JP2016154423A - Voltage balance device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage balance device capable of suppressing useless power consumption when equalizing output voltages of a plurality of secondary batteries.SOLUTION: A voltage balance device 20 comprises a plurality of high-potential-side charge circuits 41 and a plurality of low-potential-side charge circuits 42 correspondingly to a plurality of cells B (secondary batteries) that are connected in series. If output voltages of neighboring cells B are different, the high-potential-side charge circuit 41 or the low-potential-side charge circuit 42 corresponding to a cell of a higher output voltage between both cells B uses that cell B as a power source to charge a cell B of a lower output voltage. Namely, in the voltage balance device, output voltages of the plurality of cells are equalized by supplying power of a cell B of a relatively high output voltage to a cell B of a low output voltage. Therefore, in comparison with the prior arts, useless power consumption with equalizing the output voltages of a group of cells B can be suppressed.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a voltage balance device that equalizes output voltages of a plurality of secondary batteries connected in series.

  As is generally known, variations in output voltage of a plurality of secondary batteries connected in series cause overcharge and overdischarge of the secondary battery. On the other hand, there is known a voltage balance device that equalizes the output voltage of a plurality of secondary batteries by connecting a resistance discharge circuit to a secondary battery having a relatively high output voltage and forcibly discharging it. (For example, refer to Patent Document 1).

JP 2014-116992 A (paragraphs [0003], [0004])

  However, the conventional voltage balance device described above has a problem that power is wasted.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a voltage balance device capable of suppressing wasteful power consumption when equalizing output voltages of a plurality of secondary batteries.

  The invention of claim 1 made to achieve the above object is provided corresponding to each of a plurality of secondary batteries connected in series, and using the corresponding secondary battery as a power source, A plurality of high potential side charging circuits capable of charging the secondary battery adjacent to the high potential side and the plurality of secondary batteries are provided corresponding to each of the plurality of secondary batteries. A plurality of low-potential-side charging circuits capable of charging a secondary battery on the low-potential side of the secondary battery and the adjacent secondary batteries when the output voltages of the adjacent secondary batteries are different. A charge control circuit for charging the secondary battery having a low output voltage by operating the high-potential side charging circuit or the low-potential side charging circuit having a secondary battery having a high output voltage as the power source. A voltage balance device.

  According to a second aspect of the present invention, the high potential side charging circuit is provided between a negative electrode of the secondary battery serving as the power source and a positive electrode of a high potential side secondary battery that is a secondary battery adjacent to the high potential side. The first switch coil is connected to the negative electrode side of the secondary battery, the first switch element and the first diode are arranged in series in this order, and the anode of the first diode is arranged on the first switch element side A step-up type comprising: a circuit; a step-up coil connected between an anode of the first diode and a negative electrode of the high-potential side secondary battery; and a first switch control unit for turning on and off the first switch element. A low-potential side charging circuit between a positive electrode of the secondary battery serving as the power source and a negative electrode of a low-potential side secondary battery that is a secondary battery adjacent to the low-potential side; Connected to the secondary battery A second switch coil circuit in which the second switch element and the second diode are arranged in series in this order from the pole side, and the cathode of the second diode is disposed on the second switch element side; and the cathode of the second diode The step-up DC-DC converter having a step-up coil connected between the positive electrode of the low-potential side secondary battery and a second switch control unit for turning on and off the second switch element. It is a voltage balance apparatus of description.

  According to a third aspect of the present invention, the high potential side charging circuit and the low potential side charging circuit shared by the secondary battery serving as a power source are connected between a positive electrode and a negative electrode of the secondary battery and The first switch element, the boosting coil, and the second switch element share a double switch coil circuit in order from the negative electrode side, and the first diode has an anode connected to the first switch element and the first switch element. The cathode is connected to the positive electrode of the high-potential side secondary battery while the cathode is connected to the second switching element and the boosting coil while being connected to a common connection portion with the boosting coil. While being connected to the connection portion, the anode is connected to the negative electrode of the low-potential side secondary battery, and the first switch element is turned on / off while the second switch element is in the off state. The high-potential side charging circuit operates in a stopped state, the high-potential-side charging circuit operates, and the first switch element is in an off-state and the second switch element is turned on and off, so that the high-potential-side charging circuit is in a stopped state and the low-side charging circuit The voltage balance device according to claim 2, wherein the potential side charging circuit operates.

