JP6633591B2 - Equalization device - Google Patents

Description

  The present invention relates to an equalizing device.

  EVs, PHEVs, HEVs, and the like have a high-voltage battery for driving an electric motor. The high voltage battery obtains a high voltage of several hundred volts by connecting tens to hundreds of secondary batteries (hereinafter, cells) in series. In the above-described cells, a difference occurs in the amount of charge (hereinafter, SOC) due to variations in battery capacity, leakage current, and deterioration during manufacturing.

  For example, if the SOC of any one cell reaches 100% at the time of charging, further charging cannot be performed. Further, if the SOC of any one cell reaches 0% at the time of discharging, further discharging cannot be performed. For this reason, if the SOC varies, the charging and discharging efficiency deteriorates. Therefore, a cell balance circuit for equalizing the SOC of each cell has been proposed (Patent Document 1).

  In the cell balance circuit (equalizing device) of Patent Literature 1, each cell voltage is detected by a voltage detection unit, and energy is transferred from a high-voltage cell to a low-voltage cell via an inductance.

JP 2013-13292 A

  However, there is a problem that the detection accuracy of the voltage detection unit of the above-described conventional equalizing device is about ± several mV and cannot be equalized with higher accuracy.

  The present invention has been made in view of the above background, and an object of the present invention is to provide an equalizing device with improved accuracy.

  The equalizing device according to an aspect of the present invention has two input terminals, and the two input terminals receive the voltage between two terminals of three or more secondary batteries constituting the battery pack, respectively. A differential amplifier circuit that outputs a difference between the two voltages obtained between the two terminals, a plurality of switches provided between the differential amplifier circuit and the battery pack, and the differential amplifier circuit that controls the switches. A first switch control unit that switches a combination of the two secondary batteries input to the differential amplifier, a combination of the two secondary batteries input to the differential amplifier, and an output of the differential amplifier. And an equalizing unit for obtaining a magnitude relationship between the voltages of both ends of the secondary battery constituting the assembled battery and performing equalization based on the magnitude relationship obtained.

  The first switch control unit sets one of the two secondary batteries input to the differential amplifier circuit as a reference secondary battery, which is one of the secondary batteries constituting the battery pack, and The other of the secondary batteries may be sequentially switched to all of the secondary batteries constituting the battery pack except for the reference secondary battery.

  The first switch control unit controls the switch so that when the output of the differential amplifier circuit is 0, the secondary batteries input to the two input terminals of the differential amplifier circuit are replaced. It may be.

  The first switch control unit may use, as the reference secondary battery, a secondary battery that has been determined to have the highest voltage at both ends when the previous equalization is performed.

  A capacitor for holding a voltage between both ends of the secondary battery in a first state, and a voltage between both ends of the secondary battery held by the capacitor and a voltage between both ends of the secondary battery in a second state, the differential amplifier circuit A second switch control unit that controls the switch so as to be input to a second switch control unit, and a state detection unit that detects a battery state of the secondary battery based on an output of the differential amplifier circuit when controlled by the second switch control unit. And may be provided.

  According to the aspect described above, the equalization is performed based on the difference between the voltages at both ends of the two secondary batteries, thereby improving the accuracy of the equalization.

FIG. 3 is a circuit diagram showing an embodiment of a cell monitoring device incorporating the equalizing device of the present invention. 3 is a flowchart illustrating a μCOM equalization processing procedure included in the cell monitoring device of FIG. 1 according to the first embodiment. It is a flowchart which shows the equalization processing procedure of (mu) COM which comprises the cell monitoring apparatus of FIG. 1 in 2nd Embodiment.

(1st Embodiment)
Hereinafter, the cell monitoring device according to the first embodiment will be described with reference to FIG. The cell monitoring device 1 of the present embodiment is mounted on, for example, an electric vehicle and monitors cells Ce1 to Ce3 as a plurality of secondary batteries included in the battery pack 2 illustrated in FIG. 1 provided in the electric vehicle. . The cells Ce1 to Ce3 are connected to each other in series.

