JP2008206396A - Balance correcting device for secondary batteries connected in series, and its correcting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a balance correcting device for secondary batteries connected in series that can correct balance in a short time and that has good responsiveness to a sudden load change, and to provide its correcting method. <P>SOLUTION: The balance correcting device includes an inductor L, one end of which is connected to the connection point of two batteries B1, B2 standing at the front and rear positions in a line of the secondary batteries; a first switching element S1, which is connected to the other end of the inductor L and the other end of the battery B1 to form a first closed circuit during "ON" operation; a second switching element S2, which is connected to the other end of the inductor L and the other end of the battery B2 to form a second closed circuit during the "ON" operation; a signal generating circuit 10, which turns on the two switching elements by predetermined cycles complementarily; a reference voltage means, which outputs a reference voltage obtained by equally dividing a summed value of both voltages of the two batteries; and an adjustment means, which is a comparator connected to the connection points and which performs comparison with the reference voltage, returns an output of the comparator to the signal generating circuit, and revises duty ratio in the direction of making a variable amount of the balance correction converge. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a balance correction apparatus for a secondary battery connected in series and a correction method thereof, and more specifically, an improvement of a correction operation that equalizes each voltage for a plurality of secondary batteries connected in series. About.

  In a power source in which a plurality of secondary batteries are connected in series, it is necessary to equalize each voltage from the viewpoint of effective use of power and long life. As a technique for equalizing each voltage, there has been proposed a device and method for balance correction using the property of the induced electromotive force generated by the inductor, as seen in Patent Documents 1 and 2, for example. ing.

  FIG. 1 is a circuit diagram showing a conventional example of a balance correction apparatus for a secondary battery, which is disclosed in Patent Document 2. As shown in FIG. In the balance correction apparatus shown in the figure, two secondary batteries B1 and B2 are connected in series, and one end of an inductor L is connected to a connection point of the batteries B1 and B2. The switching element S1 is connected between the other end (positive terminal) of the battery B1 and the other end of the inductor L, and the switching element S2 is connected between the other end (negative terminal) of the battery B2 and the other end of the inductor L. Is connected.

  The two switching elements S1 and S2 are formed of MOSFETs, and gate drivers D1 and D2 that perform complementary operations are connected to gate terminals. A drive signal is sent from the signal generation circuit 10 to the gate drivers D1 and D2, so that when one switching element is turned on, the other switching element is turned off. .

  The signal generation circuit 10 generates a pulse train (rectangular wave) having a predetermined cycle with a duty ratio of 50% and inputs it to the gate drivers D1 and D2 during the period of executing the balance correction of these two batteries B1 and B2. Thus, the two switching elements S1 and S2 are repeatedly turned on and off in a complementary manner, and the on time and the off time become equal.

  When switching element S1 is on and switching element S2 is off, battery B1, switching element S1, and inductor L are connected to form a closed circuit (referred to as a B1 loop). When switching element S1 is off and switching element S2 is on, the battery B2, the inductor L, and the switching element S2 are connected to form a closed circuit (referred to as a B2 loop).

  When a current circulating in the forward direction flows due to the electromotive force of the battery B1 during the period of the B1 loop, the forward current increases with time at a rate of change of (e1 / Li). Here, e1 is the voltage of the battery B1, and Li is the inductance of the inductor L. Next, when the switching elements S1 and S2 are reversed from the state in which the forward current flows, and switched to the period of the B2 loop, the current flowing in the inductor L at this time is compared with the electromotive force of the battery B2. The reverse direction.

  That is, the current in the forward direction with respect to the electromotive force of the battery B1 during the period of the B1 loop is a current in the reverse direction with respect to the electromotive force of the battery B2 during the period of the B2 loop. This reverse current gradually decreases due to the electromotive force of the battery B2. The rate of change is (e2 / Li), where e2 is the voltage of battery B2.

  Therefore, the current flowing through the inductor L has a sawtooth waveform in synchronization with a rectangular wave with a duty ratio of 50%, and the current increases or decreases with the inclinations (e1 / Li) and (e2 / Li), and is viewed in a unit cycle. Then, since the first half is the portion of the induced electromotive force (counterelectromotive force), the charging time is required, and the latter half is the discharging time for storing energy in the inductor L.

