JP2014158345A - Voltage monitoring apparatus for battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the voltage from becoming non-uniform between cells, even when getting the voltage for power supply from a part of a battery pack.SOLUTION: A cell monitoring unit (CMU:Cell Monitoring Unit) 1 includes a voltage monitoring unit 12 for monitoring each voltage of a plurality of cells B1-B12 constituting a battery pack 2, and a low voltage power supply circuit 14 for generating a power supply voltage of low voltage by getting a voltage from the battery pack 2, and supplying the power supply voltage to a temperature measurement circuit 15. The battery pack 2 is constituted of a series circuit of a first block 21 consisting of cells B1-B6, and a second block 22 consisting of cells B7-B12. The low voltage power supply circuit 14 gets a voltage across the second block 22. Furthermore, a power consumption circuit 16 for getting a voltage across the first block 21, and consuming power corresponding to the power consumed in the low voltage power supply circuit 14 and the temperature measurement circuit 15 is provided.

Description

  The present invention relates to an apparatus for monitoring the voltage of an assembled battery composed of a plurality of secondary batteries.

  For example, in an electric vehicle, a high-voltage battery for driving a motor for driving and on-vehicle equipment is mounted. This high voltage battery is generally composed of a so-called assembled battery in which a plurality of secondary batteries such as lithium ion batteries are connected in series. Such an assembled battery is provided with a battery monitoring device (CMU: Cell Monitoring Unit) for monitoring the voltage and temperature of each battery in order to perform charge / discharge control of the battery (see Patent Documents 1 and 2). In addition, a discharge circuit that corrects variations in voltage between batteries by preferentially discharging high-voltage batteries with respect to individual batteries constituting the assembled battery is provided (see Patent Document 3).

  In the battery voltage monitoring device of Patent Document 1, the batteries constituting the assembled battery are grouped into a plurality of blocks, and monitoring ICs for detecting the voltage and current of each battery are provided corresponding to each block. The operation power supply is obtained from the block composed of the target battery.

  In the vehicle power supply device of Patent Document 2, the battery for traveling is divided into a plurality of battery blocks, and a plurality of voltage detection circuits for detecting the voltage of each battery block are provided, and each voltage detection circuit is connected to each battery block. It is made to operate with the supplied power.

  In the assembled battery charging device of Patent Document 3, a discharge circuit (bypass circuit) having a switching element is connected in parallel to each battery of the assembled battery, and the lowest voltage among the voltages of each battery during charging detected by the voltage detection means. And a battery in which the voltage difference between the voltage of each of the other batteries exceeds a predetermined value, the discharge circuit is turned on to discharge the battery.

JP 2011-182550 A JP 2010-81692 A JP-A-8-19188

  In patent documents 1-3, the voltage of each battery is detected by the voltage detection part connected to the assembled battery. And the power supply circuit which supplies a power supply to a voltage detection part has acquired the voltage from the both ends of the assembled battery to be monitored. At this time, since the voltage across the assembled battery is a high voltage, the power supply circuit must step down the high voltage to generate a low power supply voltage. For this reason, a circuit such as a DC-DC converter that converts a high voltage into a low voltage is required, and the configuration of the power supply circuit becomes complicated.

  Therefore, it is conceivable that the voltage required for the power supply circuit is acquired from a part of the assembled battery instead of acquiring the voltage from the entire assembled battery. According to this, since the input voltage of the power supply circuit becomes low, a complicated circuit such as a DC-DC converter becomes unnecessary.

  However, when acquiring the voltage from a part of the assembled battery, the battery that is the target of voltage acquisition is used for the power consumption by the power supply to the power supply circuit and the load compared to the battery that is not the target of voltage acquisition. The battery voltage decreases. That is, the voltage becomes nonuniform among the batteries constituting the assembled battery.

  An object of the present invention is to provide an assembled battery monitoring device in which the voltage does not become nonuniform between batteries even when a power supply voltage is acquired from a part of the assembled battery.

  An assembled battery voltage monitoring device according to the present invention includes a voltage monitoring unit that monitors each voltage of a plurality of batteries constituting the assembled battery, and obtains a voltage from the assembled battery to generate a low-voltage power supply voltage. And a power supply circuit for supplying a voltage to the load. The assembled battery is composed of a series circuit of a first block made up of a plurality or a single battery and a second block made up of a plurality or a single battery. The power supply circuit acquires a voltage from both ends of the second block. In addition, a power consumption circuit that acquires voltage from both ends of the first block and consumes power corresponding to power consumed by the power supply circuit and the load is provided.

