Charging device and power supply device

Abstract

When secondary batteries connected in series are being charged, the voltages of each cell or the remaining capacities of each battery cell may become uneven due to variations in the characteristics of each battery. The objective of the present invention is to equalize the voltages of each battery cell. The present invention contributes to Sustainable Development Goals (SDGs) "9. Industry, Innovation and Infrastructure" and "11. Sustainable Cities and Communities". This charging device for charging a plurality of secondary batteries connected in series comprises a cell balancing circuit having a plurality of terminals. A first terminal of the cell balancing circuit is connected to a low potential side of the plurality of secondary batteries, a second terminal of the cell balancing circuit serves as an intermediate terminal and is connected between the plurality of secondary batteries, and a third terminal of the cell balancing circuit is connected to a high potential side of the plurality of secondary batteries.

Description

Charging and power supplies

[0001] The present invention relates to an apparatus for charging a plurality of secondary batteries.

[0002] There are techniques for achieving high-voltage batteries by connecting multiple rechargeable battery cells in series. However, when multiple battery cells are connected in series and repeatedly charged and discharged, variations in the characteristics of each battery can cause uneven cell voltages (or remaining capacity of each battery cell). Uneven cell voltages can accelerate deterioration of some battery cells, reducing the usable capacity of the entire battery. For this reason, a proposed technique for equalizing the voltages of multiple battery cells involves monitoring the voltage of each battery cell and performing a cell balancing operation to transfer charge from higher-voltage battery cells to lower-voltage battery cells. This cell balancing operation is achieved, for example, by using inductors and capacitors between the battery cells and switches that control charge according to the voltage of each battery cell, thereby equalizing or nearly equalizing the voltages of multiple battery cells. Techniques for equalizing battery cell voltages are described, for example, in Patent Document 1 below. Furthermore, a technique for limiting the current during constant-voltage charging so as not to exceed the upper limit voltage of each battery cell connected in series is described, for example, in Patent Document 2 below.

[0003] JP 2023-84627 A JP 2000-236631 A

[0004] However, the disclosures of Patent Documents 1 and 2 have problems such as the large number of components that make up the cell balancing circuit or the circuit for limiting the upper limit voltage of the battery cells, making the battery system large, and the time required for charging being extended because the cell balancing circuit operates after the battery charging operation has finished. The present invention has been made in light of these circumstances, and aims to provide a charging device that uses a simpler cell balancing circuit.

[0005] In order to solve the above problems, one embodiment of the present invention is a charging device for charging a plurality of secondary batteries connected in series, comprising a cell balancing circuit having a plurality of terminals, a first terminal of the cell balancing circuit connected to the low potential sides of the plurality of secondary batteries, a second terminal of the cell balancing circuit serving as an intermediate terminal connected between the plurality of secondary batteries, and a third terminal of the cell balancing circuit connected to the high potential sides of the plurality of secondary batteries.

[0006] According to the present invention, a more suitable charging device can be realized.

[0007] FIG. 1 is a configuration diagram of a first embodiment of a charging device according to an embodiment of the present invention. FIG. 2 is a diagram showing a specific configuration of the first embodiment of a charging device according to an embodiment of the present invention. FIG. 3 is a configuration diagram of a charging device according to an embodiment of the present invention. FIG. 4 is a diagram showing a specific configuration of the fourth embodiment of a charging device according to an embodiment of the present invention. FIG. 5 is a diagram showing a specific configuration of the fifth embodiment of a charging device according to an embodiment of the present invention.

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the description of the embodiments, and various changes and modifications can be made by those skilled in the art within the scope of the technical ideas disclosed in this specification. Furthermore, in all drawings used to explain the embodiments of the present invention, components having the same functions are generally designated by the same reference numerals, and repeated explanations thereof may be omitted.

[0009] FIG. 1 is a diagram showing the overall configuration of a charging device according to an embodiment of the present invention. The power supply device includes a charging device and a unit battery consisting of multiple secondary batteries connected in series. The charging device, which charges batteries 103 and 104, which are secondary batteries connected in series, includes a regulation circuit 102 and a charging switch 105. The charging device may also include a power supply 101. Note that the power supply 101 does not have to be built into the charging device; that is, the power supply 101 does not need to be part of the charging device configuration and may be an external power supply separate from the charging device, such as a commercial power supply. The multiple batteries may be composed of different types of secondary batteries or may be composed of all-solid-state batteries. The regulation circuit 102 adjusts the charging voltage or charging current of the multiple secondary batteries to be charged and may be referred to as a cell balance circuit. The cell balance circuit has multiple terminals. In this embodiment, the cell balance circuit 102 has at least three terminals. The cell balance circuit 102 also includes multiple resistive elements and multiple transistors. In this embodiment, the resistive elements may also be referred to as resistors.