  Here, when the voltage e1 of the battery B1 is higher than the voltage e2 of the battery B2, the charging time is short in the first half of the unit period and the discharging time is long in the second half during the B1 loop period, and conversely, the unit period is in the B2 loop period. The charging time is longer in the first half and the discharging time is shorter in the second half. For this reason, the battery B1 on the higher voltage side is totally discharged, and the battery B2 on the lower voltage side is totally charged.

  That is, the battery B2 is charged with the output of the battery B1, and as a result, the voltage e1 of the battery B1 decreases sequentially, the voltage e2 of the battery B2 increases sequentially, and the voltage e1 and the voltage e2 is equalized.

Japanese Patent No. 3328656 JP 2001-185229 A

  By the way, such a power source using a secondary battery is required to be downsized. However, it is desirable that the capacity is large from the load side. In order to increase the capacity of each battery, the current flowing through the inductor L is increased from the viewpoint of completing the balance correction in a short time. For this reason, the specifications of the inductor L and the switching elements S1 and S2 are increased correspondingly. Since the current capacity corresponding to the increase in current is required, there is a problem that each element becomes large.

  On the other hand, after the balance correction for equalizing the voltage of each battery is completed, the current of the triangular wave flowing through the inductor flows with the positive and negative peaks having the same value. From this aspect, it is advantageous that the inductor L has a large inductance value, but the element becomes large. Further, if the inductance of the inductor L is a large value, a high current peak cannot be obtained, and it takes time to correct the balance.

  In addition, the balance correction is required not only to be completed efficiently and in a short time, but also to increase the response performance against a sudden change in load. In this way, there are conflicting problems. Conventionally, the priority issues are solved according to the purpose of use, and other adverse effects are sacrificed to some extent.

  SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems, and its object is to reduce the size of each element by restricting the current flowing through the inductor to a predetermined value, and to perform the balance correction operation in a short time and efficiently. Another object of the present invention is to provide a balance correction device for a series-connected secondary battery having good response performance against a sudden load change and a correction method thereof.

  A balance correction device for secondary batteries connected in series equalizes each voltage for a plurality of secondary batteries connected in series, and includes two batteries B1 and B2 that move back and forth in the row of secondary batteries. An inductor L having one end connected to a connection point; a first switching element S1 that is connected to the other end of the inductor L and the other end of the battery B1 to form a first closed circuit during an ON operation; A second switching element S2 that is connected to the other end and the other end of the battery B2 to form a second closed circuit during an on operation, and a signal generation circuit that complementarily turns on the switching elements S1 and S2 in a predetermined cycle Detecting means for detecting a current flowing through the switching elements S1 and S2, and the signal so that the overcurrent is reduced when the detected value of the detecting means is an overcurrent exceeding a predetermined value. And configured to include a limiting means for applying a limit to the operation of the raw circuit.

  Further, the detecting means connects a series element in which a sub-switching element and a resistor for current detection are connected in series to the switching element in parallel, and the sub-switching element is linked with the switching element in a double manner. The limiting means includes a comparator connected to the resistor, detects an overcurrent by comparing with a predetermined reference voltage, and returns the output of the comparator to the signal generation circuit to limit the overcurrent. It is good to have a configuration to do.

  In addition, an inductor L having one end connected to a connection point between two batteries B1 and B2 that are arranged in the row of the secondary batteries, and an ON operation by connecting the other end of the inductor L and the other end of the battery B1. A first switching element S1 that sometimes forms a first closed circuit; a second switching element S2 that connects to the other end of the inductor L and the other end of the battery B2 to form a second closed circuit during an on-operation; A signal generating circuit that complementarily turns on the two switching elements S1 and S2 in a predetermined cycle, and a current that flows through the inductor L to detect an overcurrent that exceeds a predetermined value so that the overcurrent is reduced. It may be configured to include a restricting means for restricting the above.

  Further, it is a balance correction method for equalizing each voltage for a plurality of secondary batteries connected in series, and one end of an inductor L is connected to a connection point between two batteries B1 and B2 that are arranged in a line of secondary batteries. A first mode in which the other end of the inductor L is connected to the other end of the battery B1 to form a first closed circuit and current is circulated, and the other end of the inductor L is connected to the battery B2. By connecting to the other end of the battery, a second closed circuit is formed and the second mode in which current is circulated is alternately repeated at a predetermined period, and the voltages of the batteries B1 and B2 are equalized. In the balance correction operation, when the current flowing through the switching elements S1 and S2 is detected and the detected value is an overcurrent exceeding a predetermined value, an overcurrent is detected with respect to the repetition period of the first and second modes. Reduce It is also possible to make apply the restriction to.