  If it does in this way, since a power supply circuit acquires a voltage from the 2nd block which is a part of assembled battery, the input voltage of a power supply circuit will become a voltage low compared with the voltage of the whole assembled battery. For this reason, a circuit such as a DC-DC converter that converts a high voltage into a low voltage is not required, and the configuration of the power supply circuit is simplified. For the first block from which the power supply voltage is not acquired, a power consumption circuit that consumes power corresponding to the power consumption in the power supply circuit and the load is provided, so the battery of the first block and the battery of the second block Each power consumed is equivalent. Thereby, it can suppress that a voltage becomes nonuniform between the batteries which comprise an assembled battery.

  In the present invention, the power consumption circuit may include a switching element that performs an on / off operation and a power consumption resistor connected in series to the switching element. In this case, the voltage monitoring unit can generate a PWM (Pulse Width Modulation) signal having a duty corresponding to the power consumed by the power supply circuit and the load, and can drive the switching element by this PWM signal. .

  In the present invention, the voltage monitoring unit includes a calculation control circuit that detects a current flowing through the load and calculates a duty of the PWM signal according to the power consumed by the power supply circuit and the load based on the detected current. Also good.

  In the present invention, the voltage monitoring unit detects a first voltage detection circuit that detects a first voltage that is a voltage across the first block of the battery pack, and a second voltage that is a voltage across the second block of the battery pack. A second voltage detection circuit, and a calculation control circuit that calculates the duty of the PWM signal according to the power consumed by the power supply circuit and the load, based on a comparison result between the first voltage and the second voltage. Good.

  In this case, the voltage monitoring unit determines whether or not the first voltage exceeds the second voltage. When the first voltage exceeds the second voltage, the PWM signal having the duty calculated by the calculation control circuit When the switching element is driven and the first voltage does not exceed the second voltage, the switching element may not be driven.

  According to the present invention, even when the power supply voltage is obtained from a part of the assembled battery, it is possible to prevent the battery voltage from becoming uneven among the batteries.

1 is a block diagram showing a first embodiment of the present invention. It is the figure which showed the specific example of the balancer circuit. It is the figure which showed the specific example of the low voltage power supply circuit. It is the figure which showed the specific example of the temperature measurement circuit. It is the figure which showed the voltage acquisition route of a low voltage power supply circuit. It is the figure which showed the voltage acquisition route | root of a power consumption circuit. It is the block diagram which showed 2nd Embodiment of this invention. It is a flowchart which shows operation | movement of 2nd Embodiment.

  Embodiments of the present invention will be described with reference to the drawings. Below, the case where this invention is applied to the assembled battery mounted in an electric vehicle is mentioned as an example.

  First, the configuration of the first embodiment will be described with reference to FIG. In FIG. 1, the assembled battery 2 is comprised by several battery B1-B12 connected in series. The assembled battery 2 is a high-voltage battery for driving a motor of an electric vehicle and a vehicle-mounted device. Each battery B1-B12 which comprises the assembled battery 2 consists of secondary batteries, such as a lithium ion battery and a lead acid battery, and is charged with the charging device which is not shown in figure. The batteries B <b> 1 to B <b> 6 constitute the first block 21, and the batteries B <b> 7 to B <b> 12 constitute the second block 22. Therefore, the assembled battery 2 is composed of a series circuit of the first block 21 and the second block 22.

  A battery monitoring device (CMU: Cell Monitoring Unit) 1 is a device that is mounted on a vehicle and monitors the voltage and temperature of the assembled battery 2. The battery monitoring device 1 includes a balancer circuit 11, a voltage monitoring unit 12, a low voltage power supply circuit 14, a temperature measurement circuit 15, and a power consumption circuit 16. Each of these elements is mounted on one circuit board. The battery monitoring device 1 constitutes a battery pack voltage monitoring device according to the present invention.

