CN103219752A - Battery voltage balancing circuit and battery module with battery voltage balancing function - Google Patents

Abstract

The present invention provides a battery voltage balancing circuit and a battery module with a battery voltage balancing function. The battery voltage balancing circuit includes a voltage judgment circuit and a discharge circuit, and is used to be connected in parallel with a battery cell. The voltage judgment circuit is used to judge a battery voltage of the battery cell. When the battery voltage of the battery cell is higher than a first preset voltage, a discharge signal is generated until the battery voltage of the battery cell is lower than a second preset voltage, wherein the first preset voltage is higher than the second preset voltage. The discharge circuit is used to be connected in parallel with the battery cell, and discharge the battery cell when receiving the discharge signal.

Description

Battery voltage balancing circuit and battery module with battery voltage balancing function

technical field

The invention relates to a battery voltage balancing circuit and a battery module with the battery voltage balancing function.

Background technique

With the development of portable electronic products, the demand for rechargeable batteries also arises. Rechargeable batteries include existing nickel-cadmium batteries, subsequent development of nickel-metal hydride batteries, lithium-ion batteries and the latest development of lithium polymer (Li-Polymer) batteries. Different types of rechargeable batteries provide different voltages, and the operating voltages required by portable electronic products are also different. Therefore, battery manufacturers will match the operating voltage of portable electronic products, and connect several batteries in series to form a battery module to provide the required voltage.

When the power of the battery is exhausted, the battery module needs to be fully charged by the charger for the next use. However, batteries vary in their storage capacity depending on manufacture or use. For example, a 7.4V lithium battery module is composed of two 3.7V lithium batteries connected in series. When leaving the factory, the storage capacity of the two batteries is 80% and 70% respectively. Since overcharging of a lithium battery will damage the battery itself, the lithium battery charger will stop charging when any one of the lithium batteries is fully charged. %. When in use, as long as the storage capacity of any one battery drops to 0% (the lower limit of battery discharge), the battery module cannot be used. Therefore, when the storage capacity of the two batteries drops to 10% and 0% respectively, it must be Recharge to use.

From the above examples, it can be seen that when the storage capacity of the batteries of the battery module is different, the actual usable electric energy of the battery module will be determined by the battery with the lowest storage capacity. In addition to the above-mentioned battery modules with different storage capacity of each battery when leaving the factory, the battery will also self-discharge when not in use. When the self-discharge rate of each battery is different, the storage capacity of the batteries will gradually become unbalanced. The actual usable electric energy of the battery module will gradually decrease with the use time of the battery, resulting in a low use efficiency of the battery module and a shorter use time.

Please refer to Figure 1, which is the digital battery balancing controller disclosed by Intersil in its ISL9208 data sheet (Datasheet). A digital cell balance controller 10 includes a cell balance microprocessor 5 and transistor switches S1-S7. The transistor switches S1-S7 are respectively connected in parallel with the battery cells BAT1-BAT7 through resistors R1-R7. The voltage of the battery unit BAT1-BAT7 is converted into a digital signal by an analog/digital converter (A/D Converter). Among them, the battery unit with higher voltage turns on the transistor switch connected in parallel with the battery unit with higher voltage, so that the charging current of each battery unit can be adjusted according to the voltage of each battery to achieve the function of balanced charging.

However, the battery voltage needs to be converted into a digital signal by an analog/digital converter before the digital battery balance microprocessor 5 can process it, and the analog/digital converter will greatly increase the chip area of the digital battery balance controller 10, so the cost is quite high. High is its disadvantage. In addition, the digital battery balancing microprocessor 5 will be limited by the original design, for example, the ISL9208 can only support a battery module composed of 5 to 7 batteries, and its applicable range will be limited accordingly.

Contents of the invention

In view of the cost of the digital battery balancing controller in the prior art and the limitation of the number of batteries that can be balanced, the present invention provides a battery voltage balancing circuit and a battery module with a battery voltage balancing function. way to balance the battery voltage. Therefore, the battery voltage balancing circuit of the present invention not only has absolute application flexibility in the number of batteries, but also has a simple circuit and a relatively low circuit cost.

