JP2008123868A - Cell voltage balancing device of secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To quickly equalize the voltages of single cells. <P>SOLUTION: In the cell voltage balancing device of a secondary battery for equalizing the cell voltages of respective single cells 1a by connecting a current path CP with resistors 3a and 3c in parallel with each of the respective single cells 1a and making a current flow to the current path CP, a current control means CC for controlling the size of the current to be made to flow to the current path CP is provided. When the voltage of the single cell 1a is elevated to be equal to or higher than a balance operation start voltage set at a voltage value lower than a charging target voltage, the current control means CC executes control for each single cell 1a so that the current made to flow to the current path CP connected in parallel with the single cell 1a may increase as the difference between the voltage of the single cell 1a and the balance operation start voltage is large, according to the difference. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an assembled battery configured by connecting a plurality of single cells in series, and a current path having a resistance is connected in parallel to each of the single cells, and each unit is configured to flow a current through the current path. The present invention relates to a cell voltage balance device for a secondary battery that equalizes the battery voltage of the battery.

When an assembled battery composed of a plurality of single cells is incorporated into a device, etc., and charged or discharged from the assembled battery, charging and discharging are performed simultaneously due to variations in the characteristics of the individual cells constituting the assembled battery. However, there are many cases where the battery characteristics such as battery voltage and internal resistance vary among the single cells due to differences in the degree of progress and deterioration of charging.
If such a variation in voltage between the single cells is left unattended, some single cells are burdened and deterioration is promoted. Therefore, as described in Patent Document 1 below, It is considered to provide a device for equalizing the voltage to suppress voltage variation between the single cells.
Various circuit configurations for equalizing the voltage of each unit cell are conceivable, but a pair of a resistor and a switch device connected in series as described in Patent Document 1 below is parallel to each unit cell. Those having a circuit configuration to be connected to are well known.
As a usage pattern of a pair of a resistor and a switch device connected in parallel with the unit cell, as described in Patent Document 1 below, when the variation between the unit cells is large, A method has been considered in which the device is switched to a closed state so that the charging current is bypassed and the cell is discharged through a pair of a resistor and a switch device.
JP-A-10-0050352

However, in the above-described conventional configuration, by equalizing the voltage of each unit cell, the resistance value of the resistor connected in parallel with each unit cell can be reduced to release a lot of current. It seems like, but in fact it doesn't go that way.
The reason for this will be briefly described with reference to FIG. 7 schematically showing the voltage change of the cell when discharging from the cell to the resistor connected in parallel with the cell.
When the current value of the current released to the resistor is set to be large, the voltage of the single cell rapidly decreases toward the target voltage for voltage equalization with the start of energization of the resistor (FIGS. 7A and 7B). )).

When the cell voltage drops to the target voltage for voltage equalization, the energization to the resistor is stopped, but when the cell voltage is rapidly reduced in this way, the energization to the resistor is stopped. However, the voltage of the single cell does not stabilize at the current voltage.
That is, even if the current supply to the resistor is stopped, the chemical reaction proceeds inside the unit cell, and the voltage of the unit cell greatly increases as shown in FIG.
As the voltage of the unit cell rises, energization to the resistor is resumed in order to reduce the voltage of the unit cell. Henceforth, the unit cell voltage decreases due to the energization of the resistor and the energization of the unit is stopped. The voltage rise is repeated, and the voltage of the unit cell rises and falls in a vibrating state.
Therefore, the current value of the current that escapes to the resistor is set to a large value so that the equalization of the voltage of the single cell proceeds rapidly, but the voltage of the single cell is changed oscillatingly so that it is not stable. It ends up.
On the other hand, if the current value of the current that escapes to the resistor connected in parallel with the unit cell is set to a small value, the above-described vibrational change in the unit cell voltage can be suppressed, but the unit cell voltage decreases. Since the speed itself is slow, voltage equalization is delayed.
The present invention has been made in view of such circumstances, and an object of the present invention is to make it possible to more quickly equalize the voltages of the unit cells.

  In the first invention of the present application, a current path having a resistance is connected in parallel to each of the unit cells, and a current is supplied to the current path with respect to the assembled battery configured by connecting a plurality of unit cells in series. In the cell voltage balance device of the secondary battery that equalizes the battery voltage of each single battery by flowing, a current control means for controlling the magnitude of the current flowing through the current path is provided, and the current control means includes the single battery When the voltage of the battery rises above the balance operation start voltage set to a voltage value lower than the charge target voltage, the difference is large depending on the difference between the voltage of the single cell and the balance operation start voltage. The unit is configured to control each unit cell so that the current flowing through the current path connected in parallel with the unit cell increases.