  According to a fourth aspect of the present invention, a common reference power supply current is preset in the plurality of high potential side charging circuits and the plurality of low potential side charging circuits, and flows out of the secondary battery serving as the power source. Current control means for controlling the current to be the reference power supply current is provided, and the current control means is provided in a closed circuit including the secondary battery serving as the power supply and the boosting coil. A current detection resistor; and the first switch control unit and the second switch control unit, wherein the first switch control unit and the second switch control unit include a reference voltage that is a substitute value of the reference power supply current; Changing the ON / OFF DUTY ratio of the first switch element based on the deviation from the terminal voltage of the current detection resistor, which is a substitute value of the current from the secondary battery, Current A voltage balancing device according to claim 3, the feedback control so that the serial reference source current.

  According to a fifth aspect of the present invention, a current flowing out from the secondary battery serving as the power source is a predetermined common reference power source current for the plurality of high potential side charging circuits and the plurality of low potential side charging circuits. The voltage balance device according to claim 1, further comprising a current control unit that performs control so that

  According to a sixth aspect of the present invention, the charge control circuit includes: a first secondary battery having an abnormally low output voltage among the plurality of secondary batteries; and a second secondary battery having an abnormally high output voltage. When there is a third secondary battery having a normal output voltage between them, all the high potential side charging circuits corresponding to the first, second and third secondary batteries or all the low potentials are provided. Side-side charging circuit is simultaneously operated to relay the third secondary battery from the second secondary battery to the first secondary battery to deliver power, and charge the first secondary battery. The voltage balance device according to claim 1.

  The voltage balance device according to claim 1 is provided with a plurality of high potential side charging circuits and a plurality of low potential side charging circuits corresponding to the plurality of secondary batteries connected in series, and the output voltage of adjacent secondary batteries. Are different from each other, the high-potential side charging circuit or the low-potential side charging circuit of the secondary battery having a high output voltage is used as a power source for the secondary battery having a low output voltage. Charge. That is, in the voltage balance device of the present invention, the power of the secondary battery having a relatively high output voltage is supplemented to the secondary battery having a low output voltage to equalize the output voltages of the plurality of secondary batteries. Compared to the above, it is possible to suppress wasteful power consumption accompanying the equalization of the output voltage of the secondary battery group.

  Here, since the high-potential side charging circuit and the low-potential side charging circuit are step-up DC-DC converters, charging can be performed more efficiently than those in which power is converted by a transformer. According to the second aspect of the present invention, since the boosting coil is shared between the high-potential side charging circuit and the low-potential side charging circuit, the cost and size of the voltage balance device can be reduced.

  Further, according to the inventions of claims 4 and 5, since charging is performed such that the current flowing out from the secondary battery serving as the power source becomes a constant reference power source current, charging is performed from the secondary battery to be charged. This prevents a situation where excessive current flows into the secondary battery. Further, since the reference power supply current is common among the plurality of high potential side charging circuits and the plurality of low potential side charging circuits, the first, second, and third as in the invention of claim 6. Relay the third secondary battery from the second secondary battery to the first secondary battery by simultaneously operating all the high potential side charging circuits or all the low potential side charging circuits corresponding to the secondary batteries. Then, power can be delivered and charged.

