Cell balancing circuit and control method

Abstract

A cell balancing circuit (100) is provided with: a first power storage device (10) that has a plurality of first battery cells (11-14); a second power storage device (20) that has a plurality of second battery cells (21-24); a bidirectional power supply device (50); a first switch circuit (30) that connects a selected first battery cell and the bidirectional power supply device (50); a second switch circuit (40) that connects a selected second battery cell and the bidirectional power supply device (50); and a control circuit (70). The control circuit (70) controls the first switch circuit (30) so as to connect the selected first battery cell and the bidirectional power supply device (50), controls the second switch circuit (40) so as to connect the selected second battery cell and the bidirectional power supply device (50), and controls the bidirectional power supply device (50) so as to perform charging and discharging between the first battery cell and the second battery cell.

Description

Cell balancing circuit and control method

[0001] The present disclosure relates to a cell balancing circuit having a cell balancing function for equalizing voltages among a plurality of battery cells, and a control method thereof.

[0002] Patent Document 1 discloses a technique for performing a cell balancing operation.

[0003] Japanese Patent Application Laid-Open No. 2005-86867

[0004] However, in the technology disclosed in Patent Document 1, when there are multiple blocks of multiple battery cells and the voltage is to be equalized for each block, a dedicated power supply must be prepared for each block to realize the cell balancing function, which results in a larger system.

[0005] Therefore, the present disclosure provides a cell balancing circuit and the like that can realize a cell balancing function that equalizes voltages for each block while suppressing an increase in the size of the system.

[0006] A cell balance circuit according to the present disclosure includes a first power storage device having a plurality of first battery cells, a second power storage device having a plurality of power storage elements, a bidirectional power supply, a first switch circuit connecting one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply, a second switch circuit connecting one first battery cell selected from the plurality of power storage elements or two or more power storage elements connected in series to the bidirectional power supply, and a control circuit that controls the first switch circuit, the second switch circuit, and the bidirectional power supply, wherein the control circuit controls the first switch circuit to connect one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply, controls the second switch circuit to connect one first battery cell selected from the plurality of power storage elements or two or more power storage elements connected in series to the bidirectional power supply, and controls the bidirectional power supply to charge and discharge the first battery cell and the power storage elements.

[0007] A control method according to the present disclosure is a control method for a cell balance circuit, the cell balance circuit comprising: a first power storage device having a plurality of first battery cells; a second power storage device having a plurality of storage elements; a bidirectional power supply; a first switch circuit connecting one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply; and a second switch circuit connecting one first battery cell selected from the plurality of storage elements or two or more storage elements connected in series to the bidirectional power supply, the control method comprising: controlling the first switch circuit to connect the one first battery cell selected from the plurality of first battery cells or the two or more first battery cells connected in series to the bidirectional power supply; controlling the second switch circuit to connect the one first battery cell selected from the plurality of storage elements or the two or more storage elements connected in series to the bidirectional power supply; and controlling the bidirectional power supply to charge and discharge the first battery cell and the storage elements.

[0008] These comprehensive or specific aspects may be realized as a system, a method, an integrated circuit, a computer program, or a computer-readable recording medium such as a CD-ROM, or may be realized as any combination of a system, a method, an integrated circuit, a computer program, and a recording medium.

[0009] According to a cell balancing circuit and the like according to an aspect of the present disclosure, it is possible to realize a cell balancing function that equalizes voltages for each block while suppressing an increase in the size of the system.

[0010] FIG. 1 is a circuit configuration diagram showing an example of a cell balance circuit according to embodiment 1. FIG. 2 is a diagram for explaining a cell balance function of the cell balance circuit according to embodiment 1. FIG. 3 is a circuit configuration diagram showing another example of the cell balance circuit according to embodiment 1. FIG. 4 is a diagram for explaining another example of the cell balance function of the cell balance circuit according to embodiment 1. FIG. 5 is a circuit configuration diagram showing an example of a cell balance circuit according to embodiment 2. FIG. 6 is a circuit configuration diagram showing another example of the cell balance circuit according to embodiment 2. FIG. 7 is a flowchart showing an example of a control method according to another embodiment.

[0011] Hereinafter, the embodiments will be specifically described with reference to the drawings.

[0012] The embodiments described below are all comprehensive or specific examples, and the numerical values, shapes, materials, components, arrangement and connection of the components, steps, and order of steps shown in the following embodiments are merely examples and are not intended to limit the present disclosure.

[0013] First Embodiment A cell balance circuit according to a first embodiment will be described below.

[0014] 1 is a circuit configuration diagram showing an example of a cell balance circuit 100 according to embodiment 1. In addition to the cell balance circuit 100, an isolated DC-DC converter 200, a load 300, and a switch 400 are also shown in FIG.

[0015] For example, the cell balancing circuit 100 is a circuit mounted on a vehicle. The vehicle is, for example, an electric vehicle. The isolated DC-DC converter 200 steps down power from a high-voltage battery (not shown), such as a lithium-ion battery, mounted on the electric vehicle, and supplies the power to the cell balancing circuit 100 and a load 300. The load 300 is, for example, an auxiliary device mounted on the vehicle. The switch 400 switches whether or not power is supplied from the isolated DC-DC converter 200 to the load 300.

[0016] The cell balancing circuit 100 includes a first power storage device 10, a second power storage device 20, a bidirectional power supply device 50, a first switch circuit 30, a second switch circuit 40, and a control circuit 70. The cell balancing circuit 100 further includes switches 61 and 62, but does not necessarily include the switches 61 and 62.