To achieve the above purpose, the present invention provides a battery voltage balancing circuit, which includes a voltage judging circuit and a discharging circuit, and is used for parallel connection with a battery unit. The voltage judging circuit is used to judge a battery voltage of the battery unit. When the battery voltage of the battery unit is higher than a first preset voltage, a discharge signal is generated until the battery voltage of the battery unit is lower than a second preset voltage. , wherein the first preset voltage is higher than the second preset voltage. The discharge circuit is connected in parallel with the battery unit, and discharges the battery unit when receiving the discharge signal.

In one embodiment, the voltage judging circuit includes a hysteresis comparator and a voltage dividing circuit, the voltage dividing circuit is connected in parallel with the battery unit, and generates a voltage dividing signal to the hysteresis comparator.

In one embodiment, the voltage judging circuit includes a first comparator, a second comparator, a voltage dividing circuit and a logic unit, the voltage dividing circuit is connected in parallel with the battery unit, and the first comparator is coupled to The voltage dividing circuit generates a first comparison signal according to whether the battery voltage of the battery unit is higher than the first preset voltage, the second comparator is coupled to the voltage dividing circuit, and generates a first comparison signal according to whether the battery voltage of the battery unit is A second comparison signal is generated lower than the second preset voltage, and the logic unit generates the discharge signal according to the first comparison signal and the second comparison signal.

In one embodiment, the voltage judging circuit includes a first metal oxide semiconductor field effect transistor, a second metal oxide semiconductor field effect transistor and a voltage divider circuit, and the voltage divider circuit is connected in parallel with the battery unit and coupled to The control terminals of the first metal oxide semiconductor field effect transistor and the second metal oxide semiconductor field effect transistor are respectively when the battery voltage of the battery unit is higher than the first preset voltage and lower than the second preset voltage changing the states of the first MOS field effect transistor and the second MOS field effect transistor.

In one embodiment, the discharge circuit is externally connected with a current limiting resistor to limit the discharge current of the battery unit discharged through the discharge circuit within a predetermined current.

In one embodiment, the voltage judging circuit further includes a delay circuit, which performs a delay judging when the battery voltage of the battery unit is higher than the first preset voltage and lower than the second preset voltage to determine Whether to generate and stop generating the discharge signal.

The present invention also provides a battery module with a battery voltage balancing function, which includes a plurality of battery cells and a plurality of battery voltage balancing circuits. Multiple battery cells are connected in series to form a battery string. Each battery voltage balancing circuit is connected in parallel with the corresponding battery unit among the plurality of battery units, and judges whether to discharge the battery unit according to the battery voltage of the corresponding battery unit. Wherein, when the battery voltage of any battery unit of the plurality of battery units is higher than a first preset voltage, the corresponding battery voltage balancing circuit discharges until the battery voltage is lower than a second preset voltage, and the first preset voltage higher than the second preset voltage.

In one embodiment, each of the battery voltage balancing circuits is an integrated circuit packaged in a single package, the package has a first pin, a second pin and a third pin, the first tube The pin is used to couple to a positive terminal of the corresponding battery unit, the second pin is used to couple to a negative terminal of the corresponding battery unit, and the third pin is coupled to the positive terminal of the corresponding battery unit through a current limiting resistor and one of the negative terminals.

In one embodiment, the voltage judging circuit further includes a delay circuit, which performs a delay judging when the battery voltage of the battery unit is higher than the first preset voltage and lower than the second preset voltage to determine Whether to generate and stop generating the discharge signal.

In one embodiment, the current limiting resistor limits a discharge current corresponding to the battery voltage balancing circuit during discharge, so that the discharge current is smaller than a charge current of the corresponding battery unit during charge.

The above summary and the following detailed description are exemplary in nature, and are intended to further illustrate the patent scope of the present invention. Other purposes and advantages of the present invention will be described in the subsequent description and accompanying drawings.

Description of drawings

Fig. 1 is the digital battery balancing controller disclosed by Intersil in its ISL9208 data sheet.

FIG. 2 is a circuit block diagram of a battery module with battery voltage balancing function according to the present invention.

FIG. 3 is a schematic circuit diagram of a battery voltage balancing circuit according to a first preferred embodiment of the present invention.

