Management device and electricity storage pack

Abstract

A first power supply circuit (11) steps down the voltage of an electricity storage module (20) to a first power supply voltage. A drive circuit (13) uses the first power supply voltage to drive a switch (RY1) connected to a power line between the electricity storage module (20) and an input / output terminal. A second power supply circuit (12) steps down the first power supply voltage to a second power supply voltage. A microcontroller (14) operates using the second power supply voltage and controls the drive circuit (13). A voltage determination circuit (15) determines the voltage of the electricity storage module (20). In a state in which the voltage of the electricity storage module (20) drops below the minimum operating voltage of the first power supply circuit (11), the second power supply voltage is generated from the voltage of the electricity storage module (20) without passing through the first power supply circuit (11).

Description

Management device and power storage pack

[0001] The present disclosure relates to a management device that manages a power storage module, and a power storage pack.

[0002] In battery packs installed in mobility devices such as electric motorcycles, electric kick scooters, and electric bicycles, a circuit configuration is often used in which the voltage of the battery module is stepped down by a switching regulator to generate the voltage used for drive circuits such as relays, and the output voltage of the switching regulator is further stepped down by a linear regulator to generate the power supply voltage for a microcontroller.

[0003] If a short circuit occurs between the terminals of the battery pack when the SOC (State of Charge) of the battery pack is low at the end of discharge, the voltage of the battery module may momentarily fall below the minimum operating voltage of the switching regulator, causing the switching regulator to turn off, which in turn turns off the linear regulator and the microcontroller.

[0004] When the switching regulator is turned off, the relay connected to the power line is turned off, protecting the battery module from short-circuit current, but the microcontroller is reset by the power off, and the history of the short circuit is not recorded. The relay is damaged by the short-circuit protection, and if the contacts are welded by the arc heat, a continuity failure occurs.

[0005] Patent Document 1 discloses a method for backing up the power supply of a first logic circuit by supplying power stored in a large-capacity capacitor to the power input terminal of the first logic circuit when the storage battery voltage drops abnormally to the point where the output voltage of the DC-DC converter circuit cannot be stabilized and the drop in output voltage of the DC-DC converter circuit is detected by an output voltage detection circuit. This method requires the inclusion of a large-capacity capacitor, which increases the circuit area and cost.

[0006] Japanese Patent Application Publication No. 5-224786

[0007] The present disclosure has been made in light of these circumstances, and an object of the present disclosure is to provide a technology that improves safety against short circuits in electricity storage packs at low cost.

[0008] In order to solve the above problem, a management device according to one aspect of the present disclosure includes a first power supply circuit that steps down a voltage of a power storage module to a first power supply voltage, a drive circuit that uses the first power supply voltage to drive a switch connected to a power line between the power storage module and an input / output terminal, a second power supply circuit that steps down the first power supply voltage to a second power supply voltage, a microcontroller that operates using the second power supply voltage and controls the drive circuit, and a voltage determination circuit that determines the voltage of the power storage module. When the voltage of the power storage module drops below a minimum operating voltage of the first power supply circuit, the second power supply voltage is generated from the voltage of the power storage module without going through the first power supply circuit.

[0009] According to the present disclosure, it is possible to improve the safety of an electricity storage pack against short circuits at low cost.

[0010] FIG. 1 is a diagram showing an example of the configuration of a battery pack according to a comparative example. FIG. 2 is a diagram showing a specific example of the behavior of current and each voltage when a short circuit occurs between the terminals of the battery pack shown in FIG. 1. FIG. 3 is a diagram showing an example of the configuration of a battery pack according to embodiment 1. FIG. 4 is a diagram showing an example of the circuit configuration of a voltage determination circuit, an auxiliary path switch, and a third power supply circuit shown in FIG. 3. FIG. 5 is a diagram showing a specific example of the behavior of current and each voltage when a short circuit occurs between the terminals of the battery pack according to embodiment 1. FIG. 6 is a diagram showing an example of the configuration of a battery pack according to embodiment 2.