[0010] As shown in FIG. 1 , cell balance circuit 102 has terminals 106, 107, and 108, which are connected to the high-potential electrode, low-potential electrode, and intermediate-potential electrode of battery 103 and battery 104 connected in series, respectively. That is, terminal 106 of cell balance circuit 102 is connected to the high-potential side (positive electrode side of the unit battery) of the multiple secondary batteries to be charged. Furthermore, when power source 101 is built into a charging device, terminal 106 of cell balance circuit 102 is connected to the high-potential side (positive electrode side) of power source 101. Terminal 107 of cell balance circuit 102 is connected to the low-potential side (negative electrode side of the unit battery) of the multiple secondary batteries to be charged. Furthermore, when power source 101 is built into a charging device, terminal 107 of cell balance circuit 102 is connected to the low-potential side (negative electrode side) of power source 101. Terminals 106 and 107 of cell balance circuit 102 are connected to the high-potential side and low-potential side of power source 101, respectively, to charge batteries 103 and 104. Terminal 108 of cell balance circuit 102 serves as an intermediate terminal and is connected between multiple secondary batteries arranged in series. Charging switch 105 is provided between power source 101 and terminal 106 of cell balance circuit 102 and controls the on / off of power source 101. The location of charging switch 105 is not limited; for example, it may be on the low-potential side, or may be located as needed. A specific configuration example of cell balance circuit 102 is shown in FIG. 2, and its operation will be described.

[0011] FIG. 2 is a diagram showing a first embodiment of a charging device according to the present invention. Cell balancing circuit 102 includes multiple resistors and multiple transistors. Transistors are semiconductor elements that amplify or switch signals, and in this embodiment, include NPN and PNP transistors. Cell balancing circuit 102 includes resistors 201, 202, and 203, an NPN transistor 204, and a PNP transistor 205. Resistors 201, 202, and 203 may be referred to as first resistor 201, second resistor 202, and third resistor 203, respectively. Resistors 201, 202, and 203 are connected in series. The base terminal of NPN transistor 204 is connected to the junction of resistor 201 and resistor 202, and the base terminal of PNP transistor 205 is connected to the junction of resistor 202 and resistor 203. Terminal 108 is connected to the emitter terminal of NPN transistor 204 and the emitter terminal of PNP transistor 205. That is, the intermediate terminal 108 is connected to the emitter terminals of the two transistors. The terminal 106, the high potential side of the resistor 201, and the collector terminal of the NPN transistor 204 are connected, and the terminal 107, the low potential side of the resistor 203, and the collector terminal of the PNP transistor 205 are connected.

[0012] Next, the cell balancing operation will be explained using Figure 2. When charging switch 105 is turned on, the voltage of power supply 101 is applied to batteries 103 and 104, which are connected in series. If the characteristics of batteries 103 and 104 are different, the voltage of battery 103 is V103, the voltage of battery 104 is V104, and the voltages of the two batteries connected to the charging device are V103 > V104, the potential at terminal 108 of cell balancing circuit 102 drops, and the voltage between the base and emitter terminals of NPN transistor 204 (VBE204) and the voltage between the base and emitter terminals of PNP transistor 205 (VBE205) become VBE204 > VBE205, and the collector current (IC204) flowing through NPN transistor 204 increases and the collector current (IC205) flowing through PNP transistor 205 decreases. As a result, collector current IC204 > collector current IC205, the current (IB103) charging battery 103 decreases relative to the current (IB104) charging battery 104, and the increase in voltage V103 of battery 103 is suppressed. At the same time as this operation, IB104 increases, promoting the increase in voltage V104 of battery 104, which acts to equalize the voltages of batteries 103 and 104. As a result of this action, as charging progresses, V103 and V104 become approximately equal voltages, and cell balance is maintained.

[0013] When charging switch 105 is turned off, resistors 201, 202, and 203 are connected in series to batteries 103 and 104, so a constant current (IR) flows through the resistors, but by increasing the resistance value, the constant current IR can be set small relative to the load connected to the batteries. Even in this case, the action of transistors 204 and 205 can maintain the potential of terminal 108 at half that of terminal 106, making it possible to correct the battery voltage imbalance.