FIG. 4 is a schematic circuit diagram of a battery voltage balancing circuit according to a second preferred embodiment of the present invention.

FIG. 5A is a schematic diagram of the battery voltage of each battery unit changing with time when the battery voltage balancing circuit of the present invention is applied.

5B is a schematic diagram of the battery voltage of each battery cell after several battery voltage balancing cycles by the battery voltage balancing circuit of the present invention.

FIG. 6 is a schematic circuit diagram of a battery voltage balancing circuit according to a third preferred embodiment of the present invention.

Explanation of main component symbols

current technology:

Cell Balancing Microprocessor 5

Digital Cell Balance Controller 10

Transistor switch S1～S7

Resistor R1～R7

Battery unit BAT1～BAT7

power supply VCC

this invention:

Battery voltage balancing circuit 100

Battery cells Cell1, Cell2, Cell3

Voltage judgment circuit VDE

Discharge circuit DIS

Positive end Bat+

Negative terminal Bat-

Discharge signal Sbal

First Comparator Com1

Second comparator Com2

Voltage divider circuit Rd, Rd2

Logic unit LOG

Voltage divider signal Vbat

Reference signal Vbal

The first reference signal Vbal1

The second reference signal Vbal2

First comparison signal Sco1

Second comparison signal Sco2

SR flip-flop FF

OR gate OG

Setting terminal S

Reset terminal R

Output Q

Discharge start signal Sst

Current limiting resistor Rin, Rout

Metal Oxide Half Field Effect Transistor M

Hysteresis comparator Chy

Battery voltage Vce1, Vce2, Vce3

Time points t0, t1, t2, t3, t4

The first preset voltage Vp1

The second preset voltage Vp2

Full charge voltage Vfull

The first metal oxide half field effect transistor M1

The second metal oxide half field effect transistor M2

Resistance Rm1, Rm2

Delay circuit Dt

The first delay circuit Dt1

Second delay circuit Dt2

First delayed signal Sdt1

Second delayed signal Sdt2

Detailed ways

Please refer to FIG. 2 , which is a circuit block diagram of a battery module with battery voltage balancing function according to the present invention. Multiple battery cells are connected in series to form a battery string. A plurality of battery voltage balancing circuits 100 connects a plurality of battery cells in parallel one-to-one. For the convenience of description, in this embodiment, three battery cells Cell1 , Cell2 and Cell3 are taken as an example for illustration. Each battery voltage balancing circuit 100 determines whether to discharge the battery unit according to the battery voltage of the corresponding battery unit. When the battery voltage of any one of the battery cells Cell1-Cell3 is higher than a first preset voltage, the corresponding battery voltage balancing circuit 100 will discharge the battery cell until the battery voltage is lower than a second preset voltage , and the first preset voltage is higher than the second preset voltage. The setting of the first preset voltage and the second preset voltage is determined according to the full charge voltage of the battery unit, generally speaking, it is set slightly lower than the full charge voltage. Since the electric quantity of the battery changes very little in the lower range of the fully charged voltage of the battery, the electric quantity of the battery unit will not be significantly affected when the battery voltage balancing circuit of the present invention balances the battery voltage.

Please refer to FIG. 3 , which is a schematic circuit diagram of a battery voltage balancing circuit according to a first preferred embodiment of the present invention. The battery voltage balance circuit is connected in parallel with a battery unit (not shown), and includes a voltage determination circuit VDE and a discharge circuit DIS. The battery voltage balancing circuit is an integrated circuit packaged in a single package, and has two pins respectively connected to a positive terminal Bat+ and a negative terminal Bat− of the battery unit. The voltage determination circuit VDE is coupled to the positive terminal Bat+ and the negative terminal Bat- of the battery unit to determine a battery voltage of the battery unit accordingly. When the battery voltage of the battery unit is higher than a first preset voltage, a discharge signal Sbal is generated until the battery voltage of the battery unit is lower than a second preset voltage, wherein the first preset voltage is higher than the second preset voltage preset voltage. The discharge circuit DIS is connected in parallel with the battery unit, that is, the discharge circuit DIS is also coupled to the positive terminal Bat+ and the negative terminal Bat− of the battery unit, and discharges the battery unit when receiving the discharge signal Sbal.

