Battery charging device and charging system
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MAXELL LTD
- Filing Date
- 2026-01-21
- Publication Date
- 2026-07-30
Smart Images
Figure JP2026001811_30072026_PF_FP_ABST
Abstract
Description
Battery Charging Device and Charging System
[0001] The present invention relates to a charging device and a charging system for charging a plurality of secondary batteries.
[0002] There is a method of connecting a plurality of rechargeable battery cells in series to realize a high-voltage battery. However, when charging and discharging are repeatedly performed in a state where a large number of battery cells are connected in series, the voltage of the battery cells (or the remaining capacity of the battery cells) may become uneven due to variations in the characteristics of each battery. The uneven voltage of each battery cell may accelerate the deterioration of some battery cells, resulting in a reduction in the usable capacity of the entire battery. For this reason, as a technique for equalizing the voltages of a plurality of battery cells, a method has been proposed in which the voltage of each battery cell is monitored and a cell balancing operation is performed to move charges from a battery cell with a high voltage to a battery cell with a low voltage. This cell balancing operation is realized, for example, by an inductor, a capacitor provided between the battery cells, and a switch that controls the charge according to the voltage of each battery cell, and the voltages of the plurality of battery cells are equalized or substantially equalized. Techniques related to the equalization of battery cell voltages are described, for example, in Patent Document 1 below. In addition, techniques related to a method of limiting the current so as not to exceed the upper limit voltage of each battery cell connected in series when performing constant voltage charging are described, for example, in Patent Document...
[0003] Japanese Patent Application Laid-Open No. 2023-84627, Japanese Patent No. 6707373
[0004] However, in the disclosures of Patent Documents 1 to 2, there are problems such that the battery system becomes large because the number of components constituting the cell balance circuit or the circuit for limiting the upper limit voltage of the battery cell is large, and the operation of the cell balance circuit requires a power source and a control circuit separate from the battery.
[0005] The present invention has been made in view of such circumstances, and an object thereof is to provide a charging device and a charging system using a simpler cell balance circuit.
[0006] To solve the above problems, one embodiment of the present invention is a charging device for charging a plurality of batteries connected in series, comprising a power supply and a plurality of cell voltage limiters. The cell voltage limiters are connected in parallel to each battery.
[0007] According to the present invention, more suitable charging devices and charging systems can be realized.
[0008] This is a configuration diagram of the first embodiment of a charging device according to one embodiment of the present invention. This is a configuration diagram of the second embodiment of a charging device according to one embodiment of the present invention. This is a diagram showing the operation of a charging device according to one embodiment of the present invention. This is a configuration diagram of the third embodiment of a charging device according to one embodiment of the present invention. This is a diagram showing the operation of a charging device according to one embodiment of the present invention. This is a diagram showing the operation of a charging device according to one embodiment of the present invention. This is a configuration diagram of the fourth embodiment of a charging device according to one embodiment of the present invention.
[0009] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that the present invention is not limited to the examples described herein, and various modifications and alterations are possible by those skilled in the art within the scope of the technical ideas disclosed herein. Furthermore, in all the drawings used to illustrate embodiments of the present invention, components having the same function are generally given the same reference numerals, and repeated descriptions may be omitted.
[0010] Figure 1 shows the overall configuration of a first embodiment of a charging device according to one embodiment of the present invention. The charging device consists of a power supply 101, a charging switch 102, and a battery unit 120. The battery unit 120 has a positive terminal 119 and a negative terminal 118. The battery unit 120 also has batteries or secondary batteries 103, 104, and 105 connected in series, and cell voltage limiters 106, 107, and 108 connected in parallel to each battery. In this embodiment, batteries 103, 104, and 105 are batteries of the same specifications, and the cell voltage limiters 106, 107, and 108 are the same circuit. Batteries 103, 104, and 105 may also be battery cells. The cell voltage limiter is a type of passive cell balancing circuit, and the cell voltage limiters 106, 107, and 108 can make the charge state of the batteries substantially uniform.