[0017] The first power storage device 10 has a plurality of first battery cells and supplies power to, for example, a load 300. The plurality of first battery cells may include two or more first battery cells connected in series, and four first battery cells 11 to 14 connected in series are shown here. The number of the plurality of first battery cells may be two, three, five or more. For example, at least one of the two or more first battery cells connected in series may be composed of two or more battery cells connected in parallel. For example, each of the plurality of first battery cells is a lithium-ion battery.

[0018] The second power storage device 20 has a plurality of second battery cells and supplies power to, for example, a load 300. The second battery cells are an example of a power storage element. The plurality of second battery cells may include two or more second battery cells connected in series. Here, four second battery cells 21 to 24 connected in series are shown. The number of the plurality of second battery cells may be two, three, five or more. For example, at least one of the two or more second battery cells connected in series may be composed of two or more battery cells connected in parallel. For example, each of the plurality of second battery cells is a lithium-ion battery. A capacitor such as an electric double layer capacitor (EDLC) may be provided instead of the second battery cells.

[0019] When the first battery cells 11-14 include first battery cells with different degrees of deterioration, there is a problem that some of the first battery cells will not be fully charged. Furthermore, when the second battery cells 21-24 include second battery cells with different degrees of deterioration, there is a problem that some of the second battery cells will not be fully charged. In response to this problem, the cell balance circuit 100 has a cell balancing function that equalizes the voltages among the first battery cells 11-14 and the voltages among the second battery cells 21-24. The cell balancing function equalizes the voltages among the first battery cells 11-14 and the voltages among the second battery cells 21-24, thereby controlling all of the first battery cells 11-14 and the second battery cells 21-24 to be as close to fully charged as possible.

[0020] For example, the cell balance circuit 100 has an active cell balance function. The active cell balance function of the cell balance circuit 100 is a function for equalizing the voltages among the first battery cells 11-14 and the voltages among the second battery cells 21-24 by transferring charge from a first battery cell having a higher voltage among the first battery cells 11-14 to a second battery cell having a lower voltage among the second battery cells 21-24, or by transferring charge from a second battery cell having a higher voltage among the second battery cells 21-24 to a first battery cell having a lower voltage among the first battery cells 11-14. Note that a passive cell balance function is a function for equalizing the voltages among multiple battery cells or multiple storage elements by discharging the charge of a battery cell or storage element having a higher voltage than other battery cells or other storage elements using a resistor or the like, but has the disadvantage that it takes a long time to equalize the voltages. In other words, the active cell balancing function has the advantage that it can equalize the voltages among a plurality of battery cells or a plurality of power storage elements in a shorter time than the passive cell balancing function.

[0021] The first power storage device 10 is used as an intermediate storage for the second power storage device 20 by the cell balancing function, and the second power storage device 20 is used as an intermediate storage for the first power storage device 10 by the cell balancing function.

[0022] The first switch circuit 30 connects one selected from the plurality of first battery cells, or two or more first battery cells connected in series, to the bidirectional power supply device 50. For example, the first switch circuit 30 has switches 31 to 38. The switches 31 to 38 are controlled by a control circuit 70 to be switched between an on state and an off state.

[0023] The second switch circuit 40 connects one selected from the plurality of second battery cells, or two or more second battery cells connected in series, to the bidirectional power supply device 50. For example, the second switch circuit 40 has switches 41 to 48. The switches 41 to 48 are controlled by the control circuit 70 to be switched between an on state and an off state.

[0024] The bidirectional power supply 50 is a DC-DC converter that boosts or drops an input voltage to a predetermined voltage and outputs the voltage. For example, the bidirectional power supply 50 supplies power stored in a first battery cell selected by a first switch circuit 30 to a second battery cell selected by a second switch circuit 40, or supplies power stored in a second battery cell selected by the second switch circuit 40 to the first battery cell selected by the first switch circuit 30. For example, the bidirectional power supply 50 is an isolated DC-DC converter. The bidirectional power supply 50 has a switch for boosting or dropping the input voltage to a predetermined voltage, and the switch is controlled by a control circuit 70.

[0025] The switch 61 is a switch that switches the supply of power stored in the first power storage device 10 to the load 300, and the switch 62 is a switch that switches the supply of power stored in the second power storage device 20 to the load 300. When the switches 61 and 62 are in the on state, power can be supplied to the load 300 from both the first power storage device 10 and the second power storage device 20. Note that only one of the switches 61 and 62 may be in the on state, and power may be supplied to the load 300 from one of the first power storage device 10 and the second power storage device 20. The switches 61 and 62 are switched between the on state and the off state by being controlled by, for example, the control circuit 70.

[0026] The control circuit 70 controls the first switch circuit 30, the second switch circuit 40, and the bidirectional power supply 50. The control circuit 70 may further control the switches 61, 62, and 400. The control circuit 70 is realized by, for example, a computer including a processor (microprocessor) and memory. The memory may be a read-only memory (ROM) or a random access memory (RAM), and may store programs executed by the processor. For example, the control circuit 70 is realized by a microcontroller. The control circuit 70 may also be realized as a function of a battery management system (BMS), etc.

