circuital current is reverse

Technical field

The present invention relates to power technology, relate in particular to a kind of prevent the reverse device of step-down buck circuital current,Converter and power supply.

Background technology

Diode rectification relatively, synchronous rectification has electric current two-way flow characteristic, therefore such topology knotStructure is all two-way topology. In non-isolated topology step-down (buck) circuit, continued flow tube diode is changed intoSynchro switch pipe is also two-way topology, and in this structure, energy both can be from power supply inlet flow to output,Also can be from output stream to input. Wherein, energy is so-called current flowing backwards problem from output stream to input.Two kinds of anti-problems of filling with of situation are particularly serious below: the first situation is that input Low ESR falls, the secondWhen situation is power supply start, there is pre-bias voltage in output.

In the second situation, adopt bus-powered power supply especially serious, because total electricity of bus load sideHold greatlyr, current flowing backwards problem more easily occurs.

For the problems referred to above, common solution has two kinds, and one is adduction road (ORING), butAlthough load isolation like this, can sacrifice efficiency, and still cannot solve the current flowing backwards problem of self.Another kind is to add delay control circuit. In buck circuit as shown in Figure 1,120 is buck circuitVirtual voltage output, before buck circuit start, output 120 is with pre-bias voltage. Buck circuitWhen work, pulse width modulation (PulseWidthModulation, PWM) controller send one group mutualThe switch controlling signal of mending, controls respectively rectifier switch pipe 106 and continued flow switch pipe Q13 alternate conduction.In buck circuit start process, control the dutycycle of rectifier switch pipe 106, ascending expansion gradually,Therefore, the ON time of continued flow switch pipe Q13 is maximum in original state, simultaneously due to output 120Have pre-bias voltage, therefore the electric current on output inductor is reverse, has formed so-called output and has flowed toThe current flowing backwards problem of input. By increasing delay control circuit, default solid in the time of buck circuit startFixed delay time is controlled the driving of continued flow switch pipe Q3 grid, makes continued flow switch pipe Q3 by one sectionThe time delay of time just enters normal switch working state, has avoided the conducting of continued flow switch pipe Q3, makesObtain and during this period of time in output inductor, can not produce reversing the current path, also just solved electric current anti-The problem of filling with. But, due to the pre-bias voltage size of the virtual voltage output of buck circuit in factBe uncertain, large time, the time of needed time delay control is short; On the contrary, little time, want large,Therefore existing fixing delay time is difficult to take into account all situations. For example, in the time that pre-bias voltage is higher,The time that still time delay is grown is controlled continued flow switch pipe Q13 and enters into normal on off state, there will be outputFilter inductance interrupter duty (DCM) is to continuous operation mode (ContinuousCurrentMode, CCM)Switch caused output voltage power down phenomenon suddenly.

Summary of the invention

In view of this, the embodiment of the present invention provides a kind of reverse dress of step-down buck circuital current that preventsPut, converter and power supply, to reach the on off state of the continued flow switch pipe that can accurately control Q13Object.

First aspect, the embodiment of the present invention provides a kind of reverse method of step-down buck circuital current that prevents,Comprise:

The work of rectifier switch pipe in the input voltage vin of described buck circuit of sampling and described buck circuitMake dutycycle D, and utilize described Vin and described D, obtain theoretical output voltage V in × D;

The actual output voltage of described theoretical output voltage and described buck circuit is compared, whenWhen described theoretical output voltage is less than described actual output voltage, control continuing in described buck circuitStream switching tube turn-offs, in the time that described theoretical output voltage is more than or equal to described actual output voltage, and controlMake the continued flow switch pipe conducting in described buck circuit.

Second aspect, the embodiment of the present invention provides a kind of reverse device of step-down buck circuital current that prevents,Comprise:

Weber generator, for input voltage vin and the described buck circuit of the described buck circuit of samplingThe work dutycycle D of middle rectifier switch pipe, and utilize described Vin and described D, obtain theoretical output electricityPress Vin × D;

Control circuit, with described weber generator be connected, for by described theoretical output voltage with described inThe actual output voltage of buck circuit compares, and when described theoretical output voltage, to be less than described reality defeatedWhile going out voltage, the continued flow switch pipe of controlling in described buck circuit turn-offs, when described theoretical output electricityWhen pressure is more than or equal to described actual output voltage, control the continued flow switch pipe in described buck circuitConducting.