  The cell monitoring device 1 executes the following three controls. First, the cell monitoring device 1 executes control for detecting the internal resistance of each of the cells Ce1 to Ce3 and detecting the state of the cells Ce1 to Ce3. In addition, the cell monitoring device 1 executes control for equalizing the voltage between both ends of the cells Ce1 to Ce3. In addition, the cell monitoring device 1 detects the voltage across the cells Ce1 to Ce3 using the CVS 18, and stops charging if at least one of the cells exceeds the threshold during charging. If there is, control is performed to stop the discharge.

  As shown in FIG. 1, the cell monitoring device 1 includes an equalizing circuit 11, a first capacitor C1 and a second capacitor C2, a changeover switch SW1 and a switch unit 12, a charge / discharge unit 13, a voltage detection unit 14, an A / D converter 15, a differential amplifier circuit 16, an A / D converter 17, a CVS 18, and a microcomputer (hereinafter referred to as μCOM) 19.

  The equalizing circuit 11 is a circuit for equalizing the cells Ce1 to Ce3. As the equalizing circuit 11, for example, a discharge method for discharging the cells Ce1 to Ce3 having a high voltage at both ends using a discharge resistor, or a charge from the cells Ce1 to Ce3 having a high voltage at both ends to a low cell Ce1 to Ce3 using a capacitor or the like is used. A well-known equalizing circuit such as a charge pump type for moving the current is used.

  The first capacitor C1 and the second capacitor C2 are capacitors for holding the bipolar voltages of the cells Ce1 to Ce3, respectively. The first capacitor C1 and the second capacitor C2 are connected to one of a plurality of cells Ce1 to Ce3 selected by a switch unit 12 described later.

  In addition, the first capacitor C1 has a single-pole plate connected to a + input which is one of two input terminals of a differential amplifier circuit 16 described later. The second capacitor C2 has a single-pole plate connected to a negative input, which is the other of two input terminals of a differential amplifier circuit 16 described later.

  The changeover switch SW1 includes a switch that switches the connection of the terminal c between the terminal a and the terminal b. The terminal a is connected to the one plate of the first capacitor C1 and the positive input of the differential amplifier circuit 16, and the terminal b is connected to the single plate of the second capacitor C2 and the negative input of the differential amplifier circuit 16. Have been. The terminal c is connected to an e + terminal of a changeover switch SW + described later. The changeover switch SW1 is a switch that selects one of the first capacitor C1 and the second capacitor C2 and connects it to the e + terminal of the changeover switch SW +.

  The switch unit 12 includes two changeover switches SW + and SW−. The changeover switch SW + includes a switch that switches the e + terminal among the a +, b +, and c + terminals. The terminals a + to c + are connected to the positive electrodes of the cells Ce1 to Ce3, respectively. The changeover switch SW + connects one positive electrode selected from the plurality of cells Ce1 to Ce3 to one pole plate of the capacitors C1 and C2 selected by the changeover switch SW1.

  The changeover switch SW- is configured by a switch that switches an e- terminal among a-, b-, and c- terminals. The terminals a- to c- are respectively connected to the negative electrodes of the cells Ce1 to Ce3. The changeover switch SW- connects one negative electrode selected from the plurality of cells Ce1 to Ce3 to the other electrode plates of the capacitors C1 and C2.

  The voltage detector 14 is a circuit that detects the bipolar voltage of the entire battery pack 2. The A / D converter 15 converts the bipolar voltage of the battery pack 2 detected by the voltage detector 14 into a digital value and supplies the digital value to the μCOM 19.

  The charging / discharging unit 13 is connected to both electrodes of the battery pack 2 and provided so as to allow a predetermined charge current Ic and discharge current Id to flow when charging and discharging the cells Ce1 to Ce3 constituting the battery pack 2. Have been. The charging / discharging unit 13 is connected to a μCOM 19 described later, and in response to a control signal from the μCOM 19, flows the charging current Ic to the cells Ce1 to Ce3 to charge the cell, and discharges the cells Ce1 to Ce3 to flow the discharging current Id. I do.

