JP2014087084A - Charging/discharging circuit for battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a charging/discharging circuit for a battery pack capable of appropriately reducing cost or the like.SOLUTION: On a path connecting a negative electrode of a first module M1 and a first inter-module electric path LM1, a 0-th intermodule switch QM0 is provided and on a path connecting positive electrodes of even-numbered (2k)th modules M(2k) (k=1, 2, ..., m/2) from a low potential side of a high voltage battery 10 and a first inter-module electric path LM1, a (2k)th inter-module switch QM(2k) is provided. Further, on a path connecting positive electrodes of odd-numbered (2k-1)th modules M(2k-1) from the low potential side of the high voltage battery 10 and a second inter-module electric path LM2, a (2k-1)th inter-module switch QM(2k-1) is provided. In addition, the first and second inter-module electric paths LM1, LM2 can be connected to an inter-module capacitor Cm by first to fourth conversion switches S1-S4.

Description

  The present invention relates to a charge / discharge circuit for an assembled battery applied to an assembled battery as a series connection body of unit batteries which are one or a plurality of adjacent battery cells.

  As this type of circuit, as can be seen in Patent Document 1 below, a circuit is known in which terminal voltages of a plurality of unit batteries (battery cells) constituting an assembled battery are equalized via a transformer. Specifically, the charge / discharge circuit includes a primary coil of a transformer connected to the output side of the assembled battery, a secondary coil of the transformer connected to each of the battery cells, and a current flow of the secondary coil. And a converter circuit for adjusting. According to the charging / discharging circuit, the battery cell having the lowest terminal voltage is intensively charged by the electric energy of each of the plurality of battery cells, and the voltage equalization process is performed to reduce the variation in the terminal voltage of the battery cells. it can.

JP-A-11-176483

  Here, if a transformer is provided in the charge / discharge circuit to perform the voltage equalization process, there is a concern that the cost and scale of the charge / discharge circuit increase.

  Such a problem is not limited to the charge / discharge circuit in which the voltage equalization process is performed, but may similarly occur in any charge / discharge circuit in which any charge / discharge process of the battery cell is performed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a new assembled battery charge / discharge circuit capable of suitably reducing cost and scale.

  In order to solve the above problems, the invention according to claim 1 is a series connection body of unit batteries (Mi, Cij: i = 1 to m, j = 1 to n) which are one or a plurality of adjacent battery cells. As an assembled battery (10), the electric storage means (Cm, Cc) for storing electric energy, and the even-numbered unit batteries (M (2k) from the low potential side among the plurality of unit batteries constituting the assembled battery ), Ci (2p): k = 1 to m / 2, p = 1 to n / 2) and the negative electrode terminal of the battery pack and the first electric path (LM1, LC1). A first opening / closing means (QM0, QM (2k), QC0, QC (2p)) provided in each of the paths and operated to open / close the path; Among the unit cells, odd-numbered unit cells (M (2k-1), Ci from the low potential side) (2p-1)) second opening / closing means provided in each of the paths connecting the respective positive electrode terminals and the second electric path (LM2, LC2) and opened / closed to open / close the path. (QM (2k-1), QC (2p-1)) and first connection means (S1, S2, S5) for selectively connecting either one of both ends of the power storage means and the first electrical path , S6) and second connection means (S3, S4, S7, S8) for selectively connecting either one of both ends of the power storage means to the second electrical path. .

  In the said invention, the said structure is employ | adopted, and charge and discharge of the charge of a unit battery via an electrical storage means can be performed without providing a transformer. Further, by adopting the above configuration, it is possible to reduce the number of first and second opening / closing means for charging and discharging the charge of the unit cell via the power storage means. For this reason, according to the said invention, the cost and scale of a charging / discharging circuit can be reduced suitably.

1 is a system configuration diagram according to a first embodiment. FIG. The block diagram of the adjustment unit in a module concerning the embodiment. The flowchart which shows the procedure of the voltage equalization process between the modules concerning the embodiment. The figure which shows the selection pattern etc. of the battery cell at the time of the charge process concerning the embodiment. The figure which shows the operation pattern of the switch at the time of the discharge process concerning the embodiment. The flowchart which shows the procedure of the voltage equalization process between the battery cells concerning the embodiment. The time chart which shows an example of the voltage equalization process concerning the embodiment. The time chart which shows the effect of the voltage equalization process concerning the embodiment.

(First embodiment)
Hereinafter, a first embodiment in which a charging / discharging circuit of an assembled battery according to the present invention is applied to a secondary battery of a vehicle (for example, a hybrid vehicle or an electric vehicle) including a rotating machine as an in-vehicle main unit, with reference to the drawings explain.