1 is a conceptual diagram of a voltage balance device and cell strings according to an embodiment of the present invention. Block diagram of voltage balance device Circuit diagram of voltage balance device Circuit diagram of individual charging circuit Circuit diagram of individual charging circuit High-potential side charging circuit schematic Circuit diagram of low potential side charging circuit

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a battery 10 mounted on a vehicle such as an electric vehicle or a hybrid vehicle. The battery 10 includes a plurality of battery packs 11 connected in parallel between a pair of battery electrodes 10A and 10B. Each battery pack 11 is a lithium ion battery cell B corresponding to the “secondary battery” of the present invention. A plurality of (for example, 96) (hereinafter simply referred to as “cell B”) are connected in series. In addition, a power conditioner 14 is connected to the pair of battery electrodes 10A and 10B, and a generator 15 and a load 17 are connected to the power conditioner 14 via a converter 16, thereby charging the battery 10. Discharge occurs. The output voltage of each cell B is an appropriate value of about 3.7V, overcharged when it is 4.5 [V] or more, and overdischarged when it is 3.5 [V] or less.

  In the following description, when the cells B are not distinguished from each other, they are simply referred to as “cell B”, and when the cells B are distinguished from each other, the cells B on the low potential side of the battery pack 11 are described. .. Are added to the end in order, for example, “cells B1, B2, B3,...”.

  One voltage balance device 20 of this embodiment is provided for each battery pack 11, and FIG. 2 shows one battery pack 11 and one voltage balance device 20 in a block diagram. As shown in the figure, the voltage balance device 20 includes a plurality of voltage detection circuits 50 and individual charging circuits 21 provided for each cell B, and one charging control circuit 40. Then, the charge overall control circuit 40 controls which of the plurality of individual charging circuits 21 is operated based on the detection result of the output voltage of each cell B by the voltage detection circuit 50 group.

  In the present embodiment, the plurality of voltage detection circuits 50 are provided as a part of the voltage balance device 20, but the voltage balance device 20 does not include the voltage detection circuit 50 group, and is installed in the vehicle. It is good also as a structure which acquires the information of the output voltage of each cell B which the circuit detected.

  Each individual charging circuit 21 operates in response to a signal from the charging overall control circuit 40, can receive power from the corresponding cell B, and charge any one of the adjacent cells B. In addition, the individual charging circuit 21 corresponding to the cell B on the highest potential side of the battery pack 11 has a configuration capable of charging only the cell B adjacent to the low potential side because there is no cell B on the higher potential side. None, the individual charging circuit 21 corresponding to the cell B on the lowest potential side has no cell B on the lower potential side, so that only the adjacent cell B on the higher potential side can be charged.

  FIG. 3 shows a circuit diagram of a plurality of individual charging circuits 21 connected to a plurality of cells B. Among the plurality of individual charging circuits 21, one cell B49 (hereinafter referred to as “the cell B49” as appropriate) is shown. 1 is shown in an excerpt in FIG. As shown in FIG. 4, the individual charging circuit 21 has a double switch coil circuit 24 according to the present invention between a pair of positive and negative electrodes of the cell B49. The double switch coil circuit 24 is formed by connecting the second switch 22, the boosting coil L1, the first switch 23, and the resistor R1 in series from the positive electrode side of the cell B49. A bypass capacitor 29 is connected between both terminals of the resistor R1.

  The first switch 23 is an N-channel MOSFET, while the second switch 22 is a P-channel MOSFET. The drain of the MOSFET as the first switch 23 and the drain of the MOSFET as the second switch 22 are connected to the boosting coil L1. In addition, the anode of the first diode D1 is connected to the common connection portion between the first switch 23 and the boosting coil L1, and the cathode of the first diode D1 is the cell B50 on the high potential side (hereinafter referred to as “ To the positive electrode of the high potential side cell B50 ". Furthermore, the cathode of the second diode D2 is connected to the common connection portion between the second switch 22 and the boosting coil L1, and the anode of the second diode D2 is the cell B48 adjacent to the low potential side (hereinafter referred to as appropriate). To the negative electrode of “low potential side cell B48”.

  A smoothing capacitor C is connected between the pair of positive and negative electrodes of each cell B in parallel with the double switch coil circuit 24. 3 to 7, the reference numeral “C” indicating each smoothing capacitor C is followed by the same number as the last number of the corresponding cells B44, B49, B50.