[0014] FIG. 3 shows a second overall configuration of a charging device according to an embodiment of the present invention. FIG. 3 is a modified example of FIG. 2 in which a control switch is added. The control switch in this embodiment may be referred to as a cell balance switch. The charging device, which charges batteries 103 and 104 connected in series, is composed of a power source 101, a cell balance circuit 110, a charging switch 105, and a cell balance switch 111. As described above, the charging device does not necessarily include the power source 101. The cell balance circuit 110 has terminals 106, 107, 108, and 109, which are connected to the high-potential electrode, low-potential electrode, and intermediate-potential electrode of the series-connected batteries 103 and 104, respectively, and the cell balance switch 111. The cell balance switch 111 is disposed between the cell balance circuit 110 and the power source 101. The cell balance switch 111 can interrupt current flowing through a resistive element. In this embodiment, the cell balance switch 111 interrupts current flowing through the resistive element under predetermined conditions. FIG. 4 shows a specific configuration example of the cell balance circuit 110, and its operation will be described.

[0015] 4 is a diagram showing a third embodiment of a charging device according to an embodiment of the present invention. Cell balance circuit 110 includes resistors 201, 202, 203, 221, 222, and 226, an NPN transistor 204, a PNP transistor 205, P-channel MOS transistors 223 and 224, and an N-channel MOS transistor 225. Resistors 201, 202, and 203 are connected in series, and the base terminal of NPN transistor 204 is connected to the junction of resistors 201 and 202, and the base terminal of PNP transistor 205 is connected to the junction of resistors 202 and 203. Terminal 108 is connected to the emitter terminal of NPN transistor 204 and the emitter terminal of PNP transistor 205 via P-channel MOS transistor 224. The high potential side of resistor 201 and the collector terminal of NPN transistor 204 are connected to terminal 106 via P-channel MOS transistor 223, and terminal 107 is connected to the low potential side of resistor 203 and the collector terminal of PNP transistor 205. Resistors 221 and 222 are connected in series between terminal 109 and terminal 107, and the gate terminal of N-channel MOS transistor 225 is connected to the connection point of resistors 221 and 222. The drain terminal of N-channel MOS transistor 225 is connected to terminal 106 via resistor 226 and further connected to the gate terminals of P-channel MOS transistors 223 and 224.

[0016] Next, the cell balancing operation will be explained using Figure 4. When charging switch 105 is turned on, the voltage of power supply 101 is applied to batteries 103 and 104, which are connected in series. In this state, only the power supply 101 charges batteries 103 and 104. Next, when cell balancing switch 111 is turned on, the divided potential created by resistors 221 and 222 is applied to the gate of N-channel MOS transistor 225, causing current from terminal 106 to flow to the drain terminal of N-channel MOS transistor 225 via resistor 226. This controls the gate terminals of P-channel MOS transistors 223 and 224 to turn them on, and establishes conduction between the drain and source of P-channel MOS transistors 223 and 224. As a result, the cell balancing operation described in Figure 2 is performed.

[0017] The cell balance switch 111 may be turned on / off in synchronization with the charging switch 105, but the battery may also be charged by keeping the cell balance switch 111 off during the constant current charging period and on only during the constant voltage charging period. Also, by keeping the cell balance switch 111 off when the charging switch 105 is off, it is possible to set the batteries 103 and 104 to a state where no accumulated charge is consumed when there is no load on them, and therefore no energy is wasted in the batteries.

[0018] As explained in the above embodiments, when there is a difference in voltage among multiple secondary batteries connected to a charging device, the cell balance circuit, which is an adjustment circuit, adjusts the charging current of the battery with the higher charging voltage to decrease relative to the charging current of the battery with the lower charging voltage, or adjusts the charging current of the battery with the lower charging voltage to increase relative to the charging current of the battery with the higher charging voltage. This makes it possible to charge secondary batteries connected in series while maintaining cell balance, and to achieve approximately the same voltage at the end of charging. This makes it possible to realize an ideal charging device.

[0019] FIG. 5 shows a third overall configuration of a charging device according to an embodiment of the present invention. This embodiment is a modified example in which multiple cell balancing circuits are provided when charging multiple secondary batteries connected in series. The charging device for charging batteries 103, 104, 113, and 114 comprises a power source 101, a first cell balancing circuit 102, a second cell balancing circuit 115, a third cell balancing circuit 116, and a charging switch 105. The first cell balancing circuit 102, the second cell balancing circuit 115, and the third cell balancing circuit 116 have the same configuration and include multiple resistors and multiple transistors. As described above, the charging device does not necessarily need to include the power source 101.