  The voltage monitoring unit 12 includes a microcomputer, and monitors each voltage of the plurality of batteries B <b> 1 to B <b> 12 constituting the assembled battery 2. For this reason, the positive electrode and the negative electrode of each battery are connected to the voltage monitoring unit 12 via a balancer circuit 11 described later. The voltage monitoring unit 12 also monitors the total voltage of the entire assembled battery 2. Therefore, the positive electrode of the battery B1 is connected to the voltage monitoring unit 12 via the balancer circuit 11 and the lines L1 and L3, and the negative electrode of the battery B12 is connected to the voltage via the balancer circuit 11 and the lines L4 and L5. It is connected to the monitoring unit 12. The voltage monitoring unit 12 includes an arithmetic control circuit 13 composed of a CPU. The voltage monitoring unit 12 communicates with a host device (not shown).

  The balancer circuit 11 is a circuit for correcting the voltage non-uniformity between the batteries due to the variation in the discharge capacity of each of the batteries B1 to B12 constituting the assembled battery 2. As shown in FIG. 2, the balancer circuit 11 includes a plurality of discharge circuits 11a, 11b, 11c,... Provided corresponding to the batteries B1, B2, B3,. Since each discharge circuit has the same configuration, the discharge circuit 11a will be described below.

  The discharge circuit 11a is a known circuit including a switching element Q2 and resistors R3 to R5. The switching element Q2 is made of, for example, an FET (Field Effect Transistor). One end of a discharging resistor R3 is connected to the drain of the switching element Q2, and the other end of the resistor R3 is connected to the positive electrode of the battery B1. The source of the switching element Q2 is connected to the negative electrode of the battery B1. As a result, a discharge path is formed from the positive electrode of the battery B1 to the negative electrode of the battery B1 via the resistor R3 and the switching element Q2. A control signal composed of a pulse signal is given to the gate of the switching element Q2 from the voltage monitoring unit 12 via the resistors R4 and R5. The switching element Q2 performs an on / off operation according to the control signal. Details of voltage equalization by the discharge circuit 11a will be described later.

  Returning to FIG. 1, the low voltage power supply circuit 14 is a circuit that obtains a voltage from a part of the assembled battery 2 and outputs a low voltage. One input terminal (+ terminal) of the low-voltage power supply circuit 14 is connected to the positive electrode of the battery B7 of the second block 22 via the line L2 and the balancer circuit 11. The other input terminal (− terminal) of the low voltage power supply circuit 14 is connected to the negative electrode of the battery B12 of the second block 22 via the line L4 and the balancer circuit 11. Thereby, the low voltage power supply circuit 14 acquires a voltage from the both ends of the 2nd block 22 of the assembled battery 2 by a route | root as shown by a thick line in FIG. The low voltage power supply circuit 14 generates a low voltage power supply voltage (for example, 5 [V]) based on the voltage acquired from the second block 22 and supplies the power supply voltage to the temperature measurement circuit 15 as a load.

  FIG. 3 shows an example of the low-voltage power supply circuit 14. The low voltage power supply circuit 14 is a well-known circuit including a switching element Q3, resistors R6 to R9, and a constant voltage element Z. The switching element Q3 is composed of a bipolar transistor, and the constant voltage element Z is composed of a shunt reference IC having a function equivalent to that of a Zener diode. A low voltage Vc determined by the output voltage of the constant voltage element Z and the resistors R8 and R9 is output from the low voltage power supply circuit 14 and supplied to the temperature measurement circuit 15 as a power supply voltage.

  The temperature measurement circuit 15 is a circuit that measures the temperature of the assembled battery 2. As shown in FIG. 4, the temperature measurement circuit 15 includes a temperature detection thermistor Th and a current detection shunt resistor Rs. The thermistor Th has a characteristic that the resistance value decreases as the temperature increases, and the resistance value increases as the temperature decreases. The thermistor Th and the resistor Rs are connected in series between the power supplies supplied from the low voltage power supply circuit 14. The voltage Vs at the connection point between the thermistor Th and the shunt resistor Rs is given to the voltage monitoring unit 12 as shown in FIG.

  The power consumption circuit 16 is a circuit that characterizes the present invention, and includes a switching element Q1, a resistor R1, and a resistor R2. The switching element Q1 is made of, for example, an FET (Field Effect Transistor). One end of a power consumption resistor R1 is connected to the drain of the switching element Q1, and the other end of the resistor R1 is connected to the battery B1 in the first block 21 of the assembled battery 2 via the line L1 and the balancer circuit 11. Is connected to the positive electrode. The source of the switching element Q1 is connected to the negative electrode of the battery B6 in the first block 21 of the assembled battery 2 via the line L2 and the balancer circuit 11. Thereby, the power consumption circuit 16 acquires a voltage from the both ends of the 1st block 21 of the assembled battery 2 by a route | root as shown by a thick line in FIG. A PWM (Pulse Width Modulation) signal is applied to the gate of the switching element Q1 from the voltage monitoring unit 12 via the resistor R2. The switching element Q1 is turned on / off by this PWM signal.