  The individual charging circuit 21 is provided with a power supply control IC 25 and a logic circuit 26 for on / off control of the first and second switches 22 and 23, and the power supply control IC 25 and the logic circuit 26 are used to control the first and second switches 22 and 23. A “first switch control unit” and a “second switch control unit” are configured. The logic circuit 26 includes an AND gate G1 and an OR gate G2. The AND gate G1 has an inverting input terminal and a non-inverting input terminal, and the OR gate G2 has a pair of non-inverting input terminals (hereinafter simply referred to as “input terminals”). The inverting input terminal of the AND gate G1 and one input terminal of the OR gate G2 are commonly connected to the output terminal of the power supply control IC 25, and the input terminal of the AND gate G1 and the other input terminal of the OR gate G2 are connected to the photocoupler. It is connected to the selection signal output terminal of the charge overall control circuit 40 via P2 (see FIG. 5).

  The charge overall control circuit 40 outputs a standby signal and a selection signal that are binary signals of “HIGH” and “LOW” to each individual charging circuit 21. The selection signal output terminal for outputting the selection signal in the charge control circuit 40 is connected to the logic circuit 26 via the photocoupler P2 as described above. On the other hand, the standby signal output terminal for outputting the standby signal in the charge control circuit 40 is connected to the power supply control IC 25 via the photocoupler P1.

  When the standby signal output from the charge control circuit 40 becomes “LOW”, the power supply control IC 25 switches the output to the logic circuit 26 alternately between “LOW” and “HIGH”. At this time, if the selection signal is “LOW”, the output of the AND gate G1 is held at “LOW”, and the output of the OR gate G2 is switched between “LOW” and “HIGH”. As a result, the second switch 22 is held ON, the first switch 23 is alternately switched between ON and OFF, and the individual charging circuit 21 is switched to the high potential side charging circuit according to the present invention shown in FIG. 41 (see FIG. 6A), the high potential side cell B50 is charged with the power of the cell B49. The high potential side charging circuit 41 will be described later together with the low potential side charging circuit 42 described below.

  On the other hand, when the standby signal is “LOW” and the selection signal is “HIGH”, the output of the OR gate G2 is held at “HIGH”, and the output of the AND gate G1 is switched between “LOW” and “HIGH”. As a result, the first switch 23 is held ON, the second switch 22 is alternately switched between ON and OFF, and the individual charging circuit 21 is switched to the low potential side charging circuit 42 according to the present invention shown in FIG. Then, the low potential side cell B48 is charged with the power of the cell B49.

  In addition, when the standby signal is set to “HIGH”, the charge overall control circuit 40 sets the selection signal to “LOW”. When the standby signal becomes “HIGH”, the power supply control IC 25 holds the output to the logic circuit 26 at “LOW”, and the logic circuit 26 is set to “LOW” from both the power supply control IC 25 and the charge control circuit 40. You will receive a signal. As a result, the outputs of the AND gate G1 and the OR gate G2 both become “LOW”, the first and second switches 22 and 23 are both turned off, and the boosting coil L1 and the like are disconnected from the cell B49.

  That is, when the charging control circuit 40 sets the standby signal to “HIGH” and the selection signal is “LOW”, it means that the standby command for prohibiting charging is given to the individual charging circuit 21, and the charging control circuit 40 waits. When the signal is “LOW” and the selection signal is “LOW”, a high-potential side cell charge command for instructing charging of the high-potential side cell B50 is given to the individual charging circuit 21, and further, charge control When the control circuit 40 sets the standby signal to “LOW” and the selection signal to “HIGH”, it means that the low-potential side cell charging command for instructing charging to the low-potential side cell B48 is given to the individual charging circuit 21.

