Cell balance circuit and control method

Abstract

A cell balance circuit (100) comprises a first electric power storage device (10) that has a plurality of first battery cells (11–14), a bidirectional electric power supply device (50), a first switch circuit (30) that connects a selected first battery cell and the bidirectional electric power supply device (50), a capacitor (25), and a control circuit (70). When the voltage of the first electric power storage device (10) is normal, the control circuit (70) connects the selected first battery cell and the bidirectional electric power supply device (50), and controls the first switch circuit (30) and the bidirectional electric power supply device (50) so that charging and discharging is performed between the selected first battery cell and the capacitor (25). When the voltage of the first electric power storage device (10) is abnormal, the control circuit (70) electrically disconnects the first electric power storage device (10) from the bidirectional electric power supply device (50), and controls the first switch circuit (30) and the bidirectional electric power supply device (50) so that electric power that has accumulated in the capacitor (25) is supplied to a load (300).

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, the technology disclosed in Patent Document 1 requires a dedicated power supply to implement the cell balancing function, which increases the system size.

[0005] Therefore, the present disclosure provides a cell balancing circuit and the like that can achieve a cell balancing function 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 and supplying power to a load; 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 backup switch connected between the bidirectional power supply and the load; a power storage element connected to the bidirectional power supply; and a control circuit that controls the first switch circuit, the bidirectional power supply, and the backup switch; when the voltage of the first power storage device is normal, 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, 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, the control circuit 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 and the backup switch to supply the power stored in the power storage element to the load.

[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 and supplying power to a load; 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 backup switch connected between the bidirectional power supply and the load; and a power storage element connected to the bidirectional power supply, wherein the control method controls, when a voltage of the first power storage device is normal, 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, and controls the bidirectional power supply to charge and discharge between the first battery cell and the power storage element; and when a 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 and the backup switch to supply power stored in the power storage element to the load.

[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 achieve a cell balancing function 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 a first embodiment. FIG. 2 is a diagram for explaining an operation at the time of startup of the cell balance circuit according to the first embodiment. FIG. 3 is a diagram for explaining an example of a cell balance function of the cell balance circuit according to the first embodiment. FIG. 4 is a diagram for explaining another example of the cell balance function of the cell balance circuit according to the first embodiment. FIG. 5 is a diagram for explaining a backup function of the cell balance circuit according to the first embodiment. FIG. 6 is a circuit configuration diagram showing another example of the cell balance circuit according to the first embodiment. FIG. 7 is a circuit configuration diagram showing an example of a cell balance circuit according to a second embodiment. FIG. 8 is a flowchart showing an example of a control method according to other embodiments.

[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 the 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 to the load 300.

[0016] The cell balancing circuit 100 includes a first power storage device 10, a bidirectional power supply device 50, a first switch circuit 30, a backup switch 60, a capacitor 25, and a control circuit 70.

[0017] The first power storage device 10 has a plurality of first battery cells and supplies power to the 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] When the first battery cells 11 to 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. To address this problem, the cell balance circuit 100 has a cell balance function that equalizes the voltages among the first battery cells 11 to 14. The cell balance function equalizes the voltages among the first battery cells 11 to 14, and controls the first battery cells 11 to 14 so that they are all as close to fully charged as possible.

[0019] For example, the cell balance circuit 100 has an active cell balancing function. The active cell balancing function of the cell balancing circuit 100 is a function for equalizing the voltages among the first battery cells 11 to 14 by transferring charge from a first battery cell with a higher voltage to a first battery cell with a lower voltage among the first battery cells 11 to 14. A passive cell balancing function equalizes the voltages among multiple battery cells by discharging the charge of a battery cell with a higher voltage than the other battery cells 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 of being able to equalize the voltages among multiple battery cells in a shorter time than the passive cell balancing function.

[0020] In addition to the cell balancing function, the cell balancing circuit 100 also has a backup function for continuing to supply power to the load 300 by using the power stored in the capacitor 25 when the voltage of the first power storage device 10 is abnormal.