  As shown in the figure, the high voltage battery 10 is an assembled battery as a series connection body of battery cells C11 to Cmn, and the terminal voltage thereof is, for example, 100 V or more. The positive terminal and the negative terminal of the high voltage battery 10 are connected to an input terminal of a power conversion circuit connected to a rotating machine (motor generator) as an in-vehicle main machine. The battery cell Cij (i = 1 to m, j = 1 to n) is a secondary battery such as a lithium ion battery. Battery cells C11 to Cmn have the same configuration except for individual differences. In this embodiment, “m” and “n” are even numbers. Further, the negative electrode potential of the high voltage battery 10 is set to a potential different from the vehicle body potential. Specifically, in the present embodiment, the median value of the positive electrode potential and the negative electrode potential of the high voltage battery 10 is set to be the vehicle body potential. This means that a series connection body of a pair of capacitors and a series connection body of a pair of resistors are connected between the positive electrode and the negative electrode of the high-voltage battery 10 and the connection points of the capacitors or the resistors are connected to the vehicle body. Can be done.

  Battery cells C11 to Cmn are modularized with n (> 2) adjacent cells being in the same group. Here, the i-th module Mi is composed of battery cells Ci1 to Cin.

  Each of the first to m-th modules M1 to Mm can be electrically connected to the inter-module capacitor Cm. Specifically, a zero inter-module switch QM0 is provided in a path connecting the negative terminal of the first module M1 and the first inter-module electrical path LM1. Also, the positive terminal of the (2k) -th module M (2k) (k = 1, 2,..., M / 2) which is an even-numbered module from the low potential side among the modules constituting the high-voltage battery 10 and the first A (2k) -th inter-module switch QM (2k) is provided in a path connecting the first inter-module electrical path LM1. Furthermore, the positive terminal of the (2k-1) -th module M (2k-1), which is an odd-numbered module from the low potential side among the modules constituting the high-voltage battery 10, and the second inter-module electrical path LM2 are connected. A (2k-1) th inter-module switch QM (2k-1) is provided in the connection path.

  One end of the inter-module capacitor Cm is connected to the first inter-module electric path LM1 via the first conversion switch S1, and the other end of the inter-module capacitor Cm is connected via the second conversion switch S2. Has been. On the other hand, the first conversion switch S1 side of both ends of the inter-module capacitor Cm is connected to the second inter-module electrical path LM2 via the third conversion switch S3, and also via the fourth conversion switch S4. The second conversion switch S2 side of both ends of the inter-module capacitor Cm is connected.

  Here, these switches QM0 to QMm, S1 to S4 have a function of preventing current from flowing from one to the other and from the other to one of the two ends of the switch when not electronically operated. In the present embodiment, a pair of N-channel MOSFETs whose sources are connected to each other are used as the switches QM0 to QMm and S1 to S4. The reason why the sources are connected is that the pair of MOSFETs can be easily driven by a single gate signal in view of the fact that the MOSFETs are driven according to the potential difference between the gate and the source.

  Regarding the switches QM0 to QMm and S1 to S4, the sources of the pair of MOSFETs are short-circuited with each other, and the gates are also short-circuited with each other. A pair of terminals on the secondary side of the photocouplers PM0 to PMm and PS1 to PS4 are connected to the source and the gate, respectively. In this embodiment, photocouplers PM0 to PMm and PS1 to PS4 are of the type that outputs voltage. This is a setting for not providing a power source for driving the switches QM0 to QMm and S1 to S4 on the secondary side of the photocouplers PM0 to PMm and PS1 to PS4. In FIG. 1, detailed illustration of the photocouplers PM1 to PMm and PS1 to PS4 is omitted.

  An electronic control unit (ECU 20) is connected to the primary side of the photocouplers PM0 to PMm and PS1 to PS4. The ECU 20 uses the auxiliary battery 30 whose terminal voltage is lower than that of the high voltage battery 10 as a power source, and sets the reference potential for the operation to a potential (vehicle body potential) that is different from the negative potential of the high voltage battery 10.

  Incidentally, the electrostatic capacity of the inter-module capacitor Cm is much smaller than the high-voltage battery 10 when the charging voltage of the inter-module capacitor Cm matches the normal terminal voltage of the high-voltage battery 10. Is set to

  The ECU 20 receives signals output from the first to mth in-module adjustment units U1 to Um via the interface 22, and based on the received signals, the 0th to mth inter-module switches QM0 to QM0. The QMm and the first to fourth conversion switches S1 to S4 are operated. Further, the ECU 20 outputs a command signal for adjusting the state of charge to each of the in-module adjustment units U1 to Um via the interface 22. Note that the interface 22 may be configured by a photocoupler or the like.

  FIG. 2 shows the configuration of the in-module adjustment units U1 to Um.

  As shown in the figure, the in-module adjustment unit Ui includes an in-module capacitor Cc, 0th to nth in-module switches QC0 to QCn, and 5th to 5th to be electrically connectable to each of the battery cells Cij. Eight conversion switches S5 to S8 are provided.

