Battery management system, start control method for power system, and vehicle

Abstract

This battery management system comprises a battery control unit that is operated using, as a power source, a first battery of a low-voltage system and controls the state of a second battery of a high-voltage system, and further comprises: a DC-DC converter that steps down the voltage of power supplied from the second battery; and a switch that generates a prescribed electrical signal indicating a state in which power cannot be supplied from the first battery to the battery control unit by switching to a connection state. When the prescribed electrical signal is generated, the power of the second battery stepped down by the DC-DC converter is supplied to the battery control unit, and the battery control unit is operated.

Description

Battery management system, power system startup control method, and vehicle

[0001] The present disclosure relates to a battery management system, a power system startup control method, and a vehicle.

[0002] In recent years, electric vehicles using a drive motor as a driving force source have been put into practical use. The drive motor is rotated by power stored in a battery, and the electric vehicle runs on the drive torque output from the drive motor. In such electric vehicles, the power system that supplies power to the drive motor, which requires high torque, is configured as a high-voltage power system equipped with a battery (high-voltage battery) that outputs a high voltage of, for example, 200 V.

[0003] In addition to the drive motor, a vehicle is also equipped with many auxiliary electrical devices such as an audio system, an air conditioning system, an electronic control unit, electronic components, etc. These electrical devices are usually powered by power supplied from a battery (low-voltage battery) that outputs a low voltage of, for example, 12 V.

[0004] Some electric vehicles equipped with a high-voltage power system are configured to step down the power of a high-voltage battery to charge a low-voltage battery. For example, Patent Documents 1 and 2 disclose techniques for stepping down the high voltage of a high-voltage battery to a low voltage and charging the low-voltage battery.

[0005] JP 2015-089171 A JP 2006-296049 A

[0006] The auxiliary electrical equipment installed in a vehicle also includes a battery management system (BMS) that manages the status of the high-voltage battery. Therefore, if power cannot be supplied from the low-voltage battery to the battery management system, the high-voltage battery cannot be started, and the vehicle may not be able to be driven. The devices disclosed in Patent Documents 1 and 2 are technologies that step down the high voltage of the high-voltage battery and charge the low-voltage battery. However, they cannot start the high-voltage power system if, for example, the low-voltage battery runs out of power before the high-voltage power system starts, or if some abnormality occurs in the power supply system from the low-voltage battery to the battery management system.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and an object of the present disclosure is to provide a battery management system, a power system startup control method, and a vehicle that can start a high-voltage power system even when power cannot be supplied from a low-voltage battery to the battery management system.

[0008] In order to solve the above problem, according to one aspect of the present disclosure, there is provided a battery management system including a battery control unit that operates using a first battery of a low-voltage system as a power source to control the state of a second battery of a high-voltage system, and further including a DC-DC converter that reduces the power supplied from the second battery, and a switch that switches to a connected state to generate a predetermined electrical signal indicating a state in which power cannot be supplied from the first battery to the battery control unit, wherein the generation of the predetermined electrical signal causes the power of the second battery reduced by the DC-DC converter to be supplied to the battery control unit, and the battery control unit operates.

[0009] In addition, in order to solve the above problem, according to another aspect of the present disclosure, there is provided a power system startup control method for starting up a power system including a second battery of a high-voltage system by a battery control unit that operates using a first battery of a low-voltage system as a power source, wherein when a predetermined electrical signal is generated indicating a state in which power cannot be supplied from the first battery to the battery control unit, the power of the second battery that has been stepped down by a DC-DC converter that steps down the power supplied from the second battery is supplied to the battery control unit, and the power system is started up by the battery control unit using the power of the second battery.

[0010] In addition, in order to solve the above problem, according to yet another aspect of the present disclosure, there is provided a vehicle equipped with a battery management system that includes a battery control unit that operates using a first battery of a low-voltage system as a power source to control the state of a second battery of a high-voltage system, wherein the battery management system further includes a DC-DC converter that reduces the voltage of the power supplied from the second battery, and a switch that, when switched to a connected state, generates a predetermined electrical signal indicating a state in which power cannot be supplied from the first battery to the battery control unit, and when the predetermined electrical signal is generated, the power of the second battery that is reduced in voltage by the DC-DC converter is supplied to the battery control unit, causing the battery control unit to operate.

[0011] As described above, according to the present disclosure, it is possible to start up the high-voltage power system even when power cannot be supplied from the low-voltage battery to the battery management system.