[0021] 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.

[0022] The capacitor 25 is connected to the bidirectional power supply 50. The capacitor 25 is an example of a power storage element. The capacitor 25 is used as intermediate storage by a cell balancing function. The capacitor 25 is also used as backup storage by a backup function. The capacitor 25 is, for example, an electric double layer capacitor (EDLC). Note that a battery cell such as a lithium ion battery (a second battery cell, described later) may be provided instead of the capacitor 25.

[0023] 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 capacitor 25, or supplies power stored in the capacitor 25 to a first battery cell selected by the first switch circuit 30. For example, the bidirectional power supply 50 is a non-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.

[0024] The backup switch 60 is connected between the bidirectional power supply 50 and the load 300. In the example shown in Fig. 1, when the backup switch 60 and the switch 38 are in the ON state, the bidirectional power supply 50 can supply the power stored in the capacitor 25 to the load 300. The backup switch 60 is switched between the ON state and the OFF state under the control of the control circuit 70.

[0025] The control circuit 70 controls the first switch circuit 30, the bidirectional power supply 50, and the backup switch 60. The control circuit 70 may also control the switch 400. The control circuit 70 is implemented 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 implemented by a microcontroller. The control circuit 70 may also be implemented as a function of a battery management system (BMS), etc.

[0026] When the voltage of the first power storage device 10 is normal, the control circuit 70 controls the first switch circuit 30 to connect one selected from the first battery cells 11-14, or two or more first battery cells connected in series, to the bidirectional power supply 50, and controls the bidirectional power supply 50 to charge and discharge the selected first battery cell and the capacitor 25. Furthermore, when the voltage of the first power storage device 10 is abnormal, the control circuit 70 controls the first switch circuit 30 to electrically disconnect the first battery cells 11-14 from the bidirectional power supply 50, and controls the bidirectional power supply 50 and the backup switch 60 to supply the power stored in the capacitor 25 to the load 300. In the example shown in FIG. 1 , the control circuit 70 also controls the switch 38.

[0027] 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.

[0028] 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.

[0029] For example, the control circuit 70 controls a switch that the bidirectional power supply device 50 has, thereby switching between supplying power from the first storage device 10 side to the capacitor 25 side and supplying power from the capacitor 25 side to the first storage device 10 side or the load 300 side.

[0030] For example, when the voltage of first power storage device 10 is abnormal, control circuit 70 turns off switches 31 to 37 and also turns off switch 400. For example, control circuit 70 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 70 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.

[0031] Next, the operation of the cell balance circuit 100 will be described in detail with reference to FIGS.

[0032] First, the operation of the cell balance circuit 100 at startup will be described with reference to FIG.

[0033] FIG. 2 is a diagram for explaining the operation at the time of startup of the cell balance circuit 100 according to the first embodiment.

[0034] For example, if a large amount of charge is stored in capacitor 25 when the vehicle is not in use, this may accelerate deterioration of capacitor 25. Therefore, when the vehicle is not in use, that is, before cell balancing circuit 100 is started (e.g., before the vehicle is started), capacitor 25 is discharged, and the charge stored in capacitor 25 is reduced. Therefore, when cell balancing circuit 100 is started, as shown in FIG. 2 , control circuit 70 charges capacitor 25 by turning on switches 31 and 38. Also, as shown in FIG. 2 , turning on switch 400 supplies power from isolated DC-DC converter 200 and first power storage device 10 to load 300.

[0035] Next, a cell balancing function for equalizing the voltages among the first battery cells 11 to 14 when the voltages among the first battery cells 11 to 14 vary will be described with reference to FIGS. 3 and 4. FIG.

[0036] FIG. 3 is a diagram for explaining an example of the cell balancing function of the cell balancing circuit 100 according to the first embodiment.