  Specifically, a 0th in-module switch QC0 is provided in a path connecting the negative terminal of the first battery cell Ci1 and the first in-module electric path LC1. Further, the positive terminals of the (2p) battery cells Ci (2p) (p = 1, 2,..., N / 2) that are even-numbered battery cells from the low potential side among the battery cells constituting the module Mi; A (2p) in-module switch QC (2p) is provided in a path connecting the first in-module electric path LC1. Furthermore, the positive terminal of the (2p-1) battery cell Ci (2p-1), which is an odd-numbered battery cell from the low potential side among the battery cells constituting the module Mi, and the second in-module electric path LC2 The (2p-1) th intra-module switch QC (2p-1) is provided in the path connecting the two.

  One end of the intra-module capacitor Cc is connected to the first intra-module electrical path LC1 via the fifth conversion switch S5, and the other end of the intra-module capacitor Cc is connected via the sixth conversion switch S6. Has been. On the other hand, the fifth conversion switch S5 side of both ends of the intra-module capacitor Cc is connected to the second in-module electric path LC2 through the seventh conversion switch S7, and also through the eighth conversion switch S8. The sixth conversion switch S6 side of both ends of the in-module capacitor Cc is connected.

  Incidentally, in the present embodiment, as these switches QC0 to QCn and S5 to S8, a pair of N-channel MOSFETs whose sources are connected are used as in the switches QM0 to QMm and S1 to S4 described above. Each of the switches QC0 to QCn and S5 to S8 is connected to each of a pair of terminals on the secondary side of the photocouplers PC0 to PCn and PS5 to PS8. In the present embodiment, as the photocouplers PC0 to PCn and PS5 to PS8, those that output voltage are used as in the photocouplers PM0 to PMm and PS1 to PS4 described above.

  The electrostatic capacity of the intra-module capacitor Cc is much smaller than the single module Mi when the charging voltage of the intra-module capacitor Cc matches the normal terminal voltage of the single module Mi. It is set to be.

  A microcomputer (microcomputer 40) is connected to the primary side of the photocouplers PC0 to PCn and PS5 to PS8. The microcomputer 40 is software processing means including a central processing unit (CPU 42). The microcomputer 40 is connected to each of the positive terminal and the negative terminal in order to detect the terminal voltages of the battery cells Ci1 to Cin. That is, the positive terminal of the battery cell Cij is connected to the microcomputer 40 via the resistor Rj, and the negative terminal of the battery cell Cij is connected to the microcomputer 40 without passing through the resistor. A capacitor Cj is connected to the battery cell Cij via a resistor Rj. The resistor Rj and the capacitor Cj constitute an RC circuit having a low-pass filter function.

  Here, the RC circuit includes a resistor Rj and a capacitor Cj, and a resistor Rn and capacitors C1 to Cn. The RC circuit composed of the resistor Rj and the capacitor Cj serves as means for outputting the terminal voltage of the battery cell Cij, and the output voltage is converted into digital data by the analog-digital converter 44 in the microcomputer 40 and is taken into the CPU 42. It is. On the other hand, the RC circuit composed of the resistor Rn and the capacitors C1 to Cn serves as means for outputting the terminal voltage of the module Mi. The output voltage is converted into digital data by the analog-digital converter 46 in the microcomputer 40, and is sent to the CPU 42. It is captured. The CPU 42 outputs the terminal voltages of the battery cells Ci1 to Cin and the terminal voltage of the module Mi to the ECU 20 as digital signals via the interface 22 shown in FIG.

  Note that the withstand voltage of the analog-digital converter 44 is lower than the maximum value of the terminal voltage of the module Mi. Therefore, a Zener diode ZDj is connected in parallel to the capacitor Cj in order to protect the analog-digital converter 44 from an excessively high voltage. Here, the breakdown voltage of the Zener diode ZDj is set to a value larger than the assumed maximum value of the terminal voltage of the battery cell Cij and lower than the withstand voltage of the analog-digital converter 44.

  Next, a voltage equalization process for reducing variations in terminal voltages of the battery cells C11 to Cmn according to the present embodiment will be described with reference to FIGS. This process includes a process of reducing the terminal voltage variation of the battery cells Ci1 to Cin in the module Mi and a process of reducing the terminal voltage variation of the modules M1 to Mm.

  FIG. 3 shows a processing procedure for reducing variations in terminal voltages of the battery cells Ci1 to Cin in the module Mi. This process is repeatedly executed, for example, at a predetermined cycle by the CPU 42 in accordance with a command from the ECU 20.

  In this series of processes, first, in step S10, the voltages Vi1 to Vin of the battery cells Ci1 to Cin constituting the i-th module Mi are detected. These voltages can be detected by the analog-digital converter 44 shown in FIG.

  In the subsequent step S12, the battery cell having the highest terminal voltage (hereinafter referred to as the highest voltage cell Cmax) and the terminal voltage having the lowest terminal voltage are selected from the battery cells constituting the i-th module Mi based on the detection value in the step S10. A battery cell (hereinafter, the lowest voltage cell Cmin) is specified.