[0011] 1 is a diagram showing an example of the configuration of a battery pack 1 according to a comparative example. The battery pack 1 is a detachable, portable, and replaceable battery pack 1, and in this specification, it is assumed that the battery pack 1 is attached to and used on an electric motorcycle.

[0012] The battery pack 1 includes a battery module 20 and a battery management device 10. The battery module 20 includes multiple cells E1-En connected in series. The number of cells connected in series is determined by the load specifications. The cells may be lithium-ion battery cells, nickel-metal hydride battery cells, lead-acid battery cells, or the like. In the following description, an example is assumed in which 14 lithium-ion battery cells (nominal voltage: 3.6-3.7V) are connected in series. In this example, the voltage Vbat of the battery module 20 ranges from 18.2V to 58.8V depending on the SOC.

[0013] A relay RY1 that switches conduction / non-conduction between the battery module 20 and the load or charger (not shown) is connected to the power line between the battery module 20 and an input / output terminal that is connected to the load (mainly the inverter and motor) of the electric motorcycle or a charger (not shown).

[0014] The battery management device 10 includes a first power supply circuit 11, a second power supply circuit 12, a drive circuit 13, and a microcontroller 14. The first power supply circuit 11 generates a first power supply voltage V1 (assumed to be 12 V in the example shown below) by stepping down the voltage Vbat of the battery module 20. The first power supply circuit 11 uses a switching regulator (for example, a flyback DC / DC converter, etc.).

[0015] The second power supply circuit 12 steps down the first power supply voltage V1 to generate a second power supply voltage VCC (assumed to be 5 V in the example shown below). The second power supply circuit 12 uses a linear regulator (for example, an LDO (Low Drop Out) regulator). A first diode D1 for preventing reverse current is connected between the output terminal of the first power supply circuit 11 and the input terminal of the second power supply circuit 12. A second diode D2 for reverse voltage protection is connected between the input terminal and output terminal of the second power supply circuit 12. A Schottky barrier diode with a low forward voltage Vf is used as the second diode D2.

[0016] The drive circuit 13 uses the first power supply voltage V1 to control the on / off of a current flowing through the drive coil of the relay RY1, thereby driving the relay RY1. The microcontroller 14 controls the entire battery pack 1. The microcontroller 14 operates using the second power supply voltage VCC.

[0017] The microcontroller 14 can control the on / off of the relay RY1 by sending a control signal to the drive circuit 13. When an overcurrent is detected, the microcontroller 14 sends an off signal to the drive circuit 13 to turn off the relay RY1. A shunt resistor (not shown) is connected to the power line, and a differential amplifier (not shown) amplifies the voltage across the shunt resistor and outputs it to the microcontroller 14 as a current value.

[0018] The microcontroller 14 determines that an overcurrent exceeding a preset value is a short-circuit current and stores a log of the short-circuit occurrence in ROM. If the positive and negative input / output terminals of the battery pack 1 are short-circuited via a conductor for some reason, a large current will flow in the power line of the battery pack 1.

[0019] 2 is a diagram showing a specific example of the behavior of current and voltage when a short circuit occurs between the terminals of the battery pack 1 shown in FIG. Hereinafter, an example will be assumed in which a first power supply circuit 11 with a minimum operating voltage of 18 V is used. When the input voltage of the first power supply circuit 11 falls below 18 V, the first power supply circuit 11 shuts down.

[0020] When a short circuit occurs between the terminals of the battery pack 1, a large current flows through the power line, causing a sudden drop in the voltage Vbat of the battery module 20. When the voltage Vbat of the battery module 20 falls below 18 V, the first power supply circuit 11 shuts down, causing the output voltage of the first power supply circuit 11 to drop from 12 V to 0 V. The lower the SOC of the battery module 20, the more likely it is that the voltage Vbat of the battery module 20 will drop to 18 V or less when a short circuit occurs.

[0021] When the output voltage of the first power supply circuit 11 becomes 0 V, the second power supply circuit 12 becomes inoperable, and the output voltage of the second power supply circuit 12 also drops from 5 V to 0 V. This causes the microcontroller 14 to lose power and shut down.