[0037] For example, the control circuit 70 has a function of detecting the voltage of each of the first battery cells 11 to 14, and based on the voltage detection results, it can detect which of the first battery cells 11 to 14 has a higher or lower voltage than the other first battery cells.

[0038] For example, let us say that the voltage of the first battery cell 12 among the first battery cells 11 to 14 is higher than the voltage of the other first battery cells 11, 13, and 14. In this case, the control circuit 70 controls the first switch circuit 30 to connect the first battery cell 12 selected from the first battery cells 11 to 14 to the bidirectional power supply 50. Specifically, the control circuit 70 turns on the switches 33 and 34 and turns off the switches 31, 32, and 35 to 38. The control circuit 70 then controls the bidirectional power supply 50 to charge the capacitor 25 from the first battery cell 12 (in other words, to discharge the first battery cell 12).

[0039] Also, for example, let us assume that the voltage of the first battery cell 12 among the first battery cells 11 to 14 is lower than the voltage of the other first battery cells 11, 13, and 14. In this case, the control circuit 70 controls the first switch circuit 30 to connect the first battery cell 12 selected from the first battery cells 11 to 14 to the bidirectional power supply 50. Specifically, the control circuit 70 turns on the switches 33 and 34 and turns off the switches 31, 32, and 35 to 38. Then, the control circuit 70 controls the bidirectional power supply 50 to charge the first battery cell 12 from the capacitor 25 (in other words, discharge the capacitor 25).

[0040] 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.

[0041] For example, let us say that the voltage of the 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. In this case, the control circuit 70 controls the first switch circuit 30 to connect the first battery cells 11 and 12 selected from the first battery cells 11 to 14 to the bidirectional power supply 50. Specifically, the control circuit 70 turns on the switches 31 and 34 and turns off the switches 32, 33, and 35 to 38. The control circuit 70 then controls the bidirectional power supply 50 to charge the capacitor 25 from the first battery cells 11 and 12 (in other words, to discharge the first battery cells 11 and 12).

[0042] Also, for example, let us assume that the voltage of the first battery cells 11 and 12 among the first battery cells 11 to 14 is lower than the voltage of the other first battery cells 13 and 14. In this case, the control circuit 70 controls the first switch circuit 30 to connect the first battery cells 11 and 12 selected from the first battery cells 11 to 14 to the bidirectional power supply 50. Specifically, the control circuit 70 turns on the switches 31 and 34 and turns off the switches 32, 33, and 35 to 38. Then, the control circuit 70 controls the bidirectional power supply 50 to charge the first battery cells 11 and 12 from the capacitor 25 (in other words, discharge the capacitor 25).

[0043] For example, the bidirectional power supply 50 outputs a voltage in a range of, for example, 2.5 V to 4.2 V when charging one first battery cell from the capacitor 25, and outputs a voltage in a range of, for example, 10 V to 16.8 V when supplying power from the capacitor 25 to the load 300. In this case, the bidirectional power supply 50 needs to have the performance to be able to output a wide range of voltages, such as 2.5 V to 16.8 V, but this causes problems such as an increase in size and high costs of the bidirectional power supply 50. In contrast, by being able to select two or more first battery cells connected in series, it is possible to suppress the increase in size and high costs of the bidirectional power supply 50.

[0044] In this way, when there is variation in the voltages among the first battery cells 11 to 14, it is possible to equalize the voltages among the first battery cells 11 to 14. 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 70 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.

[0045] Next, the operation of the backup function performed when the voltage of the first power storage device 10 is abnormal will be described with reference to FIG.

[0046] FIG. 5 is a diagram for explaining the backup function of the cell balance circuit 100 according to the first embodiment.