  In the subsequent step S14, it is determined whether or not the potential difference between the terminal voltage Vmax of the highest voltage cell Cmax and the terminal voltage Vmin of the lowest voltage cell Cmin exceeds the first specified value Ve1 (> 0). In the present embodiment, the first specified value Ve1 is set to be equal to or higher than the minimum resolution of a signal input to the CPU 42 via the analog / digital converter 44. This process causes a phenomenon (hunting) in which the terminal voltage of the battery cell fluctuates when this process is performed in a situation where the terminal voltage variation of the battery cell is small and it is not necessary to execute the voltage equalization process. It is a process for suppressing.

  If an affirmative determination is made in step S14, the process proceeds to step S16, and a plurality of battery cells Cdis that are power supply sources including the highest voltage cell Cmax are selected. In the present embodiment, three battery cells including the highest voltage cell Cmax are selected as the battery cell Cdis of the power supply source. Specifically, as shown in FIG. 4, when the highest voltage cell Cmax is Cir (r = 1, 2,..., N), the highest voltage cell Cir and the highest voltage cell Cir are basically adjacent to each other. A pair of battery cells Ci (r−1) and Ci (r + 1) is selected as the battery cell Cdis of the power supply source. However, when “r = 1” (the highest voltage cell Cmax is Ci1), there is no battery cell adjacent to the negative electrode terminal side of the highest voltage cell Cmax. Select Ci3. In addition, when “r = n” (the highest voltage cell Cmax is Cin), there is no battery cell adjacent to the positive electrode terminal side of the highest voltage cell Cmax, and therefore, the battery cell Ci ( n-2) to Cin are selected.

  By selecting a plurality of power supply source battery cells Cdis in this step, the charging current supplied from the in-module capacitor Cc to the power supply destination battery cell can be increased during the discharge process described later. The time required for equalizing the terminal voltages can be shortened.

  Returning to FIG. 3, in the following step S18, the charging process of the in-module capacitor Cc is started. Here, as shown in FIG. 4, the charging process is based on the highest voltage cell Cir, and the switches in the module and the fifth to eighth conversion switches as shown in (A-1) to (A-4) below. This is a process for operating S5 to S8.

  (A-1) In the case of “r = 1”, the 0th in-module switch QC0 and the third in-module switch QC3, and the sixth conversion switch S6 and the seventh conversion switch S7 are turned on.

  (A-2) When “2 ≦ r <n” and “r is an even number”, the (r−2) th intra-module switch QC (r−2) and the (r + 1) th intra-module switch QC (R + 1) and the sixth conversion switch S6 and the seventh conversion switch S7 are turned on.

  (A-3) When “3 ≦ r <n” and “r is an odd number”, the (r−2) th intra-module switch QC (r−2) and the (r + 1) th intra-module switch QC (R + 1) and the fifth conversion switch S5 and the eighth conversion switch S8 are turned on.

  (A-4) When “r = n”, the (n−3) th intra-module switch QC (n−3) and the nth intra-module switch QCn, the fifth conversion switch S5 and the eighth conversion The switch S8 is turned on.

  Here, for example, as shown in (A-3), the charging process when the highest voltage cell Cmax is the battery cell Ci (n−1) is the nth in-module switch QCn, the (n− This is a process of turning on the in-module switch QC (n-3), the fifth conversion switch S5, and the eighth conversion switch S8 in 3). Thereby, the series connection body of battery cells Ci (n-2) to Cin, the nth in-module switch QCn, the first in-module electric path LC1, the fifth conversion switch S5, the in-module capacitor Cc, the eighth A closed circuit including the conversion switch S8, the second in-module electric path LC2, and the (n-3) th in-module switch QC (n-3) is formed, and charging of the in-module capacitor Cc is started.

  Incidentally, in the present embodiment, the fifth to eighth conversion switches S5 to S8 are operated so that the polarity on the fifth conversion switch S5 side of both ends of the in-module capacitor Cc becomes positive.

  Returning to the description of FIG. 3, in step S20, the process waits until the first specified time T1 elapses after the charging process in step S18 is started. Here, the first specified time T1 is set to a time when it is assumed that the charging of the in-module capacitor Cc is completed by the electric energy of the battery cell Cdis of the power supply source.

  In the subsequent step S22, the charging process for the in-module capacitor Cc is completed by switching the switch that has been turned on in the process of step S18 to the off operation.

  In the subsequent step S24, the discharging process of the in-module capacitor Cc is started. In the present embodiment, the power supply destination battery cell is only the minimum voltage cell Cmin. Then, in the discharge process, when the lowest voltage cell Cmin of the power supply destination is Ciq (q = 1, 2,..., N), as shown in FIG. 5, the (q−1) -th in-module switch QC (q -1) and the q-th in-module switch QCq are turned on, and the fifth to eighth conversion switches S5 to S8 as shown in (B-1) and (B-2) below based on the lowest voltage cell Ciq. It becomes processing to operate.