That is, when the battery voltage of any single battery constituting the assembled battery becomes equal to or higher than the balance operation start voltage, the current is released to the current path connected in parallel with the single battery.
At this time, the current value of the current flowing through the current path increases as the degree to which the voltage of the single cell exceeds the balance operation start voltage is increased.
Therefore, in the case where the cells are discharged and equalized, when the voltage of the cells is far from the balance operation start voltage, the voltage of the cells decreases to the balance operation start voltage at a high speed. When the voltage of the battery approaches the balance operation start voltage, the speed at which the voltage of the cell decreases is slowed down and gradually toward the balance operation start voltage.
As a result, even if energization to the current path is stopped near the balance operation start voltage, the subsequent voltage increase of the unit cell can be sufficiently suppressed.

According to a second aspect of the present application, in addition to the configuration of the first aspect of the invention, the current path is composed of a plurality of resistors, and energization of the plurality of resistors is individually performed. A switch device is provided in the current path, and the current control means is configured to control opening and closing of the switch device.
That is, according to the difference between the voltage of the unit cell and the balance operation start voltage, the larger the difference, the larger the current flowing through the current path connected in parallel with the unit cell. As a configuration for controlling, energization is individually turned on and off for a plurality of resistors provided in the current path, and a substantial resistance value of the current path is changed in a plurality of stages.

According to a third invention of the present application, in addition to the configuration of the first invention, the current control means outputs an analog corresponding to a difference between the voltage of the unit cell and the balance operation start voltage. An arithmetic circuit and a voltage-current conversion circuit that controls the current corresponding to the output voltage of the analog arithmetic circuit to flow through the resistor in the current path are configured.
That is, according to the difference between the voltage of the unit cell and the balance operation start voltage, the larger the difference, the larger the current flowing through the current path connected in parallel with the unit cell. As a configuration for controlling, a voltage-current conversion circuit is provided, a current value to be released to the current path is set by voltage control, and a voltage for instructing the current value to the voltage-current conversion circuit is simply set. A voltage corresponding to the difference between the battery voltage and the balance operation start voltage is generated by an analog arithmetic circuit.
Therefore, the current flowing through the current path changes linearly and continuously with respect to the difference between the voltage of the unit cell and the balance operation start voltage.

According to the first aspect of the invention, when the voltage of the unit cell is far from the balance operation start voltage, the voltage of the unit cell is rapidly reduced to the balance operation start voltage, and the balance operation start voltage is reduced. Even if it approaches and stops the energization to the said current path, the subsequent voltage rise of the cell can be suppressed sufficiently.
As a result, the voltage of the unit cells can be equalized more quickly by letting the current flow to the current path.
According to the second aspect of the invention, since the plurality of resistors provided in the current path are individually turned on and off, and the substantial resistance value of the current path is changed in a plurality of stages. Quick voltage equalization can be achieved with a simple configuration.
According to the third aspect of the invention, the current flowing through the current path changes linearly and continuously with respect to the difference between the voltage of the unit cell and the balance operation start voltage. As compared with the configuration in which the resistance value of the resistor connected to the switch is controlled in a stepwise manner, it is possible to further suppress the variation in voltage of each unit cell.

That is, in the method of switching the resistance value of the resistor connected in parallel with the unit cell in a stepwise manner, even if the resistance value is set to the same value, the internal resistance varies somewhat for each unit cell. The current value of the current flowing through the subtle varies. This variation in the current value is the cause that the finally stable battery voltage varies among the single cells even when the voltage of the single cells approaches the balance operation start voltage and becomes a low current value. It becomes.
On the other hand, by adopting a circuit configuration in which the current flowing through the current path is set based on the difference between the voltage of the unit cell and the balance operation start voltage, it is affected by variations in the internal resistance of each unit cell. Therefore, the current value of the current flowing through the current path is set, and the current value changes linearly and continuously with respect to the difference between the voltage of the unit cell and the balance operation start voltage. Thus, variations in voltage between the single cells are suppressed with extremely high accuracy.