  The differential amplifier circuit 16 is a well-known differential amplifier circuit that outputs a difference voltage Vm (= output) between a + input and a − input. The A / D converter 17 converts the difference voltage Vm (= output) output from the differential amplifier circuit 16 into a digital value and supplies the digital value to the μCOM 19.

  The CVS 18 is configured by a detection circuit that detects the voltage between both ends of the cells Ce1 to Ce3, and sequentially outputs the detection results to the μCOM 19.

  The μCOM 19 is composed of a microcomputer having a well-known CPU, ROM, RAM and the like. The μCOM 19 functions as a second switch control unit and a state detection unit, controls on / off of the changeover switch SW1 and the switch unit 12, controls the charge / discharge unit 13, and detects the internal resistance of the cells Ce1 to Ce3. Execute the detection process.

  In the internal resistance detection process, in the first state, the μCOM 19 connects the e + terminal of the changeover switch SW + to the a + terminal, connects the e− terminal of the changeover switch SW− to the a− terminal, and sets the c of the changeover switch SW1 to c. Connect the terminal to terminal a. As a result, the μCOM 19 causes the first capacitor C1 to hold the voltage across the cell Ce1 in the first state. Thereafter, in the second state, the μCOM 19 connects the terminal c of the switch SW1 to the terminal b. As a result, the μCOM 19 causes the second capacitor C2 to hold the voltage across the cell Ce1 in the second state. Then, the voltage between both ends of the cell Ce <b> 1 in the first state and the second state is input to the positive input and the negative input to the differential amplifier circuit 16.

  Here, the first state and the second state indicate states in which currents flowing through the cells Ce1 to Ce3 are different. In the present embodiment, a state where the charging current Ic is flowing is defined as a first state, and a state where the discharging current Id is flowing is defined as a second state. The μCOM 19 controls the charge / discharge unit 13 based on the detection value from the voltage detection unit 14, and allows the charge current Ic and the discharge current Id to flow through the cells Ce1 to Ce3.

Further, in the internal resistance detection processing, the μCOM 19 detects the state of the cell Ce1 by detecting the internal resistance of the cell Ce1 by taking in the difference voltage Vm. More specifically, in the present embodiment, the voltage Vc1 across the cell Ce1 in the charged state is represented by the following equation (1).
Vc1 = Ve1 + r1 × Ic (1)
Ve1: electromotive force of cell Ce1, r1: internal resistance of cell Ce1

On the other hand, the voltage Vd1 across the cell Ce1 in the discharge state is represented by the following equation (2).
Vd1 = Ve1-r1 × Id (2)

  Therefore, the difference voltage Vm output from the differential amplifier circuit 16 has a value corresponding to Vc1−Vd1 = r1 × (Ic + Id), and if the charging current Ic and the discharging current Id are known in advance, the difference voltage Vm The resistance r1 can be obtained. Similarly, the internal resistances r2 and r3 of the cells Ce2 and Ce3 can be obtained.

  Further, the μCOM 19 functions as a first switch control unit and an equalizing unit, and controls on / off control of the changeover switch SW1 and the switch unit 12 and controls the equalizing circuit 11 to execute an equalizing process of the cells Ce1 to Ce3. .

  Next, details of the procedure of the equalization process of the cell monitoring device 1 described above in outline will be described below with reference to the flowchart of FIG. First, the μCOM 19 starts the equalization process before the end of charging. The μCOM 19 uses the cell Ce1 as a reference cell (reference secondary battery). The μCOM 19 connects the cell Ce1 to the first capacitor C1, and connects the cell Ce2 to the second capacitor C2 (Step S1).