In conjunction with second aspect, in the possible implementation of the first of second aspect, described control circuitComprise:

Voltage comparator circuit, with described weber generator be connected, for more described theoretical output voltage withDescribed actual output voltage, and according to comparative result output control signal;

Drive circuit, is connected with described voltage comparator circuit, for defeated according to described voltage comparator circuitThe control signal going out drives shutoff or the conducting of the continued flow switch pipe in described buck circuit.

In conjunction with the possible implementation of the first of second aspect, possible at the second of second aspectIn implementation, described voltage comparator circuit is comparator.

In conjunction with the possible implementation of the second of second aspect, possible at the third of second aspectIn implementation, also comprise: the return difference regulating resistance being connected with described comparator.

In conjunction with second aspect or second aspect first to any one in the third possible implementationPossible implementation, in the 4th kind of possible implementation of second aspect, also comprises:

Actual output voltage sample circuit, is connected with described control circuit, for to described buck electricityThe actual output voltage on road is sampled.

In conjunction with the 4th kind of possible implementation of second aspect, possible the 5th kind of second aspectIn implementation, described actual output voltage sample circuit is divider resistance circuit.

In conjunction with the 4th kind of possible implementation of second aspect, possible the 6th kind of second aspectIn implementation, also comprise the output voltage biased electrical being connected with described actual output voltage sample circuitResistance.

The third aspect, the embodiment of the present invention provides a kind of power pack with pre-bias voltage, bagDraw together and prevent the reverse dress of step-down buck circuital current described in step-down buck circuit and above-mentioned any onePut, described in prevent that the reverse device of step-down buck circuital current is connected with described buck circuit.

Fourth aspect, the embodiment of the present invention provides a kind of supply unit, comprise step-down buck circuit andDescribed in above-mentioned any one, prevent the reverse device of step-down buck circuital current, described in prevent step-down buckThe reverse device of circuital current is connected with described buck circuit.

What above-described embodiment provided prevents device, converter and the electricity that step-down buck circuital current is reverseSource, by obtaining the theoretical output voltage of buck circuit, and just theoretical output voltage and buck circuitActual output voltage compare, in the time that theoretical output voltage is less than actual output voltage, controlContinued flow switch pipe in buck circuit turn-offs, when described theoretical output voltage is more than or equal to described realityWhen output voltage, control the continued flow switch pipe conducting in buck circuit, controlled exactly buck electricityThe switch shape of the continued flow switch pipe on road, has realized at output and having existed in prebias situation, continued flow switch pipeNormal switch state open time, in output inductor without reverse irrigated current.

Brief description of the drawings

In order to be illustrated more clearly in the technical scheme in the embodiment of the present invention, in describing embodiment belowThe accompanying drawing of required use is briefly introduced, and apparently, the accompanying drawing in the following describes is only thisSome bright embodiment, for those of ordinary skill in the art, are not paying creative workPrerequisite under, can also obtain according to these accompanying drawings other accompanying drawing.

Fig. 1 is the principle schematic that prevents that electric current from pouring in down a chimney of the prior art;

Fig. 2 prevents the reverse method flow of step-down buck circuital current for what one embodiment of the invention providedFigure;

The knot that prevents the reverse device of step-down buck circuital current that Fig. 3 provides for another embodiment of the present inventionStructure schematic diagram;

Fig. 4 realizes for the reverse device of step-down buck circuital current that prevents that another embodiment of the present invention providesPrevent the general principle block diagram that electric current is reverse;

Fig. 5 does not sample in the situation of the scheme that the embodiment of the present invention provides and is with prebias output for buck circuitWhen voltage starting, pour in down a chimney the oscillogram of the actual output voltage of generation due to electric current;

Fig. 6 for the scheme that provides of the sampling embodiment of the present invention after buck circuit band prebias output voltage startTime actual output voltage oscillogram;

Fig. 7 prevents step-down buck circuital current reverse device for what another embodiment of the present invention providedApplication circuit;

Fig. 8 prevents the reverse device of step-down buck circuital current for what another embodiment of the present invention providedApplication circuit in isolated topology.