  (B-1) When “q is an odd number”, the sixth conversion switch S6 and the seventh conversion switch S7 are turned on.

  (B-2) When “q is an even number”, the fifth conversion switch S5 and the eighth conversion switch S8 are turned on.

  Here, for example, as shown in (B-1) above, the charging process when the lowest voltage cell Cmin is the battery cell Ci1 is the 0th in-module switch QC0, the 1st in-module switch QC1, This is a process of turning on the sixth conversion switch S6 and the seventh conversion switch S7. Accordingly, the intra-module capacitor Cc, the seventh conversion switch S7, the second intra-module electrical path LC2, the first intra-module switch QC1, the battery cell Ci1, the zeroth intra-module switch QC0, and the first intra-module electrical A closed circuit composed of the path LC1 and the sixth conversion switch S6 is formed, and the electric energy stored in the in-module capacitor Cc is discharged to charge the battery cell Ci1.

  Incidentally, in the discharge process, the battery cell as the power supply destination may overlap with some of the battery cells Cdis as the power supply source.

  Returning to the description of FIG. 3, in the subsequent step S26, the process waits until the second specified time T2 elapses after the discharge process in step S24 is started. Here, the second specified time T2 is set to a time when it is assumed that the charging of the minimum voltage cell Cmin is completed by the electric energy stored in the in-module capacitor Cc.

  In the subsequent step S28, the discharge process is terminated by switching the switch turned on in the process of step S24 to the off operation.

  If a negative determination is made in step S14, or if the process in step S28 is completed, this series of processes is temporarily terminated.

  Next, FIG. 6 shows a processing procedure for reducing the variation in the terminal voltage of the module Mi. This process is repeatedly executed by the ECU 20 at a predetermined cycle, for example.

  In this series of processes, first, in step S30, the terminal voltages VM1 to VMm of the first to mth modules M1 to Mm are detected. This process is a process of acquiring the terminal voltage VMi of the module Mi detected by the analog-digital converter 46 of the in-module adjustment unit Ui.

  In the subsequent step S32, the module having the highest terminal voltage (hereinafter referred to as the highest voltage module Mmax) and the module having the lowest terminal voltage (hereinafter referred to as the lowest voltage module Mmin) are identified from among the modules constituting the high voltage battery 10. To do.

  In a succeeding step S34, it is determined whether or not the potential difference between the terminal voltage VMmax of the highest voltage module Mmax and the terminal voltage VMmin of the lowest voltage module Mmin exceeds the second specified value Ve2 (> 0). In the present embodiment, the second specified value Ve2 is set to be equal to or higher than the minimum resolution of the voltage signal input to the ECU 20 via the analog / digital converter 46 or the like. This process is a process provided for the same purpose as the process of step S14 of FIG.

  If a positive determination is made in step S34, the process proceeds to step S36, and a plurality of power supply source modules Mdis including the highest voltage module Mmax are selected. In the present embodiment, the highest voltage module Mmax and a pair of modules adjacent thereto are basically selected as the power supply source module Mdis, similarly to the process in step S16 of FIG. However, when the highest voltage module Mmax is M1, there is no module adjacent to the negative terminal side of the highest voltage module Mmax, so the modules M1 to M3 are selected as the module Mdis of the power supply source. When the highest voltage module Mmax is Mm, there is no module adjacent to the positive terminal of the highest voltage module Mmax, so modules M (m−2) to Mm are selected as the module Mdis of the power supply source.

  In the subsequent step S38, the charging process for the inter-module capacitor Cm is started. Here, as in the process of step S18 of FIG. 3, the charging process is based on the maximum voltage module Mt and the following (C−), assuming that the maximum voltage module Mmax is Mt (t = 1, 2,..., M). This is a process of operating the inter-module switch and the first to fourth conversion switches S1 to S4 as in 1) to (C-4).

  (C-1) When “t = 1”, the 0th inter-module switch QM0 and the third inter-module switch QM3, and the second conversion switch S2 and the third conversion switch S3 are turned on.

  (C-2) When “2 ≦ t <m” and “t is an even number”, the (t−2) th inter-module switch QM (t−2) and the (t + 1) th inter-module switch QM (T + 1) and the second conversion switch S2 and the third conversion switch S3 are turned on.

  (C-3) When “3 ≦ t <m” and “t is an odd number”, the (t−2) -th inter-module switch QM (t−2) and the (t + 1) -th inter-module switch QM (T + 1) and the first conversion switch S1 and the fourth conversion switch S4 are turned on.

  (C-4) When “t = m”, the (m−3) th inter-module switch QM (m−3) and the mth inter-module switch QMm, and the first conversion switch S1 and the fourth conversion The switch S4 is turned on.

  In the subsequent step S40, the process waits until the third specified time T3 elapses after the charging process in step S38 is started. Here, the third specified time T3 is set to a time when it is assumed that charging of the inter-module capacitor Cm is completed by the electric energy of the module Mdis as the power supply source.