[0020] The first cell balance circuit 102 has terminals 106, 108, and 107, which are respectively connected to the high-potential electrode, intermediate-potential electrode, and low-potential electrode of the series-connected batteries 103 and 104. The second cell balance circuit 115 has terminals 117, 119, and 118, which are respectively connected to the high-potential electrode, intermediate-potential electrode, and low-potential electrode of the series-connected batteries 113 and 114. The third cell balance circuit 116 has terminals 120, 122, and 121, which are respectively connected to the high-potential electrode, intermediate-potential electrode, and low-potential electrode of the series-connected batteries 103 and 113. A specific configuration example of the cell balance circuits 102, 115, and 116 is shown in FIG. 6, and their operation will be described.

[0021] FIG. 6 is a specific configuration diagram showing a third embodiment of a charging device according to the present invention. The combination of battery 103, battery 104, and cell balance circuit 102 operates in the same manner as described in FIG. 2 , and therefore will not be described further. Furthermore, the combination of battery 113, battery 114, and cell balance circuit 115, and the combination of battery 104, battery 113, and cell balance circuit 116 operate in the same manner as described in FIG. 2 . This allows for uniform cell balance between adjacent batteries, and allows the voltages among the four batteries 103, 104, 113, and 114 to be kept approximately the same. When charging four secondary batteries, the operation of the three cell balance circuits can also make the voltages among the batteries approximately the same, resulting in a more suitable charging device.

[0022] Furthermore, when charging n secondary batteries connected in series, n-1 cell balancing circuits are sufficient. The n secondary batteries connected in series have n-1 connection points or intermediate terminals, and the n-1 cell balancing circuits are connected to the connection points or intermediate terminals (midpoints) of the n-1 secondary batteries, where n is a natural number. For the i-th battery and the (i+1)-th battery counted from the low potential side of the n-1 batteries connected in series, the first terminal of the i-th cell balancing circuit counted from the low potential side of the n-1 cell balancing circuits is connected to the negative electrode of the i-th battery, the second terminal of the i-th cell balancing circuit is connected to the positive electrode of the i-th battery, and the third terminal of the i-th cell balancing circuit is connected to the positive electrode of the (i+1)-th battery, where i is a natural number.

[0023] FIG. 7 shows a fourth overall configuration of a charging device according to an embodiment of the present invention. A charging device for charging three or more batteries will be described using an example in which n is 4. The charging device includes a power supply 101, a cell balance circuit 132, and a charging switch 105. As described above, the charging device does not necessarily include the power supply 101. The cell balance circuit 132 has three or more terminals, including terminals 133, 135, 136, 137, and 134, which are connected to five points, from the high-potential electrode to the low-potential electrode, of the series-connected batteries 103, 104, 113, and 114. A specific configuration example of the cell balance circuit 132 is shown in FIG. 8, and its operation will be described.

[0024] FIG. 8 is a specific configuration diagram showing a fourth embodiment of a charging device according to the present invention. Cell balancing circuit 132 includes a plurality of resistive elements or resistors, a plurality of NPN transistors, and a plurality of PNP transistors. Cell balancing circuit 132 is composed of resistors 141, 142, 143, 144, 145, 146, and 147, NPN transistors 148, 150, and 152, and PNP transistors 149, 151, and 153. Resistors 141, 142, 143, 144, 145, 146, and 147 are connected in series. The base terminal of NPN transistor 148 is connected to the junction of resistors 141 and 142, and the base terminal of PNP transistor 149 is connected to the junction of resistors 142 and 143. The emitter terminals of NPN transistor 148 and PNP transistor 149 are connected to terminal 135. The base terminal of NPN transistor 150 is connected to the junction of resistors 143 and 144, and the base terminal of PNP transistor 151 is connected to the junction of resistors 144 and 145. The emitter terminals of NPN transistor 150 and PNP transistor 151 are connected to terminal 136. The base terminal of NPN transistor 152 is connected to the junction of resistors 145 and 146, and the base terminal of PNP transistor 153 is connected to the junction of resistors 146 and 147. The emitter terminals of NPN transistor 152 and PNP transistor 153 are connected to terminal 137. Terminal 133, the high potential side of resistor 141, and the collector terminals of NPN transistors 148, 150, and 152 are connected, and terminal 134, the low potential side of resistor 147, and the collector terminals of PNP transistors 149, 151, and 153 are connected. The values ​​of resistors 141 to 147 are set so that the voltage between terminal 134 and terminal 137, the voltage between terminal 137 and terminal 136, the voltage between terminal 136 and terminal 135, and the voltage between terminal 135 and terminal 133 are all equal.