[0011] In the following, cell voltage limiters 106 to 108 will be described using cell voltage limiter 108 as an example. Cell voltage limiter 108 consists of resistors 111, 113, 114, and 117, NPN bipolar transistors (hereinafter referred to as NPN transistors) 112 and 115, a P-channel MOS field-effect transistor (hereinafter referred to as P-type FET) 116, and terminals 109 and 110. Specifically, cell voltage limiter 108 consists of an element in which one resistor 117 and one MOS field-effect transistor 116 are connected in series, and is connected in parallel to battery 105. The gate terminal of the MOS field-effect transistor 116 is connected to a control circuit consisting of three resistors 111, 113, and 114 and two thermally coupled bipolar transistors 112 and 115.
[0012] Next, the operation will be explained. Batteries 103, 104, and 105 are connected in series and connected to the power supply 101 via the charging switch 102. When the charging switch 102 is turned ON and current is supplied from the power supply 101 to batteries 103-105, the voltage of batteries 103-105 rises over time. Even if batteries 103-105 are manufactured to the same specifications, differences in internal battery capacity and internal resistance will cause variations in the rise of the battery voltage. As an example, Figure 4 shows the state of voltage variation. Figure 4 shows the change in the voltage of batteries 103, 104, and 105 with respect to the elapsed time since the charging switch 102 was turned ON, indicated by characteristics 301, 302, and 303. Voltage 305 shows the voltage of battery 105 at a predetermined time 306, and voltage 304 shows the standard voltage when charging the batteries.
[0013] The charging current supplied from power supply 101 decreases as charging progresses from battery 103 to battery 105, and the charging from battery 103 to battery 105 switches to constant voltage charging. The voltage setting for constant voltage charging is set to the standard voltage 304 (let's call it Vbat) multiplied by the number of batteries connected in series (3 in this embodiment). However, in the example shown in Figure 4, due to variations in the characteristics of the batteries, at a predetermined time 306, the voltage 305 of battery 105 is higher than Vbat. If the battery voltage exceeds Vbat as charging progresses, the battery life will be shortened, so it is preferable to keep the voltage 305 of battery 105 below Vbat. It is possible to improve the battery life by lowering the set voltage when power supply 101 switches to constant voltage charging, for example, by setting the voltage 305 to be lower than the voltage 304. However, this method is not preferable because it reduces the amount of charge that can be charged into the battery and makes it impossible to ensure discharge performance. In contrast, by adding a cell voltage limiter 108 in parallel with the battery 105, the battery voltage can be more appropriately controlled to prevent it from exceeding Vbat, resulting in a characteristic 307.
[0014] The operation of the cell voltage limiter 108 will now be explained. Terminal 109 of the cell voltage limiter 108 is connected to the positive terminal of the battery 105, and terminal 110 of the cell voltage limiter 108 is connected to the negative terminal of the battery 105. Between terminals 109 and 110, a resistor 111, an NPN transistor 112, and a resistor 113 are connected in that order. The base terminal and collector terminal of the NPN transistor 112 are connected. Also, between terminals 109 and 110, a resistor 114 and an NPN transistor 115 are connected, and the base terminal of the NPN transistor 115 is connected to the connection point between resistor 111 and the collector terminal of the NPN transistor 112. Between terminals 109 and 110, a P-type FET 116 and a resistor 117 are connected in that order, and the gate terminal of the P-type FET 116 is connected to the connection point between resistor 114 and the collector terminal of transistor 115. If VBE is the voltage between the base and emitter of the NPN transistor 115, hfe is the DC current amplification factor of the NPN transistor 115, R111, R113, R114, and R117 are the resistance values of resistors 111, 113, 114, and 117, and V105 is the voltage of battery 105, then the collector current Ic of the NPN transistor 115 can be expressed by the following equation (1): Ic = hfe * (V105 - VBE) / R111 ... (1)
[0015] If Vth is the threshold voltage between the gate terminal and the source terminal for the source terminal and drain terminal of the P-type FET 116 to conduct, then current flows through resistor 117 when the following condition (2) is met. The current Im flowing through resistor 117 is expressed by the following equation (3). Vth < Ic * R114 ... (2) Im = V105 / R117 ... (3)
[0016] The relationship between V105 and Im + Ic is shown in Figure 3. In Figure 3, characteristic 201 shows the characteristics of the current flowing from terminal 109 to terminal 110 with respect to V105, voltage 203 is the voltage when the condition by equation (2) is met, and voltage 202 is Vbat. Current 205 is approximately 1 / 2 of Im or 1 / 2 of Im, and current 204 (Im) can be determined approximately by equation (3), and is the branch current relative to the current that charges the battery. Since the branch current is the current that flows from terminal 109 to terminal 110, the current that charges the battery 105 is branched by the cell voltage limiter 108, suppressing the charging of the battery 105 and suppressing the rise in the voltage of the battery 105. Due to the operation of the cell voltage limiter 108 as described above, the battery voltage shown in Figure 4 can be made to have characteristics 307 such that it does not exceed Vbat, improving the lifespan and maintaining the amount of charge that can be charged into the battery.