[0012] FIG. 1 is an explanatory diagram showing an example of the configuration of a power system for the drivetrain of an electric vehicle to which a battery management system according to a first embodiment is applied. FIG. 2 is a block diagram showing the configuration of a power system for the drivetrain of an electric vehicle to which a battery management system according to the same embodiment is applied. FIG. 3 is a schematic diagram showing an example of the configuration of a battery management system according to the same embodiment. FIG. 4 is an explanatory diagram showing the functions of a battery control unit of the battery management system according to the same embodiment, divided into blocks. FIG. 5 is a flowchart showing an example of a startup process of the power system by the battery management system according to the same embodiment. FIG. 6 is a schematic diagram showing a configuration of a battery management system according to a modified example of the same embodiment. FIG. 7 is a schematic diagram showing an example of the configuration of a battery management system according to a second embodiment. FIG. 8 is a schematic diagram showing an example of the configuration of a battery management system according to a third embodiment. FIG. 9 is a schematic diagram showing an example of the configuration of a battery management system according to a fourth embodiment. FIG. 10 is a flowchart showing an example of a startup process of the power system by the battery management system according to the same embodiment.

[0013] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0014] <<1. First embodiment>> <1-1. Overall configuration of electric vehicle> First, an example of the configuration of an electric vehicle equipped with a battery management system according to an embodiment of the present disclosure will be described.

[0015] Fig. 1 is an explanatory diagram showing an example of the configuration of a power system 10 for the drive train of an electric vehicle 1. Fig. 2 is a block diagram showing the configuration of the power system 10 for the drive train of the electric vehicle 1.

[0016] The power system 10 includes a power generation device 30, a first battery 14, a second battery 15, a power converter 17, a drive motor 19, and a control device 20. The electric vehicle 1 is an electric vehicle that uses, as a drive power source, the drive motor 19, which is driven using power generated by the power generation device 30. The power system 10 is configured as a series hybrid system that extends the cruising range of the electric vehicle 1 by charging the second battery 15 with power generated by the power generation device 30.

[0017] The power generation device 30 may be, for example, a fuel cell, a turbine power generation device, or an engine power generation device, but there is no particular limitation on the type of power generation device 30. The electric vehicle 1 may also be an electric vehicle that does not have a power generation device and is configured to charge the second battery 15 by receiving power from an external charging device.

[0018] The power converter 17 is configured to include an inverter and a converter. When the electric vehicle 1 accelerates, the power converter 17 converts DC current supplied from the power generation device 30 or the second battery 15 into AC current and supplies the AC current to the drive motor 19, thereby causing the drive motor 19 to output drive torque. When the electric vehicle 1 decelerates, the power converter 17 causes the drive motor 19 to regenerate power and converts the generated AC current into DC current to charge the second battery 15.

[0019] 1 is a front-wheel drive vehicle, and a drive motor 19 outputs drive torque that is transmitted to the left and right front wheels via a differential mechanism 5 and a front drive shaft 4. The drive motor 19 is, for example, a three-phase AC radial motor, and outputs drive torque when AC current is supplied via a power converter 17 when the electric vehicle 1 accelerates. Meanwhile, the drive motor 19 generates electricity by regenerating power when the electric vehicle 1 decelerates.

[0020] The drive motor 19 may be an axial gap motor. The electric vehicle 1 may be a rear-wheel drive vehicle or a four-wheel drive vehicle. The electric vehicle 1 may be provided with a front-wheel drive motor and a rear-wheel drive motor, or may be provided with a drive motor for each of the four wheels.

[0021] The first battery 14 is a so-called auxiliary battery provided in the electric vehicle 1, and is a low-voltage battery rated at, for example, 12 V. The first battery 14 is a low-voltage power source that supplies power to the power generation device 30, a battery management system (BMS) 16, a power converter 17, the control device 20, and various other electrical components.

[0022] The second battery 15 is a battery with a rated voltage higher than that of the first battery 14 and is a high-voltage power source that supplies power to the drive motor 19. The rated voltage of the second battery 15 is, for example, 24 V, 40 V, or 200 V, but is not particularly limited thereto. The second battery 15 is configured by connecting multiple battery cells in series. The second battery 15 may also be configured by connecting battery modules in series, each of which has multiple battery cells connected in series. The second battery 15 stores the power generated by the drive motor 19 through regeneration and the power generated by the power generation device 30.