[0027] The control circuit 70 controls the first switch circuit 30 to connect one selected from the first battery cells 11 to 14, or two or more first battery cells connected in series, to the bidirectional power supply device 50, controls the second switch circuit 40 to connect one selected from the second battery cells 21 to 24, or two or more second battery cells connected in series, to the bidirectional power supply device 50, and controls the bidirectional power supply device 50 to charge and discharge the first battery cell and the second battery cell.

[0028] For example, the control circuit 70 can select the first battery cell 11 and connect the first battery cell 11 to the bidirectional power supply 50 by turning on the switches 31 and 32 of the first switch circuit 30 and turning off the switches 33 to 38. Similarly, the control circuit 70 can select the first battery cell 12 and connect the first battery cell 12 to the bidirectional power supply 50 by turning on the switches 33 and 34 of the first switch circuit 30 and turning off the switches 31, 32, and 35 to 38. Similarly, the control circuit 70 can select the first battery cell 13 and connect the first battery cell 13 to the bidirectional power supply 50 by turning on the switches 35 and 36 of the first switch circuit 30 and turning off the switches 31 to 34, 37, and 38. Similarly, the control circuit 70 can select the first battery cell 14 and connect the first battery cell 14 to the bidirectional power supply device 50 by turning on the switches 37 and 38 of the first switch circuit 30 and turning off the switches 31 to 36.

[0029] Furthermore, for example, the control circuit 70 may select two or more first battery cells that are adjacently connected in series, and control the first switch circuit 30 to connect the two or more first battery cells to the bidirectional power supply 50. For example, the control circuit 70 can select the first battery cells 11 and 12 that are connected in series and connect the first battery cells 11 and 12 to the bidirectional power supply 50 by turning on the switches 31 and 34 of the first switch circuit 30 and turning off the switches 32, 33, 35 to 38.

[0030] For example, the control circuit 70 can select the second battery cell 21 and connect the second battery cell 21 to the bidirectional power supply 50 by turning on the switches 41 and 42 of the second switch circuit 40 and turning off the switches 43 to 48. Similarly, the control circuit 70 can select the second battery cell 22 and connect the second battery cell 22 to the bidirectional power supply 50 by turning on the switches 43 and 44 of the second switch circuit 40 and turning off the switches 41, 42, and 45 to 48. Similarly, the control circuit 70 can select the second battery cell 23 and connect the second battery cell 23 to the bidirectional power supply 50 by turning on the switches 45 and 46 of the second switch circuit 40 and turning off the switches 41 to 44, 47, and 48. Similarly, the control circuit 70 can select the second battery cell 24 and connect the second battery cell 24 to the bidirectional power supply device 50 by turning on the switches 47 and 48 of the second switch circuit 40 and turning off the switches 41 to 46.

[0031] Furthermore, for example, the control circuit 70 may select two or more second battery cells that are adjacently connected in series, and control the second switch circuit 40 to connect the two or more second battery cells to the bidirectional power supply 50. For example, the control circuit 70 can select the second battery cells 23 and 24 that are connected in series and connect the second battery cells 23 and 24 to the bidirectional power supply 50 by turning on the switches 45 and 48 of the second switch circuit 40 and turning off the switches 41 to 44, 46, and 47.

[0032] For example, the control circuit 70 controls a switch provided in the bidirectional power supply device 50 to switch between supplying power from the first storage device 10 to the second storage device 20 and supplying power from the second storage device 20 to the first storage device 10.

[0033] Next, the operation of the cell balance circuit 100 will be described in detail with reference to FIG.

[0034] FIG. 2 is a diagram for explaining the cell balancing function of the cell balancing circuit 100 according to the first embodiment.

[0035] For example, the control circuit 70 has a function of detecting the voltage of each of the first battery cells 11 to 14, and can detect, based on the voltage detection results, which of the first battery cells 11 to 14 has a higher or lower voltage than the other first battery cells. Also, for example, the control circuit 70 has a function of detecting the voltage of each of the second battery cells 21 to 24, and can detect, based on the voltage detection results, which of the second battery cells 21 to 24 has a higher or lower voltage than the other second battery cells.

[0036] For example, suppose that the voltage of the first battery cell 11 among the first battery cells 11-14 is lower than the other first battery cells 12-14, and the voltage of the second battery cell 24 among the second battery cells 21-24 is higher than the other second battery cells 21-23. In this case, the control circuit 70 controls the first switch circuit 30 to connect the first battery cell 11 selected from the first battery cells 11-14 to the bidirectional power supply 50, and controls the second switch circuit 40 to connect the second battery cell 24 selected from the second battery cells 21-24 to the bidirectional power supply 50. Specifically, the control circuit 70 turns on switches 31 and 32, turns off switches 33-38, turns on switches 47 and 48, and turns off switches 41-46. The control circuit 70 then controls the bidirectional power supply 50 to charge the first battery cell 11 from the second battery cell 24 (in other words, to discharge the second battery cell 24).

[0037] Although an example in which one battery cell is selected has been described in FIG. 2, two or more battery cells may be selected.

[0038] For example, let us assume that the voltage of first battery cells 11 and 12 among the first battery cells 11 to 14 is higher than the voltage of the other first battery cells 13 and 14, and that the voltage of second battery cells 23 and 24 among the second battery cells 21 to 24 is lower than the voltage of the other second battery cells 21 and 22. In this case, the control circuit 70 controls the first switch circuit 30 to connect first battery cells 11 and 12 selected from the first battery cells 11 to 14 to the bidirectional power supply device 50, and controls the second switch circuit 40 to connect second battery cells 23 and 24 selected from the second battery cells 21 to 24 to the bidirectional power supply device 50. Specifically, the control circuit 70 turns on switches 31 and 34, turns off switches 32, 33, and 35 to 38, turns on switches 45 and 48, and turns off switches 41 to 44, 46, and 47. The control circuit 70 then controls the bidirectional power supply 50 to charge the second battery cells 23 and 24 from the first battery cells 11 and 12 (in other words, discharge the first battery cells 11 and 12).