The voltage determination circuit VDE includes a first comparator Com1 , a second comparator Com2 , a voltage dividing circuit Rd and a logic unit LOG. The voltage dividing circuit Rd includes two resistors connected in series, coupled to the positive terminal Bat+ and the negative terminal Bat− of the battery unit to generate a voltage dividing signal Vbat according to the battery voltage of the battery unit. The first comparator Com1 is coupled to the voltage dividing circuit Rd, its non-inverting input terminal receives the voltage dividing signal Vbat, and its inverting input terminal receives a first reference signal Vbal1 representing the first preset voltage, and the voltage dividing signal Vbat When the level is higher than the level of the first reference signal Vbal1, a first comparison signal Sco1 is generated. The second comparator Com2 is coupled to the voltage divider circuit Rd, and its inverting input terminal receives the divided voltage signal Vbat, and its non-inverted input terminal receives a second reference signal Vbal2 representing the second preset voltage. When the level is lower than the level of the second reference signal Vbal2, a second comparison signal Sco2 is generated. The logic unit LOG includes an SR flip-flop FF and an OR gate OG, and generates the discharge signal Sbal according to the first comparison signal Sco1 and the second comparison signal Sco2. A set terminal S of the SR flip-flop FF is coupled to the first comparator Com1, and a reset terminal R is coupled to the second comparator Com2. The OR gate OG is coupled to the first comparator Com1 and an output terminal Q of the SR flip-flop FF. When the first comparator Com1 outputs the first comparison signal Sco1, the SR flip-flop FF is triggered to output a discharge start signal Sst. At this time, the OR gate OG generates the discharge signal Sbal according to the first comparison signal Sco1 and the discharge start signal Sst. When the battery voltage of the battery cell drops from higher than the first preset voltage to lower than the second preset voltage, the second comparator Com2 generates a second comparison signal Sco2 to make the SR flip-flop FF stop generating the discharge start signal Sst. At this time, the battery voltage of the battery unit is also lower than the first preset voltage so that the first comparator Com1 also stops generating the first comparison signal Sco1, so the OR gate OG stops generating the discharge signal Sbal. The discharge circuit DIS includes a MOSFET M and a built-in current limiting resistor Rin. The MOS field effect transistor M receives the discharge signal Sbal and turns on, so that the battery cell flows out a current from the positive terminal Bat+ through the discharge circuit DIS and flows out from the negative terminal Bat- of the battery cell, so as to reduce the battery voltage of the battery cell. Generally speaking, when the battery unit is being charged, the battery voltage is higher than the first preset voltage. The current-limiting resistor Rin is used to limit the magnitude of a discharge current that flows through the discharge circuit DIS when the battery voltage balance circuit is discharging, so that the discharge current is less than a predetermined current (that is, the minimum charging current of the battery unit when charging), so as to ensure that the battery The cell's battery voltage can still continue to rise toward the fully charged battery voltage until it stops being charged. In the battery voltage balancing circuit of the present invention, when the battery voltage of the battery unit is between the first preset voltage and the second preset voltage but not higher than the first preset voltage, the first comparator Com1 will not output the first comparison signal Sco1, and the default of the SR flip-flop FF is not to output the discharge start signal Sst. Therefore, in the above situation, the battery voltage balancing circuit of the present invention will not discharge the battery cells.

Please refer to FIG. 4 , which is a schematic circuit diagram of a battery voltage balancing circuit according to a second preferred embodiment of the present invention. The battery voltage balancing circuit is coupled to a positive terminal Bat+ and a negative terminal Bat− of a battery unit (not shown) to form a parallel connection with the battery unit. A battery voltage balancing circuit, a voltage judging circuit VDE and a discharging circuit DIS. The voltage determination circuit VDE is coupled to the positive terminal Bat+ and the negative terminal Bat- of the battery unit to determine a battery voltage of the battery unit accordingly. When the battery voltage of the battery unit is higher than a first preset voltage, a discharge signal Sbal is generated until the battery voltage of the battery unit is lower than a second preset voltage, wherein the first preset voltage is higher than the second preset voltage Voltage. The discharge circuit DIS is connected in parallel with the battery unit, that is, the discharge circuit DIS is also coupled to the positive terminal Bat+ and the negative terminal Bat− of the battery unit, and discharges the battery unit when receiving the discharge signal Sbal.