[0023] The second battery 15 is housed in a battery pack together with a battery management system 16 that manages the status of the second battery 15. The battery management system 16 is composed of an electronic circuit including one or more control units (controllers) and various peripheral components. The battery management system 16 has functions of starting up the second battery 15 and monitoring the voltage, current, and temperature of the multiple battery cells that make up the second battery 15. The controller provided in the battery management system 16 operates using the low-voltage first battery 14 as a power source. A switch 41 that can be operated by a passenger such as the driver of the electric vehicle 1 is connected to the second battery 15.

[0024] The control device 20 includes one or more processors that control the operation of the power generation device 30 and the traction motor 19. The control device 20 is configured to be able to acquire status information such as the voltage, current, and temperature of the second battery 15 from the battery management system 16. The control device 20 may be divided into multiple control devices, each with a function for controlling the operation of the power converter 17 and controlling the driving or regeneration of the traction motor 19, a function for controlling the power generation of the power generation device 30, and a function for controlling the charging of the second battery 15. In this case, the multiple control devices are connected to a communication bus such as a CAN (Controller Area Network) and are configured to be able to send and receive messages to and from each other.

[0025] <1-2. Battery Management System> Next, the battery management system according to this embodiment will be described in detail.

[0026] As described above, the power system 10 including the second battery 15, which is a high-voltage power source, is activated and made operational by the battery management system 16. Since each control unit included in the battery management system 16 is one of the low-voltage electrical components, the power system 10 cannot be activated in a state where power supply from the first battery 14 to the battery management system 16 is disabled.

[0027] In contrast, the battery management system 16 of this embodiment is equipped with a DC-DC converter that reduces the power supplied from the second battery 15, and the battery control unit of the battery management system 16 is configured to start up upon receiving a predetermined electrical signal indicating that power cannot be supplied from the first battery 14 to the battery control unit, and to operate using the power of the second battery 15 that has been reduced in voltage by the DC-DC converter.

[0028] 3 is a schematic diagram showing an example of the configuration of the battery management system 16 according to this embodiment. The battery management system 16 includes a battery control unit 61, a first power supply circuit 63, an isolated DC-DC converter 65, a second power supply circuit 67, a voltage divider circuit 69, and a switch 41.

[0029] The battery control unit 61 includes one or more processors such as CPUs (Central Processing Units) and memories, and executes various arithmetic processes by executing computer programs to control the state of the second battery 15. Part or all of the battery control unit 61 may be configured with updatable firmware or the like, or may be a program module or the like that is executed by commands from the CPU or the like.

[0030] The memory is configured to include one or more storage elements such as RAM (Random Access Memory) and ROM (Read Only Memory), or storage devices such as SSD (Solid State Drive), and is communicably connected to the processor. However, the type and number of memories are not particularly limited.

[0031] In the battery management system 16 according to this embodiment, the battery control unit 61 activates each control unit (not shown) provided in the battery management system 16, and puts the high-voltage power system 10 including the second battery 15 into a state in which it can be driven.

[0032] The first power supply circuit 63 is driven by power supplied from the low-voltage first battery 14, and supplies power to the battery control unit 61. Hereinafter, the power supplied from the first power supply circuit 63 to the battery control unit 61 will be referred to as the "normal power supply."

[0033] The isolated DC-DC converter 65 steps down the output voltage of the second battery 15 and supplies power to the battery control unit 61. The isolated DC-DC converter 65 starts up when it receives a DC-DC start signal output from the battery control unit 61, and supplies the stepped-down power to the battery control unit 61. Hereinafter, the power supplied from the isolated DC-DC converter 65 to the battery control unit 61 will be referred to as the "emergency power supply."

[0034] The second power supply circuit 67 generates a predetermined electric signal when energized and transmits the predetermined electric signal to the battery control unit 61. The second power supply circuit 67 operates on low-voltage power divided by the voltage divider circuit 69.

[0035] The voltage dividing circuit 69 is provided between the second battery 15 and the second power supply circuit 67, and is configured to divide the output voltage of the second battery 15 and supply the divided voltage to the second power supply circuit 67. In this embodiment, the voltage dividing circuit 69 is configured to divide the output voltage of the second battery 15 using a first resistor divider 75a and a second resistor divider 75b.