[0039] Also, for example, suppose that the voltage of first battery cells 11 and 12 among first battery cells 11 to 14 is lower than the other first battery cells 13 and 14, and the voltage of second battery cells 23 and 24 among second battery cells 21 to 24 is higher than the other second battery cells 21 and 22. In this case, the control circuit 70 controls the first switch circuit 30 to connect first battery cells 11 and 12 selected from among first battery cells 11 to 14 to the bidirectional power supply device 50, and controls the second switch circuit 40 to connect second battery cells 23 and 24 selected from among second battery cells 21 to 24 to the bidirectional power supply device 50. Specifically, the control circuit 70 turns on switches 31 and 34, turns off switches 32, 33, and 35 to 38, turns on switches 45 and 48, and turns off switches 41 to 44, 46, and 47. Then, the control circuit 70 controls the bidirectional power supply 50 to charge the first battery cells 11 and 12 from the second battery cells 23 and 24 (in other words, discharge the second battery cells 23 and 24).

[0040] In this way, when the voltage between the first battery cells 11 to 14 and the voltage between the second battery cells 21 to 24 vary, the voltage between the first battery cells 11 to 14 and the voltage between the second battery cells 21 to 24 can be equalized.

[0041] Although FIG. 1 illustrates an example in which the first storage device 10 and the second storage device 20 are connected in parallel, the first storage device 10 and the second storage device 20 may be connected in series.

[0042] FIG. 3 is a circuit configuration diagram showing another example of the cell balance circuit 100 according to the first embodiment.

[0043] FIG. 4 is a diagram for explaining another example of the cell balancing function of the cell balancing circuit 100 according to the first embodiment.

[0044] Even when the first power storage device 10 and the second power storage device 20 are connected in series as shown in Fig. 3, the cell balancing function can be realized in the same way as when the first power storage device 10 and the second power storage device 20 are connected in parallel as shown in Fig. 1. The only difference between Fig. 2 and Fig. 4 is whether the first power storage device 10 and the second power storage device 20 are connected in series or in parallel, and the explanation of the cell balancing function is the same as that explained in Fig. 2 etc., so the explanation will be omitted.

[0045] As described above, the first power storage device 10 and the second power storage device 20 use each other as intermediate storage devices and share a single bidirectional power supply for charging and discharging. Therefore, by charging and discharging between a first battery cell with a high or low voltage in a block of the first power storage device 10 and a storage element with a low or high voltage in a block of the second power storage device 20, voltage equalization is possible in the first power storage device 10 and voltage equalization is possible in the second power storage device 20. Therefore, there is no need to provide a dedicated power supply for achieving the cell balancing function for each block. This makes it possible to achieve the cell balancing function of equalizing voltages for each block while suppressing an increase in the system size. The blocks may be connected in parallel as shown in FIG. 1 or in series as shown in FIG. 3.

[0046] The cell balancing function of the cell balancing circuit 100 is an active type cell balancing function that charges and discharges between the first battery cell and the second battery cell via the bidirectional power supply device 50. Therefore, the voltages between the first battery cells 11-14 and the second battery cells 21-24 can be equalized in a shorter time than with a passive type cell balancing function that uses a resistor or the like to discharge the charge of a battery cell that has a higher voltage than the other battery cells.

[0047] Second Embodiment Next, a cell balance circuit according to a second embodiment will be described.

[0048] FIG. 5 is a circuit configuration diagram showing an example of a cell balance circuit 100a according to the second embodiment.

[0049] The cell balance circuit 100a according to the second embodiment differs from the cell balance circuit 100 according to the first embodiment in that it includes a bidirectional power supply 50a, a control circuit 70a, and a backup switch 60 instead of the bidirectional power supply 50, the control circuit 70, and the switches 61 and 62. Since the other points are basically the same as those in the first embodiment, the following description will focus on the differences.

[0050] In addition to the cell balancing function of the cell balancing circuit 100, the cell balancing circuit 100a has a backup function for continuing to supply power to the load 300 by using the power stored in the second power storage device 20 when the voltage of the first power storage device 10 is abnormal.

[0051] The second power storage device 20 is used as an intermediate storage device by a cell balancing function. The second power storage device 20 is also used as a backup storage device by a backup function. For example, when the voltage of the first power storage device 10 is normal, the second power storage device 20 does not need to supply power to the load 300.

[0052] The bidirectional power supply 50a is a DC-DC converter that boosts or drops an input voltage to a predetermined voltage and outputs the voltage. For example, the bidirectional power supply 50a supplies power stored in a first battery cell selected by a first switch circuit 30 to a second battery cell selected by a second switch circuit 40, or supplies power stored in a second battery cell selected by the second switch circuit 40 to the first battery cell selected by the first switch circuit 30. For example, the bidirectional power supply 50a is a non-isolated DC-DC converter. The bidirectional power supply 50a has a switch for boosting or dropping the input voltage to a predetermined voltage, and the switch is controlled by a control circuit 70a. In the example shown in FIG. 5 , when the backup switch 60 and the switch 38 are in the on state, the bidirectional power supply 50a can supply power stored in the second battery cells 21-24 to the load 300.