[0047] For example, as shown in FIG. 5 , assume 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 to drop below the voltage required for the operation of the load 300. In this case, the control circuit 70 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 50. Specifically, the control circuit 70 turns off the switches 31 to 37 to electrically disconnect the first battery cells 11 to 14 from the bidirectional power supply 50. At this time, the control circuit 70 may also turn off the switch 400 to electrically disconnect the first battery cells 11 to 14 from the load 300. The control circuit 70 also controls the bidirectional power supply 50 to supply the power stored in the capacitor 25 to the load 300. The control circuit 70 also turns on the backup switch 60. The control circuit 70 also turns on the switch 38 to connect the negative terminal of the bidirectional power supply 50 and the negative terminal of the load 300.

[0048] In this way, when the voltage of the first storage device 10 is abnormal, the power stored in the capacitor 25 can be supplied to the load 300, so that the power supply to the load 300 can be continued.

[0049] 1 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 100 may further include a backup switch 61.

[0050] FIG. 6 is a circuit configuration diagram showing another example of the cell balance circuit 100 according to the first embodiment.

[0051] 6 , when the backup switches 60 and 61 are in the ON state, the bidirectional power supply 50 can supply the power stored in the capacitor 25 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 70.

[0052] 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 70 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 50. Specifically, the control circuit 70 turns off the switches 31 to 38 to electrically disconnect the first battery cells 11 to 14 from the bidirectional power supply 50. At this time, the control circuit 70 may also turn off the switch 400 to electrically disconnect the first battery cells 11 to 14 from the load 300. The control circuit 70 also controls the bidirectional power supply 50 to supply the power stored in the capacitor 25 to the load 300. The control circuit 70 also turns on the backup switches 60 and 61.

[0053] 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 capacitor 25 can be supplied to load 300, so that power supply to load 300 can be continued.

[0054] As described above, since the capacitor 25 and bidirectional power supply 50 for the backup function are also used for the cell balancing function, there is no need to provide a dedicated power supply for the cell balancing function, which makes it possible to suppress increases in system size and cost. Furthermore, the cell balancing function of the cell balancing circuit 100 is an active type cell balancing function in which charging and discharging are performed between the first battery cell and the capacitor 25 via the bidirectional power supply 50. Therefore, the voltages among the first battery cells 11 to 14 can be equalized in a shorter time than with a passive type cell balancing function in which a resistor or the like is used to discharge the charge of a battery cell that has a higher voltage than the other battery cells.

[0055] Second Embodiment Next, a cell balance circuit according to a second embodiment will be described.

[0056] FIG. 7 is a circuit configuration diagram showing an example of a cell balance circuit 100a according to the second embodiment.

[0057] 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 second power storage device 20, a bidirectional power supply device 50a, and a control circuit 70a instead of the capacitor 25, the bidirectional power supply device 50, and the control circuit 70, and further includes a second switch circuit 40. Since the other points are basically the same as those in the first embodiment, the following description will focus on the differences.

[0058] The second power storage device 20 has a plurality of second battery cells. In the first embodiment, an example in which the capacitor 25 is an example of a power storage element is described, but in the second embodiment, an example in which the second battery cell is an example of a power storage element is described. 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. The second power storage device 20 may have a plurality of capacitors, such as EDLCs, instead of the plurality of second battery cells.

[0059] 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 100a 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.

[0060] For example, the cell balance circuit 100a has an active cell balance function that equalizes 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.

[0061] In addition to the cell balancing function, the cell balancing circuit 100a also 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.

[0062] The second power storage device 20 is used as an intermediate storage device by the cell balancing function, and is also used as a backup storage device by the backup function.

[0063] 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 50a. For example, the second switch circuit 40 has switches 41 to 48. The switches 41 to 48 are switched between an on state and an off state by being controlled by the control circuit 70a.

[0064] 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. 7, 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. As described with reference to FIG. 6, the cell balance circuit 100a may also include a backup switch 61. In this case, when the backup switches 60 and 61 are in the on state, the bidirectional power supply 50 a can supply the power stored in the second battery cells 21 to 24 to the load 300 .

[0065] 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.

[0066] 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 first battery cells connected in series 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 second battery cells connected in series to the bidirectional power supply device 50a, and controls the bidirectional power supply device 50a to charge and discharge between the first battery cell and the 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.