[0017] Figure 2 shows the configuration of a charging device according to one embodiment of the present invention. The charging device consists of a power supply 101, a charging switch 102, a control switch 123, and a battery unit 121. The battery unit 121 has a positive terminal 119, a negative terminal 118, and a control terminal 122. The battery unit 121 also has batteries or secondary batteries 103, 104, and 105 connected in series, and cell voltage limiters 106, 107, and 108 connected in parallel to the positive terminal of each battery via P-type FETs 124, 125, and 126.
[0018] Multiple cell voltage limiters 106, 107, and 108 are connected in series with multiple MOS field-effect transistors (P-type FETs) 124, 125, and 126. The gate terminals of the P-type FETs 124, 125, and 126 are connected to an element composed of one or more of the following: a diode, a resistor, and an N-channel MOS field-effect transistor. In this embodiment, the gate terminal of P-type FET 124 is connected to the resistor of a series element composed of a diode 128 and a resistor 129. The gate terminal of P-type FET 125 is connected to an element composed of a resistor 130. The gate terminal of P-type FET 126 is connected to the resistor of a series element composed of a resistor 131 and an N-channel MOS field-effect transistor (hereinafter referred to as N-type FET) 127. Alternatively, a first series element is formed by connecting a diode 128 and a resistor 129, a resistor 130, a resistor 131, and a first N-type MOS field-effect transistor 127 in series. The gate terminals of the multiple P-type MOS field-effect transistors 124, 125, and 126 are connected to the connection point of the resistor of the first series element, the diode terminal of the first series element is connected to the high-potential side of the power supply, and the first N-type MOS field-effect transistor 127 is connected to the low-potential side of the power supply.
[0019] The control switch 123 is connected to resistors 132 and 133 via control terminal 122, and the gate terminal of the N-type FET 127 is connected to the connection point between resistors 132 and 133.
[0020] Let me explain the differences between Figure 1 and Figure 2. In Figure 1, the cell voltage limiters 106, 107, and 108 are always connected in parallel to the batteries 103, 104, and 105. In Figure 2, however, the cell voltage limiters 106, 107, and 108 are configured to be connected in parallel to the batteries 103, 104, and 105 at any desired timing based on control information from the control terminal 122.
[0021] Next, the operation will be described. When the charging switch 102 is turned ON and current is supplied from the power supply 101 to batteries 103-105, the voltage of batteries 103-105 increases over time. The charging current supplied from the power supply 101 decreases as the charging of batteries 103-105 progresses, and the charging of batteries 103-105 switches to constant voltage charging. At the same time as the switch to constant voltage charging, the control switch 123 is turned ON. The voltage of the power supply 101 is divided by resistors 132 and 133 via the control terminal 122 and applied to the gate terminal of the N-type FET 127, turning the N-type FET 127 ON and making the drain terminal and source terminal conductive. As the N-type FET 127 becomes conductive, current flows from the power supply 101 to the diode 128 and resistors 129, 130, and 131. As a result, the voltage at the gate terminals of the P-type FETs 124, 125, and 126 drops below the voltage at the source terminals. This causes the source and drain terminals of the P-type FETs 124, 125, and 126 to conduct electricity, and the cell voltage limiters 106, 107, and 108 are connected in parallel to the batteries 103, 104, and 105, respectively. This allows the cell voltage limiters 106, 107, and 108 to perform their predetermined operations.