[0053] The control circuit 70a controls the first switch circuit 30, the second switch circuit 40, the bidirectional power supply 50a, and the backup switch 60. The control circuit 70a may also control the switch 400. The control circuit 70a is realized by, for example, a computer including a processor (microprocessor) and memory. The memory may be a ROM or RAM, and may store programs executed by the processor. For example, the control circuit 70a is realized by a microcontroller. The control circuit 70a may also be realized as a function of a battery management system (BMS) or the like.

[0054] When the voltage of the first power storage device 10 is normal, the control circuit 70a controls the first switch circuit 30 to connect one selected from the first battery cells 11-14 or two or more series-connected first battery cells to the bidirectional power supply device 50a, controls the second switch circuit 40 to connect one selected from the second battery cells 21-24 or two or more series-connected second battery cells to the bidirectional power supply device 50a, and controls the bidirectional power supply device 50a to charge and discharge between the selected first battery cell and the selected second battery cell. Furthermore, when the voltage of the first power storage device 10 is abnormal, the control circuit 70a controls the first switch circuit 30 to electrically disconnect the first battery cells 11-14 from the bidirectional power supply device 50a, and controls the bidirectional power supply device 50a and the backup switch 60 to supply the power stored in the second battery cells 21-24 to the load 300. In the example shown in FIG. 5 , the control circuit 70a also controls the switch 38.

[0055] The method of controlling the first switch circuit 30 and the second switch circuit 40 by the control circuit 70a is basically the same as that in the first embodiment, so the following description will focus on the differences.

[0056] For example, the control circuit 70a controls a switch included in the bidirectional power supply device 50a to switch between supplying power from the first storage device 10 to the second storage device 20 and supplying power from the second storage device 20 to the first storage device 10 or the load 300.

[0057] For example, when the voltage of first power storage device 10 is abnormal, control circuit 70a turns off switches 31 to 37 and also turns off switch 400. For example, control circuit 70a has a function of detecting the voltage of first power storage device 10, and controls first switch circuit 30 and switch 400 based on the voltage detection result. For example, control circuit 70a determines whether the voltage of first power storage device 10 is normal (specifically, determines whether the voltage of first power storage device 10 is equal to or higher than a predetermined voltage), and controls first switch circuit 30 and switch 400 based on the voltage determination result.

[0058] Next, the operation of the cell balance circuit 100a will be described in detail.

[0059] First, we will explain the cell balancing function that equalizes the voltages between the first battery cells 11 to 14 and the voltages between the second battery cells 21 to 24 when there is variation in the voltages between the first battery cells 11 to 14 and the voltages between the second battery cells 21 to 24.

[0060] For example, the control circuit 70a has a function of detecting the voltage of each of the first battery cells 11 to 14, and can detect, based on the voltage detection results, which of the first battery cells 11 to 14 has a higher or lower voltage than the other first battery cells. Also, for example, the control circuit 70a has a function of detecting the voltage of each of the second battery cells 21 to 24, and can detect, based on the voltage detection results, which of the second battery cells 21 to 24 has a higher or lower voltage than the other second battery cells.

[0061] For example, suppose that the voltage of the first battery cell 11 among the first battery cells 11-14 is higher than the other first battery cells 12-14, and the voltage of the second battery cell 24 among the second battery cells 21-24 is lower than the other second battery cells 21-23. In this case, the control circuit 70a controls the first switch circuit 30 to connect the first battery cell 11 selected from the first battery cells 11-14 to the bidirectional power supply device 50a, and controls the second switch circuit 40 to connect the second battery cell 24 selected from the second battery cells 21-24 to the bidirectional power supply device 50a. Specifically, the control circuit 70a turns on switches 31 and 32, turns off switches 33-38, turns on switches 47 and 48, and turns off switches 41-46. Then, the control circuit 70a controls the bidirectional power supply device 50a so as to charge the second battery cell 24 from the first battery cell 11 (in other words, discharge the first battery cell 11).

[0062] Also, for example, suppose that the voltage of the first battery cell 11 among the first battery cells 11-14 is lower than the other first battery cells 12-14, and the voltage of the second battery cell 24 among the second battery cells 21-24 is higher than the other second battery cells 21-23. In this case, the control circuit 70a controls the first switch circuit 30 to connect the first battery cell 11 selected from the first battery cells 11-14 to the bidirectional power supply device 50a, and controls the second switch circuit 40 to connect the second battery cell 24 selected from the second battery cells 21-24 to the bidirectional power supply device 50a. Specifically, the control circuit 70a turns on switches 31 and 32, turns off switches 33-38, turns on switches 47 and 48, and turns off switches 41-46. Then, the control circuit 70a controls the bidirectional power supply device 50a so as to charge the first battery cell 11 from the second battery cell 24 (in other words, discharge the second battery cell 24).

[0063] Also, two or more battery cells may be selected.