  Next, the operation of the first embodiment will be described. In the battery monitoring device 1, the voltage monitoring unit 12 detects the voltages of the batteries B1 to B12, and controls the balancer circuit 11 based on the detection result. Specifically, the voltage monitoring unit 12 turns on the switching element Q2 of the discharge circuits 11a, 11b, 11c (see FIG. 2) corresponding to the high voltage battery and operates the discharge circuit. Therefore, prioritize battery discharge. Further, the voltage monitoring unit 12 turns off the switching element Q2 of the discharge circuits 11a, 11b, 11c,. Prioritize charging. As a result, the voltage of a battery having a high voltage is reduced by discharging, and the voltage of a battery having a low voltage is increased by charging, so that the voltage of each battery is equalized.

  When the low-voltage power supply circuit 14 acquires the voltage from the entire assembled battery 2, the voltage non-uniformity between the batteries B1 to B12 constituting the assembled battery 2 is small, and the voltage equalization by the balancer circuit 11 as described above is performed. It is sufficient to perform the process. However, when the low-voltage power supply circuit 14 obtains a voltage from the second block 22 that is a part of the assembled battery 2 as in the present embodiment, if no measures are taken for the first block 21, The batteries B7 to B12 in the block 22 are discharged earlier than the batteries B1 to B6 in the first block 21. As a result, the degree of voltage non-uniformity between the first block 21 and the second block 22 is significantly increased. In this case, the balancer circuit 11 can no longer cope. Therefore, in the present invention, the battery voltage is equalized by the power consumption circuit 16 separately from the equalization of the battery voltage by the balancer circuit 11. The details will be described below.

  In the power consumption circuit 16, while the switching element Q1 is turned on by the PWM signal supplied from the voltage monitoring unit 12, a current flows through the resistor R1 and the switching element Q1 based on the voltage acquired from the first block 21. . This current consumes power in the resistor R1 and the switching element Q1. This power consumption is determined according to the ON time of the switching element Q1, that is, the duty of the PWM signal. Therefore, the duty of the PWM signal is determined so that the power consumed by the resistor R1 and the switching element Q1 is equivalent to the power consumed by the low voltage power supply circuit 14 and the temperature measurement circuit 15.

  Specifically, the voltage monitoring unit 12 acquires the voltage Vs detected by the shunt resistor Rs (FIG. 4) of the temperature measurement circuit 15 at regular intervals. The calculation control circuit 13 of the voltage monitoring unit 12 calculates the current Is flowing through the temperature measurement circuit 15 based on the acquired voltage Vs, and is further consumed by the low voltage power supply circuit 14 and the temperature measurement circuit 15 by this current Is. The consumed power P is calculated. Then, the arithmetic control circuit 13 determines the duty of the PWM signal so that the power consumed by the resistor R1 and the switching element Q1 by the current flowing when the switching element Q1 of the power consumption circuit 16 is turned on becomes equal to the power consumption P described above. Is calculated.

  When the duty is determined in this way, the voltage monitoring unit 12 generates a PWM signal having the duty and outputs the PWM signal to the gate of the switching element Q1 of the power consumption circuit 16. The switching element Q1 is turned on for a time corresponding to the duty of the PWM signal, and a current flows through the resistor R1 and the switching element Q1 during this on period. As a result, the power consumption circuit 16 consumes power corresponding to the power consumed by the low voltage power supply circuit 14 and the temperature measurement circuit 15.

  The calculation control circuit 13 of the voltage monitoring unit 12 also calculates the temperature of the assembled battery 2 based on the voltage Vs acquired from the temperature measurement circuit 15. The calculated temperature is sent from the voltage monitoring unit 12 to a host device (not shown). When the temperature value is abnormal, the host device controls the charging device (not shown) and performs processing such as stopping charging of the assembled battery 2.