[0022] When the control switch 123 is in the off state, the voltage at the gate terminal of the N-type FET 127 becomes equal to the voltage at the source terminal, and the N-type FET 127 is in the off state, so the drain terminal and source terminal become non-conductive. Because the N-type FET 127 is non-conductive, the current flowing from the power supply 101 to the diode 128 and resistors 129, 130, and 131 is interrupted. As a result, the voltage at the gate terminals of the P-type FETs 124, 125, and 126 becomes equal to or approximately equal to the power supply voltage, and equal to or higher than the voltage at the source terminal, so the source terminals and drain terminals of the P-type FETs 124, 125, and 126 become non-conductive. Consequently, the cell voltage limiters 106, 107, and 108 are isolated from the batteries 103, 104, and 105, and the cell voltage limiters 106, 107, and 108 do not operate at all.
[0023] The effect of the embodiment in Figure 2 is that, similar to the embodiment in Figure 1, in addition to improving the lifespan of batteries 103, 104, and 105 by the cell voltage limiters 106, 107, and 108, the internal power consumption of batteries 103, 104, and 105 can be suppressed when the battery unit 121 is disconnected at terminals 119, 118, and 122.
[0024] Figure 5 shows the configuration of a third embodiment of a charging device according to one embodiment of the present invention. The charging device consists of a power supply 101, a charging switch 102, and a battery unit 120. The battery unit 120 has a positive terminal 119 and a negative terminal 118. The battery unit 120 also includes a plurality of batteries or secondary batteries connected in series, and a cell voltage limiter connected in parallel to each battery or secondary battery. The secondary batteries may be all-solid-state batteries made of a solid electrolyte. The solid electrolyte may be an oxide-based solid electrolyte, a sulfide-based material, etc. This embodiment will be described as an example of three batteries or secondary batteries connected in series. Battery 103 is connected in parallel to cell voltage limiter 106, battery 104 is connected in parallel to cell voltage limiter 107, and battery 105 is connected in parallel to cell voltage limiter 108. In this embodiment, batteries 103, 104, and 105 are batteries of the same specifications, and cell voltage limiters 106, 107, and 108 are the same circuit. The cell voltage limiters 106, 107, and 108 each include a reference voltage generation circuit, a detection circuit that detects a voltage obtained by dividing the cell voltage, and a comparison control circuit that receives and compares the voltages from the reference voltage generation circuit and the detection circuit.
[0025] In the following, cell voltage limiters 106 to 108 will be described using cell voltage limiter 108 as an example. A cell voltage limiter comprises a resistor, an NPN transistor, a PNP bipolar transistor (hereinafter referred to as PNP transistor), an N-type FET, and terminals. The cell voltage limiter 108 in this embodiment is composed of a plurality of resistors 401 to 409, a plurality of NPN transistors 410 to 414, a PNP transistor, PNP transistors 415 and 416, an N-type FET 417, terminal 109, and terminal 110. Specifically, the cell voltage limiter 108 is composed of an element in which a resistor 409 and an N-channel MOS field-effect transistor (N-type FET) 417 are connected in series, and is connected in parallel to the battery 105. By controlling the voltage of the gate terminal of the N-type FET 417, the current flowing from terminal 109 to terminal 110 via the element in which the resistor 409 and the N-type FET 417 are connected in series is controlled.
[0026] Next, the operation will be explained. Batteries 103, 104, and 105 are connected in series and connected to the power supply 101 via the charging switch 102. When the charging switch 102 is turned on and current is supplied from the power supply 101 to batteries 103-105 without a cell voltage limiter, the voltage of batteries 103-105 rises over time. Even if batteries 103-105 are manufactured to the same specifications, differences in internal battery capacity and internal resistance will cause variations in the rise of the battery voltage. As an example, Figure 4 shows the state of voltage variation. Figure 4 shows the change in voltage of batteries 103, 104, and 105 with respect to the elapsed time since the charging switch 102 was turned on, as shown by characteristics 301, 302, and 303. Voltage 305 shows the voltage of battery 105 at a predetermined time 306, and voltage 304 shows the standard voltage when charging the batteries.