  In addition, an inductor L having one end connected to a connection point between two batteries B1 and B2 that are arranged in the row of the secondary batteries, and an ON operation by connecting the other end of the inductor L and the other end of the battery B1. A first switching element S1 that sometimes forms a first closed circuit; a second switching element S2 that connects to the other end of the inductor L and the other end of the battery B2 to form a second closed circuit during an on-operation; The inductor L may be a non-linear inductor provided with a signal generation circuit that complementarily turns on the two switching elements S1 and S2 in a predetermined cycle.

  In order to achieve the above-described object, a balance correction apparatus for secondary batteries connected in series according to the present invention equalizes each voltage for a plurality of secondary batteries connected in series, and the secondary battery Inductor L having one end connected to the connection point of two batteries B1 and B2 that are back and forth in the line of the line, and connected to the other end of the inductor L and the other end of the battery B1, and a first closed circuit at the time of on operation A first switching element S1 to be formed; a second switching element S2 that is connected to the other end of the inductor L and the other end of the battery B2 to form a second closed circuit during an on-operation; and the two switching elements S1 , S2 are complementarily turned on in a predetermined cycle, reference voltage means for outputting a reference voltage obtained by equally dividing the sum of both voltages for the batteries B1 and B2, and a circuit connected to the connection point. The output compare of the comparator performed between a and the reference voltage comparator may change the amount of balance correction duty ratio is returned to the signal generator is a configuration and an adjusting means for modifying the direction to converge.

  Further, the reference voltage means has a configuration in which two resistors R1 and R2 having the same value are connected in series and both ends of the series element are connected in parallel to the batteries B1 and B2, and the series element includes It is advisable to provide a switch means that is interposed in series and disconnects the connection with the batteries B1 and B2 during the off operation.

  Further, it is a balance correction method for equalizing each voltage for a plurality of secondary batteries connected in series, and one end of an inductor L is connected to a connection point between two batteries B1 and B2 that are arranged in a line of secondary batteries. A first mode in which the other end of the inductor L is connected to the other end of the battery B1 to form a first closed circuit and current is circulated, and the other end of the inductor L is connected to the battery B2. By connecting to the other end of the battery, a second closed circuit is formed and the second mode in which current is circulated is alternately repeated at a predetermined period, and the voltages of the batteries B1 and B2 are equalized. In the balance correction operation, a reference voltage obtained by equally dividing the sum of both voltages for the batteries B1 and B2 is detected, and the reference voltage and the voltage at the connection point are compared to determine the first and second voltages. For the repetition period of the mode Variation of the balance correction is corrected in a direction to converge the duty ratio.

  With this configuration, in the present invention, the current flowing through the switching elements S1 and S2 is detected, and when the detected value is an overcurrent exceeding a predetermined value, the signal generation circuit is operated so that the overcurrent is reduced. Put a limit. In this case, the duty ratio is controlled by limiting the repetition period of the first and second modes. Therefore, the current flowing through the inductor L can be limited to a predetermined value, and as a result, the inductor L and the switching elements S1 and S2 can be reduced in size.

  Further, the current flowing through the inductor L may be detected and a restriction may be applied so that the overcurrent is reduced when the overcurrent exceeds a predetermined value. As a limiting means, a resistor is connected in series with the inductor. Alternatively, the current flowing through the inductor can be limited by appropriately adjusting the resistance component inherent in the inductor.

  In addition, when the inductor L is a non-linear inductor, the inductance decreases with a negative slope with respect to an increase in current, so that the voltages of the batteries B1 and B2 are equalized and the balance is generally good. Then, since the current is small in both the B1 loop and the B2 loop, the inductance becomes a large value. As a result, in the balance correction circuit, the reactive current is reduced, loss is reduced, and efficiency is improved. On the other hand, in a situation where the voltage difference between the batteries is large and unbalanced, the current for balance correction is large, and the correction operation can be performed quickly in a short time, and at this time, the inductance becomes a small value.

  Further, a reference voltage obtained by equally dividing the sum of both voltages for the batteries B1 and B2 is detected, and the reference voltage and the voltage at the battery connection point are compared, and the repetition cycle of the first and second modes is determined. Modifying the duty ratio so that the amount of change in balance correction converges results in pulse width control that varies the duty ratio, resulting in a duty ratio that automates balance correction. As a result, the balance correction operation can be performed in a short time, and the efficiency is high, and the response performance to a sudden load change is good. Further, since the reference voltage means disconnects the connection from the battery B1, B2 side by the switch means, it is possible to stop unnecessary current consumption.