[0064] For example, suppose that the voltage of first battery cells 11 and 12 among the first battery cells 11 to 14 is higher than the voltage of the other first battery cells 13 and 14, and the voltage of second battery cells 23 and 24 among the second battery cells 21 to 24 is lower than the voltage of the other second battery cells 21 and 22. In this case, the control circuit 70a controls the first switch circuit 30 to connect first battery cells 11 and 12 selected from the first battery cells 11 to 14 to the bidirectional power supply device 50a, and controls the second switch circuit 40 to connect second battery cells 23 and 24 selected from the second battery cells 21 to 24 to the bidirectional power supply device 50a. Specifically, the control circuit 70a turns on switches 31 and 34, turns off switches 32, 33, and 35 to 38, turns on switches 45 and 48, and turns off switches 41 to 44, 46, and 47. The control circuit 70a then controls the bidirectional power supply device 50a to charge the second battery cells 23 and 24 from the first battery cells 11 and 12 (in other words, discharge the first battery cells 11 and 12).

[0065] Also, for example, suppose that the voltage of first battery cells 11 and 12 among first battery cells 11 to 14 is lower than the other first battery cells 13 and 14, and the voltage of second battery cells 23 and 24 among second battery cells 21 to 24 is higher than the other second battery cells 21 and 22. In this case, the control circuit 70a controls the first switch circuit 30 to connect first battery cells 11 and 12 selected from among first battery cells 11 to 14 to the bidirectional power supply device 50a, and controls the second switch circuit 40 to connect second battery cells 23 and 24 selected from among second battery cells 21 to 24 to the bidirectional power supply device 50a. Specifically, the control circuit 70a turns on switches 31 and 34, turns off switches 32, 33, and 35 to 38, turns on switches 45 and 48, and turns off switches 41 to 44, 46, and 47. The control circuit 70a then controls the bidirectional power supply 50a to charge the first battery cells 11 and 12 from the second battery cells 23 and 24 (in other words, discharge the second battery cells 23 and 24).

[0066] In this way, when there is variation in the voltages among the first battery cells 11 to 14 and the voltages among the second battery cells 21 to 24, the voltages among the first battery cells 11 to 14 and the voltages among the second battery cells 21 to 24 can be equalized. Note that the operation using the cell balancing function is performed when the voltage of the first power storage device 10 is normal. In other words, when the control circuit 70a determines that the voltage of the first power storage device 10 is normal (specifically, when it determines that the voltage of the first power storage device 10 is equal to or higher than a predetermined voltage), the operation using the cell balancing function is performed.

[0067] Next, the operation of the backup function that is performed when the voltage of the first power storage device 10 is abnormal will be described.

[0068] For example, suppose that one of the first battery cells 11 to 14 fails, causing the voltage of the first power storage device 10 to become abnormal and drop below the voltage required for the operation of the load 300. In this case, the control circuit 70a determines that the voltage of the first power storage device 10 is abnormal (specifically, determines that the voltage of the first power storage device 10 is lower than a predetermined voltage) and controls the first switch circuit 30 to electrically disconnect the first battery cells 11 to 14 from the bidirectional power supply device 50a. Specifically, the control circuit 70a turns off the switches 31 to 37 to electrically disconnect the first battery cells 11 to 14 from the bidirectional power supply device 50a. At this time, the control circuit 70a may also turn off the switch 400 to electrically disconnect the first battery cells 11 to 14 from the load 300. The control circuit 70a also controls the bidirectional power supply 50a to supply the power stored in the second power storage device 20 (second battery cells 21 to 24) to the load 300. The control circuit 70a also turns on the backup switch 60. The control circuit 70a also turns on the switch 38 to connect the negative terminal of the bidirectional power supply 50a and the negative terminal of the load 300.

[0069] In this way, when the voltage of the first storage device 10 is abnormal, the power stored in the second storage device 20 can be supplied to the load 300, so that the power supply to the load 300 can be continued.

[0070] 5 illustrates an example in which the switch 38 of the first switch circuit 30 is controlled to be in the on state during backup, but the present invention is not limited to this. For example, as shown in FIG. 6, the cell balance circuit 100a may further include a backup switch 61.

[0071] FIG. 6 is a circuit configuration diagram showing another example of the cell balance circuit 100a according to the second embodiment.

[0072] 6, when the backup switches 60 and 61 are in the ON state, the bidirectional power supply device 50a can supply the power stored in the second power storage device 20 to the load 300. The backup switches 60 and 61 are switched between the ON state and the OFF state under the control of the control circuit 70a.

[0073] For example, suppose that the first battery cell 11 fails, causing the voltage of the first power storage device 10 to become abnormal, and the voltage of the first power storage device 10 drops below the voltage required for the operation of the load 300. In this case, the control circuit 70a determines that the voltage of the first power storage device 10 is abnormal (specifically, determines that the voltage of the first power storage device 10 is lower than a predetermined voltage) and controls the first switch circuit 30 to electrically disconnect the first battery cells 11 to 14 from the bidirectional power supply device 50a. Specifically, the control circuit 70a turns off the switches 31 to 38 to electrically disconnect the first battery cells 11 to 14 from the bidirectional power supply device 50a. At this time, the control circuit 70a may also turn off the switch 400 to electrically disconnect the first battery cells 11 to 14 from the load 300. The control circuit 70a also controls the bidirectional power supply device 50a to supply the power stored in the second power storage device 20 to the load 300. The control circuit 70a also turns on the backup switches 60 and 61.

[0074] In this way, even in the circuit example shown in Figure 6, if the voltage of the first storage device 10 is abnormal, the power stored in the second storage device 20 can be supplied to the load 300, so that the power supply to the load 300 can be continued.