[0027] The charging current supplied from power supply 101 decreases as charging of batteries 103 to 105 progresses, and the charging of batteries 103 to 105 switches to constant voltage charging. The voltage setting for constant voltage charging is set to a number of times the standard voltage 304 (let's call it Vbat) that is connected in series with the batteries (in this embodiment, three times the number of batteries). However, in the example shown in Figure 4, due to variations in the characteristics of the batteries, at a predetermined time 306, the voltage 305 of battery 105 is higher than Vbat. If the voltage of battery 105 exceeds Vbat as charging progresses, the battery life will be shortened, so it is preferable to keep the voltage 305 of battery 105 below Vbat. It is possible to improve the battery life by lowering the set voltage when power supply 101 switches to constant voltage charging, for example, by setting the voltage 305 to be lower than the voltage 304. However, this method is not preferable because it reduces the amount of charge that can be charged into the battery and makes it impossible to ensure discharge performance. In contrast, by adding a cell voltage limiter 108 in parallel with the battery 105, the battery voltage can be more appropriately controlled to prevent it from exceeding Vbat, resulting in a characteristic 307.
[0028] A reference voltage generation circuit, consisting of resistors 401, 402, 403, NPN transistor 410, NPN transistor 411, NPN transistor 412, and resistor 404, is connected between terminals 109 and 110. The output voltage of the reference voltage generation circuit is output as a reference voltage to the collector terminal of NPN transistor 412. Specifically, the output voltage value of the reference voltage generation circuit is set to be high at low temperatures and low at high temperatures. The output voltage value of the reference voltage generation circuit is set to be higher as the temperature decreases and lower as the temperature increases. NPN transistors 410 and 411 are thermally coupled and constitute a first current mirror, so their collector currents are equal, and a stable voltage value can be obtained at the base terminal of the NPN transistor with respect to temperature changes. Specifically, NPN transistors 410 and 411 are thermally coupled and constitute a current mirror. A current mirror is a circuit that copies the electric current like a mirror, meaning it can output an input current with almost perfect accuracy. Furthermore, current mirror circuits have the advantage of suppressing the effects of characteristic variations due to temperature changes. The reference voltage output can be arbitrarily adjusted by setting the ratio of resistors 403 and 404 to add either positive or negative changes due to temperature variations.
[0029] Furthermore, a series element consisting of resistors 405 and 406 is connected between terminals 109 and 110. The voltage between terminals 109 and 110 is divided by resistors 405 and 406 to form a detection circuit, which is output as a detection voltage. In addition, a comparator control circuit consisting of PNP transistors 415 and 416, NPN transistors 413 and 414, resistors 407 and 408 is connected between terminals 109 and 110. The comparator control circuit consists of a differential amplifier circuit using two thermally coupled NPN transistors 413 and 414, a second current mirror circuit using PNP transistors 415 and 416, and a control circuit using resistor 408. The output of the comparator control circuit is connected to the gate terminal of an N-type FET 417. In other words, the gate terminal of a MOS field-effect transistor is connected to a control circuit that consists of a reference voltage generation circuit, a detection circuit that detects a voltage obtained by dividing the cell voltage, and a comparison circuit that receives and compares the voltages from the reference voltage generation circuit and the detection circuit.
[0030] In the comparator control circuit, the detection voltage (Vdet) input to the base terminal of the NPN transistor 413 is compared with the reference voltage (Vref) input to the base terminal of the NPN transistor 414. If Vdet > Vref, the collector current of the NPN transistor 413 increases, increasing the current flowing through the resistor 408 via the PNP transistors 415 and 416 that constitute the second current mirror, thereby raising the output voltage (control voltage) of the control circuit. The control voltage of the comparator control circuit is input to the gate terminal of the N-type FET 417. When the control voltage increases, the drain current increases, allowing the current flowing from terminal 109 to terminal 110 to increase, which becomes the branch current for charging the battery 105. Since the branch current is the current flowing from terminal 109 to terminal 110, the current for charging the battery 105 is branched at the cell voltage limiter 108, suppressing the charging of the battery 105 and preventing the battery voltage from rising. The operation of the cell voltage limiter 108 described above makes it possible to set the battery voltage shown in Figure 4 to a characteristic 307 such that it does not exceed Vbat, thereby improving the lifespan and maintaining the amount of charge that can be charged into the battery.