  The balance correction device for secondary batteries connected in series according to the present invention detects a reference voltage obtained by equally dividing the sum of both voltages for the batteries B1 and B2, and compares the reference voltage with the voltage at the battery connection point. Thus, since the duty ratio is corrected so that the amount of change in balance correction converges, pulse width control that varies the duty ratio can be performed. Since the duty ratio is such that the balance correction is automated, the balance correction operation can be performed in a short time and the efficiency is high, and the response performance to a sudden load change is good.

(First form (reference example))
FIG. 2 is a circuit diagram showing a first embodiment (reference example) of a balance correction apparatus according to the present invention. In the present embodiment (reference example), the balance correction device is configured to use the induced electromotive force generated by the inductor, and is basically the same as the conventional example shown in FIG. .

  That is, in the balance correction device, two secondary batteries B1 and B2 are connected in series, and one end of the inductor L is connected to the connection point of the batteries B1 and B2. The switching element S1 is connected between the other end (positive terminal) of the battery B1 and the other end of the inductor L, and the switching element S2 is connected between the other end (negative terminal) of the battery B2 and the other end of the inductor L. Is connected.

  Each switching element S1, S2 is connected in parallel with a series element in which a sub switching element S3 (S4) and a resistor R1 (R2) for current detection are connected in series, and the sub switching elements S3, S4 are connected in parallel. It is configured to move in a double manner in conjunction with each switching element S1, S2. This is because when the switching elements S1 and S2 are turned on, the sub-switching elements S3 and S4 are also turned on twice, and the current is shunted. Therefore, the voltage is monitored on the side of the sub-switching elements of the resistors R1 and R2. As a result, the current flowing through the switching elements S1 and S2 can be known, which serves as a current detection means.

  The two switching elements S1 and S2 and the two sub-switching elements S3 and S4 are made of MOSFETs, and gate drivers D1 and D2 that operate in a complementary manner are connected to gate terminals, and a signal generation circuit 10 is connected to these gate drivers D1 and D2. By sending a drive signal from, when one of the double switching elements is turned on, the other double is turned off.

  The signal generation circuit 10 generates a pulse train (rectangular wave) having a predetermined cycle with a duty ratio of 50% and inputs it to the gate drivers D1 and D2 during a period of executing the balance correction of the batteries B1 and B2. Thus, the two switching elements S1 and S2 are repeatedly turned on and off in a complementary manner, and the on time and the off time are equal.

  The sub-switching element side of each resistor R1, R2 is connected to the input terminal of the comparator 20. The comparator 20 connects the reference voltage V1 (V2) to the other input terminal, and the output terminal is the gate driver D3 (D4). ) To the operation control unit of the signal generation circuit 10.

  The comparator 20 detects an overcurrent by comparing with a preset reference voltage V1 (V2), and when the detected value of the detection means is an overcurrent exceeding a predetermined value, the operation control unit of the signal generation circuit 10 This is a limiting means for performing a signal sending operation to limit the overcurrent to be reduced. As a limiting operation, when an overcurrent is detected in one of the switching elements S1 and S2, an operation is performed to turn off the corresponding switching element, and the duty ratio is controlled.

  In this way, the current flowing through the switching elements S1 and S2 is detected, and when the detected value is an overcurrent exceeding a predetermined value, the operation of the signal generation circuit 10 is limited so that the overcurrent is reduced, and the duty is Since the ratio is controlled, the current flowing through the inductor L can be limited to a predetermined value. As a result, the inductor L and the switching elements S1 and S2 can be reduced in size, and the balance correction device can be reduced in size.

  By the way, it is good also as a structure which restrict | limits the electric current which flows through the inductor L in the electric current limitation in balance correction. Specifically, the configuration shown in FIGS. 3 and 4 may be used.

  In Example 1 shown in FIG. 3, a resistor R3 is connected in series to the inductor L, and the resistor R3 serves as a limiter that suppresses a current in the inductor L. In addition, the example 2 shown in FIG. 4 is configured to use the resistance component Rdc that the inductor L has equivalently, and by appropriately setting the resistance component Rdc itself, it functions as a limiter that suppresses the current in the inductor L.