Hereinafter, the case where the embodiment of the cell voltage balance device of the secondary battery of the present invention is provided as a part of a charging device of a lithium ion battery which is an example of a secondary battery will be described based on the drawings.
<First Embodiment>
As shown in FIG. 1, a lithium ion battery 1 to be charged in the first embodiment is configured as a battery pack by connecting a plurality of single cells 1a in series. The charging device BC for charging includes a charging power source 2 that supplies a charging current to the lithium ion battery 1 and a cell voltage balance device 3.
The charging device BC of the first embodiment is assumed to be mounted on a mobile object such as an aircraft or an automobile together with the lithium ion battery 1 to be charged, and supply a large current to a power device or the like of the mobile object. Although the number of unit cells 1a constituting the lithium ion battery 1 is larger than that shown in FIG. 1, it is assumed that the number of unit cells 1a is four for convenience of explanation.
In the first embodiment, the unit cell 1a may be appropriately expressed as “cell” in the drawings and the like.

In the cell voltage balance device 3, a pair of a resistor 3a and a switch device 3b that are connected in series and a pair of a resistor 3c and a switch device 3d that are also connected in series are connected in parallel to each of the unit cells 1a. A current path CP having resistors 3a and 3c is connected in parallel with each of the single cells 1a.
The circuit portion corresponding to each unit cell 1a of the cell voltage balance device 3 is further provided with a control circuit 3e for controlling opening / closing (ON / OFF) of the switch devices 3b and 3d.
The switch devices 3b and 3d are composed of bipolar transistors.
The control circuit 3e controls the opening and closing of the switch devices 3b and 3d and causes the current to flow through the current path CP, thereby equalizing the battery voltage of each unit cell 1a.

In the first embodiment, the resistor 3a is set to 75Ω, the resistor 3c is set to 22Ω, and the resistors 3a and 3c having different resistance values are used.
In this way, the resistance provided in the current path CP is constituted by a plurality of resistors 3a and 3c, and the current path CP is provided with switch devices 3b and 3d for individually turning on and off the plurality of resistors 3a and 3c. The switch devices 3b and 3d are appropriately switched to open and close to switch the effective impedance of the current path CP.

  Regarding the effective impedance switching in the current path CP, for convenience, when both the switch devices 3b and 3d are closed (on state) and both the resistors 3a and 3c are energized, “mode 1”, the switch device 3b is in the open state (off state), the switch device 3d is in the closed state (on state), and only the resistor 3c is energized without energizing the resistor 3a is “mode 2”, and the switch device 3b is in the closed state (on) State), the switch device 3d is in the open state (off state), the case where only the resistor 3a is energized and the resistor 3c is not energized is "mode 3", and both the switch devices 3b and 3d are in the open state (off state) The case where the resistors 3a and 3c are not energized will be described as “mode 4”.

  Assuming that the voltage of the unit cell 1a is 4.0 V, the current path CP is 262 mA in the “mode 1”, the current path CP is 182 mA in the “mode 2”, and the current path CP is “mode 3”. In 53 mA, “mode 4”, a current of 0 mA flows in the current path CP, and the current supplied from the charging power source 2 or the discharge current from the unit cell 1 a is released to the current path CP.

The control circuit 3e switches on and off the switching devices 3b and 3d as described above, and sets them to “mode 1”, “mode 2”, “mode 3” and “mode 4” as shown in FIG. It has a circuit.
The control circuit 3e shown in FIG. 2 is an extracted control circuit 3e corresponding to one single cell 1a, and in order to make the connection state of the circuit easy to understand, the single cell 1a, resistors 3a and 3c, and a switch device 3b and 3d are also illustrated.

The control circuit 3e switches between the above four modes according to the voltage of the unit cell 1a.
Specifically, the control circuit 3e sets “mode 4” when the voltage (cell voltage) of the unit cell 1a indicated by the vertical axis in FIG. The switch devices 3b and 3d are controlled to be opened and closed so that “3” is set to “mode 2” when “Vm” or more and less than “Vt”, and “mode 1” is set to “Vt” or more.
Here, Vt>Vm>Vb> 0, “Vt” is a charging target voltage of each unit cell 1a by the charging device BC, and “Vb” is set to a voltage lower than the charging target voltage. This is the balance operation start voltage.
Here, “Vm” is set at an intermediate position between “Vb” and “Vt”.
As a specific numerical example, “Vt” can be set to 4.025V, “Vm” can be set to 4.013V, and “Vb” can be set to 4.0000V.