[0031] Figure 6 shows an example of the operating characteristics of a cell voltage limiter when using a third embodiment of the present invention. As an example, it shows the case when the limiter operating voltage of cell voltage limiters 106, 107, and 108 is set to around 2.6 (V). In Figure 6, the horizontal axis represents the voltage value supplied from the power supply 101, the first vertical axis represents the voltage between terminals 109 and 110 (limiter voltage), and the second vertical axis represents the current value flowing through resistor 409. Graph 601 shows the current flowing through resistor 409, and it can be seen that current starts to flow when the voltage supplied from the power supply 101 exceeds approximately 8 (V). Correspondingly, graph 602 shows the voltage between terminals 109 and 110, and it can be seen that when the voltage supplied from the power supply 101 exceeds approximately 8 (V), it is limited to a constant value of around 2.6 (V).
[0032] In this embodiment, the cell voltage limiter is composed of electronic components and may be arranged in the order of secondary battery (e.g., all-solid-state battery), then electronic components, or in the order of electronic components, then secondary battery (e.g., all-solid-state battery), starting from the heat source. The electronic components constituting the cell voltage limiter have multiple transistors. The multiple transistors are bipolar transistors. Two sets of thermally coupled NPN transistors and one set of PNP transistors form a current mirror circuit or a differential amplifier circuit. The thermally coupled transistor sets have matching characteristics regardless of their position from the heat source, and the cell voltage limiter in this embodiment includes at least one current mirror circuit and one differential amplifier circuit.
[0033] Figure 7 shows an example of the temperature characteristics of a cell voltage limiter when using the third embodiment of the present invention. In Figure 7, the horizontal axis represents temperature, and the vertical axis represents the voltage value between terminals 109 and 110. If the ratio of resistors 403 to 404 is set to approximately 1:9, the limiter voltage of the cell voltage limiter will remain almost constant regardless of temperature, as shown in Figure 7, and the characteristics shown in graph 603 will be almost constant. The characteristics shown in graph 603 show that, for example, if the ratio of resistors 403 to 404 is set to approximately 1:16, a change of 100°C will result in a change of about 1.2 (V).
[0034] The reason for setting these characteristics is that, during charging and discharging, lowering the voltage applied to the battery at high temperatures suppresses battery degradation and extends its lifespan. In particular, when performing cyclic charging and discharging, charging and discharging in a high-temperature environment shortens battery life, so it is appropriate to design the circuit to lower the limit voltage as much as possible, which can be achieved in this embodiment by changing the resistance ratio. Furthermore, while using the circuit configuration of this embodiment as an IC (Integrated Circuit) has the advantage of reducing the number of components, for operating requirements exceeding 150°C, it is more advantageous to use individual components that can withstand higher temperatures.
[0035] Figure 8 shows the configuration of a fourth embodiment of a charging device according to one embodiment of the present invention. The charging device consists of a power supply 101, a charging switch 102, a control switch 123, and a battery unit 121. The battery unit 121 has a positive terminal 119, a negative terminal 118, and a control terminal 122. The battery unit 121 also has batteries or secondary batteries 103, 104, and 105 connected in series, and cell voltage limiters 106, 107, and 108 connected in parallel to the positive terminal of each battery via P-type FETs 124, 125, and 126, respectively. The differences between Figure 5 and Figure 8 are the same as the differences between Figure 1 and Figure 2, and are identical except for the difference in the internal circuit configuration of the cell voltage limiters 106, 107, and 108, so an explanation is omitted. The effect of the embodiment in Figure 8 is that, similar to the embodiment in Figure 5, in addition to improving the lifespan of batteries 103, 104, and 105 by the cell voltage limiters 106, 107, and 108, the internal power consumption of batteries 103, 104, and 105 can be suppressed when the battery unit 121 is disconnected at terminals 119, 118, and 122.
[0036] Furthermore, according to this embodiment, when a solid-state battery is used, the solid-state battery and electronic components will be placed near a heat source. Regarding their arrangement, it is desirable to place components with higher heat resistance temperatures closer to the heat source. For example, if the heat resistance temperature of the solid-state battery is higher than that of the electronic components, the electronic components should be placed as far away from the heat source as possible. Conversely, if the heat resistance temperature of the electronic components is higher than that of the solid-state battery, it is effective to place the solid-state battery as far away from the heat source as possible.