[0025] Next, the cell balancing operation will be described. When the charging switch 105 is turned on, the voltage of the power source 101 is applied to the batteries 103, 104, 113, and 114 connected in series.

[0026] Assume that batteries 103, 104, 113, and 114 have different characteristics, causing the voltages of the batteries to vary, and that battery 113 has the lowest voltage. In this case, the potential at terminal 137 increases while the potential at terminal 136 decreases. When the voltage at terminal 137 increases, the voltage between the base and emitter of PNP transistor 153 increases, and the voltage between the base and emitter of NPN transistor 152 decreases. As a result, the emitter current (IE152) of NPN transistor 152 decreases, and the emitter current (IE153) of PNP transistor 153 increases, and the difference current (IE153-IE152) becomes a first action that increases the charging current of battery 113.

[0027] Furthermore, when the voltage at terminal 136 drops, the voltage between the base and emitter terminals of NPN transistor 150 increases, and the voltage between the base and emitter terminals of PNP transistor 151 decreases. As a result, the emitter current (IE150) of NPN transistor 150 increases, and the emitter current (IE151) of PNP transistor 151 decreases, resulting in a second action of increasing the charging current of battery 113.

[0028] The first and second effects work together to increase the charging current of the battery 113, and the voltage of the battery 113 therefore rises.

[0029] On the other hand, suppose the battery with the highest voltage is battery 104. In this case, the potential at terminal 136 drops and at the same time the potential at terminal 135 rises. When the potential at terminal 136 drops, the voltage between the base and emitter terminals of NPN transistor 150 increases, and the voltage between the base and emitter terminals of PNP transistor 151 decreases. As a result, the emitter current (IE150) of NPN transistor 150 increases and the emitter current (IE151) of PNP transistor 151 decreases, resulting in a third action of increasing the charging current to the series element of battery 113 and battery 114.

[0030] Furthermore, when the voltage at terminal 135 rises, the voltage between the base and emitter terminals of PNP transistor 149 increases, and the voltage between the base and emitter terminals of NPN transistor 148 decreases. As a result, the emitter current (IE149) of PNP transistor 149 increases, and the emitter current (IE148) of NPN transistor 148 decreases, resulting in a fourth action of increasing the charging current of battery 103.

[0031] The third and fourth effects work together to increase the charging current of the batteries 113, 114, and 103, so that the voltages of the batteries 113, 114, and 103 rise and the voltage of the battery 104 drops relatively.

[0032] The operation described above has the effect of automatically correcting the voltage balance among the four cells even if the voltages are out of balance, and it is possible to maintain approximately the same voltage among the four batteries 103, 104, 113, and 114. This makes it possible to realize a suitable charging device.

[0033] 8 , an example of a charging device that charges four secondary batteries connected in series and in which the cell balance circuit has five terminals has been described. However, when charging n secondary batteries connected in series, the cell balance circuit has n+1 terminals, and the n secondary batteries connected in series each have n−1 connection points or intermediate terminals (middle points), and the intermediate terminals (connection points or middle points) of the n−1 secondary batteries are connected to the n−1 terminals of the cell balance circuit, where n is a natural number. The cell balance circuit is also composed of 2n−1 resistors, n−1 NPN transistors, and n−1 PNP transistors, and the ith intermediate point or intermediate terminal, counted from the low-potential side of the n secondary batteries connected in series, is connected to the emitter terminal of the ith NPN transistor and the emitter terminal of the ith PNP transistor.

[0034] If the voltage of one of two adjacent secondary battery cells becomes high, the charging current to the lower voltage cell is increased to increase the cell voltage, and if the voltage of one of two adjacent battery cells becomes low, the charging current to the higher voltage cell is reduced to prevent an increase in the cell voltage, so that the voltages of the two adjacent battery cells become approximately equal at the end of charging. Alternatively, if the voltage of one of two adjacent battery cells becomes high, the charging current to the lower voltage cell is increased to increase the cell voltage, and if the voltage of one of two adjacent battery cells becomes low, the charging current to the higher voltage cell is reduced.