  According to the first embodiment described above, the low voltage power supply circuit 14 obtains a voltage from the second block 22 that is a part of the assembled battery 2, so that the input voltage of the low voltage power supply circuit 14 is the entire assembled battery 2. The voltage is lower than the voltage of. Therefore, a circuit such as a DC-DC converter that converts a high voltage to a low voltage is not necessary, and the configuration of the low voltage power supply circuit 14 is simplified. For the first block 21 from which the voltage for power supply is not acquired, the power consumption circuit 16 that consumes power corresponding to the power consumption in the low voltage power supply circuit 14 and the temperature measurement circuit 15 is provided. The electric power consumed by the batteries B1 to B6 and the batteries B7 to B12 of the second block 22 are equal. Thereby, it can suppress that a voltage becomes nonuniform between the batteries which comprise the assembled battery 2. FIG.

  Next, a second embodiment of the present invention will be described. First, the configuration of the second embodiment will be described with reference to FIG. 7, the same reference numerals as those in FIG. 1 are given to the same or corresponding parts as those in FIG.

  In the second embodiment, the voltage monitoring unit 12 includes a first voltage detection circuit 17, a second voltage detection circuit 18, and an arithmetic control circuit 19. The first voltage detection circuit 17 detects a first voltage that is a voltage across the first block 21 of the assembled battery 2. The second voltage detection circuit 18 detects a second voltage that is a voltage across the second block 22 of the assembled battery 2. The arithmetic control circuit 19 calculates the duty of the PWM signal according to the power consumed by the low voltage power supply circuit 14 and the temperature measurement circuit 15 based on the comparison result between the first voltage and the second voltage (details will be described later). ). About another structure, it is the same as 1st Embodiment of FIG.

  Next, the operation of the second embodiment will be described. Since the operation of the balancer circuit 11 is the same as that of the first embodiment, the description thereof is omitted. Hereinafter, the voltage equalization by the power consumption circuit 16 will be described with reference to the flowchart of FIG. Each step in FIG. 8 is executed by the voltage monitoring unit 12 at regular intervals.

  In step S1, the first voltage detection circuit 17 detects the voltage of the first block 21 (first voltage V1), and the second voltage detection circuit 18 detects the voltage of the second block 22 (second voltage V2). .

  Next, in step S2, the first voltage V1 detected in step S1 is compared with the second voltage V2. In step S3, it is determined whether or not the first voltage V1 exceeds the second voltage V2. As a result of the determination, if the first voltage V1 exceeds the second voltage V2 (step S3; YES), the process proceeds to step S4.

  In step S4, the arithmetic control circuit 19 calculates the duty of the PWM signal based on the comparison result between the first voltage V1 and the second voltage V2. Specifically, the arithmetic control circuit 19 calculates a difference ΔV = V1−V2 between the first voltage V1 and the second voltage V2. Based on this voltage difference ΔV, the duty of the PWM signal necessary for the power consumption circuit 16 to consume the power corresponding to the power consumed by the low voltage power supply circuit 14 and the temperature measurement circuit 15 is calculated. . It is required that the power consumption circuit 16 consumes a larger amount of power as the voltage difference ΔV is larger.

  In step S5, a PWM signal having the duty calculated in step S4 is generated by the voltage monitoring unit 12, and the switching element Q1 of the power consumption circuit 16 is driven by this PWM signal.

  On the other hand, if the result of determination in step S3 is that the first voltage V1 does not exceed the second voltage V2 (step S3; NO), the process ends without executing steps S4 to S5. In this case, if the first voltage V1 and the second voltage V2 are equal, the voltage is equalized between the first block 21 and the second block 22, so that it is not necessary to drive the power consumption circuit 16. . If the first voltage V1 is smaller than the second voltage V2, the second voltage V2 of the second block 22 continues to decrease due to power consumption in the low-voltage power supply circuit 14 and the temperature measurement circuit 15, and eventually the first block. Therefore, the power consumption circuit 16 does not need to be driven. Therefore, in any case, the switching element Q1 of the power consumption circuit 16 is not driven.

  According to the second embodiment described above, similarly to the first embodiment, the low-voltage power supply circuit 14 obtains a voltage from the second block 22 that is a part of the assembled battery 2. The input voltage is lower than the voltage of the entire assembled battery 2. Therefore, a circuit such as a DC-DC converter that converts a high voltage to a low voltage is not necessary, and the configuration of the low voltage power supply circuit 14 is simplified. For the first block 21 from which the voltage for power supply is not acquired, the power consumption circuit 16 that consumes power corresponding to the power consumption in the low voltage power supply circuit 14 and the temperature measurement circuit 15 is provided. The electric power consumed by the batteries B1 to B6 and the batteries B7 to B12 of the second block 22 are equal. Thereby, it can suppress that a voltage becomes nonuniform between the batteries which comprise the assembled battery 2. FIG.