[0037] The present invention automatically adjusts the charging current or charging voltage when charging multiple batteries or secondary batteries connected in series, if there is a voltage difference between the multiple batteries or secondary batteries, by arranging one or more adjustment circuits or cell voltage limiters, so that the voltages of each battery 103, 104, and 105 can be made approximately the same at the end of charging. The voltage limiter circuit according to the present invention can be applied over a wide temperature range and is therefore suitable for use in combination with all-solid-state batteries (secondary batteries). Examples of applications include power supply systems for MWD (Measuring While Drilling) and LWD (Logging While Drilling) in underground resource exploration devices, which sense the orientation, inclination, and geological evaluation of the drilling site while drilling and transmit data, and charge / discharge devices for high-temperature environments at drilling sites with ambient temperatures of 100 to 200°C.
[0038] Furthermore, the technology according to this embodiment makes it possible to provide an energy-efficient charging and discharging system. This contributes to the United Nations' Sustainable Development Goals (SDGs) "9. Build resilient infrastructure, promote inclusive and sustainable industrialization and foster innovation" and "11. Make cities and human settlements inclusive, safe, and resilient."
[0039] Although various embodiments have been described in detail above, the present invention is not limited to the embodiments described above and includes various modifications. For example, the embodiments described above are detailed explanations of the entire system in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.
[0040] 101...Power supply, 102...Charging switch, 103...Battery, 104...Battery, 105...Battery, 106...Cell voltage limiter, 107...Cell voltage limiter, 108...Cell voltage limiter
Claims
1. A charging device for charging multiple batteries connected in series, comprising a power supply and multiple cell voltage limiters, wherein the cell voltage limiters are connected in parallel to each of the multiple batteries.
2. A charging device according to claim 1, wherein the cell voltage limiter is composed of an element in which at least one resistor and at least one MOS type field-effect transistor are connected in series, and is connected in parallel to the battery.
3. A charging device according to claim 2, wherein the gate terminal of the MOS field-effect transistor is connected to a control circuit comprising three resistors and two thermally coupled bipolar transistors.
4. A charging device for charging multiple batteries connected in series, comprising a power supply, multiple cell voltage limiters, and multiple MOS-type field-effect transistors, wherein the multiple cell voltage limiters and the multiple MOS-type field-effect transistors are connected in series, and the cell voltage limiters are connected in parallel to each of the multiple batteries.
5. A charging device according to claim 4, comprising: a diode; a plurality of resistors; and a first MOS-type field-effect transistor, wherein the diode, the resistors, and the first MOS-type field-effect transistor are connected in series to form a first series element, the gate terminals of the plurality of MOS-type field-effect transistors are connected to the connection point of the resistors of the first series element, the diode terminals of the first series element are connected to the high-potential side of the power supply, and the first MOS-type field-effect transistor is connected to the low-potential side of the power supply.
6. A charging device according to claim 3, wherein two thermally coupled bipolar transistors form a current mirror circuit, and the cell voltage limiter has at least one current mirror circuit.
7. A charging device according to claim 2, wherein the gate terminal of the MOS field-effect transistor is connected to a control circuit comprising a reference voltage generation circuit, a detection circuit for detecting a voltage obtained by dividing the cell voltage, and a comparison control circuit that receives and compares the voltages of the reference voltage generation circuit and the detection circuit.
8. A charging device according to claim 7, wherein the output voltage value of the reference voltage generation circuit is set to a high voltage at low temperatures and a low voltage at high temperatures.
9. A charging device according to claim 8, wherein the battery is a solid-state battery.
10. A charging device according to claim 1, wherein the battery is a solid-state battery, the cell voltage limiter is composed of an electronic component, and the solid-state battery and the electronic component are arranged in order of proximity to the heat source.
11. A charging device according to claim 1, wherein the battery is a solid-state battery, the cell voltage limiter is composed of an electronic component, and the electronic component and the solid-state battery are arranged in order of proximity to the heat source.
12. A charging device according to claim 2, wherein the cell voltage limiter comprises a reference voltage generation circuit having a first current mirror circuit formed by two thermally coupled bipolar transistors, a detection circuit for detecting a voltage obtained by dividing the cell voltage, a comparison control circuit having a differential amplifier circuit formed by two thermally coupled bipolar transistors and a second current mirror circuit formed by two thermally coupled bipolar transistors, and the voltages of the reference voltage generation circuit and the detection circuit are input to the comparison control circuit.
13. A charging system comprising a charging device according to any one of claims 1 to 12.