[0036] The voltage divider circuit 69 includes a switch 41. The switch 41 switches between supplying and blocking the low-voltage power divided by the voltage divider circuit 69 to the second power supply circuit 67. When the switch 41 is switched to the connected state, the low-voltage power divided by the voltage divider circuit 69 is supplied to the second power supply circuit 67. As a result, the second power supply circuit 67 transmits an electric signal to the battery control unit 61.

[0037] The switch 41 is a switch that can be operated by a passenger such as a driver of the electric vehicle 1. It is preferable that the switch 41 is a physical switch that can be mechanically switched on and off so that the switch 41 can be operated even when the power of the first battery 14 is depleted.

[0038] (1-2-2. Configuration of Battery Control Unit) When the power system 10 is started, the battery control unit 61 sets the operating mode of the second battery 15 to normal mode or emergency mode depending on the state of the switch 41. In normal mode, the battery control unit 61 operates the battery management system 16 using low-voltage power supplied from the first battery 14 of the low-voltage system without starting the isolated DC-DC converter 65. In normal mode, the second battery 15 can be charged and discharged within a range equal to or less than a preset maximum output. Therefore, the control device 20 can control the charging and discharging of the second battery 15 depending on the required acceleration or deceleration due to manual driving or automatic driving control.

[0039] Furthermore, in the emergency mode, the battery control unit 61 activates the isolated DC-DC converter 65 and operates the battery management system 16 with low-voltage power obtained by stepping down the output voltage of the second battery 15 in the high-voltage system. In the emergency mode, a limit is placed on the maximum output of the second battery 15. Therefore, the control device 20 can run the electric vehicle 1 with a small torque. The emergency mode state is a state in which the power of the first battery 14 is depleted or there is a possibility that an abnormality has occurred in the low-voltage system, and the electric vehicle 1 is run with a small torque so that it can reach a repair shop or dealer.

[0040] 4 is an explanatory diagram showing the functions of the battery control unit 61 in blocks. The battery control unit 61 includes a battery control processing unit 91 and a DCDC activation processing unit 93. The battery control processing unit 91 and the DCDC activation processing unit 93 may be functions realized by a processor executing a program, or may be configured to be realized by hardware such as an analog circuit.

[0041] The battery control processing unit 91 is started up by receiving normal power supply from the first power supply circuit 63, and starts up each control unit of the battery management system 16. While receiving normal power supply from the first power supply circuit 63, the battery control processing unit 91 sets the operation mode of the second battery 15 to the normal mode, and enables charging and discharging of the second battery 15 within a range equal to or less than a preset maximum output.

[0042] Furthermore, when the battery control processing unit 91 is unable to receive normal power from the first power supply circuit 63, it operates by receiving emergency power from the isolated DC-DC converter 65 and starts up each control unit of the battery management system 16. The battery control processing unit 91 starts up when it receives a predetermined electrical signal indicating that power cannot be supplied from the first battery 14 to the battery control unit 61, and outputs a command to the DCDC start-up processing unit 93 to start up the isolated DC-DC converter 65.

[0043] While receiving emergency power supply from the isolated DC-DC converter 65, the battery control processing unit 91 sets the operation mode of the second battery 15 to the emergency mode and limits the maximum output of the second battery 15. The limited maximum output is set to an appropriate value that allows the electric vehicle 1 to run with a small torque.

[0044] The DCDC startup processing unit 93 executes processing to start up the isolated DCDC converter 65. The DCDC startup processing unit 93 outputs a DCDC startup signal to the isolated DCDC converter 65 in accordance with a command from the battery control processing unit 91.

[0045] 1-3. Operation of the Battery Management System So far, we have described an example of the configuration of the battery management system 16. Next, we will describe an example of the process of starting up the power system by the battery management system 16.

[0046] 5 is a flowchart showing an example of a startup process of the power system 10 by the battery management system 16. When the power supply of the electric vehicle 1 is turned on and the vehicle system is started (step S11), the power system 10 is initialized and the operation mode is reset (step S13).

[0047] Next, the battery control processor 91 determines whether the switch 41 has been switched to the connected state (ON state) (step S15). The process of determining whether the switch 41 has been switched to the connected state (ON state) corresponds to the process of determining whether a predetermined electrical signal has been acquired. If the switch 41 has not been switched to the connected state, i.e., if the predetermined electrical signal has not been acquired (S15 / No), the battery control processor 91 sets the operating mode to the normal mode (step S17). In this case, the battery control processor 91 receives normal power supply from the first power supply circuit 63 and starts up the respective control units of the battery management system 16. This starts up the high-voltage power system 10, enabling charging and discharging of the second battery 15 within a range below a preset maximum output.