The step S1 will be described in detail. The μCOM 19 connects the cell Ce1 to the first capacitor C1, waits for a predetermined time such that the voltage across the first capacitor C1 becomes equal to the voltage Vc1 across the cell Ce1, and waits for the second time. The cell Ce2 is connected to the capacitor C2. By this step S1, the voltage Vc1 across the cell Ce1 is input to the + input and the voltage Vc2 across the cell Ce2 is input to the − input to the differential amplifier circuit 16. At this time, the difference voltage Vm output from the differential amplifier circuit 16 is represented by the following equation (4).
Vm = (Vc1−Vc2) × Av (4)

  Next, the μCOM 19 takes in the difference voltage Vm shown in Expression (4) (Step S2). Here, if Vc1> Vc2, the difference voltage Vm shown in Expression (4) becomes larger than 0. On the other hand, if Vc1 ≦ Vc2, the difference voltage Vm shown in Expression (4) becomes 0, and it is indistinguishable whether Vc1 = Vc2 or Vc1 <Vc2. Moreover, if Vc1 <Vc2, it is not possible to determine the difference.

Therefore, after that, the μCOM 19 exchanges the cells Ce1 and Ce2 input to the differential amplifier circuit 16 (Step S3). In step S3, the μCOM 19 connects the cell Ce2 to the first capacitor C1 and connects the cell Ce2 to the second capacitor C2 in the same procedure as in step S1. As a result, the voltage Vc2 across the cell Ce2 is input to the + input and the voltage Vc1 across the cell Ce1 is input to the-input to the differential amplifier circuit 16. At this time, the difference voltage Vm output from the differential amplifier circuit 16 is represented by the following equation (5).
Vm = (Vc2−Vc1) × Av (5)

Next, the μCOM 19 takes in the difference voltage Vm shown in Expression (5) (Step S4). Thereafter, the μCOM 19 connects the cell Ce1 to the first capacitor C1 and connects the cell Ce3 to the second capacitor C2 according to the same procedure as in Step S1 (Step S5). As a result, the voltage Vc1 across the cell Ce1 is input to the + input and the voltage Vc3 across the cell Ce3 is input to the − input to the differential amplifier circuit 16. At this time, the difference voltage Vm output from the differential amplifier circuit 16 is represented by the following equation (6).
Vm = (Vc1−Vc3) × Av (6)

Next, the μCOM 19 takes in the difference voltage Vm shown in Expression (6) (Step S6). Thereafter, the μCOM 19 replaces the cells Ce1 and Ce3 input to the differential amplifier circuit 16 (Step S7). In step S7, the μCOM 19 connects the cell Ce3 to the first capacitor C1 and connects the cell Ce1 to the second capacitor C2 in the same procedure as in step S1. As a result, the voltage Vc3 across the cell Ce3 is input to the + input and the voltage Vc1 across the cell Ce1 is input to the − input to the differential amplifier circuit 16. At this time, the difference voltage Vm output from the differential amplifier circuit 16 is represented by the following equation (7).
Vm = (Vc3−Vc1) × Av (7)

  Next, the μCOM 19 takes in the difference voltage Vm shown in Expression (7) (Step S8). Thereafter, the μCOM 19 obtains the magnitude relationship between the cells Ce1 to Ce3 based on the difference voltages Vm shown in the expressions (4) to (7) (step S9). That is, the μCOM 19 can determine the magnitude relationship between Vc1 and Vc2 based on the difference voltage Vm of the equations (4) and (5) taken in steps S2 and S4. μCOM determines that Vc1> Vc2 if the difference voltage Vm in the equation (4) is greater than 0, and determines that Vc1 <Vc2 if the difference voltage Vm in the equation (5) is greater than 0. If the difference voltage Vm = 0 in (5), it is determined that Vc1 = Vc2.

  Further, the μCOM 19 can determine the magnitude relationship between Vc1 and Vc3 based on the difference voltage Vm of the equations (6) and (7) taken in steps S6 and S8. μCOM determines that Vc1> Vc3 if the differential voltage Vm in the equation (6) is greater than 0, and determines that Vc1 <Vc3 if the differential voltage Vm in the equation (7) is greater than 0. If the difference voltage Vm = 0 in (7), it is determined that Vc1 = Vc3.

  When determining that Vc1> Vc2 and Vc1> Vc3, the μCOM 19 determines the magnitude of Vc2 and Vc3 based on the magnitude of the difference voltage Vm of the equations (4) and (6) taken in steps S2 and S6. When determining that Vc1 <Vc2 and Vc1 <Vc3, the μCOM 19 determines the magnitude of Vc2 and Vc3 based on the magnitude of the difference voltage Vm in Equations (5) and (7) taken in Steps S4 and S8.