  The individual charging circuit 21 that has received the high-potential side cell charging command from the charging overall control circuit 40 becomes the high-potential side charging circuit 41 of FIG. The high-potential side charging circuit 41 is shown schematically in FIG. 6B, and is a step-up DC-DC converter that operates as follows. That is, when the first switch 23 is turned on, a current flows from the cell B49 to the boosting coil L1, and the current gradually increases due to the inductance of the boosting coil L1. Then, before the current flowing through the boosting coil L1 is saturated, the first switch 23 is turned off, and a large current suddenly flows into the boosting coil L1 due to electromagnetic induction, and the output voltage of the cell B49 is applied to both ends of the boosting coil L1. A higher induced voltage is generated, and a current flows through a closed circuit including the boosting coil L1, the first diode D1, and the high potential side cell B50 by the induced voltage. By repeating this operation, the individual charging circuit 21 (high potential side charging circuit 41) charges the high potential side cell B50 using the cell B49 as a power source.

  The above-described ON / OFF control of the first switch 23 is performed by the power supply control IC 25. Here, a common reference voltage which is a substitute value of the reference power supply current according to the present invention is set in the power supply control ICs 25 of all the individual charging circuits 21. Then, the power supply control IC 25 takes in the voltage between both terminals of the resistor R1 as a substitute value of the current flowing out from the cell B49, obtains a deviation from the reference voltage, and based on the deviation, the ON / OFF DUTY ratio of the first switch 23 (For example, ON DUTY ratio) is changed, and feedback control is performed so that the current from the cell B49 becomes the reference power supply current.

  The individual charging circuit 21 that has received the low-potential side cell charging command from the charging overall control circuit 40 becomes the low-potential side charging circuit 42 of FIG. The low potential side charging circuit 42 is also a step-up DC-DC converter (see FIG. 7B), operates in the same manner as the above-described high potential side charging circuit 41, and uses the cell B49 as a power source. The potential side cell B48 is charged. That is, according to the configuration of the present embodiment, the power supply control IC 25 can control the high-potential side charging circuit 41 and the low-potential side charging circuit 42 without distinction.

  As described above, the individual charging circuit 21 corresponding to the cell B at the end on the high potential side of the battery pack 11 (see FIG. 2) only needs to charge the cell B adjacent on the low potential side. 4 to eliminate the first diode D1, the first switch 23, and the OR gate G2, and the individual charging circuit 21 corresponding to the cell B at the end of the battery pack 11 on the low potential side. Since only the cell B adjacent to the high potential side needs to be charged, the second diode D2, the second switch 22, and the AND gate G1 are excluded from the individual charging circuit 21 shown in FIG.

  The charge overall control circuit 40 repeatedly executes a potential difference detection process (not shown) at a predetermined cycle (for example, 10 [msec]), and each cell B adjacent to each other among the plurality of cells B of the battery pack 11 (see FIG. 2). The output voltage difference between the two is obtained, and compared with a predetermined allowable voltage difference, a pair of cells B in which the output voltage difference exceeds the allowable voltage difference and is adjacent (hereinafter referred to as “charge / discharge pair”). Identify. Then, a high potential side cell charge command or a low potential side cell charge command is given to the individual charge circuit 21 that uses the cell B having a high output voltage as a power source among the charge / discharge pairs required to make the individual charge circuit 21 a high potential. The battery B is operated as the side charging circuit 41 or the low potential side charging circuit 42, and the cell B having the low output voltage is charged in the charge / discharge pair. Further, as a result of the charging, if the output voltage difference between both cells B of the charge / discharge pair becomes smaller than the allowable voltage difference (that is, the output voltages of both cells B of the charge / discharge pair required are the same within the allowable voltage difference range). Then, the charging overall control circuit 40 gives a standby command to the individual charging circuit 21 to stop the charging. Thereby, the output voltage of a pair of cells B, which is a charge / discharge pair, is brought close to the average of the output voltages of both the cells B.