[0067] The method of controlling the first switch circuit 30, the backup switch 60 and the switch 400 by the control circuit 70a is basically the same as that in the first embodiment, so the following description will focus on the differences.

[0068] For example, the control circuit 70a can select the second battery cell 21 and connect the second battery cell 21 to the bidirectional power supply 50a 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 70a can select the second battery cell 22 and connect the second battery cell 22 to the bidirectional power supply 50a 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 70a can select the second battery cell 23 and connect the second battery cell 23 to the bidirectional power supply 50a 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 70a can select the second battery cell 24 and connect the second battery cell 24 to the bidirectional power supply device 50a by turning on the switches 47 and 48 of the second switch circuit 40 and turning off the switches 41 to 46.

[0069] Furthermore, for example, the control circuit 70a may select two or more second battery cells connected adjacently in series, and control the second switch circuit 40 to connect the two or more second battery cells to the bidirectional power supply 50a. For example, the control circuit 70a can select the second battery cells 23 and 24 connected in series and connect the second battery cells 23 and 24 to the bidirectional power supply 50a 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.

[0070] 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.

[0071] Next, the operation of the cell balance circuit 100a will be described in detail.

[0072] 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.

[0073] 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.

[0074] 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).

[0075] 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).

[0076] Also, two or more battery cells may be selected.

[0077] 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).

[0078] 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).

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] As described above, the backup function allows power stored in multiple power storage elements (e.g., second battery cells 21-24) rather than a single power storage element to be supplied to load 300, thereby enabling the backup function to operate for a long period of time. Furthermore, while equalizing the voltages among first battery cells 11-14, the voltages among second battery cells 21-24 used for the backup function and cell balancing function can also be equalized.

[0084] (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.

[0085] 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.

[0086] FIG. 8 is a flowchart showing an example of a control method according to another embodiment.

[0087] 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 and supplying power to a load, a bidirectional power supply device, a first switch circuit connecting 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, a backup switch connected between the bidirectional power supply device and the load, and a power storage element connected to the bidirectional power supply device, and as shown in FIG. 8, when the voltage of the first power storage device is normal (Yes in step S11), The first switch circuit is controlled to connect one selected from the above, or two or more first battery cells connected in series, to the bidirectional power supply (step S12), the bidirectional power supply is controlled to charge and discharge between the selected first battery cell and the power storage element (step S13), and if the voltage of the first power storage element is abnormal (No in step S11), the first switch circuit is controlled to electrically disconnect the plurality of first battery cells from the bidirectional power supply (step S14), and the bidirectional power supply and the backup switch are controlled to supply the power stored in the power storage element to the load (step S15).

[0088] 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.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0095] (Technology 1) A cell balancing circuit comprising: a first power storage device having a plurality of first battery cells and supplying power to a load; 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 backup switch connected between the bidirectional power supply and the load; a power storage element connected to the bidirectional power supply; and a control circuit that controls the first switch circuit, the bidirectional power supply, and the backup switch, wherein, when the voltage of the first power storage device is normal, 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, 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 and the backup switch to supply power stored in the power storage element to the load.

[0096] According to this, the storage element and bidirectional power supply device for the backup function are also used for the cell balancing function, eliminating the need for a dedicated power supply for the cell balancing function and suppressing increases in system size and cost. Furthermore, the cell balancing function of the cell balancing circuit is an active cell balancing function in which charging and discharging are performed between the first battery cell and the storage element via the bidirectional power supply device. Therefore, the voltages among the multiple first battery cells can be equalized in a shorter time than with a passive cell balancing function in which a resistor or the like is used to discharge the charge of a battery cell with a higher voltage than the other battery cells.

[0097] (Technology 2) The cell balancing circuit according to Technology 1, wherein the storage element is a capacitor or a second battery cell.

[0098] In this way, the power storage element shared by the cell balancing function and the backup function may be a capacitor or a battery cell.