[0048] When normal power is not supplied from the first power supply circuit 63, the battery management system 16 does not start even if the switch 41 is not switched to the connected state, and the power system 10 is maintained in a stopped state. Therefore, the passenger of the electric vehicle 1 will realize that the power system 10 will not start and the electric vehicle 1 cannot be driven, and will take action to switch the switch 41 to the connected state.

[0049] Thereafter, while the vehicle system is running (step S19 / No), the battery control processing unit 91 repeatedly determines whether the switch 41 has been switched to the connected state, and maintains the operating mode in the normal mode unless the switch 41 is switched to the connected state. Also, when the vehicle system is stopped (step S19 / Yes), the battery management system 16 terminates its operation.

[0050] On the other hand, when the switch 41 is switched to the connected state, that is, when the battery control processing unit 91 acquires the predetermined electrical signal (S15 / Yes), the battery control processing unit 91 causes the DCDC startup processing unit 93 to start up the isolated DCDC converter 65 (step S21). The DCDC startup processing unit 93 outputs a DCDC startup signal to the isolated DCDC converter 65. As a result, the isolated DCDC converter 65 to which the DCDC startup signal has been input starts up, and low-voltage power obtained by stepping down the power of the high-voltage second battery 15 begins to be supplied to the battery control unit 61.

[0051] Next, the battery control processor 91 sets the operation mode to the emergency mode (step S23). In this case, the battery control processor 91 operates by receiving emergency power from the isolated DC-DC converter 65 and starts up each control unit of the battery management system 16. This starts up the high-voltage power system 10. However, the battery control processor 91 limits the maximum output of the second battery 15 to a preset output. Therefore, the electric vehicle 1 can be driven with a small torque, allowing the driver to drive the electric vehicle 1 to a repair shop or the like.

[0052] Thereafter, while the vehicle system is activated (step S25 / No), the battery control processing unit 91 maintains the operation mode in the emergency mode. Furthermore, when the vehicle system is stopped (step S25 / Yes), the battery management system 16 terminates its operation.

[0053] <1-4. Effects> As described above, the battery management system 16 according to this embodiment includes the isolated DC-DC converter 65 that steps down the power supplied from the second battery 15, and the battery control unit 61 is activated upon receiving a predetermined electrical signal indicating that power supply from the first battery 14 to the battery control unit 61 is disabled, and operates using the power of the second battery 15 that has been stepped down by the isolated DC-DC converter 65. As a result, even when the battery control unit 61 cannot receive low-voltage power from the first battery 14, such as when the first battery 14 is depleted, the battery management system 16 can be activated using high-voltage power output from the second battery 15. This makes it possible to activate the high-voltage power system 10, allowing the electric vehicle 1 to be moved to a repair shop or the like.

[0054] Furthermore, the battery management system 16 according to this embodiment sets the operation mode of the power system 10 to an emergency mode when started using high-voltage power output from the second battery 15. This allows the electric vehicle 1 to run with the output torque of the electric vehicle 1 suppressed when an abnormality occurs in the first battery 14 or the low-voltage power system, thereby preventing the occurrence of a related abnormality.

[0055] <1-5. Modifications> The battery management system according to the first embodiment described above can be modified in various ways. Some modifications of the battery management system according to this embodiment will be described below.

[0056] 6 is a schematic diagram showing the configuration of a battery management system 101 according to a modification of the present embodiment. In the battery management system 101 according to the modification, the configuration of a voltage divider circuit 103 is different from the configuration of the voltage divider circuit 69 of the battery management system 16 according to the above embodiment.

[0057] In the modified example, the voltage divider circuit 103 is configured to divide a low voltage from some battery cells or battery modules of the second battery 15. The battery management system 101 having such a voltage divider circuit 103 operates in the same manner as the battery management system 16 according to the above embodiment, and can start up the battery management system 101 by using the high-voltage power output from the second battery 15 even when the battery control unit 61 cannot receive low-voltage power from the first battery 14.

[0058] <<2. Second Embodiment>> Next, a battery management system according to a second embodiment of the present disclosure will be described.

[0059] 7 is a schematic diagram showing the configuration of a battery management system 105 according to the second embodiment. The battery management system 105 according to the second embodiment has a configuration in which the second power supply circuit 67 is operated by a power generation switch 107 that generates back electromotive force by switching operation, instead of operating the second power supply circuit 67 by generating a low voltage using a voltage divider circuit.