[0075] As described above, the second power storage device 20 and the bidirectional power supply device 50a can also be used for the backup function. Furthermore, the backup function allows the power stored in the second battery cells 21 to 24 to be supplied to the load 300, so the backup function can be operated for a long period of time.

[0076] (Other Embodiments) As described above, the embodiments have been described as examples of the technology according to the present disclosure. However, the technology according to the present disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made as appropriate. For example, the following modifications are also included in one embodiment of the present disclosure.

[0077] For example, the present disclosure can be realized not only as a cell balancing circuit, but also as a control method including steps (processing) performed by components (for example, a control circuit) that make up the cell balancing circuit.

[0078] FIG. 7 is a flowchart showing an example of a control method according to another embodiment.

[0079] The control method is a control method for a cell balance circuit, the cell balance circuit including a first power storage device having a plurality of first battery cells, a second power storage device having a plurality of power storage elements, a bidirectional power supply device, a first switch circuit connecting one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply device, and a second switch circuit connecting one first battery cell selected from the plurality of power storage elements or two or more power storage elements connected in series to the bidirectional power supply device, and as shown in FIG. 7 , the control method controls the first switch circuit to connect one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply device (step S11), controls the second switch circuit to connect one first battery cell selected from the plurality of power storage elements or two or more power storage elements connected in series to the bidirectional power supply device (step S12), and controls the bidirectional power supply to charge and discharge the first battery cell and the power storage elements (step S13).

[0080] For example, the present disclosure can be realized as a program for causing a computer (processor) to execute steps included in the control method. Furthermore, the present disclosure can be realized as a non-transitory computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

[0081] For example, when the present disclosure is realized as a program (software), each step is performed by running the program using hardware resources such as a computer's CPU, memory, input / output circuits, etc. In other words, each step is performed by the CPU acquiring data from memory or input / output circuits, etc., performing calculations, and outputting the calculation results to memory or input / output circuits, etc.

[0082] In the above-described embodiments, each component included in the cell balancing circuit may be configured with dedicated hardware, or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or processor reading and executing a software program recorded on a recording medium such as a hard disk or semiconductor memory.

[0083] Some or all of the functions of the cell balancing circuits according to the above embodiments are typically implemented as an LSI, which is an integrated circuit. These may be implemented individually on a single chip, or some or all of them may be integrated on a single chip. Furthermore, the implementation of the integrated circuit is not limited to an LSI, and may be implemented using a dedicated circuit or a general-purpose processor. An FPGA (Field Programmable Gate Array), which can be programmed after LSI manufacturing, or a reconfigurable processor, which can reconfigure the connections and settings of circuit cells within an LSI, may also be used.

[0084] Furthermore, if an integrated circuit technology that can replace LSIs emerges due to advances in semiconductor technology or other derivative technologies, it is natural that each component included in the cell balancing circuit can be integrated using that technology.

[0085] In addition, this disclosure also includes forms obtained by making various modifications to the embodiments that a person skilled in the art would think of, and forms realized by arbitrarily combining the components and functions in each embodiment within the scope of the present disclosure.

[0086] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0087] (Technology 1) A cell balancing circuit comprising: a first power storage device having a plurality of first battery cells; a second power storage device having a plurality of storage elements; a bidirectional power supply; a first switch circuit connecting one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply; a second switch circuit connecting one first battery cell selected from the plurality of storage elements or two or more storage elements connected in series to the bidirectional power supply; and a control circuit that controls the first switch circuit, the second switch circuit, and the bidirectional power supply, wherein the control circuit controls the first switch circuit to connect one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply, controls the second switch circuit to connect one first battery cell selected from the plurality of storage elements or two or more storage elements connected in series to the bidirectional power supply, and controls the bidirectional power supply to charge and discharge between the first battery cell and the storage elements.

[0088] According to this configuration, the first and second power storage devices use each other as intermediate storage and share a single bidirectional power supply for charging and discharging. Therefore, by charging and discharging between a first battery cell with a higher or lower voltage in a block of the first power storage device and a storage element with a lower or higher voltage in a block of the second power storage device, voltage equalization is possible in the first power storage device and voltage equalization is possible in the second power storage device. Therefore, there is no need to provide a dedicated power supply for each block to achieve the cell balancing function, and the cell balancing function that equalizes voltages for each block can be achieved while suppressing an increase in system size. Furthermore, the cell balancing function of the cell balancing circuit is an active type cell balancing function in which charging and discharging are performed between the first battery cell and the storage elements via the bidirectional power supply. Therefore, the voltages among the multiple first battery cells and the multiple storage elements can be equalized in a shorter time than a passive type cell balancing function in which a battery cell or storage element with a higher voltage than other battery cells or other storage elements is discharged using a resistor or the like.

[0089] (Technology 2) The cell balancing circuit according to Technology 1, wherein each of the plurality of power storage elements is a capacitor or a second battery cell.

[0090] In this way, the storage elements for which voltage equalization is performed in the second storage device may be capacitors or battery cells.

[0091] (Technology 3) The cell balancing circuit according to Technology 1 or 2, wherein the bidirectional power supply device is an isolated DC-DC converter.

[0092] In this way, the bidirectional power supply device used to charge and discharge between the first power storage device and the second power storage device may be an isolated DC-DC converter.

