CN203241519U - Voltage measurement circuit for single cells of lithium-ion power batteries - Google Patents

The utility model discloses a voltage measurement circuit for the single cells of lithium-ion power batteries. The voltage measurement circuit comprises a battery pack composed of a plurality of single-cell batteries which are connected in series, wherein the negative electrode of the battery pack is grounded, and the positive electrode of each single-cell battery in the battery pack is connected with a voltage-dividing resistor in series and then connected to the drain electrode of an MOS (metal oxide semiconductor) transistor; the source electrodes of the MOS transistors are connected in parallel and then connected to the positive input terminal of a voltage follower, and the grid electrodes of the MOS transistors are connected to an MCU (microprogrammed control unit) respectively; a resistor and a capacitor which are connected in parallel are connected between the positive input terminal of the voltage follower and the ground, the negative input terminal and the output terminal of the voltage follower are shorted, and the output terminal of the voltage follower is connected with an A/D (analogue/digital) converter; and the A/D converter is connected with the MCU. The voltage measurement circuit disclosed by the utility model is used for accurately acquiring the voltage of each of the single cells which are connected in series in the lithium-ion power battery pack in real time, thus providing a powerful judgement basis for over-charging and over-discharging protection and equilibrium control for the lithium-ion power batteries, prolonging the service life of the battery pack, and preventing serious accidents such as fire and explosion.

Lithium-ion-power cell monomer battery core tension measuring circuit

Technical field

The utility model belongs to the battery cell monitoring technical field, is used for online protection and the voltage measurement of balanced control procedure monomer battery core of lithium-ion-power cell group.

Background technology

Lithium-ion-power cell is large owing to its specific energy, sparking voltage is high, have extended cycle life, memory-less effect, have that quick charge capability, self-discharge rate are little, energy-saving and environmental protection come into one's own.Because the lithium-ion battery monomer capacity is excessive, produces easily high temperature, bring out unsafe factor, so high capacity lithium ion battery must form electric battery by series-parallel mode.The inconsistency of cell itself will affect life-span and the performance of whole electric battery.Simultaneously, during the charging of lithium ion single battery core upper voltage limit is arranged, when battery core voltage is higher than certain value, can produce the phenomenon of overcharging; Lower voltage limit is also arranged during discharge, when battery core voltage is lower than certain value, can produce the overdischarge phenomenon.Battery overcharge or overdischarge all can cause dangers, can produce blast when serious.

In sum, in lithium ion battery group charge and discharge process, must detect accurately the voltage of each monomer battery core, in order to electric battery is protected and balanced control online.The technological means that adopts at present mainly contains:

One, adopt special multichannel monomer battery core voltage checking chip, to series connection monomer battery core voltage in the electric battery measure (referring to document: power supply control technology [J]. automatic electronic, 2010 (32): 66-68.And: based on 12 joint lithium battery management systems [J] of MSP430 single-chip microcomputer. power technology, 2011 (35): 514-516.）。This scheme need to be selected expensive special chip, significantly increases system cost, and simultaneously, peripheral circuit is complicated, and extensibility is relatively poor.

Two, adopt the mode of patrolling and examining that series connection monomer battery core voltage in the electric battery is measured.Comprise:

1) by switching device (relay) timesharing the voltage signal of monomer battery core is switched to same differential amplifier, behind signal condition with an A/D converter sample (referring to document: based on the cell management system of electric automobile [J] of dual CAN bus. automobile engineering, 2008 (30): 788-791,795.And: a kind of design of Novel lithium battery management system and realization [J]. automated manufacturing, 2010 (32): 197-198,225.）。There are several shortcomings in the method: the complicated signal conditioning circuit of needs is nursed one's health battery core voltage to the A/D converter range ability; The impedance of mechanical switch device contacts is larger, produces larger measuring error, and along with the prolongation of service time, error will further increase.

2) adopt microprocessor to control light-operated metal-oxide-semiconductor switch, timesharing switches to same differential amplifier with the voltage signal of monomer battery core, behind signal condition with an A/D converter sample (referring to document: battery management system of pure electric automobile research and design [J]. observation and control technology, 2010 (29): 54-57.）。There are several shortcomings in the method: the complicated signal conditioning circuit of needs is nursed one's health battery core voltage to the A/D converter range ability.Need to increase independent current source level before and after the light-operated metal-oxide-semiconductor is powered, increase the complicacy of circuit when significantly improving system cost.

The utility model content

The purpose of this utility model is to provide a kind of lithium-ion-power cell monomer battery core tension measuring circuit, the monomer battery core voltage measurement of respectively connecting in the lithium-ion-power cell group of realization low-cost and high-precision.

The technical solution of the utility model is as follows:

A kind of lithium-ion-power cell monomer battery core tension measuring circuit comprises the electric battery that the single cell battery by a plurality of series connection forms; The minus earth of described electric battery is connected to the drain electrode of a metal-oxide-semiconductor behind divider resistance of the positive pole of each single cell battery series connection in the described electric battery; Be connected to the positive input terminal of voltage follower after the source electrode parallel connection of described each metal-oxide-semiconductor, the grid of described each metal-oxide-semiconductor is connected to respectively MCU; Be connected with resistance in parallel and electric capacity between the positive input terminal of described voltage follower and the ground, the negative input end of described voltage follower and output terminal short circuit, the output terminal of described voltage follower is connected to A/D converter; Described A/D converter is connected with MCU.