Detailed description of the invention

In order to make the object, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing to thisInvention is described in further detail, and obviously, described embodiment is only a part of enforcement of the present inventionExample, instead of whole embodiment. Based on the embodiment in the present invention, those of ordinary skill in the art existDo not make all other embodiment that obtain under creative work prerequisite, all belong to the present invention protectionScope.

Fig. 2 prevents the reverse method flow of step-down buck circuital current for what one embodiment of the invention providedFigure. As shown in Figure 2, suppose that the output of a certain buck circuit has pre-bias voltage, prevent this buckThe reverse method of circuital current comprises:

Rectifier switch pipe in the input voltage vin of step 21, this buck circuit of sampling and this buck circuitWork dutycycle D, and utilize Vin and D, obtain theoretical output voltage V in × D. For example can adoptWeber the generator rectifier switch pipe in the input voltage vin of this buck circuit and this buck circuit of samplingWork dutycycle D, and utilize Vin and D, obtain theoretical output voltage V in × D.

Step 22, the actual output voltage of above-mentioned theory output voltage and this buck circuit is compared,In the time that theoretical output voltage is less than actual output voltage, the continued flow switch pipe of controlling in this buck circuit turn-offs,In the time that theoretical output voltage is more than or equal to actual output voltage, control the continued flow switch in this buck circuitPipe conducting, thus controlled exactly the on off state of continued flow switch pipe, realized exist at output pre-Under bias conditions, continued flow switch pipe normal switch state open time, in output inductor without reverse irrigated current.

Method shown in the present embodiment is by obtaining the theoretical output voltage of buck circuit, and just theoretical defeatedThe actual output voltage that goes out voltage and buck circuit compares, when theoretical output voltage is less than actual outputWhen voltage, the continued flow switch pipe of controlling in buck circuit turn-offs, when described theoretical output voltage be greater than or etc.In the time of described actual output voltage, control the continued flow switch pipe conducting in buck circuit, control exactlyThe switch shape of the continued flow switch pipe of buck circuit, has realized at output and having existed in prebias situation, afterflowSwitching tube normal switch state open time, in output inductor without reverse irrigated current.

The knot that prevents the reverse device of step-down buck circuital current that Fig. 3 provides for another embodiment of the present inventionStructure schematic diagram. Device shown in the present embodiment is for the method providing embodiment illustrated in fig. 2 is provided, as figureShown in 3, this device comprises: weber generator 31 and control circuit 32.

The output of supposing a certain buck circuit has pre-bias voltage, prevents that buck circuital current is reverseDevice in, weber generator 31 input voltage vin for this buck circuit of sampling and this buck electricityThe work dutycycle D of rectifier switch pipe in road, and utilize Vin and D, obtain theoretical output voltage V in×D；

Control circuit 32 with weber generator 31 be connected, for by above-mentioned theory output voltage V in × DCompare with the actual output voltage of this buck circuit, when theoretical output voltage is less than actual output voltageTime, the continued flow switch pipe of controlling in buck circuit turn-offs, when theoretical output voltage is more than or equal to actual defeatedWhile going out voltage, control the continued flow switch pipe conducting in this buck circuit.

Further, control circuit 32 can comprise: voltage comparator circuit and drive circuit.

Wherein, voltage comparator circuit with weber generator 31 be connected, for above-mentioned theory output voltage relativelyWith above-mentioned actual output voltage, and according to comparative result output control signal.

Drive circuit is connected with voltage comparator circuit, for the control signal of exporting according to voltage comparator circuitDrive shutoff or the conducting of the continued flow switch pipe in this buck circuit.

Further, voltage comparator circuit can be comparator.

Further, prevent that the reverse device of buck circuital current from also can comprise: the return difference being connected with comparatorRegulating resistance.

Further, prevent that the reverse device of buck circuital current from also can comprise: actual output voltage sampling electricityRoad, this actual output voltage sample circuit is connected with above-mentioned control circuit 32, for to this buck circuitActual output voltage sample.

Further, actual output voltage sample circuit can be divider resistance circuit.