The control circuit 3e includes a Zener diode 41 that outputs a reference voltage corresponding to “Vb”, a Zener diode 42 that outputs a reference voltage corresponding to “Vm”, and a Zener that outputs a reference voltage corresponding to “Vt”. The diode 43 is provided, and the reference voltage output from the Zener diodes 41, 42, 43 and the voltage (cell voltage) of the unit cell 1a are compared by the comparators 44, 45, 46, 47, The above modes are switched according to the output of the comparison result.
As a power source for generating these reference voltages, a voltage of, for example, 15 V is separately supplied from a pair of terminals T1 and T2.

In the case of switching the mode as described above, the switch device 3d is in the closed state (ON state) in “mode 1” and “mode 2”, and in the open state (OFF state) in “mode 3” and “mode 4”. Therefore, only the comparison with the voltage “Vm” is sufficient, and the switch device 3d is output by the output of the comparator 47 that compares the output of the Zener diode 42 that outputs the reference voltage corresponding to “Vm” with the voltage (cell voltage) of the unit cell 1a. Is driving directly.
On the other hand, when the switch device 3b sequentially shifts from “mode 1” to “mode 4” or vice versa, the switch device 3b is alternately switched between a closed state (on state) and an open state (off state).

In order to perform such a switching operation, the output of the comparator 44 that compares the output of the Zener diode 41 that outputs the reference voltage corresponding to “Vb” and the voltage (cell voltage) of the unit cell 1a, and “Vm” The output of the Zener diode 42 that outputs the corresponding reference voltage and the output of the comparator 45 that compares the voltage (cell voltage) of the unit cell 1a are input to the exclusive OR gate 48 and further correspond to “Vt”. The output of the comparator 46 that compares the output of the Zener diode 43 that outputs the reference voltage to the voltage of the single cell 1a (cell voltage) and the output of the exclusive OR gate 48 are input to the OR gate 49, The switch device 3b is driven by the output of the OR gate 49.
In FIG. 2, the logical value “1” is made to correspond to the H level, and the exclusive OR gate 48 outputs “1” only in the voltage range of “mode 3”, and the comparator 46 is in “mode 1”. The switch device 3b that outputs “1” only in the voltage range and is driven by the OR of the OR gate 49 is in the closed state (ON state) in the “mode 1” and “mode 3” voltage ranges. )

With the circuit operation as described above, each control circuit 3e opens both of the switch devices 3b and 3d when the voltage of the corresponding cell 1a is less than 4.000V (mode 4), 4.000V or more. If it is less than 4.013V, the switch device 3b is closed and the switch device 3d is opened (mode 3). If it is 4.013V or more and less than 4.025V, the switch device 3b is open and the switch device 3d is closed (mode 2), and if it is 4.025 V or higher, both switch devices 3b and 3d are closed (mode 1).
Thereby, the control circuit 3e which is the current control means CC controls the opening and closing of the switch devices 3b and 3d, and the voltage of the unit cell 1a is set to a voltage value lower than “Vt” (charge target voltage). When the voltage rises above “Vb” (balance operation start voltage), the larger the difference between the voltage of the cell 1 a and “Vb” (balance operation start voltage), the more the cell 1 a The magnitude of the current flowing through the current path CP is controlled for each unit cell 1a so that the current flowing through the current path CP connected in parallel is increased.

For example, when a new lithium ion battery 1 is incorporated in the charging device BC and the voltage of each unit cell 1a is in the state shown in FIG. 3, the current from the charging power source 2 is not supplied. The current in the current path CP connected in parallel to each unit cell 1a is in the state shown in FIG.
Four unit cells 1a connected in series are expressed as “# 1”, “# 2”, “# 3”, “# 4” from the higher voltage side, and are “Vm” or more and less than “Vt” The “# 1” unit cell 1a becomes “mode 2” and the current flows through the resistor 3c, and the “# 2” unit cell 1a which is “Vt” or more becomes “mode 1”. The current flows through both the resistors 3a and 3c, and the cell # 1 of “# 3” that is equal to or higher than “Vb” and lower than “Vm” becomes “mode 3” and the current flows through the resistor 3a. The unit cell 1a of “# 4” that is less than “Vb” is in “mode 4” and is not energized in any of the resistors 3a and 3c.
In FIG. 4, in order to display the setting state of the switch devices 3b and 3d in an easy-to-see manner, the open / closed state is indicated by a general switch symbol.