[0035] In this embodiment, when charging a plurality of secondary batteries connected in series, if a difference in voltage occurs among the plurality of secondary batteries, by providing one or more adjustment circuits or cell balance circuits, the charging current or charging voltage can be automatically adjusted to make the voltages approximately the same at the end of charging, thereby realizing a more suitable charging device. This improves the performance of a power supply device equipped with the charging device of this embodiment and a unit battery consisting of a plurality of secondary batteries connected in series.

[0036] An example of the configuration of a charging device will be described as a fifth embodiment of the present invention. The charging device according to this embodiment can be applied with the basic configuration of the configurations shown in the drawings described in the first embodiment. In this fifth embodiment, differences from the first embodiment will be mainly described, and repeated description of the same configuration as the first embodiment will be omitted.

[0037] As shown in FIG. 9 , the cell balance circuit 102 (balancing circuit) of this embodiment, like the cell balance circuit 102 of the first embodiment, has terminals 106, 107, and 108, which are connected to the high-potential electrode, low-potential electrode, and intermediate-potential electrode of the series-connected battery 103 and battery 104, respectively. That is, the terminal 106 of the cell balance circuit 102 is connected to the high-potential side (positive electrode side of the unit battery) of the multiple secondary batteries to be charged. Furthermore, when the power source 101 is built into a charging device, the terminal 106 of the cell balance circuit 102 is connected to the high-potential side (positive electrode side) of the power source 101. The terminal 107 of the balancing circuit 102 is connected to the low-potential side (negative electrode side of the unit battery) of the multiple secondary batteries to be charged. Furthermore, when the power source 101 is built into a charging device, the terminal 107 of the cell balance circuit 102 is connected to the low-potential side (negative electrode side) of the power source 101. Terminals 106 and 107 of balancing circuit 102 are connected to the high-potential side and low-potential side of power supply 101, respectively, and charge batteries 103 and 104. Terminal 108 of balancing circuit 102 serves as an intermediate terminal and is connected between the two secondary batteries arranged in series. Charging switch 105 is provided between power supply 101 and terminal 106 of balancing circuit 102. The location of charging switch 105 is not limited; for example, it may be on the low-potential side, or may be arranged as needed. The specific operation of balancing circuit 102 will now be described.

[0038] 9 is a diagram showing a fifth embodiment of a charging device according to the present invention. Balancing circuit 102 includes a plurality of resistors and a plurality of diodes. Balancing circuit 102 is configured with resistors 211 and 213 and diodes 212, 214, 215, and 216. Resistors 211 and 213 may be referred to as first resistor 211 and second resistor 213, respectively. Diodes 212, 214, 215, and 216 may be referred to as first diode 212, second diode 214, third diode 215, and fourth diode 216, respectively.

[0039] Between terminal 106 and terminal 108 of balance circuit 102, a series element consisting of resistor 211 and diode 212 is connected, and further connected in parallel with diode 215. Specifically, one terminal of resistor 211 is connected to terminal 106, the other terminal of resistor 211 is connected to the anode side or anode terminal of diode 212, and the cathode side or cathode terminal of diode 215 is connected to terminal 106. Between terminal 108 and terminal 107, a series element consisting of resistor 213 and diode 214 is connected, and further connected in parallel with diode 216. Specifically, one terminal of resistor 213 is connected to the anode side or anode terminal of diode 214, and the cathode side or cathode terminal of diode 214 is connected to terminal 107. The anode side or anode terminal of diode 216 is connected to terminal 107. Furthermore, the connection point between the cathode side of diode 212 and the other terminal of resistor 213 is connected to the connection point between the anode side of diode 215 and the cathode side of diode 216 , and these two connection points are connected to terminal 108 .

[0040] The balancing circuit includes four diodes and two resistors. One terminal of a first resistor is connected to the anode terminal of the first diode, the cathode terminal of the first diode is connected to one terminal of a second resistor, and the other terminal of the second resistor is connected to the anode terminal of the second diode. The anode terminal of a third diode is connected to the cathode terminal of a fourth diode. A junction point between the cathode terminal of the first diode and the second resistor is connected to a junction point between the third diode and the fourth diode. A junction point between the other terminal of the first resistor and the cathode terminal of the third diode is connected to a high potential side of a power supply, and a junction point between the cathode terminal of the second diode and the anode terminal of the fourth diode is connected to a low potential side of the power supply.