  In the subsequent step S42, the process of charging the inter-module capacitor Cm is completed by switching the switch that was turned on in the process of step S38 to the off operation.

  In a succeeding step S44, discharge processing of the inter-module capacitor Cm is started. In the present embodiment, only the lowest voltage module Mmin is selected as the power supply destination module Mdis. The discharge process is performed in the same manner as the process in step S24 of FIG. Specifically, if the minimum voltage module Mmin of the power supply destination is Mu (u = 1, 2,..., M), the discharge process is performed by the (u−1) inter-module switch QM (u−1) and u The inter-module switch QMu is turned on, and the first to fourth conversion switches S1 to S4 are operated as shown in (D-1) and (D-2) below based on the lowest voltage module Mu. .

  (D-1) When “u is an odd number”, the second conversion switch S2 and the third conversion switch S3 are turned on.

  (D-2) When “u is an even number”, the first conversion switch S1 and the fourth conversion switch S4 are turned on.

  In subsequent step S46, the process waits until the fourth specified time T4 elapses after the discharge process in step S44 is started. Here, the fourth specified time T4 is set to a time when it is assumed that charging of the minimum voltage module Mmin is completed by the electric energy stored in the inter-module capacitor Cm.

  In the subsequent step S48, the discharge process is completed by switching the switch turned on in the process of step S44 to the off operation.

  If a negative determination is made in step S34, or if the process of step S48 is completed, this series of processes is temporarily terminated.

  Next, FIG. 7 shows an example of a process for reducing variations in terminal voltages of battery cells in the voltage equalization process. Specifically, FIG. 7A shows the transition of the current Ic flowing through the in-module capacitor Cc and the charging voltage Vc of the in-module capacitor Cc, and FIG. 7B shows the transition of the operating state of the switch used in the charging process. FIG.7 (c) shows transition of the operation state of the switch used by discharge processing. In FIG. 7, when the number of battery cells is 6, the power supply source battery cells are Ci4 to Ci6, and the power supply destination battery cell is Ci1.

  Next, FIG. 8 shows an example of the effect of the voltage equalization process when the number of battery cells is six. According to this process, the terminal voltages of the battery cells can be quickly equalized.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) In-module capacitor Cc, 0th to nth in-module switches QC0 to QCn, first in-module electric path LC1, second in-module electric path LC2, and fifth to eighth conversion switches S5 to S8 The charging / discharging circuit provided with was adopted. For this reason, unlike the technique described in Patent Document 1, the terminal voltages of the battery cells can be equalized without providing an expensive transformer. For this reason, the cost and scale of the charge / discharge circuit of the high-voltage battery 10 can be reduced.

  Incidentally, the following configuration may be adopted as a configuration for equalizing the terminal voltages of the battery cells via the in-module capacitor Cc. Specifically, the fifth to eighth conversion switches S5 to S8 are removed, the first in-module electric path LC1 is directly connected to one end of the in-module capacitor Cc, and the second end is connected to the other end of the in-module capacitor Cc. The in-module electrical path LC2 is directly connected. Then, each of the positive terminals of each battery cell is connected to the first in-module electric path LC1 via a series connection body of a pair of N channel MOSFETs, and each of the negative terminals of each battery cell is connected to a pair of N channels. It is connected to the second in-module electrical path LC2 via a MOSFET series connection.

  However, in such a configuration, since the number of battery cells is very large, the number of the pair of MOSFETs that connect the battery cells and the electric path is very large. On the other hand, according to this embodiment, although the fifth to eighth conversion switches S5 to S8 are added, the number of series-connected bodies of a pair of N-channel MOSFETs connecting the battery cell and the electric path is substantially reduced. Can be halved. For this reason, the cost and scale of the charge / discharge circuit can be further reduced.

  (2) Charge including the inter-module capacitor Cm, the 0th to m-th module switches QM0 to QMm, the first inter-module electric path LM1, the second inter-module electric path LM2, and the first to fourth conversion switches. A discharge circuit was adopted. For this reason, it is possible to suitably reduce the cost and scale of the charge / discharge circuit as described in the section of the effect (1).

  (3) In the voltage equalization process, three battery cells (modules) that include the highest voltage cell Cmax (maximum voltage module Mmax) and are adjacent are selected as the battery cell Cdis (module Mdis) of the power supply source. For this reason, the charging current supplied from the in-module capacitor Cc (inter-module capacitor Cm) to the minimum voltage cell Cmin (minimum voltage module Mmin) can be increased during the discharge process, and the terminal voltage of the battery cell (module) can be evenly distributed. The time required for conversion can be shortened.