[0022] If the relay RY1 has an a-contact, when the first power supply circuit 11 shuts down, current cannot flow through the drive coil of the relay RY1, causing the relay RY1 to turn off. This restores the voltage Vbat of the battery module 20, and when the voltage Vbat of the battery module 20 exceeds 18 V, the first power supply circuit 11 starts up, causing the output voltage of the first power supply circuit 11 to rise from 0 V to 12 V. When the output voltage of the first power supply circuit 11 rises to 12 V, the second power supply circuit 12 starts up, causing the output voltage of the second power supply circuit 12 to rise from 0 V to 5 V. This restores power to the microcontroller 14, allowing it to start up.

[0023] When the microcontroller 14 shuts down due to a power loss, the RAM is reset, and the log of the short circuit occurrence is lost before it can be written to the ROM. As a result, it is not possible to determine that the relay RY1 through which a large current flows is faulty, and the relay RY1 continues to be used in an unsafe state.

[0024] Fig. 3 is a diagram showing an example of the configuration of the battery pack 1 according to embodiment 1. The configuration of the battery management device 10 of the battery pack 1 according to embodiment 1 is obtained by adding a voltage determination circuit 15, an auxiliary path switch 16, and a third power supply circuit 17 to the configuration of the battery management device 10 according to the comparative example shown in Fig. 1.

[0025] The voltage determination circuit 15 determines whether the voltage Vbat of the battery module 20 is less than a threshold voltage, which is the minimum operating voltage of the first power supply circuit 11 plus a predetermined value. The threshold voltage may be set to the maximum operating voltage of the second power supply circuit 12. The voltage determination circuit 15 turns on the auxiliary path switch 16 when the voltage Vbat of the battery module 20 falls below the threshold voltage. The auxiliary path switch 16 is connected between the power line and the third power supply circuit 17 and is controlled to be on / off according to the determination result of the voltage determination circuit 15. The voltage determination circuit 15 controls the auxiliary path switch 16 to an off state when the voltage Vbat of the battery module 20 is higher than the minimum operating voltage of the first power supply circuit 11, and controls the auxiliary path switch 16 to an on state when the voltage Vbat of the battery module 20 drops below the minimum operating voltage of the first power supply circuit 11.

[0026] When the auxiliary path switch 16 is in the on state, the third power supply circuit 17 steps down the voltage Vbat of the battery module 20 to generate the second power supply voltage VCC. A linear regulator is used for the third power supply circuit 17. A third diode D3 for preventing backflow is connected between the output terminal of the third power supply circuit 17 and the supply line of the second power supply voltage VCC. The third power supply circuit 17 is configured as a linear regulator that is simpler than the second power supply circuit 12.

[0027] 4 is a diagram showing an example of the circuit configuration of the voltage evaluation circuit 15, auxiliary path switch 16, and third power supply circuit 17 shown in FIG. 3. The voltage evaluation circuit 15 includes a first resistor R1, a first Zener diode ZD1, a second resistor R2, a first P-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) Mp1, and a second Zener diode ZD2. The auxiliary path switch 16 includes a third resistor R3, a second P-channel MOSFET (Mp1), and a third Zener diode ZD3.

[0028] A first resistor R1 and a first Zener diode ZD1 are connected in series between the positive and negative terminals of the battery module 20. In the example shown in Fig. 4, the first Zener diode ZD1 has a breakdown voltage of 18 V.

[0029] The source terminal of the first P-channel MOSFET (Mp1) is connected to the positive terminal of the battery module 20, and the gate terminal of the first P-channel MOSFET (Mp1) is connected to the connection point of the first resistor R1 and the first Zener diode ZD1 via the second resistor R2. A second Zener diode ZD2 for protecting the first P-channel MOSFET (Mp1) is connected between the gate terminal and source terminal of the first P-channel MOSFET (Mp1).

[0030] The source terminal of the second P-channel MOSFET (Mp2) is connected to the positive terminal of the battery module 20, and the gate terminal of the second P-channel MOSFET (Mp2) is connected to the connection point between the drain terminal of the first P-channel MOSFET (Mp1) and a third resistor R3. The other end of the third resistor R3 is connected to the negative terminal of the battery module 20. A third Zener diode ZD3 for protecting the second P-channel MOSFET (Mp2) is connected between the gate terminal and source terminal of the second P-channel MOSFET (Mp2).