[0041] Next, the cell balancing operation will be explained using Figure 9. When charging switch 105 is turned on, the voltage of power supply 101 is applied to secondary batteries 103 and 104 connected in series. Normally, the potential of terminal 108 is maintained at half the potential of terminal 106. However, if the characteristics of batteries 103 and 104 differ and the battery voltages V103 > V104, the voltage of diode 212 (V212) becomes larger than the voltage of diode 214 (V214), and the current (I211) flowing through resistor 211 becomes larger than the current (I213) flowing through resistor 213. As a result, the current (IB103) charging battery 103 decreases compared to the current (IB104) charging battery 104, suppressing the increase in voltage V103 of battery 103. At the same time as this operation, IB104 increases, promoting an increase in the voltage V104 of battery 104, which acts to equalize the voltages of battery 103 and battery 104. As a result of this action, as charging progresses, V103 and V104 become approximately equal voltages, and cell balance is maintained.

[0042] When charging switch 105 is turned off, resistors 211 and 213 and diodes 212 and 214 are connected in series between battery 103 and battery 104, causing a constant current (IR) to flow through the resistors. Resistors 211 and 213 are set to have large values ​​and small IR relative to the load connected to the batteries. However, when there is no load, a phenomenon called polarity reversal is likely to occur due to variations in the voltages of batteries 103 and 104. Diodes 215 and 216 are connected to prevent this polarity reversal. For example, if the potential of battery 104 reverses and exceeds the forward voltage (VF216) of diode 216, diode 216 turns on, suppressing polarity reversal below VF216, thereby correcting the battery voltage imbalance.

[0043] Furthermore, because the diode 212 is connected in series with the resistor 211, if the voltage of the battery 103 becomes lower than the forward voltage of the diode 212, the current flowing through the resistor 211 decreases, and the post-discharge voltage of the battery is kept at 0.7 (V). This has the effect of preventing over-discharge. The same operation occurs for the battery 104, so the post-discharge voltages can be made uniform, and the effect of simply ensuring cell balance during discharge is obtained.

[0044] When charging n secondary batteries connected in series, n-1 balancing circuits are sufficient. The n secondary batteries connected in series have n-1 connection points or intermediate terminals, and the n-1 balancing circuits are connected to the connection points or intermediate terminals (midpoints) of the n-1 secondary batteries, where n is a natural number. For the i-th battery and the (i+1)-th battery counted from the low potential side of the n secondary batteries connected in series, the first terminal of the i-th balancing circuit counted from the low potential side of the n-1 balancing circuits is connected to the negative electrode of the i-th battery, the second terminal of the i-th balancing circuit is connected to the positive electrode of the i-th battery, and the third terminal of the i-th balancing circuit is connected to the positive electrode of the (i+1)-th battery, where i is a natural number.

[0045] As described in the above embodiments, secondary batteries connected in series can be charged while maintaining a balance, and the voltages of the two batteries can be made approximately equal at the end of charging, thereby achieving a more suitable charging device. According to an embodiment of the present invention, when the voltage of one of two adjacent secondary battery cells becomes high, the charging current to the lower-voltage cell is increased to increase the cell voltage, and when the voltage of one of the two adjacent battery cells becomes low, the charging current to the higher-voltage cell is reduced to prevent an increase in the cell voltage, thereby making the voltages of the two adjacent battery cells approximately equal at the end of charging. In this way, the performance of a power supply device including the charging device of this embodiment and a unit battery consisting of multiple secondary batteries connected in series can be improved.

[0046] Furthermore, the technology according to this embodiment can provide a charge / discharge system with excellent energy efficiency, which contributes to the achievement of "9. Build resilient infrastructure, promote inclusive and sustainable industrialization, promote inclusive and sustainable technological development, and make sustainable use of resources" and "11. Make cities and towns sustainable and livable" of the Sustainable Development Goals (SDGs) advocated by the United Nations.

[0047] Although various embodiments have been described above in detail, the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments are detailed descriptions of the entire system in order to clearly explain the present invention, and the present invention is not necessarily limited to a system including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0048] 101...power supply, 102...cell balance circuit, 103...battery, 104...battery, 105...charging switch

Claims

1. A charging device for charging a plurality of secondary batteries connected in series, comprising: a cell balancing circuit having a plurality of resistors and a plurality of terminals, a first terminal of the cell balancing circuit connected to the low potential side of the plurality of secondary batteries, a second terminal of the cell balancing circuit being an intermediate terminal connected between the plurality of secondary batteries, and a third terminal of the cell balancing circuit connected to the high potential side of the plurality of secondary batteries.