Further, prevent that the reverse device of buck circuital current from also can comprise and actual output voltage sampling electricityThe output voltage biasing resistor that road is connected, taking the initial output state that ensures comparator as low level.

Device shown in the present embodiment by weber generator obtain the theoretical output voltage of buck circuit, andActual output voltage by the just theoretical output voltage of control circuit and buck circuit compares, and works as reasonWhen opinion output voltage is less than actual output voltage, the continued flow switch pipe of controlling in buck circuit turn-offs, and works as instituteWhen stating theoretical output voltage and being more than or equal to described actual output voltage, the afterflow of controlling in buck circuit is openedClose pipe conducting, controlled exactly the switch shape of the continued flow switch pipe of buck circuit, realized at outputExist in prebias situation, when continued flow switch pipe normal switch state is opened, in output inductor, nothing is fallenFill with electric current.

Fig. 4 realizes for the reverse device of step-down buck circuital current that prevents that another embodiment of the present invention providesPrevent the general principle block diagram that electric current is reverse. In the present embodiment, control circuit is comparator 42.

Prevent in the reverse device of step-down buck circuital current weber generator 41 input of power supply of samplingThe work dutycycle of rectifier switch pipe 106 in voltage Vin and buck circuit, and calculating output this momentVin × D's is long-pending. The 104th, the pwm signal of control rectifier switch pipe 106, the 112nd, control metal-oxide-semiconductorThe pwm signal of Q13 grid, the 118th, inductance.

At buck circuit in continuous current mode pattern (ContinuousCurrentMode, CCM)When lower, buck Circuit theory output voltage V o=Vin × D.

During due to buck circuit start, pulse width modulation (PulseWidthModulation, PWM)Controller 102 is controlled the ascending expansion gradually of dutycycle of rectifier switch pipe, starts at buck circuitWhen work, D value is 0, and along with the time of work increases, D value becomes greatly gradually to certain certain value, and inputsVoltage Vin is constant, and therefore, buck Circuit theory output voltage V o becomes large to fixing gradually since 0Output valve. And buck circuit is owing to there being pre-bias voltage, therefore, its actual output voltage V outInitial value be pre-bias voltage value, in the process of buck circuit start, pour in down a chimney if there is electric current,The waveform of buck circuit actual output voltage Vout120 as shown in Figure 5, is reaching normal output voltageBefore, because electric current pours in down a chimney the situation of reduction suddenly that occurs.

At buck circuit actual output voltage, Vout120 is less than in the process of pre-bias voltage(Vo < Vout), in this process, if open the continued flow switch pipe of buck circuit, output inductorWill there is reverse reverse irrigated current, occur the situation shown in Fig. 5, therefore, in this process, close interruptedStream switching tube, with regard to having solved the problem that electric current as shown in Figure 5 pours in down a chimney, makes the waveform of Vout as Fig. 6Shown in. As Vo > when=Vout, can there is not reverse reverse irrigated current in output inductor, now open buckThe continued flow switch pipe of circuit.

In the present embodiment, prevent that the reverse device of step-down buck circuital current is by relatively Vin of comparator 42The size of × D and Vout, the pwm signal 112 of metal-oxide-semiconductor Q13 grid is controlled in output, controlsIn the moment that the continued flow switch pipe normal switch state of buck circuit is opened, exist partially pre-in the output of buck circuitPut under voltage condition, realize and starting without reverse irrigated current.

Fig. 7 for another embodiment of the present invention provide prevent the reverse device of step-down buck circuital current shouldUse circuit diagram.

In Buck circuit, HS_DRV is the control signal of rectifier switch pipe Q1, and LS_DRV is afterflowThe control signal of switching tube Q2, COMP is regulating error signal, passes through sampling by regulating error circuitActual output voltage Vout and compare etc. and to process with reference voltage Vref after, output error regulates letterNumber COMP so that PWM controller according to regulating error signal COMP output HS_DRV andLS_DRV。

In the present embodiment, weber generator comprise resistance R 3, R2 and filter capacitor C3 and switching tube Q3.Q3 is operated on off state, and its turn-on and turn-off are synchronizeed with the rectifier switch pipe Q1 in buck circuit,When Q1 conducting, Q3 cut-off; Otherwise when Q1 cut-off, Q3 conducting. Input voltage vin like this, through electricityResistance R2, the filtered average voltage size of capacitor C 3 are theoretical output voltage V o=Vin × D, wherein,D is the conducting dutycycle of rectifier switch pipe Q1.