  The adjustment of the resistance component Rdc inherent to the inductor L is to appropriately set the cross-sectional area (wire diameter) and length of the winding, and to appropriately set the R component related to the frequency characteristics of the inductor L, and both This can be done by optimizing the overall characteristic value. In this case, the number of parts related to limiting the current flowing through the inductor L is small, and the balance correction apparatus can be simply downsized.

(Second form (reference example))
FIG. 5 is a circuit diagram showing a second embodiment (reference example) of the balance correction apparatus according to the present invention. In the second mode (reference example), the current detecting unit and the limiting unit for limiting the overcurrent to be reduced are omitted in the first mode (reference example). However, the inductor L is a non-linear type inductor. In addition, the same code | symbol is attached | subjected to the component similar to the 1st form (reference example) mentioned above, and the description is abbreviate | omitted.

  FIG. 6 is a graph showing the current characteristics of the nonlinear inductor. FIG. 7 is a timing chart showing the waveforms of the respective parts in the balance correction operation. The complementary pulse waveforms sent to the gate terminals of the switching elements S1 and S2 and the inductor current synchronized with the pulse trains (S1, S2). The waveform is shown.

  As shown in FIG. 6, the non-linear inductor has an inductance that decreases with a negative slope as the current increases. For this reason, in a situation where the voltages of the batteries B1 and B2 are equalized and the balance is generally good, the current is small in both the B1 loop and the B2 loop, so the inductance becomes a large value. As a result, in the balance correction circuit, the reactive current is reduced, loss is reduced, and efficiency is improved. Conversely, in a situation where the voltage difference between the batteries is large and unbalanced, as shown in FIG. 7, the current for balance correction is large, and the correction operation can be performed quickly in a short time. At this time, the inductance becomes a small value. Become.

Magnetic flux density B is
B = (AL / A) x N · I
Can be shown. Here, AL is the inductance per turn of the inductor, A is the core cross-sectional area of the inductor L, N is the number of turns of the inductor L, and I is the current. When the core of the inductor L is formed of a ferrite material, the magnetic flux density B is saturated unless it is 0.4 or less.
B ≤ 0.4
Therefore, it can be said that the core sectional area A may be small. That is, if the inductor L is a non-linear inductor, it can be further reduced in size and efficiency is improved.

(Third embodiment)
FIG. 8 is a circuit diagram showing a third embodiment of the balance correction apparatus according to the present invention. In the third embodiment, the current detecting means and the limiting means for limiting the overcurrent to be reduced in the first form (reference example) are omitted. Basically, it is the same as the conventional example shown in FIG. 1 described above, but includes a reference voltage means using resistors R4 and R5 connected in series and an adjusting means using a comparator 20, and changes the duty ratio in balance correction. It is configured to correct the direction in which the amount converges. In addition, the same code | symbol is attached | subjected to the component similar to the 1st form mentioned above, and the description is abbreviate | omitted.

  As the reference voltage means, two resistors R4 and R5 having the same value are connected in series, and both ends of the series element are connected in parallel to the batteries B1 and B2. The connection point (reference voltage) of the resistors R4 and R5 and the connection point of the batteries B1 and B2 are connected to the input terminal of the comparator 20, and the output terminal of the comparator 20 is connected to the operation control unit of the signal generation circuit 10. is doing.

  For this reason, a reference voltage obtained by equally dividing the sum of both voltages of the batteries B1 and B2 appears at the connection point of the resistors R4 and R5. Since the comparator 20 compares the actual voltage value with the reference voltage, the output becomes a deviation amount, that is, a correction value with respect to the reference voltage, and this is sent to the operation control unit of the signal generation circuit 10. The operation is to correct the ratio so that the amount of change in balance correction converges.

  In other words, the control here detects a reference voltage obtained by equally dividing the sum of both voltages for the batteries B1 and B2, compares the reference voltage with the voltage at the connection point, and performs a comparison between the B1 loop and the B2 loop. With respect to the repetition period, the duty ratio is corrected so that the amount of change in balance correction converges, and pulse width control is performed to vary the duty ratio.

  According to the pulse width control, if there is a sudden change in the load in the state where the equivalent series resistances of the two batteries B1 and B2 are different, the battery with a small equivalent series resistance compensates for the change in the current of the large battery, Can be small. That is, the duty ratio is such that the balance correction is automated by the pulse width control. As a result, the balance correction operation can be performed in a short time with high efficiency, and the response performance to a sudden load change is good.