2. A charging device according to claim 1, wherein the cell balance circuit is composed of three resistors, an NPN transistor and a PNP transistor, and the intermediate terminal is connected to the emitter terminals of the two transistors.

3. A charging device as described in claim 2, wherein the three resistors are connected in series in the order of a first resistor, a second resistor, and a third resistor; a base terminal of the NPN transistor is connected to a connection point between the first resistor and the second resistor; a collector terminal of the NPN transistor is connected to the side opposite the connection point of the first resistor; a base terminal of the PNP transistor is connected to a connection point between the second resistor and the third resistor; a collector terminal of the PNP transistor is connected to the side opposite the connection point of the third resistor; an emitter terminal of the NPN transistor and an emitter terminal of the PNP transistor are connected, and the two emitter terminals are connected to the second terminal.

4. A charging device according to claim 1, wherein the cell balance circuit has three resistors, an NPN transistor, a PNP transistor, and two P-channel MOS transistors, the intermediate terminal is connected to the emitter terminals of the two transistors via a first P-channel MOS transistor, and the collector terminal of the NPN transistor is connected to the power supply via a second P-channel MOS transistor.

5. The charging device according to claim 1, wherein the cell balance circuit is connected to a power source via a control switch.

6. A charging device according to claim 1, comprising n-1 cell balance circuits, the n secondary batteries connected in series each having n-1 intermediate terminals, and the n-1 cell balance circuits each being connected to the n-1 intermediate terminals.

7. A charging device as claimed in claim 6, wherein, for the i-th secondary battery and the (i+1)th secondary battery from the low potential side of n secondary batteries connected in series, a first terminal of the i-th cell balance circuit from the low potential side of the n-1 cell balance circuits is connected to the negative electrode of the i-th secondary battery, a second terminal of the i-th cell balance circuit is connected to the positive electrode of the i-th secondary battery, and a third terminal of the i-th cell balance circuit is connected to the positive electrode of the i+1th secondary battery.

8. A charging device as described in claim 1, wherein when the number of secondary batteries connected in series is n, the n secondary batteries have n-1 connection points or intermediate terminals, and the n-1 terminals of the cell balance circuit are respectively connected to the connection points of the n-1 secondary batteries.

9. A charging device as described in claim 8, wherein the cell balance circuit is composed of 2n-1 resistors, n-1 NPN transistors, and n-1 PNP transistors, and the i-th intermediate terminal from the low potential side of the n secondary batteries connected in series is connected to the emitter terminal of the i-th NPN transistor from the low potential side and the emitter terminal of the i-th PNP transistor from the low potential side.

10. A charging device according to any one of claims 1 to 9, wherein the cell balance circuit adjusts the charging voltage or the charging current when a difference occurs in the charging voltages of the multiple secondary batteries during charging.

11. A power supply device comprising the charging device according to claim 10 and a unit battery consisting of a plurality of secondary batteries connected in series.

12. The power supply device according to claim 11, wherein the secondary battery is an all-solid-state battery.

13. A charging device as claimed in claim 1, wherein the cell balance circuit has two diodes connected in series, the two sets of series elements connected in series and the two diodes connected in series are connected in parallel, and the connection point of the two sets of series elements and the connection point of the two diodes are connected.

14. A charging device as described in claim 1, wherein the cell balance circuit comprises four diodes and two resistors, one terminal of a first resistor is connected to an anode terminal of a first diode, a cathode terminal of the first diode is connected to one terminal of a second resistor, the other terminal of the second resistor is connected to an anode terminal of a second diode, the anode terminal of the third diode is connected to a cathode terminal of a fourth diode, a connection point between the cathode terminal of the first diode and the second resistor and a connection point between the third diode and the fourth diode is connected, the connection point between the other terminal of the first resistor and the cathode terminal of the third diode is connected to the high potential side of the multiple secondary batteries, and a connection point between the cathode terminal of the second diode and the anode terminal of the fourth diode is connected to the low potential side of the multiple secondary batteries.

15. A power supply device comprising the charging device according to claim 13 or 14, and a unit battery consisting of a plurality of secondary batteries connected in series.

16. The power supply device according to claim 15, wherein the secondary battery is an all-solid-state battery.

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