Useful technique effect of the present utility model is:

The utility model accurately gathers the monomer battery core voltage of respectively connecting in the lithium-ion-power cell group in real time; for lithium-ion-power cell overcharges, over and balanced control provide strong basis for estimation; prolong electric battery serviceable life, prevent the major accidents such as fire, blast.

The additional advantage of the utility model provides in the embodiment description partly below, and part will become obviously from the following description, or recognize by practice of the present utility model.

Description of drawings

Fig. 1 is circuit theory diagrams of the present utility model.

Fig. 2 is the circuit theory diagrams of an embodiment of the utility model.

Fig. 3 is voltage calibration man-machine interface figure of the present utility model.

Embodiment

Below in conjunction with accompanying drawing embodiment of the present utility model is described further.

On circuit design, the technology that the utility model adopts hyperchannel to switch.The voltage of each test point V1～Vn among Fig. 1, multi-channel electronic switch by Low ESR metal-oxide-semiconductor Q1～Qn composition, in conjunction with the MCU programmed control, the bleeder circuit dividing potential drop is delivered in timesharing, again through delivering to same A/D converter after the voltage follower U1 buffering, finish respectively the connect measurement of monomer battery core voltage of electric battery, thereby realize the hardware circuit time-sharing multiplex, reduce cost.Wherein, each divider resistance (R1～Rn, and R) is selected same material resistance, reduces because of the different measuring error that cause of temperature coefficient.

The voltage calibration mode that realizes based on foregoing circuit is as follows:

(inconsistency that R1～Rn) is intrinsic, the actual intrinsic standoff ratio of each passage is different from theoretical value, will cause monomer battery core voltage measurement error because of each passage divider resistance.The utility model adopts linear correction method that the voltage of measuring is proofreaied and correct.

V _BT1, V _BT2V _BTnBe respectively 1～n monomer battery core (voltage of BT1～BTn).V _nVoltage for each test point.

Then: V _BTn=V _n-V _N-1As n〉1 the time (1)

V _BT1=V ₁When n=1

V _n=(R+R _n)/R*V _in （2）

The magnitude of voltage of each test point that calculates according to the divider resistance nominal resistance (calibration) is designated as V _{N does not calibrate}

Then have: V _{N does not calibrate}=(R _Nominal+ R _{The n nominal})/R _Nominal* V _In

For reducing the caused monomer battery core voltage measurement error of inconsistency (the resistance error is inconsistent) owing to divider resistance, increase calibration factor K _{The n calibration}, formula (2) is converted to:

V _n=K _{The n calibration}* V _{N does not calibrate}=K _{The n calibration}* (R _Nominal+ R _{The n nominal})/R _Nominal* V _In(3)

K _{The n calibration}=V _{The n calibration}/ V _{N does not calibrate}(4)

Wherein, V _{The n calibration}The test point V that records for instrumentation _nThe magnitude of voltage at place.

Select same material resistance because of divider resistance, temperature coefficient is also identical, through primary calibration, can in the situation of not changing divider resistance, guarantee monomer battery core voltage measurement precision.Simultaneously, because voltage calibration point in the utility model is identical with measurement point, cumulative errors have been avoided.

Below be an embodiment of the present utility model.

Fig. 3 is the voltage calibration picture of above-described embodiment.At host computer voltage calibration picture the magnitude of voltage that utilizes instrument to record each test point is set, through communication set voltage is sent to MCU, in MCU, calculate each calibration factor K according to formula (4) _{The n calibration}It should be noted that calibration factor K _{The n calibration}Determine only need carry out once; Because calibration factor K _{The n calibration}Be the intrinsic coefficient for the utility model circuit, it does not change with the change of measuring battery; Therefore, with this calibration factor K _{The n calibration}Be built among the MCU.In the ensuing course of work, calculate voltage V after the calibration of each test point according to formula (3) _n, calculate at last the voltage V of the monomer battery core of respectively connecting in the lithium ion battery group according to formula (1) _BTn

Among Fig. 3, " actual measurement " is that each test point is without the voltage (V of calibration _{N does not calibrate}); " calibration value " is for to utilize instrument to record the voltage (V of each test point _{The n calibration}); " calibration " is through each monomer battery core voltage (V after the calibration _BTn).

Above-described only is preferred implementation of the present utility model, and the utility model is not limited to above embodiment.Be appreciated that other improvement and variation that those skilled in the art directly derive or associate under the prerequisite that does not break away from basic conception of the present utility model, all should think to be included within the protection domain of the present utility model.

1. lithium-ion-power cell monomer battery core tension measuring circuit is characterized in that: comprise the electric battery that the single cell battery by a plurality of series connection forms; The minus earth of described electric battery is connected to the drain electrode of a metal-oxide-semiconductor behind divider resistance of the positive pole of each single cell battery series connection in the described electric battery; Be connected to the positive input terminal of voltage follower after the source electrode parallel connection of described each metal-oxide-semiconductor, the grid of described each metal-oxide-semiconductor is connected to respectively MCU; Be connected with resistance in parallel and electric capacity between the positive input terminal of described voltage follower and the ground, the negative input end of described voltage follower and output terminal short circuit, the output terminal of described voltage follower is connected to A/D converter; Described A/D converter is connected with MCU.