By controlling the current flowing through the current path CP in this way, the larger the difference between the voltage of the unit cell 1a and the balance operation start voltage, the greater the current discharged from the unit cell 1a, or from the charging power source 2. The greater the difference between the voltage of the single cell 1a and the balance operation start voltage is, the larger the current that releases the supply current to the current path CP without passing through the single cell 1a, the more the voltage of the single cell 1a becomes the balance operation start voltage. The rate of approaching or the degree to which the voltage rise of the unit cell 1a is suppressed increases.
Thereby, the voltage of each unit cell 1a is equalized efficiently.

<Second Embodiment>
The lithium ion battery 1 to be charged in the second embodiment is the same as that in the first embodiment, and as shown in FIG. 5, a plurality of unit cells 1a are connected in series to form an assembled battery. Has been.
Similarly to the first embodiment, the charging device BC for charging the lithium ion battery 1 includes a charging power source 2 that supplies a charging current to the lithium ion battery 1 and a cell voltage balance device 3. It is.
The charging device BC of the second embodiment is also assumed to be mounted on a mobile object such as an aircraft or an automobile together with the lithium-ion battery 1 to be charged, and supply a large current to the power equipment of the mobile object. In this embodiment, the number of single cells 1a is assumed to be four for convenience of explanation.

In the cell voltage balance device 3 of the present embodiment, a voltage equalizing circuit 10 having a function corresponding to the resistors 3a and 3c, the switch devices 3b and 3d, and the control circuit 3e in the first embodiment is provided for each unit cell 1a. It has been.
The circuit configuration of the voltage equalization circuit 10 corresponding to each unit cell 1a is the same, and is configured by the circuit shown in FIG.

In the voltage equalization circuit 10 shown in FIG. 6, a current path CP including resistors 11 and 12 and a bipolar transistor 13 is connected in parallel with the unit cell 1a, and the current flowing through the current path CP is controlled. For this purpose, an analog arithmetic circuit 14 and a voltage-current conversion circuit 15 are provided.
Under the control of the analog arithmetic circuit 14 and the voltage-current conversion circuit 15, the battery voltage of each unit cell 1a is equalized by passing a current through the current path CP.

The analog arithmetic circuit 14 is a circuit that outputs a voltage corresponding to the difference between the voltage of the unit cell 1a and the balance operation start voltage similar to that of the first embodiment, and includes resistors 21, 22, 23, and 24, an operational amplifier 25, and the like. Constitutes a differential amplifier.
One voltage of the two inputs of the analog arithmetic circuit 14 is input from the connection point of the series-connected resistors 26 and 27, and the other voltage is input from the connection point of the series-connected resistor 28 and the Zener diode 29. The

As for the ratio of the resistance values of the resistor 26 and the resistor 27, if the balance operation start voltage is set to 4.000 V as in the first embodiment, the voltage across the resistor 26 and the resistor 27 connected in series is 4. When the voltage is 0 V, the voltage across the resistor 27 input to the operational amplifier 25 is set to match the reference voltage output from the Zener diode 29.
Therefore, the output voltage of the analog arithmetic circuit 14 (the output voltage of the operational amplifier 25) is a set multiple (resistors 21, 22, 23, 24, 26, 27) of the difference between the voltage of the unit cell 1a and the balance operation start voltage. When the voltage of the unit cell 1a is 4.0V, the output voltage of the analog arithmetic circuit 14 is 0V.

The voltage-current conversion circuit 15 includes an operational amplifier 31 and an FET type transistor 32.
The feedback circuit is configured so that the voltage generated by the resistor 12 is input to the inverting input of the operational amplifier 31, and the operational amplifier 31 has both the output voltage of the analog arithmetic circuit 14 (the output voltage of the operational amplifier 25) and both ends of the resistor 12. The transistors 32 and 13 are controlled so that the voltages match.
Therefore, the voltage corresponding to the output voltage of the analog arithmetic circuit 14 is controlled to flow through the resistors 11 and 12 of the current path CP.