[0060] The battery management system 105 includes a battery control unit 61, a first power supply circuit 63, an isolated DC-DC converter 65, a second power supply circuit 67, and a power generation switch 107. The power generation switch 107 is a switch that does not require a power source and generates an electrical signal by itself using energy generated when the switch is pressed. For example, the power generation switch 107 rectifies the back electromotive force generated when the switch is pressed using a rectifier circuit to generate a predetermined electrical signal and transmit it to the second power supply circuit 67. The power generation switch 107 is also called a kinetic switch, and a known switch may be used.

[0061] In the battery management system 105 according to this embodiment, the battery control unit 61 is also started up upon receiving a predetermined electrical signal indicating that power supply from the first battery 14 to the battery control unit 61 is disabled, and operates using power from the second battery 15 that has been stepped down by the isolated DC-DC converter 65. The battery management system 105 having such a configuration operates in the same manner as the battery management system 16 according to the first embodiment, and therefore, even if the battery control unit 61 cannot receive low-voltage power from the first battery 14, such as when the first battery 14 is depleted, the battery management system 105 can be started up using high-voltage power output from the second battery 15.

[0062] In particular, the battery management system 105 according to the second embodiment does not require a power supply and a voltage divider circuit that generate a predetermined electrical signal for starting the isolated DC-DC converter 65, thereby simplifying the circuit configuration.

[0063] <<3. Third Embodiment>> Next, a battery management system according to a third embodiment of the present disclosure will be described.

[0064] In the battery management systems according to the first and second embodiments described above, the battery control unit 61 is activated upon receiving a predetermined electrical signal indicating a state in which power cannot be supplied from the first battery 14 to the battery control unit 61, thereby activating the isolated DC-DC converter 65. The battery management system according to the third embodiment has a configuration in which a predetermined electrical signal indicating a state in which power cannot be supplied from the first battery 14 to the battery control unit 61 is input directly to the isolated DC-DC converter 65.

[0065] 8 is a schematic diagram showing an example of a battery management system 111 according to a third embodiment, configured by modifying the configuration of the battery management system 16 according to the first embodiment shown in FIG. 3 . The battery management system 111 includes a battery control unit 61, a first power supply circuit 63, an isolated DC-DC converter 65, a second power supply circuit 67, a voltage divider circuit 69, and a switch 41. In this embodiment, a predetermined electrical signal generated by the second power supply circuit 67 is directly transmitted to the isolated DC-DC converter 65. The isolated DC-DC converter 65 is activated upon receiving the predetermined electrical signal, and reduces the output power of the high-voltage second battery 15 and supplies the reduced power to the battery control unit 61.

[0066] In the battery management system 111 according to this embodiment, the battery control unit 61 does not have a function (a DCDC startup processing unit) for sending a DCDC startup signal to the isolated DCDC converter 65. Therefore, the battery control unit 61 switches the operation mode of the power system 10 between the normal mode and the emergency mode depending on whether the battery system 10 has been started up by receiving normal power from the first power supply circuit 63 or by receiving emergency power from the isolated DCDC converter 65.

[0067] In the battery management system 111 according to this embodiment, the isolated DC-DC converter 65 is activated upon receiving a predetermined electrical signal indicating that power supply from the first battery 14 to the battery control unit 61 is disabled, and steps down the power of the second battery 15 and supplies it to the battery control unit 61. Even in the battery management system 111 having such a configuration, even when the battery control unit 61 cannot receive low-voltage power from the first battery 14, for example, when the first battery 14 is depleted, the battery management system 111 can be activated by using high-voltage power output from the second battery 15.

[0068] Similarly, a configuration in which a predetermined electrical signal generated by the second power supply circuit 67 is directly transmitted to the isolated DC-DC converter 65 can be applied to the battery management system 101 according to the modified example of the first embodiment shown in FIG. 6 and the battery management system 105 according to the second embodiment shown in FIG. 7 .

[0069] <<4. Fourth Embodiment>> Next, a battery management system according to a fourth embodiment of the present disclosure will be described.

[0070] 9 is a schematic diagram showing the configuration of a battery management system 113 according to the fourth embodiment. The battery management system 113 according to the fourth embodiment has a configuration in which, when the isolated DC-DC converter 65 is in an operating state and the switch 41 is in a connected state, the battery control unit 61 is started up and operates using low-voltage power supplied from the isolated DC-DC converter 65.