[0099] (Technology 3) The cell balancing circuit according to Technology 1 or 2, wherein the bidirectional power supply device is a non-isolated DC-DC converter.

[0100] In this way, the bidirectional power supply device shared by the cell balancing function and the backup function may be a non-isolated DC-DC converter.

[0101] (Technology 4) The cell balance circuit further includes a second power storage device having a plurality of the power storage elements, and a second switch circuit that connects 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 control circuit controls the first switch circuit, the second switch circuit, the bidirectional power supply device, and the backup switch, and controls the first switch circuit 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 when the voltage of the first power storage device is normal, and the cell balance circuit controls the second switch circuit to connect one or two or more storage elements connected in series to the bidirectional power supply, controls the bidirectional power supply to charge and discharge between the first battery cell and the storage element, and, when a voltage of the first storage element 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 power stored in the plurality of storage elements to the load.

[0102] According to this, the backup function can supply power stored in multiple storage elements, rather than a single storage element, to a load, allowing the backup function to operate for a long period of time. Also, while equalizing the voltages among the multiple first battery cells, the voltages among the multiple storage elements used for the backup function and the cell balancing function can also be equalized.

[0103] (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 and supplying power to a load; 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 backup switch connected between the bidirectional power supply and the load; and a power storage element connected to the bidirectional power supply, wherein the control method controls, when a voltage of the first power storage device is normal, 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, and controls the bidirectional power supply to charge and discharge between the first battery cell and the power storage element; and when a 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 and the backup switch to supply power stored in the power storage element to the load.

[0104] This makes it possible to provide a control method that can realize a cell balancing function while suppressing an increase in the size of the system.

[0105] The present disclosure can be applied to a cell balancing circuit that equalizes the voltages among a plurality of battery cells.

[0106] 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 25 Capacitor 30 First switch circuit 31, 32, 33, 34, 35, 36, 37, 38, 41, 42, 43, 44, 45, 46, 47, 48, 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 and supplying power to a load, a bidirectional power supply device, a first switch circuit connecting one selected from the plurality of first battery cells or two or more first battery cells connected in series and the bidirectional power supply device, a backup switch connected between the bidirectional power supply device and the load, a power storage element connected to the bidirectional power supply device, and a control circuit controlling the first switch circuit, the bidirectional power supply device, and the backup switch, wherein the control circuit controls the first switch circuit to connect one selected from the plurality of first battery cells or two or more first battery cells connected in series and the bidirectional power supply device when the voltage of the first power storage device is normal, and controls the bidirectional power supply device to perform charge and discharge between 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 device, and controls the bidirectional power supply device and the backup switch to supply the power stored in the power storage element to the load, a cell balance circuit.

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

3. The cell balance circuit according to claim 1, wherein the bidirectional power supply device is a non-insulated DC-DC converter.

4. The cell balance circuit further includes: a second power storage device having a plurality of the power storage elements; and a second switch circuit that connects one selected from among the plurality of power storage elements or two or more power storage elements connected in series and the bidirectional power supply device. 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 control circuit controls the first switch circuit to connect one selected from among the plurality of first battery cells or two or more first battery cells connected in series and the bidirectional power supply device, controls the second switch circuit to connect one selected from among the plurality of power storage elements 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. When the voltage of the first power storage device is abnormal, the control circuit controls the first switch circuit to electrically disconnect the plurality of first battery cells from the bidirectional power supply device, and controls the bidirectional power supply device, the second switch circuit, and the backup switch to supply the power stored in the plurality of power storage elements to the load. The cell balance circuit according to any one of claims 1 to 3.

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 and supplying power to a load; a bidirectional power supply device; a first switch circuit connecting 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; a backup switch connected between the bidirectional power supply device and the load; and a power storage element connected to the bidirectional power supply device. In the control method, 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 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 and the backup switch are controlled to supply the power stored in the power storage element to the load.

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