In summary, when the voltage of the cell 1a is “Vc” and the balance operation start voltage is “Vb”, the current “I” flowing through the resistors 11 and 12 of the current path CP is I = β × (Vc− Vb). Here, “β” is a proportionality coefficient.
For example, when the resistance values of the resistors 12, 21, 22, 23, 24, 26, and 27 are determined so that β = 1.3 under the condition of Vb = 4.0000V, Vc = 4.0V, 4 When .05V, 4.10V, 4.15V, and 4.20V, the current values flowing in the current path CP are I = 0 mA, 65.0 mA, 130 mA, 195 mA, and 260 mA, respectively.

  This is because the voltage of the unit cell 1a is lower than the charging target voltage ("Vt": the same as in the first embodiment) in the current control means CC configured to include the analog arithmetic circuit 14 and the voltage-current conversion circuit 15. When the voltage rises to a value equal to or higher than the balance operation start voltage (“Vb”) set in the voltage value, the difference between the voltage of the single cell 1a and the balance operation start voltage increases as the difference increases. Control is performed for each unit cell 1a so that the current flowing through the current path CP connected in parallel with the battery 1a becomes large.

As in the first embodiment, the current flowing through the current path CP is controlled in this way, so that the larger the difference between the voltage of the unit cell 1a and the balance operation start voltage, the greater the discharge from the unit cell 1a. The larger the difference between the voltage of the unit cell 1a and the balance operation start voltage is, the larger the current or the current that releases the supply current from the charging power source 2 to the current path CP without passing through the unit cell 1a. The speed at which the voltage of 1a approaches the balance operation start voltage, or the degree to which the voltage increase of the unit cell 1a is suppressed increases.
Thereby, the voltage of each unit cell 1a is equalized efficiently.

<Other embodiments>
Hereinafter, other embodiments of the present invention will be listed.
(1) In the first embodiment described above, the effective impedance of the current path CP is switched to a total of four stages by switching energization / non-energization of each of the resistors 3a and 3c connected in parallel, thereby allowing the current path CP to flow. Although the magnitude of the current is controlled, the connection form of the plurality of resistors in the current path CP can be variously changed by combining series connection or parallel connection.
(2) In the first embodiment described above, the effective impedance of the current path CP is switched to a total of four stages by switching the energization / non-energization of the resistors 3a and 3c connected in parallel to flow through the current path CP. Although the magnitude of the current is controlled, the magnitude of the current may be controlled by switching the resistance value in multiple stages using, for example, a digital control potentiometer.

1 is an overall configuration diagram of a circuit according to a first embodiment of the present invention. 1 is a circuit diagram of a main part according to a first embodiment of the present invention. The figure which shows the voltage dispersion | variation of the cell concerning 1st Embodiment of this invention. The figure which shows the state of the electricity supply path | route of the current path concerning 1st Embodiment of this invention. Overall configuration diagram of a circuit according to a second embodiment of the present invention. Main part circuit diagram concerning 2nd Embodiment of this invention Diagram for explaining the state of change when equalizing uniformly with a large current

Explanation of symbols

1 assembled battery 1a single cell 3a, 3c, 11, 12 resistance 3b, 3d switch device 14 analog operation circuit 15 voltage-current conversion circuit CC current control means CP current path

Claims (3)

With respect to an assembled battery configured by connecting a plurality of single cells in series, a current path having resistance is connected in parallel with each of the single cells, and a current is passed through the current path, whereby the battery voltage of each single cell is A cell voltage balancing device for a secondary battery that equalizes
Current control means for controlling the magnitude of the current flowing in the current path is provided;
The current control means is configured such that when the voltage of the unit cell rises above the balance operation start voltage set to a voltage value lower than the charge target voltage, the difference between the unit cell voltage and the balance operation start voltage Accordingly, the secondary battery is configured to control each unit cell so that the larger the difference is, the larger the current flowing through the current path connected in parallel with the unit cell is. Battery cell voltage balance device. The current path is composed of a plurality of resistors, and the current path is provided with a switch device for individually turning on and off the plurality of resistors.
2. The cell voltage balance device for a secondary battery according to claim 1, wherein the current control means is configured to control opening and closing of the switch device.   The current control means includes an analog arithmetic circuit that outputs a voltage corresponding to a difference between the voltage of the unit cell and the balance operation start voltage, and a current corresponding to an output voltage of the analog arithmetic circuit is the resistance of the current path. The cell voltage balance apparatus of the secondary battery of Claim 1 comprised including the voltage-current conversion circuit controlled so that it may flow into.

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