  Next, the μCOM 19 controls the equalizing circuit 11 based on the magnitude relation of the cells Ce1 to Ce3 obtained in step S9 to perform equalization (step S10), and ends the processing. In step S10, the μCOM 19 performs a well-known equalization that discharges the cell having the highest voltage across the cell and transfers the charge from the cell having the highest voltage to the cell having the lowest voltage.

  According to the above-described first embodiment, the differential amplifier circuit 16 receives two terminal voltages of the plurality of cells Ce1 to Ce3, respectively, and outputs a difference between the two input terminal voltages. The changeover switch SW1 and the switch unit 12 are provided between the differential amplifier circuit 16 and the plurality of cells Ce1 to Ce3. The μCOM 19 controls the changeover switch SW1 and the switch unit 12 to switch the combination of the two cells Ce1 to Ce3 input to the differential amplifier circuit 16. Further, the μCOM 19 obtains the magnitude relationship between the plurality of cells Ce1 to Ce3 based on the combination of the two cells Ce1 to Ce3 input to the differential amplifier circuit 16 and the difference voltage Vm of the differential amplifier circuit 16, Equalization is performed based on the obtained magnitude relationship. As described above, by performing equalization based on the difference between the voltages Vc1 to Vc3 across the two cells Ce1 to Ce3, the accuracy of equalization can be improved. That is, since the difference voltage between the cells Ce1 to Ce3 is smaller than the voltage across the cells Ce1 to Ce3, the resolution of the A / D conversion is increased, the magnitude relationship can be obtained with high accuracy, and the equalization accuracy can be obtained. Improvement can be achieved.

  According to the first embodiment described above, the μCOM 19 sets one of the two cells input to the differential amplifier circuit 16 as the reference cell Ce1, and sets the other of the two cells as the plurality of cells Ce1 to Ce3. Of these, the cells are sequentially switched to cells Ce2 and Ce3 excluding the reference cell Ce1. This makes it possible to easily determine the magnitude relationship between the plurality of cells Ce1 to Ce3.

  Further, according to the above-described first embodiment, the μCOM 19 is held in the second capacitor C2 and the voltage across the cells Ce1 to Ce3 in the first state held in the first capacitor C1 in the state detection process. The changeover switch SW + and the switch unit 12 are controlled such that the voltage across the cells Ce1 to Ce3 in the second state is input to the differential amplifier circuit 16. The μCOM 19 detects the battery state of the cells Ce1 to Ce3 based on the difference voltage Vm of the differential amplifier circuit 16 at this time. As a result, the differential amplifier circuit 16 can be used for both equalization and state detection, and cost reduction can be achieved.

  In the above-described first embodiment, the control of the charge / discharge unit 13 by the μCOM 19 causes the secondary batteries Ce1 to Ce3 to be in the first state (the state where the charging current Ic is flowing) and the second state (the state where the discharging current Id is flowing). Is flowing), but is not limited to this. A change in the charge / discharge current associated with driving the load of the vehicle may be used. That is, the first state may be set before the change of the charge / discharge current of the vehicle, and the second state may be set after the change.

(2nd Embodiment)
Next, a cell monitoring device according to the second embodiment will be described. Since the configuration of the cell monitoring device of the first embodiment is the same as that of the cell monitoring device of the second embodiment, a detailed description of the configuration will be omitted. A major difference between the first embodiment and the second embodiment is the equalization processing procedure executed by the μCOM 19.

  In the first embodiment, two cells input to the differential amplifier circuit 16 are exchanged even if the difference voltage Vm taken in steps S2 and S6 is not 0. However, if the difference voltage Vm taken in Steps S2 and S6 is not 0, the magnitude relationship between the two cells input to the differential amplifier circuit 16 can be determined, so that it is not necessary to perform the replacement (Steps S5 and S6). It is not necessary to perform S6, S7, and S8). Thus, in the second embodiment, the μCOM 19 replaces the two cells input to the differential amplifier circuit 16 when the taken difference voltage Vm is 0.