[0071] The battery management system 113 according to this embodiment includes a battery control unit 61, a first power supply circuit 63, an isolated DC-DC converter 65, and a switch 41. The switch 41 is provided in a current path connecting the isolated DC-DC converter 65 and the battery control unit 61, and switches between supplying and cutting off low-voltage power from the isolated DC-DC converter 65 to the battery control unit 61.

[0072] In the battery management system 113, the isolated DC-DC converter 65 is maintained in a constantly operating state after the vehicle system is started up. The battery control unit 61 is started up by receiving low-voltage power from the isolated DC-DC converter 65 by switching the switch 41, and is operated by receiving power from the second battery 15 whose voltage has been stepped down by the isolated DC-DC converter 65. In this embodiment, the low-voltage power supplied to the battery control unit 61 from the isolated DC-DC converter 65 by switching the switch 41 corresponds to a predetermined electrical signal.

[0073] 10 is a flowchart showing an example of a startup process of the power system 10 by the battery management system 113 according to this embodiment. When the power supply of the electric vehicle 1 is turned on and the vehicle system is started (step S31), the power system 10 is initialized and the operation mode is reset (step S33).

[0074] Next, the battery control unit 61 determines whether the switch 41 has been switched to the connected state (ON state) (step S35). The process of determining whether the switch 41 has been switched to the connected state (ON state) corresponds to the process of determining whether a predetermined electrical signal has been acquired. If the switch 41 has not been switched to the connected state, i.e., if the predetermined electrical signal has not been acquired (S35 / No), the battery control unit 61 sets the operating mode to the normal mode (step S37). In this case, the battery control unit 61 receives normal power supply from the first power supply circuit 63 and starts up, activating each control unit of the battery management system 113. This activates the high-voltage power system 10, enabling charging and discharging of the second battery 15 within a range not exceeding a preset maximum output.

[0075] As explained in the first embodiment, when normal power is not supplied from the first power supply circuit 63, the battery management system 113 does not start up and the power system 10 is maintained in a stopped state even if the switch 41 is not switched to the connected state. Therefore, the passenger of the electric vehicle 1 will realize that the power system 10 will not start up and the electric vehicle 1 cannot be driven, and will take action to switch the switch 41 to the connected state.

[0076] Thereafter, while the vehicle system is running (step S39 / No), the battery control unit 61 repeatedly determines whether the switch 41 has been switched to the connected state, and maintains the operating mode in the normal mode unless the switch 41 is switched to the connected state. Also, when the vehicle system is stopped (step S39 / Yes), the battery management system 113 terminates its operation.

[0077] On the other hand, when the switch 41 is switched to the connected state, that is, when the predetermined electrical signal is received (S35 / Yes), the battery control unit 61 is activated and sets the operation mode to the emergency mode (step S41). In this case, the battery control unit 61 receives emergency power supply from the isolated DC-DC converter 65 and activates the respective control units of the battery management system 113. This activates the high-voltage power system 10. However, the battery control unit 61 limits the maximum output of the second battery 15 to a preset output. Therefore, the electric vehicle 1 can be driven with a small torque, allowing the driver to drive the electric vehicle 1 to a repair shop, etc.

[0078] Thereafter, while the vehicle system is activated (step S43 / No), the battery control unit 61 maintains the operation mode in the emergency mode. When the vehicle system is stopped (step S43 / Yes), the battery management system 113 terminates its operation.

[0079] As described above, in the battery management system 113 according to this embodiment, the battery control unit 61 is started up upon receiving a predetermined electrical signal indicating that power supply from the first battery 14 to the battery control unit 61 is disabled, and operates using the power of the second battery 15 that has been stepped down by the isolated DC-DC converter 65. As a result, even if the battery control unit 61 cannot receive low-voltage power from the first battery 14, such as when the first battery 14 is depleted, the battery management system 16 can be started up using high-voltage power output from the second battery 15.

[0080] In particular, the battery management system 113 according to the fourth embodiment does not require a voltage divider circuit that supplies low-voltage power to a power supply circuit that generates a predetermined electrical signal for starting the isolated DC-DC converter 65, thereby simplifying the circuit configuration.

[0081] Although the preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the technology of the present disclosure is not limited to such examples. It is clear that a person skilled in the art of the technology to which the present disclosure pertains can conceive of various modified or altered examples within the scope of the technical ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure.