[0031] When the voltage of the battery module 20 is higher than 18 V, the first Zener diode ZD1 is conductive, causing the first P-channel MOSFET (Mp1) to be conductive and the second P-channel MOSFET (Mp2) to be non-conductive. When the voltage of the battery module 20 drops to 18 V or lower, the first Zener diode ZD1 is non-conductive, causing the first P-channel MOSFET (Mp1) to be non-conductive and the second P-channel MOSFET (Mp2) to be conductive.

[0032] The third power supply circuit 17 includes a fourth resistor R4, a fourth Zener diode ZD4, and an NPN transistor Qn1. The collector terminal of the NPN transistor Qn1 is connected to the drain terminal of the second P-channel MOSFET (Mp2). The fourth resistor R4 and the fourth Zener diode ZD4 are connected in series between the drain terminal of the second P-channel MOSFET (Mp2) and the negative terminal of the battery module 20. In the example shown in FIG. 4 , the fourth Zener diode ZD4 has a breakdown voltage of 5 V. The base terminal of the NPN transistor Qn1 is connected to the connection point between the fourth resistor R4 and the fourth Zener diode ZD4.

[0033] When the voltage input to the collector terminal of the NPN transistor Qn1 (≈ the voltage of the battery module 20) is 5 V or higher, approximately 5 V is output from the emitter terminal (strictly speaking, 5 - (base-emitter voltage of the NPN transistor Qn1) V). When the voltage input to the collector terminal of the NPN transistor Qn1 is less than 5 V, a voltage obtained by subtracting (the base-emitter voltage of the NPN transistor Qn1) from the voltage applied to the fourth Zener diode ZD4 is output from the emitter terminal.

[0034] The linear regulator used in the second power supply circuit 12 is a high-precision linear regulator that employs a control IC that adaptively controls the base voltage in accordance with the error between the output voltage and the reference voltage. The linear regulator used in the third power supply circuit 17 is used for a short period of time in an emergency until a log of the short-circuit occurrence is written to ROM, and since its operating voltage can be kept low, a simple, low-cost linear regulator is sufficient. As described above, the third power supply circuit 17 operates when the voltage Vbat of the battery module 20 falls below a threshold voltage (e.g., the maximum operating voltage of the second power supply circuit 12), so a linear regulator with a low operating voltage can be used.

[0035] Fig. 5 is a diagram showing a specific example of the behavior of current and each voltage when a short circuit occurs between the terminals of the battery pack 1 according to embodiment 1. In the example of a short circuit occurs between the terminals of the battery pack 1 according to the comparative example shown in Fig. 2, when the voltage Vbat of the battery module 20 becomes 18 V or less, the first power supply circuit 11 shuts down, the output voltage of the second power supply circuit 12 drops to 0 V, and the microcontroller 14 loses power and shuts down.

[0036] In contrast, in the first embodiment, even if the voltage Vbat of the battery module 20 falls below 18 V and the first power supply circuit 11 shuts down, the microcontroller 14 continues to operate because 5 V is supplied from the third power supply circuit 17 to the microcontroller 14. Therefore, the microcontroller 14 can detect the occurrence of a short circuit and save a log in ROM, and can determine that the relay RY1 through which a large current has flowed has failed.

[0037] FIG. 6 is a diagram showing an example of the configuration of a battery pack 1 according to a second embodiment. The configuration of the battery management device 10 of the battery pack 1 according to the second embodiment is the same as the configuration of the battery management device 10 according to the first embodiment shown in FIG. 4 except that the third power supply circuit 17 is omitted and the auxiliary path switch 16 is connected between the power line and the second power supply circuit 12. When the auxiliary path switch 16 is in the on state, the second power supply circuit 12 steps down the voltage Vbat of the battery module 20 to generate the second power supply voltage VCC. When the auxiliary path switch 16 is in the on state and the first power supply circuit 11 is shut down, the input of the second power supply circuit 12 is only the voltage Vbat of the battery module 20. When a short circuit occurs between the terminals of the battery pack 1 according to the second embodiment, the behavior of the current and each voltage is the same as that shown in FIG. 5.