[0093] (Technology 4) The cell balancing circuit according to Technology 1 or 2, wherein the first power storage device supplies power to a load, and the cell balancing circuit further includes a backup switch connected between the bidirectional power supply and the load, and the control circuit controls the first switch circuit, the second switch circuit, the bidirectional power supply, and the backup switch, and, when the voltage of the first power storage device is normal, controls the first switch circuit to connect one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply, controls the second switch circuit to connect one first battery cell selected from the plurality of power storage elements or two or more first battery cells connected in series to the bidirectional power supply, and controls the bidirectional power supply to charge and discharge the first battery cell and the power storage element, and, when the voltage of the first power storage device is abnormal, controls the first switch circuit to electrically disconnect the plurality of first battery cells from the bidirectional power supply, and controls the bidirectional power supply, the second switch circuit, and the backup switch to supply the power stored in the plurality of power storage elements to the load.

[0094] This allows the second power storage device and the bidirectional power supply device to be used for a backup function, and the backup function can be used to supply power stored in the multiple power storage elements to a load, allowing the backup function to operate for a long period of time.

[0095] (Technology 5) A control method for a cell balance circuit, the cell balance circuit comprising: a first power storage device having a plurality of first battery cells; a second power storage device having a plurality of power storage elements; a bidirectional power supply; a first switch circuit connecting one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply; and a second switch circuit connecting one first battery cell selected from the plurality of power storage elements or two or more power storage elements connected in series to the bidirectional power supply, the control method controlling the first switch circuit to connect one first battery cell selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply; controlling the second switch circuit to connect one first battery cell selected from the plurality of power storage elements or two or more power storage elements connected in series to the bidirectional power supply; and controlling the bidirectional power supply to charge and discharge the first battery cell and the power storage elements.

[0096] This makes it possible to provide a control method that can realize a cell balancing function that equalizes the voltage for each block while suppressing an increase in the size of the system.

[0097] The present disclosure can be applied to a cell balancing circuit that equalizes the voltages among a plurality of battery cells.

[0098] REFERENCE SIGNS LIST 10 First power storage device 11, 12, 13, 14 First battery cell 20 Second power storage device 21, 22, 23, 24 Second battery cell 30 First switch circuit 31, 32, 33, 34, 35, 36, 37, 38, 41, 42, 43, 44, 45, 46, 47, 48, 61, 62, 400 Switch 40 Second switch circuit 50, 50a Bidirectional power supply device 60, 61 Backup switch 70, 70a Control circuit 100, 100a Cell balance circuit 200 Isolated DC-DC converter 300 Load

Claims

1. A first power storage device having a plurality of first battery cells, a second power storage device having a plurality of power storage elements, a bidirectional power supply device, a first switch circuit connecting one of the plurality of first battery cells selected therefrom, or two or more first battery cells connected in series, and the bidirectional power supply device, a second switch circuit connecting one of the plurality of power storage elements selected therefrom, or two or more power storage elements connected in series, and the bidirectional power supply device, and a control circuit controlling the first switch circuit, the second switch circuit, and the bidirectional power supply device, wherein the control circuit controls the first switch circuit to connect one of the plurality of first battery cells selected therefrom, or two or more first battery cells connected in series, and the bidirectional power supply device, controls the second switch circuit to connect one of the plurality of power storage elements selected therefrom, or two or more power storage elements connected in series, and the bidirectional power supply device, and controls the bidirectional power supply device to perform charge and discharge between the first battery cell and the power storage element, a cell balance circuit.

2. The cell balance circuit according to claim 1, wherein each of the plurality of power storage elements is a capacitor or a second battery cell.

3. The cell balance circuit according to claim 1 or 2, wherein the bidirectional power supply device is an isolated DC-DC converter.

4. The first power storage device supplies power to a load, and the cell balance circuit further includes a backup switch connected between the bidirectional power supply device and the load. The control circuit controls the first switch circuit, the second switch circuit, the bidirectional power supply device, and the backup switch. When the voltage of the first power storage device is normal, the first switch circuit is controlled to connect one selected from the plurality of first battery cells or two or more first battery cells connected in series to the bidirectional power supply device, and the second switch circuit is controlled to connect one selected from the plurality of power storage elements or two or more power storage elements connected in series to the bidirectional power supply device, and the bidirectional power supply device is controlled to perform charge and discharge between the first battery cell and the power storage element. When the voltage of the first power storage device is abnormal, the first switch circuit is controlled to electrically disconnect the plurality of first battery cells from the bidirectional power supply device, and the bidirectional power supply device, the second switch circuit, and the backup switch are controlled to supply the power stored in the plurality of power storage elements to the load. The cell balance circuit according to claim 1 or 2.

5. A method for controlling a cell balance circuit, wherein the cell balance circuit includes: a first power storage device having a plurality of first battery cells; a second power storage device having a plurality of power storage elements; a bidirectional power supply device; a first switch circuit that connects one of the plurality of first battery cells selected therefrom, or two or more first battery cells connected in series, to the bidirectional power supply device; and a second switch circuit that connects one of the plurality of power storage elements selected therefrom, or two or more power storage elements connected in series, to the bidirectional power supply device. In the control method, the first switch circuit is controlled to connect one of the plurality of first battery cells selected therefrom, or two or more first battery cells connected in series, to the bidirectional power supply device, the second switch circuit is controlled to connect one of the plurality of power storage elements selected therefrom, or two or more power storage elements connected in series, to the bidirectional power supply device, and the bidirectional power supply device is controlled to perform charge and discharge between the first battery cell and the power storage element. Control method.

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