[0082] 1: Electric vehicle 10: Power system 14: First battery 15: Second battery 16, 101, 105, 111, 113: Battery management system 17: Power converter 19: Drive motor 20: Control device 30: Power generation device 41: Switch 61: Battery control unit 63: First power supply circuit 65: Isolated DC-DC converter 67: Second power supply circuit 69, 103: Voltage divider circuit 107: Power generation switch

Claims

1. A battery management system comprising a battery control unit that operates using a first battery in a low-voltage system as a power source to control the state of a second battery in a high-voltage system, further comprising: a DC-DC converter that reduces the voltage of the power supplied from the second battery; and a switch that generates a predetermined electrical signal when switched to a connected state to indicate that power cannot be supplied from the first battery to the battery control unit; wherein, when the predetermined electrical signal is generated, the power of the second battery, which is reduced in voltage by the DC-DC converter, is supplied to the battery control unit, causing the battery control unit to operate.

2. The battery management system according to claim 1, wherein the battery control unit and the DC-DC converter are provided in a battery pack including the second battery.

3. The battery management system of claim 1, further comprising: a voltage divider circuit that divides the output voltage of the second battery; and a power supply circuit that operates on low-voltage power divided by the voltage divider circuit; wherein the switch switches between supplying and cutting off the divided low-voltage power to the power supply circuit; the power supply circuit receives the low-voltage power by switching the switch and transmits the specified electrical signal to the battery control unit; and the battery control unit starts up upon receiving the specified electrical signal and starts up the DCDC converter, and operates on the power of the second battery whose voltage has been reduced by the DCDC converter.

4. A battery management system as described in claim 1, further comprising: a voltage divider circuit that divides the output voltage of the second battery; and a power supply circuit that operates with low-voltage power divided by the voltage divider circuit; wherein the switch switches between supplying and cutting off the divided low-voltage power to the power supply circuit; the power supply circuit receives the low-voltage power by switching the switch and transmits the specified electrical signal to the DCDC converter; the DCDC converter starts up upon receiving the specified electrical signal; and the battery control unit operates by receiving the power of the second battery whose voltage has been reduced by the DCDC converter.

5. The battery management system of claim 1, wherein the switch is a power generation switch that generates power by switch operation, and further comprising a power supply circuit that operates with the power generated by the power generation switch, wherein the power supply circuit receives the power generated by the power generation switch and transmits the specified electrical signal to the battery control unit, and wherein the battery control unit receives the specified electrical signal to start up and start up the DCDC converter, and operates with the power of the second battery whose voltage has been stepped down by the DCDC converter.

6. The battery management system of claim 1, wherein the switch is a power generation switch that generates power by switch operation, and further comprising a power supply circuit that operates with the power generated by the power generation switch, wherein the power supply circuit receives the power generated by the power generation switch and transmits the specified electrical signal to the DCDC converter, wherein the DCDC converter is started up upon receiving the specified electrical signal, and wherein the battery control unit operates by receiving the power of the second battery whose voltage has been stepped down by the DCDC converter.

7. The battery management system described in claim 1, wherein the switch is provided in a current path connecting the DC-DC converter and the battery control unit, and switches between supplying and cutting off the low-voltage power from the DC-DC converter to the battery control unit, and the battery control unit is started up by receiving the specified electrical signal from the DC-DC converter by switching the switch, and operates by receiving power from the second battery whose voltage has been reduced by the DC-DC converter.

8. A power system startup control method for starting up a power system including a second battery of a high-voltage system by a battery control unit that operates using a first battery of a low-voltage system as a power source, wherein, when a predetermined electrical signal is generated indicating a state in which power cannot be supplied from the first battery to the battery control unit, the power of the second battery that has been stepped down by a DC-DC converter that steps down the power supplied from the second battery is supplied to the battery control unit, and the power system is started up by the battery control unit using the power of the second battery.

9. A vehicle equipped with a battery management system that operates using a first battery in a low-voltage system as a power source and has a battery control unit that controls the state of a second battery in a high-voltage system, wherein the battery management system further comprises: a DC-DC converter that reduces the voltage of the power supplied from the second battery; and a switch that, when switched to a connected state, generates a predetermined electrical signal indicating that power cannot be supplied from the first battery to the battery control unit; and when the predetermined electrical signal is generated, the power of the second battery, which is reduced in voltage by the DC-DC converter, is supplied to the battery control unit, causing the battery control unit to operate.

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