[0038] As described above, according to this embodiment, when the voltage Vbat of the battery module 20 drops below the minimum operating voltage of the first power supply circuit 11, the second power supply voltage VCC is generated directly from the voltage Vbat of the battery module 20 by the third power supply circuit 17 or the second power supply circuit 12, without going through the first power supply circuit 11. This makes it possible to improve the safety of the battery pack 1 against short circuits at low cost.

[0039] As a countermeasure against short circuits between terminals of the battery pack 1, it is possible to use a first power supply circuit 11 with a wide operating voltage range, but this would significantly increase the cost of the first power supply circuit 11. The voltage determination circuit 15, auxiliary path switch 16, and third power supply circuit 17 shown in the first embodiment can be configured without using a control IC as shown in Figure 4, and can be realized at low cost. In the second embodiment, the third power supply circuit 17 can be omitted, further reducing costs.

[0040] Furthermore, in the second embodiment, the provision of auxiliary path switch 16 makes it possible to keep low the voltage Vbat directly input from battery module 20 to second power supply circuit 12, thereby narrowing the operating voltage range of second power supply circuit 12 and reducing the cost of second power supply circuit 12. Note that in the first embodiment, the operating voltage range of third power supply circuit 17 can be freely set without being restricted by first power supply voltage V1. If a linear regulator with a low maximum operating voltage is used for second power supply circuit 12 and a circuit configuration is desired in which auxiliary path switch 16 is turned on at a voltage higher than the maximum operating voltage of second power supply circuit 12, the circuit configuration of the first embodiment can be adopted and the maximum operating voltage of third power supply circuit 17 can be set higher than the maximum operating voltage of second power supply circuit 12.

[0041] The present disclosure has been described above based on the embodiments. The embodiments are merely examples, and it will be understood by those skilled in the art that various modifications are possible in the combination of the respective components and processing steps, and that such modifications are also within the scope of the present disclosure.

[0042] In the above-described embodiment, an example was described in which the relay RY1 was used as a switch connected to a power line that conducts / interrupts the load current. In this regard, a semiconductor switch (e.g., a MOSFET or an IGBT (Insulated Gate Bipolar Transistor)) may be used instead of the relay RY1. Because semiconductor switches do not have mechanical contacts, the contacts will not weld, but the risk of a conduction failure increases when subjected to a large current. Therefore, if a set number of short circuits occur, it is recommended that the semiconductor switch be determined to be faulty and replaced. In this embodiment, the microcontroller 14 can accurately record the number of short circuit occurrences and the short circuit current in a log, thereby accurately determining when to replace the semiconductor switch.

[0043] In the above embodiment, an example has been described in which the battery pack 1 incorporating the battery module 20 is used. In this regard, a capacitor pack incorporating a capacitor module including an electric double layer capacitor cell, a lithium ion capacitor cell, or the like may also be used. In this specification, the battery pack and the capacitor pack are collectively referred to as a power storage pack.

[0044] In the above-described embodiment, an electric motorcycle is assumed as the device to which the battery pack 1 is mounted. However, the device to which the battery pack 1 is mounted may also be an electric kick scooter, a micro EV, a multicopter (drone), an electric ship, an electric boat, a robot vacuum cleaner, or the like.

[0045] The embodiment may be specified by the following items.