  In the present invention, various embodiments other than those described above can be adopted. For example, in each of the embodiments described above, the number of batteries in the first block 21 of the assembled battery 2 and the number of batteries in the second block 22 are the same (both are six), but the number of batteries in each of the blocks 21 and 22 is the same. May be different. Further, the number of batteries in each of the blocks 21 and 22 is not limited to a plurality, and may be a single (one).

  In each of the embodiments described above, the PWM signal is used as the drive signal for the switching element Q1 of the power consumption circuit 16. However, any drive signal other than the PWM signal may be used as long as it is a signal for controlling on / off of the switching element Q1. It may be used. Further, in each of the embodiments described above, an FET is used as the switching element Q1, but a transistor, a relay, or the like may be used instead of the FET.

  In each of the above-described embodiments, the temperature measurement circuit 15 is taken as an example of the load of the low voltage power supply circuit 14, but the load of the low voltage power supply circuit 14 is a load other than the temperature measurement circuit (for example, a communication IC). It may be.

  In the second embodiment, the arithmetic control circuit 19 calculates the duty of the PWM signal based on the difference between the first voltage and the second voltage, but based on the ratio between the first voltage and the second voltage. Thus, the duty of the PWM signal may be calculated.

  Further, in each of the embodiments described above, an example in which the present invention is applied to an assembled battery mounted on an electric vehicle has been described. However, the present invention can also be applied to an assembled battery used for purposes other than an electric vehicle. .

DESCRIPTION OF SYMBOLS 1 Battery monitoring apparatus 2 Battery assembly 12 Voltage monitoring part 13 Operation control circuit 14 Low voltage power supply circuit 15 Temperature measurement circuit 16 Power consumption circuit 17 1st voltage detection circuit 18 2nd voltage detection circuit 19 Operation control circuit 21 1st block 22 2nd 2 blocks B1-B12 Battery R1 Resistance Q1 Switching element

Claims (5)

A voltage monitoring unit for monitoring each voltage of a plurality of batteries constituting the assembled battery;
In the voltage monitoring device for the assembled battery, comprising a power supply circuit that obtains a voltage from the assembled battery and generates a low-voltage power supply voltage and supplies the power supply voltage to a load.
The assembled battery is composed of a series circuit of a first block composed of a plurality or a single battery and a second block composed of a plurality or a single battery,
The power supply circuit obtains a voltage from both ends of the second block;
An assembled battery voltage monitoring device comprising a power consumption circuit that obtains a voltage from both ends of the first block and consumes power corresponding to power consumed by the power supply circuit and the load. In the assembled battery voltage monitoring device according to claim 1,
The power consumption circuit includes a switching element that performs an on / off operation, and a resistor for power consumption connected in series to the switching element,
The voltage monitoring unit generates a PWM signal having a duty corresponding to the power consumed by the power supply circuit and the load, and drives the switching element by the PWM signal. . In the assembled battery voltage monitoring device according to claim 2,
The voltage monitoring unit
An assembled battery comprising: an arithmetic control circuit that detects a current flowing through the load and calculates a duty of the PWM signal according to the power consumed by the power supply circuit and the load based on the detected current Voltage monitoring device. In the assembled battery voltage monitoring device according to claim 2,
The voltage monitoring unit
A first voltage detection circuit that detects a first voltage that is a voltage across the first block;
A second voltage detection circuit for detecting a second voltage that is a voltage across the second block;
An arithmetic control circuit for calculating a duty of the PWM signal according to the power consumed by the power supply circuit and the load, based on a comparison result between the first voltage and the second voltage;
An assembled battery voltage monitoring apparatus comprising: In the assembled battery voltage monitoring device according to claim 4,
The voltage monitoring unit
Determining whether the first voltage exceeds the second voltage;
When the first voltage exceeds the second voltage, the switching element is driven by a PWM signal having a duty calculated by the calculation control circuit,
When the first voltage does not exceed the second voltage, the switching element is not driven.

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