  (4) In the voltage equalization process, only the lowest voltage cell Cmin (minimum voltage module Mmin) was selected as the battery cell (module) of the power supply destination. For this reason, the terminal voltage of the battery cell (module) having the lowest voltage can be quickly increased, and the difference between the maximum value and the minimum value among the terminal voltages of the plurality of battery cells (modules) can be quickly reduced.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, in the voltage equalization process, the method for selecting the battery cell Cdis or module Mdis as the power supply source is changed. Specifically, only the highest voltage cell Cmax or the highest voltage module Mmax is selected as the battery cell Cdis or module Mdis of the power supply source.

  Incidentally, in this case, the operation pattern of the switch in the charging process will be the same as the operation pattern of the switch in the discharging process shown in FIG. 5 described as an example of the process of reducing the variation in the terminal voltage of the battery cell.

  According to the present embodiment described above, the effects (1), (2), and (4) of the first embodiment can be obtained.

(Other embodiments)
Each of the above embodiments may be modified as follows.

  In each of the above embodiments, the number “m” of modules constituting the high voltage battery 10 or the number “n” of battery cells constituting the module may be an odd number.

  -"Selection means" is not restricted to what was illustrated to said each embodiment. For example, a unit battery that is higher than the average voltage of a plurality of unit batteries is selected as a unit battery (battery cell or module) of a power supply source, and a unit battery that is lower than the average voltage is used as a unit battery of a power supply destination May be selected. In this case, since it is necessary that the number of unit batteries of the power supply destination and the power supply source is an odd number, for example, a unit battery having a terminal voltage in the vicinity of the average voltage is selected from either the power supply source or the power supply destination. Or a process of removing the selected unit battery from the power supply source or the power supply destination.

  The numbers of the power supply source and the power supply destination selected by the “selection unit” may be variably set without being fixed. Specifically, for example, the larger the charging current to the power supply destination unit battery in one cycle of the pair of charging and discharging processes, the more the number of power supply unit cells and the power supply unit battery. What is necessary is just to variably set the number of these unit batteries so that the absolute value of the difference of the numbers becomes large.

  The number of power supply source unit cells selected by the “selection unit” is not limited to three and may be an odd number of five or more. Further, the number of unit batteries as power supply destinations may be an odd number of 3 or more. Further, the number of unit batteries as power supply destinations may be larger than the number of unit batteries as power supply sources.

  The “parameter having a positive correlation with the electric energy stored in the unit battery” is not limited to the terminal voltage of the battery cell. For example, the charging rate (SOC: ratio of the actual charge amount to the full charge amount) or the charge amount of the battery cell may be used. By the way, the charging rate of the battery cell is, for example, the battery terminal open voltage calculated based on the detected value of the terminal voltage of the battery cell, the current amount, and the internal resistance information of each battery cell, the open terminal voltage and the charging rate. What is necessary is just to calculate from related information. The charge amount may be calculated by multiplying the charge rate by the full charge amount of the battery cell.

  In the charging process shown in FIG. 3, the fifth to eighth conversion switches S5 to S8 are operated so that the polarity on the fifth conversion switch S5 side of both ends of the in-module capacitor Cc is negative. Also good. In this case, when the lowest voltage cell Cmin of the power supply destination is Ciq (q = 1, 2,..., N), in the discharge process, when “q is an even number”, the sixth conversion switch S6 and the seventh conversion switch The switch S7 is turned on, and when the “q is an odd number”, the fifth conversion switch S5 and the eighth conversion switch S8 may be turned on. The same applies to the charging process shown in FIG.

  -"Operation means" is not restricted to what performs a voltage equalization process. For example, when the temperature of the high voltage battery 10 is low, a temperature increase control process for increasing the temperature of the high voltage battery 10 by repeating the charge / discharge process between battery cells or modules may be performed. In this case, the larger the charge / discharge current, the greater the amount of heat generated by the internal resistance of the battery cell, and the higher the rate of temperature rise. For this reason, as the temperature of the high-voltage battery 10 is lower, the number of power supply source battery cells may be increased, or the number of power supply destination battery cells may be decreased. Even in this case, the number of the first and second opening / closing means for performing the temperature increase control process can be reduced. In the temperature rise control process, each terminal voltage (a parameter having a positive correlation with the electric energy stored in the unit battery) of each unit battery (battery cell or module) selected as the power supply source is supplied with power. It is not necessary to be at a level higher than the terminal voltage of each unit cell selected as the first. That is, the voltage at both ends of one or a plurality of battery cells selected as a power supply source may be higher than the voltage at both ends of one or a plurality of battery cells selected as a power supply destination.

  The “battery charging / discharging circuit” is not limited to one in which charging / discharging is performed between unit cells via the power storage means. For example, a process of opening / closing the first and second opening / closing means and the first and second connecting means so that an AC voltage is applied to the power storage means may be performed. According to this process, the DC voltage of the high-voltage battery 10 can be converted into an AC voltage, and the converted AC voltage can be output to the outside via the storage means. Even in this case, the number of first and second opening / closing means for performing the above processing can be reduced.