(Fourth embodiment)
FIG. 9 is a circuit diagram showing a fourth embodiment of the balance correction apparatus according to the present invention. In the fourth embodiment, switch means 30 for separating the reference voltage means is added to the third embodiment, and the same components as those in the first embodiment (reference example) described above. Are denoted by the same reference numerals and description thereof is omitted.

  The switch means 30 has a configuration in which the emitter and collector of the transistor 31 are interposed in series with a series element formed of resistors R4 and R5 to perform a switch operation, and a resistor 32 is connected between the base and emitter of the transistor 31 and the base. A resistor 33 and a diode 34 are connected to form a signal terminal 35, and an H level or L level signal is applied to the signal terminal 35.

  Therefore, by setting the signal terminal 35 to the L level, the transistor 31 is turned on, the reference voltage means by the resistors R4 and R5 functions, and the pulse width control for varying the duty ratio can be performed on the signal generation circuit 10. Conversely, when the signal terminal 35 is at the H level, the transistor 31 is turned off, and the resistors R4 and R5 can be disconnected from the batteries B1 and B2. That is, during the off operation, unnecessary current does not flow to the resistances R4 and R5, and the circuit related to the pulse width control can stop the operation.

It is a circuit diagram which shows the prior art example of the balance correction apparatus of a secondary battery. It is a circuit diagram showing the 1st form (reference example) of a balance amendment device. It is a circuit diagram which shows the other example 1 of a balance correction apparatus. It is a circuit diagram which shows the other example 2 of a balance correction apparatus. It is a circuit diagram which shows the 2nd form (reference example) of the balance correction apparatus which concerns on this invention. It is a graph which shows the current characteristic of a nonlinear inductor. It is a timing diagram which shows the waveform of each part in the operation | movement of balance correction. It is a circuit diagram which shows 3rd Embodiment of the balance correction apparatus which concerns on this invention. It is a circuit diagram which shows 4th Embodiment of the balance correction apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Signal generation circuit 20 Comparator 30 Switch means 31 Transistor 32, 33 Resistor 34 Diode 35 Signal terminal B1, B2 Battery L Inductor S1, S2 Switching element S3, S4 Sub switching element R1, R2, R3, R4, R5 Resistor D1, D2 , D3, D4 Gate driver V1, V2 Reference voltage

Claims (3)

A balance correction device that equalizes each voltage for a plurality of secondary batteries connected in series,
An inductor L having one end connected to a connection point between the two batteries B1 and B2 that are arranged in the row of the secondary batteries, and the other end of the inductor L and the other end of the battery B1 are connected at the time of an on operation. A first switching element S1 that forms one closed circuit; a second switching element S2 that connects to the other end of the inductor L and the other end of the battery B2 to form a second closed circuit during an on-operation; A signal generating circuit for complementarily turning on the two switching elements S1 and S2 in a predetermined cycle; a reference voltage means for outputting a reference voltage obtained by equally dividing the sum of both voltages for the batteries B1 and B2; A comparator that is connected and compares with the reference voltage and returns the output of the comparator to the signal generation circuit to adjust the duty ratio so that the amount of change in balance correction converges 2 battery balance correction device connected in series, characterized in that it comprises a stage.   The reference voltage means has a configuration in which two resistors R1 and R2 having the same value are connected in series and both ends of the series element are connected in parallel to the batteries B1 and B2, and in series with the series element. 2. The balance correction apparatus for a series-connected secondary battery according to claim 1, further comprising switch means for interposing and disconnecting the connection to the battery B1, B2 side during an off operation. A balance correction method for equalizing each voltage for a plurality of secondary batteries connected in series,
One end of the inductor L is connected to a connection point between two batteries B1 and B2 that are arranged in the row of secondary batteries, and the other end of the inductor L is connected to the other end of the battery B1. A first mode in which a current is circulated by forming a closed circuit; and a second mode in which a second closed circuit is formed by circulating the current by connecting the other end of the inductor L to the other end of the battery B2. In an operation of balance correction for performing the operation of alternately repeating at predetermined intervals for an appropriate period and equalizing the voltages of the batteries B1 and B2,
For the batteries B1 and B2, a reference voltage obtained by equally dividing the sum of both voltages is detected, the reference voltage is compared with the voltage at the connection point, and the repetition cycle of the first and second modes is determined. A method for correcting a balance of secondary batteries connected in series, wherein the duty ratio is corrected so that the amount of change in balance correction converges.

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