  In addition, when the above-described processing is performed, for example, when the cell B49 charges the low potential side cell B48, the output voltage difference between the cell B49 and the high potential side cell B50 exceeds the allowable voltage difference. Then, the cell B49 is charged by the power of the high potential side cell B50, and as a result, the output voltage difference between the high potential side cell B50 and the adjacent cell B51 on the high potential side becomes an allowable voltage difference. When it exceeds, cell B50 will be charged with the electric power of cell B51. Thus, the plurality of cells B may be charged and discharged in conjunction with each other, and as a result, the output voltage of the entire cell B of the battery pack 11 is made uniform.

  In addition, the charge control circuit 40 includes a first cell B (cell B close to an overdischarge state) having an abnormally low output voltage among a plurality of cells B and a second cell B (excessive voltage) having an abnormally high output voltage. All of the cells corresponding to the first, second, and third cells B are detected when the cell B) close to the charged state is detected with the third cell B having a normal output voltage sandwiched between them. The high potential side charging circuit 41 or all of the low potential side charging circuits 42 are simultaneously operated to relay power from the second cell B to the first cell B through the third cell B. Thereby, the 1st cell B near an overdischarge state and the 2nd cell B near an overcharge state can be immediately returned to a normal state. At this time, all the power supply control ICs 25 of the high-potential side charging circuit 41 or the low-potential side charging circuit 42 control the current flowing out from the cell B serving as the power source to be a constant reference power supply current. The variation in the output voltage of the third cell B is suppressed by the relay.

  As described above, in the voltage balance device 20 according to the present embodiment, the power of the cell B having a relatively high output voltage is supplemented to the cell B having a low output voltage to equalize the output voltages of the plurality of cells B. Compared to the above, wasteful power consumption associated with equalizing the output voltage of the cell B group can be suppressed. In addition, since the high potential side charging circuit 41 and the low potential side charging circuit 42 are step-up DC-DC converters, charging can be performed with small components more efficiently than those in which power is converted by a transformer. Furthermore, since the boosting coil L1, the power supply control IC 25, and the logic circuit 26 are shared between the high potential side charging circuit 41 and the low potential side charging circuit 42, the cost and size of the voltage balance device 20 can be reduced. Moreover, since the high potential side charging circuit 41 and the low potential side charging circuit 42 are controlled so that the current flowing out from the cell B serving as the power source becomes a constant reference power source current, charging is performed from the cell B to be charged. This prevents a situation where an excessive current flows into the cell B. Further, since the reference power supply current is common between the plurality of high potential side charging circuits 41 and the plurality of low potential side charging circuits 42, charging is performed so that power is sequentially delivered to the plurality of cells B. be able to.

[Other Embodiments]
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.

(1) In the voltage balance device 20 of the above embodiment, the high potential side charging circuit 41 and the low potential side charging circuit 42 share the boosting coil L1, the resistor R1, the power supply control IC 25, etc. The charging circuit 41 and the low potential side charging circuit 42 may be separately provided.

(2) The voltage balance device 20 has been used to protect the secondary battery group (cell B group) mounted on the vehicle, but is not limited thereto, for example, for home appliances and medical devices. You may use for protection of the secondary battery group provided.

(3) In the embodiment, one cell B is used as one secondary battery according to the present invention, and the individual charging circuit 21 is provided for each secondary battery. However, a plurality of cells B are connected in parallel or in series. A cell group formed by connecting the cells may be provided as a single secondary battery according to the present invention, and an individual charging circuit 21 may be provided for each secondary battery.

DESCRIPTION OF SYMBOLS 10 Battery 20 Voltage balance apparatus 22 2nd switch 23 1st switch 25 Power supply control IC (1st switch control part, 2nd switch control part)
26 Logic circuit (first switch control unit, second switch control unit)
40 charging control circuit 41 high potential side charging circuit 42 low potential side charging circuit B cell (secondary battery)
D1 1st diode D2 2nd diode L1 Boosting coil

Claims (6)