  Next, details of the equalization processing procedure of the cell monitoring device 1 according to the second embodiment described above will be described below with reference to the flowchart of FIG. First, the μCOM 19 starts the equalization process before the end of charging. The μCOM 19 connects the cell Ce1 to the first capacitor C1 and connects the cell Ce2 to the second capacitor C2, using the cell Ce1 as a reference cell, as in Step S1 of the first embodiment (Step S11).

By this step S11, the differential voltage Vm output from the differential amplifier circuit 16 is represented by the following equation (4).
Vm = (Vc1−Vc2) × Av (4)

Next, the μCOM 19 takes in the difference voltage Vm shown in Expression (4) (Step S12). Thereafter, the μCOM 19 determines whether or not the difference voltage Vm captured in Step S12 is 0 (Step S13). When the difference voltage Vm is 0 (Y in step S13), the μCOM 19 switches the inputs of the differential amplifier circuit 16 (step S14). In step S14, the μCOM 19 connects the cell Ce2 to the first capacitor C1 and connects the cell Ce1 to the second capacitor C2, as in step S3 of the first embodiment. At this time, the difference voltage Vm output from the differential amplifier circuit 16 is represented by the following equation (5).
Vm = (Vc2−Vc1) × Av (5)

  Next, the μCOM 19 fetches the difference voltage Vm shown in Expression (5) (Step S15), and proceeds to Step S16. On the other hand, when the difference voltage Vm is greater than 0 (N in step S13), the μCOM 19 immediately proceeds to step S16 without proceeding to steps S14 and S15.

In step S16, the μCOM 19 connects the cell Ce1 to the first capacitor C1, and connects the cell Ce3 to the second capacitor C2, as in step S5 of the first embodiment. At this time, the difference voltage Vm output from the differential amplifier circuit 16 is represented by the following equation (6).
Vm = (Vc1−Vc3) × Av (6)

Next, the μCOM 19 takes in the difference voltage Vm shown in Expression (6) (Step S17). Thereafter, the μCOM 19 determines whether or not the difference voltage Vm captured in Step S17 is 0 (Step S18). If the difference voltage Vm is 0 (Y in step S18), the μCOM 19 switches the input of the differential amplifier circuit 16 (step S19). In step S19, the μCOM 19 connects the cell Ce3 to the first capacitor C1, and connects the cell Ce1 to the second capacitor C2. At this time, the difference voltage Vm output from the differential amplifier circuit 16 is represented by the following equation (7).
Vm = (Vc3−Vc1) × Av (7)

  Next, the μCOM 19 takes in the difference voltage Vm shown in Expression (7) (Step S20), and then proceeds to Step S21. On the other hand, when the difference voltage Vm is larger than 0 (N in step S18), the μCOM 19 immediately proceeds to step S21 without proceeding to steps S19 and S20. In step S21, the μCOM 19 obtains the magnitude relationship between the cells Ce1 to Ce3 based on the acquired difference voltage Vm shown in the equations (4) to (7), similarly to step S9 of the first embodiment.

  Next, the μCOM 19 controls the equalization circuit 11 based on the magnitude relation of the cells Ce1 to Ce3 obtained in step S21 to perform equalization (step S22), and ends the processing.

  According to the above-described second embodiment, when the differential voltage Vm of the differential amplifier circuit 16 is 0, the μCOM 19 switches the cells Ce1 to Ce3 input to the + input and the − input of the differential amplifier circuit 16. And the switch SW + and the switch unit 12 are controlled. As a result, when the differential voltage Vm of the differential amplifier circuit 16 is greater than 0, the input of the differential amplifier circuit 16 is not replaced, so that the processing speed can be improved.

  In the first and second embodiments described above, the cell Ce1 is used as the reference cell. However, the present invention is not limited to this. The reference cell may be one of the cells Ce1 to Ce3, and may be the cell Ce2 or the cell Ce3.