Voltage comparator circuit comprises comparator U2B. One end of comparator U2B by divider resistance R4 andR9, sampling actual output voltage Vout, the other end is by the weber generator sampling buck of input voltageThe theoretical output voltage V o of circuit, by more theoretical output voltage V o and actual output voltage VoutSize, control the driver output with door U1. Particularly, as Vin × D > when Vout, comparatorU2B output switching activity is high, is input to and door U1, and the synchronous rectification of continued flow switch pipe Q2 drivesLS_DRV, through outputing to driver with door U1, makes Q2 work in normal switch state. Otherwise, whenWhen Vin × D < Vout, comparator U2B output remains low, and it is low exporting with door U1 always, Q2Can only pass through body diode one-way conduction, realize the inhibition of reversing the current, solve the reverse of electric currentPour in down a chimney problem.

Further, resistance R 10 is the return difference regulating resistance of comparator U2B, has avoided comparator U2BOutput vibration. Resistance R 7 is output voltage biasing resistor, ensures that original state comparator U2B is output asLow.

Further, prevent that the reverse device of step-down buck circuital current from also comprising clamp circuit, clamp circuitComprise transistor Q4, resistance R 8, capacitor C 4 and diode VD1, ensure the magnitude of voltage of Vin × D notExceed the scope of permission, simultaneously when PWM controller is buck circuit while not working without PWM output,The base stage of transistor Q4 is dragged down, Q4 conducting, making the initial voltage of capacitor C 3 is zero, under being ready toThe original state in a moment.

Fig. 8 for another embodiment of the present invention provide prevent the reverse device of step-down buck circuital current everyFrom the application circuit in topology.

In the present embodiment, prevent that the work of the reverse device of step-down buck circuital current in isolated topology is formerReason is with as similar in the operation principle in Fig. 7 in non-isolated topology, and difference is, in the present embodiment, forThe sampling of input voltage is by sampling resistor R3, from output inductor L1 front end, transformer T1Centre cap on get. The sampling of actual output voltage is still by the dividing potential drop of R4, R9, is input toOne of voltage comparator U2B brings in realization. The conducting of switching tube Q3 is subject to bridge type topology secondary synchronously wholeStream signal SYNQ1 and SYNQ2 control, as long as one of synchronous driving is controlled as low, just turn-off Q3,Former limit input voltage, by the filtering of resistance R 3, R2 and capacitor C 3, just can obtain the volt of input voltageSecond, integral mean voltage Vin × D was theoretical output voltage V o.

The device that above-described embodiment provides does not rely on control loop, but directly compares PWM output voltBe theoretical output voltage and actual output voltage second, is chosen in theoretical output voltage and is more than or equal to actual defeatedThe moment that goes out voltage drives start-up time as synchronous rectification, has obtained optimum efficiency.

The technical scheme highly versatile that above-described embodiment provides, portable strong in other words, no matter PWMWhether controller adopts the slow startup of hardware, still adopts closed loop to delay, and it is realized to prebias function, anti-Only current flowing backwards, without impact, as long as theoretical output voltage is more than or equal to output voltage, can enable synchronousRectification drives, and makes pre-biased circuit prevent current flowing backwards function more comprehensively, falls for input Low ESRSituation, also can lead to superpotential judgement, turn-offs rapidly synchronous rectification and drives, and suppresses current flowing backwards.

The present invention can be applied to any circuit that has counnter attack and prebias requirement, as AC/DC, DC/DCDeng.

Finally it should be noted that: above each embodiment is only in order to technical scheme of the present invention to be described, but not rightIts restriction; Although the present invention is had been described in detail with reference to aforementioned each embodiment, this area commonTechnical staff is to be understood that: its technical scheme that still can record aforementioned each embodiment is modified,Or some or all of technical characterictic is wherein equal to replacement; And these amendments or replacement, andDo not make the essence of appropriate technical solution depart from the scope of various embodiments of the present invention technical scheme.