It is provided corresponding to each of a plurality of secondary batteries connected in series, and the secondary battery adjacent to the high potential side of the secondary battery can be charged using the corresponding secondary battery as a power source. A plurality of high potential side charging circuits;
A plurality of low batteries provided corresponding to each of the plurality of secondary batteries and capable of charging a secondary battery adjacent to the low potential side of the secondary battery using the corresponding secondary battery as a power source. A potential side charging circuit;
When the output voltages of adjacent secondary batteries are different, the high-potential side charging circuit or the low-potential side charging circuit using the secondary battery having a high output voltage as the power source among the adjacent secondary batteries is operated. And a charge control circuit for charging the secondary battery having a low output voltage. The high potential side charging circuit includes:
Connected between the negative electrode of the secondary battery serving as the power source and the positive electrode of a high potential side secondary battery that is the secondary battery adjacent to the high potential side, and the first from the negative electrode side of the secondary battery A first switch coil circuit in which a switch element and a first diode are arranged in series in order and an anode of the first diode is disposed on the first switch element side; an anode of the first diode; A step-up DC-DC converter having a step-up coil connected between a negative electrode of a secondary battery and a first switch control unit for turning on and off the first switch element;
The low potential side charging circuit is:
Connected between the positive electrode of the secondary battery serving as the power source and the negative electrode of the low-potential side secondary battery, which is the secondary battery adjacent to the low-potential side, and second from the positive electrode side of the secondary battery. A second switch coil circuit in which a switch element and a second diode are arranged in series in order, and a cathode of the second diode is arranged on the second switch element side; a cathode of the second diode; 2. The voltage balance device according to claim 1, wherein the voltage balance device is a step-up DC-DC converter having a step-up coil connected between a positive electrode of a secondary battery and a second switch control unit that turns on and off the second switch element. . The high-potential side charging circuit and the low-potential side charging circuit shared by the secondary battery serving as a power source are connected between a positive electrode and a negative electrode of the secondary battery and are connected to the first switch from the negative electrode side. Sharing a double switch coil circuit in which the element, the step-up coil and the second switch element are arranged in series,
The first diode has an anode connected to a common connection portion between the first switch element and the boosting coil, and a cathode connected to a positive electrode of the high potential side secondary battery,
The second diode has a cathode connected to a common connection portion between the second switch element and the boosting coil, and an anode connected to a negative electrode of the low potential side secondary battery,
When the second switch element is turned off and the first switch element is turned on and off, the low potential side charging circuit is stopped and the high potential side charging circuit is operated. When the first switch element is turned off and the 3. The voltage balance device according to claim 2, wherein the low potential side charging circuit operates while the high potential side charging circuit is stopped by turning on and off the second switch element. A common reference power supply current is preset in the plurality of high potential side charging circuits and the plurality of low potential side charging circuits, and a current flowing out from the secondary battery serving as the power supply is the reference power supply. Current control means for controlling to become current is provided,
The current control means includes: a current detection resistor provided in a closed circuit including the secondary battery serving as the power source and the boosting coil; and the first switch control unit and the second switch control unit. Become
The first switch control unit and the second switch control unit have a reference voltage that is a substitute value of the reference power supply current and a terminal voltage of the current detection resistor that is a substitute value of the current from the secondary battery. 4. The voltage balance device according to claim 3, wherein the ON / OFF DUTY ratio of the first switch element is changed on the basis of the deviation of the first switch element and feedback control is performed so that a current from the secondary battery becomes the reference power supply current.   A current that controls the plurality of high-potential side charging circuits and the plurality of low-potential side charging circuits so that the current flowing out of the secondary battery serving as the power source becomes a predetermined common reference power source current. The voltage balance apparatus according to claim 1, further comprising a control unit.   The charge control circuit includes a normal output voltage between the first secondary battery having an abnormally low output voltage and the second secondary battery having an abnormally high output voltage among the plurality of secondary batteries. When the third secondary battery is present, all the high potential side charging circuits or all the low potential side charging circuits corresponding to the first, second, and third secondary batteries are operated simultaneously. And transferring the power from the second secondary battery to the first secondary battery via the third secondary battery to charge the first secondary battery. The voltage balance apparatus as described.

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