[0046] [Item 1] A management device (10) comprising: a first power supply circuit (11) that steps down a voltage of a storage module (20) to a first power supply voltage; a drive circuit (13) that uses the first power supply voltage to drive a switch (RY1) connected to a power line between the storage module (20) and an input / output terminal; a second power supply circuit (12) that steps down the first power supply voltage to a second power supply voltage; a microcontroller (14) that operates using the second power supply voltage and controls the drive circuit (13); and a voltage determination circuit (15) that determines the voltage of the storage module (20), wherein when the voltage of the storage module (20) drops below a minimum operating voltage of the first power supply circuit (11), the second power supply voltage is generated from the voltage of the storage module (20) without going through the first power supply circuit (11). This can improve the safety of the storage pack (1) against short circuits at low cost. [Item 2] The management device (10) according to Item 1, wherein the microcontroller (14) controls the drive circuit (13) to turn off the switch (RY1) when a short-circuit current flows through the power line and records the occurrence of the short circuit. This allows the storage module (20) to be protected from short-circuit current while keeping a history of damage to circuit components. [Item 3] The management device (10) according to Item 1 or 2, further comprising: a third power supply circuit (17) that steps down the voltage of the storage module (20) to the second power supply voltage; and an auxiliary path switch (16) connected between the power line and the third power supply circuit (17), wherein the voltage determination circuit (15) controls the auxiliary path switch (16) to an on state when the voltage of the storage module (20) drops below the minimum operating voltage of the first power supply circuit (11). This allows the power supply voltage to continue to be supplied to the microcontroller (14) even if the operation of the first power supply circuit (11) stops.[Item 4] The management device (10) according to Item 1 or 2 further includes an auxiliary path switch (16) connected between the power line and the second power supply circuit (12), and the voltage determination circuit (15) controls the auxiliary path switch (16) to an on state when the voltage of the energy storage module (20) drops below the minimum operating voltage of the first power supply circuit (11). This allows the power supply voltage to continue to be supplied to the microcontroller (14) even when the operation of the first power supply circuit (11) stops. [Item 5] The management device (10) according to Item 1 or 2, wherein the switch (RY1) is a relay (RY1). This reduces the risk of continuing to use a relay (RY1) with a contact failure. [Item 6] The energy storage pack (1) includes an energy storage module (20) in which a plurality of cells are connected in series, and the management device (10) according to Item 1 or 2. This allows the safety of the energy storage pack (1) against short circuits to be improved at low cost.

[0047] The present invention can be used in an electricity storage pack used in electric mobility.

[0048] 1 Battery pack, 10 Battery management device, 11 First power supply circuit, 12 Second power supply circuit, 13 Drive circuit, 14 Microcontroller, 15 Voltage determination circuit, 16 Auxiliary path switch, 17 Third power supply circuit, 20 Battery module, E1-En Cell, RY1 Relay, D1-D3 Diodes, ZD1-ZD4 Zener diodes, R1-R4 Resistor, Mp1 First P-channel MOSFET, Mp2 Second P-channel MOSFET, Qn1 NPN transistor.

Claims

1. A management device comprising: a first power supply circuit that steps down the voltage of a storage module to a first power supply voltage; a drive circuit that uses the first power supply voltage to drive a switch connected to a power line between the storage module and an input / output terminal; a second power supply circuit that steps down the first power supply voltage to a second power supply voltage; a microcontroller that operates using the second power supply voltage and controls the drive circuit; and a voltage determination circuit that determines the voltage of the storage module, wherein when the voltage of the storage module drops below the minimum operating voltage of the first power supply circuit, the second power supply voltage is generated from the voltage of the storage module without going through the first power supply circuit.

2. The management device according to claim 1, wherein the microcontroller controls the drive circuit so that the switch is turned off when a short-circuit current flows through the power line, and records the occurrence of the short circuit.

3. The management device according to claim 1 or 2, further comprising: a third power supply circuit that reduces the voltage of the storage module to the second power supply voltage; and an auxiliary path switch connected between the power line and the third power supply circuit, wherein the voltage determination circuit controls the auxiliary path switch to an on state when the voltage of the storage module has dropped below the minimum operating voltage of the first power supply circuit.

4. The management device according to claim 1 or 2, further comprising an auxiliary path switch connected between the power line and the second power supply circuit, wherein the voltage determination circuit controls the auxiliary path switch to an on state when the voltage of the storage module drops below the minimum operating voltage of the first power supply circuit.

5. The management device according to claim 1 or 2, wherein the switch is a relay.

6. An electricity storage pack comprising: an electricity storage module in which a plurality of cells are connected in series; and the management device according to claim 1 or 2.

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