(Third embodiment)
Next, a cell monitoring device according to a third embodiment will be described. Since the configuration of the cell monitoring device of the second embodiment is the same as that of the cell monitoring device of the third embodiment, a detailed description of the configuration will be omitted.

  In the above-described second embodiment, the cell Ce1 is used as the reference cell. However, the present invention is not limited to this. The cells Ce <b> 1 to Ce <b> 3 determined to have the highest voltage at both ends by the previous equalization may be input to the + input of the differential amplifier circuit 16 as reference cells. As a result, the probability that the differential voltage of the differential amplifier circuit 16 becomes 0 (that is, the probability of becoming Y in steps S13 and S18) is reduced, the probability of replacing the input of the differential amplifier circuit 16 is reduced, and the processing speed is reduced. Can be faster.

  According to the first to third embodiments described above, the differential amplifier circuit 16 is used for both the state detection processing and the equalization processing. However, the present invention is not limited to this. Separate differential amplifier circuits 16 may be used for the state detection processing and the equalization processing. In this case, the capacitors C1 and C2 are not essential for the differential amplifier circuit 16 used in the equalization processing.

  Further, in the first to third embodiments described above, two capacitors C1 and C2 are provided, but the invention is not limited to this. A single capacitor may be used to hold the secondary batteries Ce1 to Ce3 in the first state, and the secondary batteries Ce1 to Ce3 in the second state may be directly input to the differential amplifier circuit 16. .

  Further, the μCOM 19 may compare the difference voltage Vm captured by the above-described equalization process with the voltages Vc1 to Vc3 across the cells Ce1 to Ce3 detected by the CVS 18 to detect the failure of the CVS 18. Good. For example, the μCOM 19 detects a failure of the CVS 18 when the difference voltage Vm between the cells Ce1 and Ce2 and the difference obtained from the voltages Vc1 and Vc2 across the cells Ce1 and Ce2 detected by the CVS 18 are significantly different. You may.

  Note that the present invention is not limited to the above embodiment. That is, various modifications can be made without departing from the gist of the present invention.

1 cell monitoring device (equalization device)
12 Switch unit (switch)
16 differential amplifier circuit 19 μCOM (first switch control unit, equalization unit)
C1 First capacitor (capacitor)
Ce1-Ce3 cell (secondary battery)
SW + changeover switch (switch)

Claims (5)

It has two input terminals, and two terminal voltages of three or more rechargeable batteries constituting the battery pack are respectively input to the two input terminals, and outputs a difference between the two input terminal voltages. A differential amplifier circuit,
A plurality of switches provided between the differential amplifier circuit and the battery pack;
A first switch control unit that controls the switch to switch a combination of the two secondary batteries input to the differential amplifier circuit;
Based on the combination of the two secondary batteries input to the differential amplifier circuit and the output of the differential amplifier circuit, the magnitude relationship between the voltages across the secondary batteries constituting the battery pack was determined and determined. An equalizing device comprising: an equalizing unit that performs equalization based on a magnitude relationship.   The first switch control unit sets one of the two secondary batteries input to the differential amplifier circuit as a reference secondary battery, which is one of the secondary batteries constituting the battery pack, and The equalization apparatus according to claim 1, wherein the other of the secondary batteries is sequentially switched to all of the secondary batteries constituting the battery pack except for the reference secondary battery.   The first switch control unit controls the switch such that when the output of the differential amplifier circuit is 0, the secondary batteries input to the two input terminals of the differential amplifier circuit are replaced. The equalizing device according to claim 1 or 2, wherein:   3. The equalization apparatus according to claim 2, wherein the first switch control unit sets, as the reference secondary battery, a secondary battery that has been determined to have the highest voltage at both ends when the previous equalization is performed. 4. . A capacitor for holding a voltage across the secondary battery in the first state;
A second switch control unit that controls the switch so that the voltage across the secondary battery held by the capacitor and the voltage across the secondary battery in the second state inputs the input to the differential amplifier circuit;
5. A state detection unit that detects a battery state of the secondary battery based on an output of the differential amplifier circuit at the time of control by the second switch control unit. 6. Item 2. An equalizing device according to item 1.

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