The voltage determination circuit VDE includes a hysteresis comparator Chy and a voltage divider circuit Rd. The voltage divider circuit Rd generates a voltage divider signal Vbat according to the battery voltage of the battery unit. The hysteresis comparator Chy receives the divided voltage signal Vbat and a reference signal Vbal. The hysteresis comparator Chy has an upper voltage value and a lower voltage value according to the reference signal Vbal and the set hysteresis range, wherein the upper voltage value is higher than the lower voltage value. When the level of the divided voltage signal Vbat is higher than the level of the upper voltage value, the hysteresis comparator Chy generates the discharge signal Sbal until the level of the divided voltage signal Vbat is lower than the level of the lower voltage value. The discharge circuit DIS includes a metal oxide semiconductor field effect transistor M, and a current limiting resistor Rout is externally connected to the battery unit through a pin. In this embodiment, the current-limiting resistor Rout is coupled between the discharge circuit DIS and the positive terminal Bat+ of the battery unit, but in practical applications, it may also be coupled between the discharge circuit DIS and the negative terminal Bat- of the battery unit, and achieve the same current limiting effect. Although connecting the current-limiting resistor Rout in an external manner will increase the pins of the battery voltage balancing circuit of the present invention into three pins, the resistance value of the current-limiting resistor Rout can be flexibly adjusted according to the type of battery unit and the charger used in practice. Wait for different environments to choose and set.

Please refer to FIG. 5A , which is a schematic diagram showing the battery voltages Vce1 , Vce2 , and Vce3 of each battery unit changing with time when the battery voltage balancing circuit of the present invention is applied. Before the time point t0, the battery cells are in the charging state (Charging), so the battery voltages Vce1, Vce2, Vce3 gradually increase with time. When the battery voltage Vce3 is higher than a first preset voltage Vp1, the corresponding battery voltage balancing circuit starts to discharge, so that the rising rate of the battery voltage Vce3 slows down. At time point t0, the battery voltage Vce3 reaches a full charge voltage Vfull, and the battery unit stops charging and is in a non-charging state (Non-Charging). Since the battery voltages Vce1 and Vce2 are not higher than the first preset voltage Vp1, the corresponding battery voltage balancing circuit will not discharge, so only the battery voltage Vce3 continues to drop and reaches a second preset voltage Vp2 at the time point t1. End this cell voltage balancing cycle. Comparing the battery voltages Vce1 , Vce2 , and Vce3 at the time point t0 and the time point t1 , it can be seen that the difference between the battery voltages Vce1 , Vce2 , and Vce3 is reduced after the operation of the battery voltage balancing circuit of the present invention. Please refer to FIG. 5B , which is a schematic diagram of the battery voltages Vce1 , Vce2 , and Vce3 of each battery cell after several battery voltage balancing cycles by the battery voltage balancing circuit of the present invention. The time point t0 is the time point when the first charging of the battery unit ends, and the time points t1, t2, t3, t4 are the time points when the battery voltage is charged and each battery voltage balancing cycle ends. As shown in FIG. 5B , the battery voltage balancing circuit of the present invention tries to adjust the battery voltage of each battery unit to be between the first preset voltage Vp1 and the second preset voltage Vp2 . In a more extreme situation, if the battery voltage gap of the battery cells is too large, when the battery voltage of any battery cell is charged to the full charge voltage, there may be some battery cells whose battery voltage is still lower than the second preset voltage Vp2, However, after a limited number of battery voltage balancing cycles, the battery voltages of the battery cells can be guaranteed to be between the first preset voltage Vp1 and the second preset voltage Vp2, and even the battery voltages are adjusted to the same voltage as shown in FIG. 5B , that is, at the end of charging, the battery voltages of the battery cells are all higher than the first preset voltage Vp1 and are uniformly discharged to the second preset voltage Vp2.

Please refer to FIG. 6 , which is a schematic circuit diagram of a battery voltage balancing circuit according to a third preferred embodiment of the present invention. The battery voltage balancing circuit is coupled to a positive terminal Bat+ and a negative terminal Bat− of a battery unit (not shown) to form a parallel connection with the battery unit. A battery voltage balancing circuit, a voltage judging circuit VDE and a discharging circuit DIS. The voltage determination circuit VDE is coupled to the positive terminal Bat+ and the negative terminal Bat- of the battery unit to determine a battery voltage of the battery unit accordingly. When the battery voltage of the battery unit is higher than a first preset voltage, a discharge signal Sbal is generated until the battery voltage of the battery unit is lower than a second preset voltage, wherein the first preset voltage is higher than the second preset voltage preset voltage. The discharge circuit DIS is connected in parallel with the battery unit, and discharges the battery unit when receiving the discharge signal Sbal.

The voltage determination circuit VDE includes a voltage divider circuit Rd2 , a first MOS field effect transistor M1 , a second MOS field effect transistor M2 , resistors Rm1 , Rm2 , a delay circuit Dt and a logic unit LOG. The first MOS field effect transistor M1 and the resistor Rm1 are connected in series between the positive terminal Bat+ and the negative terminal Bat- of the battery cell, and the second MOS field effect transistor M2 and the resistor Rm2 are also connected in series to the positive terminal Bat+ of the battery cell. And between the negative terminal Bat-. The voltage dividing circuit Rd2 is coupled to the control terminals (ie gates) of the first MOS field effect transistor M1 and the second MOS field effect transistor M2 . The voltage dividing circuit Rd2 of this embodiment has three resistors connected in series, and the resistance of the middle resistor is relatively small. In this way, there will be a difference in level of the voltage signal generated by the voltage divider circuit Rd2 received by the control terminals of the first MOS field effect transistor M1 and the second MOS field effect transistor M2, thereby making the first MOS field effect transistor M2 When the half field effect transistor M1 and the second metal oxide half field effect transistor M2 are turned on, the corresponding battery voltages will be different. The delay circuit Dt has a first delay circuit Dt1 and a second delay circuit Dt2. When the battery voltage of the battery unit is higher than the first preset voltage and lower than the second preset voltage, a delay judgment is performed to determine whether to generate and Stop generating the discharge signal Sbal. The first delay circuit Dt1 is coupled to the connection point of the first MOS field effect transistor M1 and the resistor Rm1, and generates a first delay signal when the first MOS field effect transistor M1 is turned on for a first predetermined time. Sdt1, and stop generating the first delay signal Sdt1 when the first MOSFET M1 is turned off for a first predetermined time. The second delay circuit Dt2 is coupled to the connection point of the second MOS field effect transistor M2 and the resistor Rm2, and generates a second delay signal when the second MOS field effect transistor M2 is turned on for a second predetermined time. Sdt2, and stop generating the second delay signal Sdt2 when the second MOSFET M2 is turned off for a second predetermined time. The time lengths of the first predetermined time and the second predetermined time may be set to be the same. The logic unit LOG generates the discharge signal Sbal when receiving the first delay signal Sdt1 and the second delay signal Sdt2 at the same time, so that the discharge circuit DIS discharges the battery unit, and then when both the first delay signal Sdt1 and the second delay signal Sdt2 stop generating , stop generating the discharging signal Sbal, so as to stop discharging the battery unit. The discharge circuit DIS includes a metal oxide semiconductor field effect transistor M, and a current limiting resistor Rout is externally connected to the battery unit through a pin. The delay circuit Dt can also be applied to the embodiments shown in FIG. 3 and FIG. 4 to avoid the influence of noise on the circuit.

As mentioned above, the present invention fully complies with the three requirements of a patent: novelty, advancement and industrial applicability. The present invention has been disclosed above with preferred embodiments, but those skilled in the art should understand that the embodiments are only used to describe the present invention, and should not be construed as limiting the scope of the present invention. It should be noted that all changes and substitutions equivalent to this embodiment should be considered within the scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope defined in the claims.

Claims (10)

1. a voltage balance of battery circuit is characterized in that, and is in parallel with a battery unit, comprises:

One voltage decision circuitry, in order to judge a cell voltage of this battery unit, when this cell voltage of this battery unit is higher than one first predeterminated voltage, produce a discharge signal, till this cell voltage of this battery unit was lower than one second predeterminated voltage, wherein this first predeterminated voltage was higher than this second predeterminated voltage; And

One discharge circuit in order in parallel with this battery unit, when receiving this discharge signal, discharges to this battery unit.

2. voltage balance of battery circuit according to claim 1 is characterized in that, wherein this voltage decision circuitry comprises a hysteresis comparator and a bleeder circuit, and this bleeder circuit is in parallel with this battery unit, and produces a voltage division signal to this hysteresis comparator.

3. voltage balance of battery circuit according to claim 1, it is characterized in that, wherein this voltage decision circuitry comprises one first comparator, one second comparator, one bleeder circuit and a logical block, this bleeder circuit is in parallel with this battery unit, this first comparator couples this bleeder circuit, whether be higher than this first predeterminated voltage according to this cell voltage of this battery unit and produce one first comparison signal, this second comparator couples this bleeder circuit, whether be lower than this second predeterminated voltage according to this cell voltage of this battery unit and produce one second comparison signal, this logical block produces this discharge signal according to this first comparison signal and this second comparison signal.

4. voltage balance of battery circuit according to claim 1, it is characterized in that, wherein this voltage decision circuitry comprises one first metal-oxide half field effect transistor, one second metal-oxide half field effect transistor and a bleeder circuit, this bleeder circuit is in parallel with this battery unit, and couple the control end of this first metal-oxide half field effect transistor and this second metal-oxide half field effect transistor, when being higher than this first predeterminated voltage and being lower than this second predeterminated voltage, this cell voltage of this battery unit changes the state of this first metal-oxide half field effect transistor and this second metal-oxide half field effect transistor respectively.

5. according to each described voltage balance of battery circuit of claim 1 to 4, it is characterized in that the external current-limiting resistance of this discharge circuit wherein is to limit a discharging current that this battery unit discharges by this discharge circuit within a scheduled current.

6. according to each described voltage balance of battery circuit in the claim 1 to 4, it is characterized in that, wherein this voltage decision circuitry also comprises a delay circuit, when this cell voltage of this battery unit is higher than this first predeterminated voltage and is lower than this second predeterminated voltage, carry out one and postpone to judge, whether produce and stop to produce this discharge signal with decision.

7. the battery module of a tool voltage balance of battery function is characterized in that, comprises:

A plurality of battery units, these a plurality of battery units are connected into a battery strings; And

A plurality of voltage balance of battery circuit, corresponding battery unit in each voltage balance of battery circuit these a plurality of battery units in parallel judges whether this battery unit is discharged according to the cell voltage of this correspondence battery unit;

Wherein, when the cell voltage of arbitrary battery unit of these a plurality of battery units is higher than one first predeterminated voltage, corresponding voltage balance of battery circuit discharges till this cell voltage is lower than one second predeterminated voltage, and this first predeterminated voltage is higher than this second predeterminated voltage.

8. the battery module of tool voltage balance of battery function according to claim 7, it is characterized in that, wherein each this voltage balance of battery circuit is an integrated circuit, be packaged in the single packaging body, this packaging body has one first pin, one second pin and a three-prong, this first pin is in order to couple an anode of corresponding battery unit, this second pin is in order to coupling a negative terminal of corresponding battery unit, this three-prong by a current-limiting resistance be coupled to this anode of corresponding battery unit and this negative terminal one of them.

9. according to the battery module of each described tool voltage balance of battery function of claim 7 to 8, it is characterized in that, wherein this voltage decision circuitry also comprises a delay circuit, when this cell voltage of this battery unit is higher than this first predeterminated voltage and is lower than this second predeterminated voltage, carry out one and postpone to judge, whether produce and stop to produce this discharge signal with decision.

10. the battery module of tool voltage balance of battery function according to claim 8, it is characterized in that, wherein this current-limiting resistance limits the discharging current of corresponding voltage balance of battery circuit when discharging, and makes this discharging current less than the charging current of corresponding battery unit when charging.

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