  The intra-module switch, the inter-module switch, and the first to eighth conversion switches are not limited to a series connection body of a pair of N-channel MOSFETs. For example, a series connection body of a pair of P-channel MOSFETs may be used. In this case, the sources may be short-circuited to facilitate driving of the pair of MOSFETs. However, the drains of the pair of MOSFETs may be short-circuited. In this case, although it becomes difficult to drive a pair of MOSFETs with a single gate signal, current flow through the body diodes of the MOSFETs can be prevented. Further, for example, the in-module switch or the like may be composed of a pair of IGBTs and a diode connected in antiparallel to each of the pair of IGBTs.

  The “power storage means” is not limited to a capacitor, and may be other means as long as it has a similar function.

  The “battery cell” is not limited to a secondary battery such as lithium ion, but may be a fuel cell, for example.

  -The application object of this invention is not restricted to a vehicle-mounted assembled battery.

  DESCRIPTION OF SYMBOLS 10 ... High voltage battery, Mi (i = 1-m) ... Module, Cij (j = 1-n) ... Battery cell, Cm ... Inter-module capacitor, Cc ... In-module capacitor, LM1 ... First inter-module electrical path , LM2 ... second inter-module electrical path, LC1 ... first intra-module electrical path, LC2 ... second intra-module electrical path, QM0, QMi ... inter-module switch, QC0, QCj ... intra-module switch, S1 to S8 ... first to eighth conversion switches.

Claims (8)

Applied to a battery pack (10) as a series connection body of unit batteries (Mi, Cij: i = 1 to m, j = 1 to n) which are one or a plurality of adjacent battery cells,
Power storage means (Cm, Cc) for storing electrical energy;
Among the plurality of unit batteries constituting the assembled battery, even-numbered unit batteries (M (2k), Ci (2p): k = 1 to m / 2, p = 1 to n / 2) from the low potential side. First opening / closing means provided on each of the positive terminals and each of the paths connecting the negative terminal of the assembled battery and the first electric path (LM1, LC1) and opened / closed to open / close the path. (QM0, QM (2k), QC0, QC (2p)),
Each of the positive terminals of the odd-numbered unit cells (M (2k-1), Ci (2p-1)) from the low potential side and the second electric path (LM2) among the plurality of unit cells constituting the assembled battery. , LC2) and a second opening / closing means (QM (2k-1), QC (2p-1)) that is provided in each of the paths that connect to each other and that is opened and closed to open and close the paths,
First connection means (S1, S2, S5, S6) for selectively connecting any one of both ends of the power storage means and the first electrical path;
Second connection means (S3, S4, S7, S8) for selectively connecting any one of both ends of the power storage means and the second electrical path;
A charge / discharge circuit for an assembled battery, comprising: Selecting means (20, 42) for selecting an odd number of unit cells as a power source unit cell from among the plurality of unit cells, and selecting an odd number of unit cells as a power source unit cell; ,
The first opening / closing means, the second opening / closing means, the first connecting means, and the like so as to supply electric power from the unit battery of the power supply source to the unit battery of the power supply destination via the power storage means; Operating means (20, 42) for opening and closing the second connecting means;
The charge / discharge circuit of the assembled battery according to claim 1, further comprising:   The selection means selects at least a unit battery having a high value of a parameter having a positive correlation with the electric energy stored in the unit battery as the unit battery of the power supply source, and 3. The assembled battery charge / discharge circuit according to claim 2, wherein at least a unit battery having a low parameter value is selected as a unit battery. Voltage detecting means (44, 46) for detecting the voltage of each of the plurality of unit cells;
4. The assembled battery according to claim 3, wherein the selection unit selects a unit cell including a unit cell corresponding to the maximum value of the voltage detected by the voltage detection unit as the unit battery of the power supply source. Charging and discharging circuit.   5. The assembled battery according to claim 4, wherein the selection unit selects a plurality of unit batteries that include a unit battery corresponding to the maximum value and that are connected in series as the unit battery of the power supply source. Charge / discharge circuit. Voltage detecting means (44, 46) for detecting the voltage of each of the plurality of unit cells;
The said selection means selects the unit battery containing the unit battery corresponding to the minimum value of the voltage detected by the said voltage detection means as the unit battery of the said electric power supply destination, The any one of Claims 3-5 characterized by the above-mentioned. An assembled battery charge / discharge circuit according to claim 1.   7. The assembled battery charge / discharge circuit according to claim 6, wherein the selection unit selects only a unit battery corresponding to the minimum value as the unit battery of the power supply destination. The first connection means includes
A first switching element (S1, S5) for opening and closing between one end of the power storage means and the first electrical path;
A second switching element (S2, S6) for opening and closing between the other of the both ends of the power storage means and the first electrical path;
With
The second connection means includes
A third switching element (S3, S7) for opening and closing between one end of the power storage means and the second electrical path;
A fourth switching element (S4, S8) for opening and closing between the other of the both ends of the power storage means and the second electrical path;
The charge / discharge circuit for an assembled battery according to claim 1, comprising: