JP2017225320A - Power supply system for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply system for an electric vehicle, which can safely release a system switch even when communication failure occurs.SOLUTION: In a power supply system 2, a first DDC 28 is connected between a main power line 10a on side closer to a PCU than an SMR 20 and a sub-power line 24, and a second DDC 30 is connected between a main power line 10b on a side closer to a main battery than the SMR 20 and the sub-power line 24. When communication failure with an HV-ECU 45 occurs, a DDC-ECU 43 controls the first DDC 28 by setting a first voltage to an output target voltage, and controls a second DDC 30 by setting a second voltage higher than the first voltage to the output target voltage. When a vehicle main switch 46 is turned off during occurrence of communication failure, the HV-ECU 45 controls a low-voltage device 41 so that the total power consumption of the low-voltage device 41 does not exceed the maximum output power of the second DDC 30 and releases the SMR 20.SELECTED DRAWING: Figure 1

Description

  The present specification discloses a power supply system for an electric vehicle. The “electric vehicle” in this specification includes a hybrid vehicle including both a motor and an engine.

  The electric vehicle includes a traveling motor and a low-voltage device that operates at a voltage lower than the driving voltage of the traveling motor. Therefore, a power supply system for an electric vehicle is required to have a capability of supplying high-voltage power to a circuit that drives a traveling motor and supplying low-voltage power to a low-voltage device. An example of such a power supply system is disclosed in Patent Document 1. The power supply system of Patent Document 1 includes a main battery, a main power line, a sub power line, a system switch, two DC-DC converters (first and second DC-DC converters), and a controller. The electric vehicle includes a power control unit that converts power supplied from the main battery into power for driving the traveling motor, and the power control unit and the main battery are connected by a main power line. The system switch is provided in the main power supply line, and switches between conduction and non-conduction between the main battery and the power control unit. Note that setting the main power line to be conductive may be referred to as “closing the system switch”, and setting the main power line to be non-conductive may be referred to as “opening the system switch”.

  The sub power line transmits driving power to the low voltage device. The first DC-DC converter is connected between the main power line and the sub power line closer to the power control unit than the system switch, and can perform a step-down operation in which the power of the main power line is stepped down and supplied to the sub power line. The second DC-DC converter is connected between the main power line and the sub power line closer to the main battery than the system switch, and can perform a step-down operation that steps down the power of the main power line and supplies it to the sub power line. The controller controls the first and second DC-DC converters.

  The system switch is opened and closed according to ON / OFF of a vehicle main switch (start switch) operated by the user. While the vehicle main switch is OFF, the system switch is opened, and the high-voltage system (travel motor and power control unit) is completely disconnected from the main battery, ensuring reliable safety of the vehicle.

  Until the system switch is closed, the controller controls the second DC-DC converter, and power is supplied to the low voltage device via the sub power line. After the system switch is closed, the controller appropriately controls the first and second DC-DC converters to cover the power consumption of the entire low voltage device.

  As illustrated in FIG. 5 of Patent Document 1, when the vehicle main switch is switched from ON to OFF, the controller stops the first DC-DC converter and then opens the system switch. If the system switch is opened while the first DC-DC converter is operating, that is, with current flowing through the system switch, a spike-like noise current is generated, which damages the system switch and the device connected to the system switch. Because there is a risk of receiving.

JP 2008-5622 A

  The electric system of an electric vehicle in recent years has become complicated, and a plurality of controllers control various devices while communicating with each other. Typically, in addition to the controller that controls the first and second DC-DC converters, a controller that monitors the operation of the vehicle main switch and controls the system switch may be provided. For convenience of explanation, the former controller is referred to as a DDC controller, and the latter controller is referred to as a main controller. When the vehicle main switch is switched from ON to OFF, the main controller instructs the DDC controller to stop the first DC-DC converter, and then opens the system switch.

  When communication failure occurs between the main controller and the DDC controller when the main controller and the DDC controller are in the above-described cooperative relationship, the following problem occurs. As mentioned above, it is desirable to stop the first DC-DC converter prior to opening the system switch. However, if a communication failure occurs, the DDC controller cannot receive a command from the main controller, so the main controller must open the system switch during the operation of the first DC-DC converter. If the system switch is opened while a current is flowing through the system switch, a spike noise current may be generated as described above. In order to avoid generation of noise current when the system switch is opened, it is conceivable to stop the first DC-DC converter when communication failure occurs. However, it is desirable that the vehicle can travel after the communication failure occurs until the vehicle main switch is turned off. If the first DC-DC converter is stopped, there is a possibility that the power supplied to the low-voltage device is insufficient, and in that case, there is a possibility that the running may be hindered.

  In this specification, even when a communication failure occurs between the DDC controller and the main controller, it is possible to supply sufficient power to the low-voltage device during traveling, and when the vehicle main switch is turned off, the system switch Provide technology that can be safely opened.

  A power supply system disclosed in this specification includes a main battery, a main power line, a sub power line, a system switch, first and second DC-DC converters, a DDC controller, and a main controller. The main power line connects the power control unit and the main battery. The power control unit is a device that converts electric power supplied from the main battery into electric power for driving the traveling motor. The sub power line transmits power to a low voltage device that operates at a lower voltage than the main battery. The system switch is provided in the main power line and switches between conduction and non-conduction between the main battery and the power control unit. The first DC-DC converter is connected between the main power line and the sub power line closer to the power control unit than the system switch, and can perform a step-down operation in which the power of the main power line is stepped down and supplied to the sub power line. The second DC-DC converter is connected between the main power line and the sub power line closer to the main battery than the system switch, and can perform a step-down operation that steps down the power of the main power line and supplies it to the sub power line. The DDC controller controls the first and second DC-DC converters. When the vehicle main switch is switched from ON to OFF, the main controller transmits a stop command signal for stopping the first DC-DC converter to the DDC controller, and then opens the system switch. When communication failure occurs with the main controller, the DDC controller sets the output target voltage of the first DC-DC converter to the first voltage to control the first DC-DC converter, and the second DC-DC converter The output target voltage is set to a second voltage higher than the first voltage to control the second DC-DC converter. When the vehicle main switch is switched from ON to OFF while a communication failure occurs, the main controller does not transmit a stop command signal, and the total power consumption of the plurality of low-voltage devices is equal to that of the second DC-DC converter. Control the low-voltage equipment so that the maximum output power is not exceeded, and open the system switch.

  Both the first and second DC-DC converters are connected to the sub power line. Therefore, since the second voltage is higher than the first voltage, even if the first DC-DC converter is operating, virtually no power is output, and only the second DC-DC converter supplies power to the low-voltage device. Become. The output power of the second DC-DC converter has a limit, and when the total power consumption of the low voltage device exceeds the maximum output power of the second DC-DC converter, the output voltage of the second DC-DC converter decreases. When the output voltage of the second DC-DC converter falls below the first voltage, power supply from the first DC-DC converter also begins. Thus, sufficient power can be supplied to the low voltage device.

  On the other hand, if the main switch of the main controller is switched from ON to OFF during communication failure, the main controller has a low voltage so that the total power consumption of the low voltage device does not exceed the maximum output power of the second DC-DC converter. Control the equipment. If the total power consumption of the low-voltage device does not exceed the maximum output voltage, the second DC-DC converter can hold the second voltage that is the output target voltage, and the first DC-DC converter does not output power. At this time, no current flows through the system switch. In such a state, the main controller opens the system switch. Therefore, the system switch can be opened safely without generating spike-like noise current.

  The power system for an electric vehicle disclosed in this specification provides sufficient power for low-voltage devices during driving even when communication failure occurs between the DDC controller and the main controller and the two controllers cannot cooperate. The system switch can be safely opened when the vehicle main switch is turned off.

  Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the electric power system of the hybrid vehicle containing the power supply system of an Example. FIG. 2A shows processing of the DDC controller when communication failure is detected. FIG. 2B shows processing of the main controller when the vehicle main switch is turned off after communication failure occurs.

  A power supply system 2 according to an embodiment will be described with reference to the drawings. The power supply system 2 is mounted on the hybrid vehicle 100. FIG. 1 shows a block diagram of an electric system of hybrid vehicle 100 including power supply system 2. The hybrid vehicle 100 can travel with the power of the engine 61 and / or the power of the first motor 6 and the second motor 8. When the motor is used, the hybrid vehicle 100 drives the second motor 8 with electric power supplied from the main battery 4 and rotates driving wheels (not shown) with the power of the second motor 8. When traveling using the engine 61, the hybrid vehicle 100 starts the engine 61 using the first motor 6 as a cell motor. The hybrid vehicle 100 transmits a part of the power generated by the engine 61 to the drive wheels by the power distribution mechanism 62, while transmitting the remaining power to the first motor 6 to generate power by the first motor 6. To do. The electric power generated by the first motor 6 can be supplied to the second motor 8 and used for rotating the drive wheels, or can be used for charging the main battery 4.

  In addition, when driving | running | working using the engine 61, it is also possible to supply electric power from the main battery 4 to the 2nd motor 8, and to increase a driving force. On the other hand, when the traveling hybrid vehicle 100 decelerates, the regenerative power generation can be performed by the second motor 8, and the main battery 4 can be charged with the power generated by the second motor 8. Thus, the first motor 6 and the second motor 8 also function as a generator. In that sense, the first motor 6 and the second motor 8 can be referred to as “motor generators”. In FIG. 1, “MG1” represents the first motor 6 (first motor generator), and “MG2” represents the second motor 8 (second motor generator). The first motor 6 and the second motor 8 can also be referred to as “travel motors”. “PCU” in FIG. 1 indicates a power control unit 12 to be described later.

  The power supply system 2 includes a main battery 4, a sub battery 22, a system main relay 20, a first DC-DC converter 28, a second DC-DC converter 30, a DDC control unit 43, and an HV control unit 45. Hereinafter, for the sake of simplicity, the system main relay 20 is denoted as SMR 20, the DDC control unit 43 is denoted as DDC-ECU 43, and the HV control unit 45 is denoted as HV-ECU 45 for convenience. Further, the first DC-DC converter 28 is represented as a first DDC 28, and the second DC-DC converter 30 is represented as a second DDC 30. In FIG. 1, the first DDC 28 is represented as “DDC1”, and the second DDC 30 is represented as “DDC2”. Further, a power control unit 12 to be described later is referred to as PCU 12.

  The DDC-ECU 43 is connected to the first DDC 28, the second DDC 30, the PCU 12, and the like via the communication line 47, and controls them. The PCU 12 (power control unit 12) is a device that converts electric power supplied from the main battery 4 into electric power for driving the traveling motor. The DDC-ECU 43 and the HV-ECU 45 are connected by a communication line 44. The HV-ECU 45 and the SMR 20 are connected by a communication line 48. The HV-ECU 45 is connected to the vehicle main switch 46 via the communication line 49. The vehicle main switch 46 is a switch provided in the driver's seat of the vehicle, and is a switch that activates the entire vehicle system. The vehicle main switch 46 is sometimes referred to as an ignition switch, and may be referred to as a start switch in an electric vehicle (hybrid vehicle).

  The main battery 4 is a secondary battery (rechargeable battery) such as a nickel metal hydride battery or a lithium ion battery. In the present embodiment, the voltage of the main battery 4 is about 300 V (volts). The main battery 4 is connected to the PCU 12 via the main power line 10. The main power line 10 is provided with an SMR 20. The SMR 20 switches between conduction and non-conduction between the main battery 4 and the PCU 12. Note that “non-conduction” may be expressed as “shut off”. Further, the connection between the main battery 4 and the PCU 12 may be expressed as “close the SMR 20”, and the disconnection between the main battery 4 and the PCU 12 may be expressed as “opening the SMR 20”.

  The PCU 12 is provided between the main battery 4 and the first motor 6 and the second motor 8. The PCU 12 includes smoothing capacitors 14 and 15, a converter 16, and an inverter 17. The smoothing capacitor 14 smoothes the current of the main power line 10. In more detail, the smoothing capacitor 14 smoothes the electric current supplied from the main battery 4. Smoothing capacitor 15 smoothes the electric current flowing between converter 16 and inverter 17.

  The PCU 12 converts electric power supplied from the main battery 4 into electric power for driving the first motor 6 and the second motor 8 (traveling motor). The converter 16 boosts the voltage of the power supplied from the main battery 4 to a voltage suitable for driving the first motor 6 and the second motor 8 as necessary. The converter 16 also reduces the voltage of the power generated by the first motor 6 and the second motor 8 to a voltage suitable for charging the main battery 4. That is, the converter 16 is a bidirectional DC-DC converter. A plurality of power elements through which current from the main battery 4 flows is mounted on the converter 16. Since the circuit configuration of the bidirectional DC-DC converter is well known, detailed description thereof is omitted. In this embodiment, the voltage used for driving the first motor 6 and the second motor 8 is about 600V.

  The inverter 17 includes two sets of inverter circuits corresponding to each of the two motors (the first motor 6 and the second motor 8). The inverter 17 converts the DC power supplied from the converter 16 into U-phase, V-phase, and W-phase AC power and supplies three-phase AC power for driving the first motor 6 and the second motor 8. The three-phase AC power generated by the 1 motor 6 and the second motor 8 is converted into DC power and supplied to the converter 16. Further, the inverter 17 temporarily converts the three-phase AC power generated by one of the first motor 6 and the second motor 8 into DC power, and further converts it into three-phase AC power. It is also supplied to the other side of the motor 8. A plurality of power elements through which current from the main battery 4 flows is also mounted on the inverter 17. Since the configuration of the inverter circuit is well known, detailed description thereof is omitted.

  An air conditioner 50 is also connected to the main power line 10 a closer to the PCU 12 than the SMR 20. Since the air conditioner 50 consumes a large amount of power, it is connected to the main power line 10 instead of the sub power line 24 (described later), and is supplied with power from the main battery 4.

  The sub battery 22 will be described. The output voltage of the sub battery 22 is lower than the output voltage of the main battery 4. The sub-battery 22 is typically a secondary battery (a rechargeable battery) configured by a lead storage battery. In this embodiment, the voltage of the sub battery 22 is about 13V. The sub battery 22 is connected to the low voltage device 41 through the sub power line 24. The low voltage device 41 is a general term for devices that operate on the voltage of the sub battery 22 (in other words, a voltage lower than the voltage of the main battery 4). The sub power line 24 transmits power from the sub battery 22 (or from the first DDC 28 and the second DDC 30 described later) to the low voltage device 41. Examples of the low voltage device 41 include a brake lamp 41a and a headlight 41b. Other examples of the low voltage device 41 include a room lamp, a navigation device, and an audio device. The DDC-ECU 43 and the HV-ECU 45 also receive power supply from the sub-battery 22 as one of low voltage devices. Note that control units that are important for running ability, such as the DDC-ECU 43 and the HV-ECU 45, have their own batteries, and can operate for a predetermined period without the supply of power from the sub power line 24. The conductive body of the vehicle may also serve as the negative electrode line of the sub power line 24. The potential of the negative electrode line is sometimes called a ground potential (reference potential).

  A first DDC 28 (first DC-DC converter) is connected between the main power line 10 a on the PCU 12 side of the SMR 20 and the sub power line 24. The first DDC 28 can perform a step-down operation in which the power flowing through the main power line 10 is stepped down and supplied to the sub power line 24 and a step-up operation in which the power flowing through the sub power line 24 is stepped up and supplied to the main power line 10. Typically, the step-down operation is to step down the power of the main battery 4 and supply it to the sub power line 24. The first DDC 28 is also a bi-directional DC-DC converter like the previous converter 16. In the hybrid vehicle 100, the first DDC 28 performs the step-down operation, so that the sub-battery 22 can be charged with the regenerative power generated by the first motor 6 and the second motor 8 even when the SMR 20 is non-conductive. . Further, in the hybrid vehicle 100, the first DDC 28 performs the step-up operation, so that the first motor 6 and the second motor 8 can be driven using the power of the sub-battery 22 even when the SMR 20 is non-conductive. Further, when the second DDC 30 described later performs a step-down operation and the first DDC 28 performs a step-up operation, the power of the main battery 4 is supplied to the PCU 12 even when the SMR 20 is non-conductive, and the first motor 6 and the second motor 8 are driven. You can also

  A second DDC 30 (second DC-DC converter) is connected between the main power line 10 b on the main battery 4 side and the sub power line 24 with respect to the SMR 20. The second DDC 30 can perform a step-down operation in which the power flowing through the main power line 10 is stepped down and supplied to the sub power line 24. The second DDC 30 is a so-called step-down converter. In hybrid vehicle 100, when SMR 20 is conductive, first DDC 28 performs a step-down operation, and second DDC 30 performs a step-down operation. Thereby, the power from the main battery 4 and the power generated by the first motor 6 and the second motor 8 can be charged to the sub-battery 22 through both the first DDC 28 and the second DDC 30. In this case, the current supplied to the sub-battery 22 is greater than when charging the sub-battery 22 via either the first DDC 28 or the second DDC 30. Therefore, the time required for charging the sub battery 22 is shortened.

  The SMR 20 is opened while the vehicle main switch 46 is OFF, and cuts off between the main battery 4 and the PCU 12. The HV-ECU 45 monitors the state of the vehicle main switch 46. When the vehicle main switch 46 is switched from OFF to ON, the SMR 20 is closed and the main battery 4 and the PCU 12 are connected. When the main battery 4 and the PCU 12 are connected, the first motor 6 and the second motor 8 can be supplied with power, that is, the vehicle can run.

  When the SMR 20 is connected in a state where the smoothing capacitor 14 is discharged, that is, in a state where the voltage across the smoothing capacitor 14 is low, an inrush current flows from the main battery 4 to the PCU 12 (converter 16 and inverter 17). The inrush current may damage the power elements of the converter 16 and the inverter 17. Therefore, the HV-ECU 45 sends a command to the DDC-ECU 43 prior to closing the SMR 20, and charges (precharges) the smoothing capacitor 14 using the first DDC 28 and the second DDC 30. More specifically, the DDC-ECU 43 causes the second DDC 30 to perform a step-down operation to supply the power of the main battery 4 to the sub power line 24, and also causes the first DDC 28 to perform a step-up operation, The power is supplied to the main power line 10 a closer to the PCU 12 than the SMR 20 through the sub power line 24. Since the smoothing capacitor 14 is connected in parallel to the main power line 10a closer to the PCU 12 than the SMR 20, the smoothing capacitor 14 is precharged with the power of the main battery 4 by the above processing. When the precharge is completed, the HV-ECU 45 closes the SMR 20. After the precharge, since the voltage on the main battery 4 side of the SMR 20 and the voltage on the PCU 12 side are substantially equal, no inrush current flows.

  After the SMR 20 is closed, the DDC-ECU 43 switches the operation of the first DDC 28 from the step-up operation to the step-down operation. That is, the DDC-ECU 43 controls the first DDC 28 so that the power of the main power line 10 is stepped down and supplied to the sub power line 24. After the SMR 20 is closed, the DDC-ECU 43 adjusts the outputs of the first DDC 28 and the second DDC 30 according to the total power consumption of the plurality of low voltage devices 41.

  The HV-ECU 45 and the DDC-ECU 43 are communicably connected via a communication line 44. The DDC-ECU 43 is a power system controller that controls the PCU 12, the first DDC 28, and the second DDC 30. On the other hand, the HV-ECU 45 monitors the state of the switches operated by the user such as the vehicle main switch 46, and calculates the driving torque required for the vehicle from the accelerator opening, the vehicle speed, the remaining amount of the main battery 4, and the like. The target drive torque of the engine 61 and the target drive torque of the motors 6 and 8 are distributed. The HV-ECU 45 is a controller for a command tower that controls the entire vehicle.

  Processing of the HV-ECU 45 and the DDC-ECU 43 when the vehicle main switch 46 is switched from ON to OFF will be described. When the vehicle main switch 46 is switched from ON to OFF, the HV-ECU 45 transmits a stop command signal for stopping the first DDC 28 to the DDC-ECU 43 via the communication line 44. The DDC-ECU 43 that has received the stop command signal stops the first DDC 28. At this time, the second DDC 30 continues the step-down operation, and power supply from the main battery 4 to the sub power line 24 is continued through the second DDC 30. Therefore, even if the vehicle main switch 46 is switched to OFF, the low voltage device 41 can be continuously used.

  After the first DDC 28 stops, the HV-ECU 45 opens the SRM 20. Thus, after the vehicle main switch 46 is turned off, the SMR 20 is opened and the main battery 4 is completely disconnected from the PCU 12. The vehicle main switch 46 can be accurately switched in three stages, and they are called Ready-ON, Ready-OFF, and OFF. “Ready-ON” means a state in which the vehicle can travel, and corresponds to “ON” in the above description of this embodiment. “Ready-OFF” means that the SMR 20 is in an open state and cannot travel, but the low-voltage device 41 is available. “OFF” in the above description of this embodiment corresponds to “Ready-OFF”. “OFF” means a state in which other low-voltage devices 41 cannot be used except for a device for starting the system (such as the HV-ECU 45). When the vehicle main switch 46 is switched from Ray-OFF to OFF, the HV-ECU 45 instructs the DDC-ECU 43 to stop the second DDC 30.

  In this specification, since the processing at the time of switching of the SMR 20 is focused, among the three stages of the vehicle main switch 46 (Ready-ON / Ready-OFF / OFF), “Ready” The description will be continued by referring to “ON” as “ON” and “Ready-OFF” as “OFF”.

  If a communication failure occurs between the HV-ECU 45 and the DDC-ECU 43, the DDC-ECU 43 cannot receive a stop command signal from the HV-ECU 45. When the HV-ECU 45 detects that the vehicle main switch 46 has been switched from ON to OFF, the HV-ECU 45 must open the SMR 20 but cannot stop the first DDC 28 prior to opening the SMR 20. If the SMR 20 is opened while the first DDC 28 is operating and a current is flowing through the SMR 20, an arc discharge occurs at the contact of the SMR 20 or a spike-like noise current occurs at the main power line 10, causing the SMR 20 and other devices to be opened. May be damaged. Although it is conceivable to stop the first DDC 28 when communication failure occurs, if so, power is supplied from the sub-battery 22 and the second DDC 30 to the low-voltage device 41, but power supply from the first DDC 28 is lost. There is a risk that it may interfere with running. Therefore, when a communication failure occurs between the DDC-ECU 43 and the HV-ECU 45, the power supply system 2 performs the processing of the flowchart of FIG. 2 while ensuring sufficient power supply to the low-voltage device 41 during traveling. When the vehicle main switch 46 is turned off, the SMR 20 is safely opened.

  For example, the following method is used to detect a communication failure. The communication line 44 is, for example, a CAN (Control Area Network). When the communication line 44 between the DDC-ECU 43 and the HV-ECU 45 is a CAN (Control Area Network), a handshake protocol is executed for exchanging data. Therefore, a communication failure can be detected by the handshake protocol. When communication between the DDC-ECU 43 and the HV-ECU 45 is performed by another protocol, for example, a communication failure can be detected by a check function such as CRC.

  FIG. 2A shows processing of the DDC-ECU 43 when a communication failure is detected. FIG. 2B shows processing of the HV-ECU 45 when the vehicle main switch 46 is switched from ON to OFF after detecting a communication failure. When the DDC-ECU 43 detects a communication failure, the DDC-ECU 43 executes constant voltage control for holding the output voltage at the voltage V1 with respect to the first DDC 28 (S2). Further, the DDC-ECU 43 executes constant voltage control for holding the output voltage at the voltage V2 with respect to the second DDC 30 (S2). In other words, the DDC-ECU 43 sets the output target voltage of the first DDC 28 to the voltage V1 to control the first DDC 28 at a constant voltage, and sets the output target voltage of the second DDC 30 to the voltage V2 to set the second DDC 30 to a constant voltage. Control. Here, the voltage V2 is set to a value larger than the voltage V1. Further, the voltage V1 and the voltage V2 are set to be equal to or higher than the operating voltage of the low voltage device 41. Furthermore, the voltage V1 and the voltage V2 are set to values higher than the output voltage of the sub battery 22. When step S2 is executed, the power supply to the plurality of low-voltage devices 41 is as follows. When the total power consumption of the plurality of low-voltage devices 41 is smaller than the maximum output voltage of the second DDC 30, the second DDC 30 can hold the voltage V2 that is the output target voltage. Since the output target voltage V1 of the first DDC 28 is lower than the voltage V2, the output is substantially zero even if the first DDC 28 is operating. That is, power is supplied to the low voltage device 41 only from the second DDC 30. Further, since both the voltage V1 and the voltage V2 are higher than the output voltage of the sub battery 22, when the output voltage of the first DDC 28 or the second DDC 30 is higher than the voltage V1, no power is output from the sub battery 22.

  While traveling, various low-voltage devices 41 are started and stopped, and the output is changed. That is, during traveling, the total power consumption of the plurality of low voltage devices 41 changes. The power that can be output by the second DDC 30 is limited. If the total power consumption exceeds the maximum output voltage of the second DDC 30, the second DDC 30 cannot hold the output voltage at the voltage V2, and the output voltage decreases. When the output voltage of the second DDC 30 becomes equal to or lower than the voltage V1, power is output from the first DDC 28 whose output target voltage is set to the voltage V1. The low-voltage device 41 is supplied with power from both the first DDC 28 and the second DDC 30, and sufficient power can be supplied to the low-voltage device 41. Even if communication failure occurs between the HV-ECU 45 and the DDC-ECU 43 during traveling, sufficient power can be continuously supplied to the low-voltage device 41. Note that when the power is insufficient even with the total output of the first DDC 28 and the second DDC 30, the output voltage of the first DDC 28 and the output voltage of the second DDC 30 both decrease. The output voltage of the first DDC 28 and the second DDC 30 is the output voltage of the sub-battery 22. If it becomes lower than that, electric power is also supplied from the sub-battery 22 to the low-voltage device 41.

  On the other hand, when the HV-ECU 45 detects that the vehicle main switch 46 is switched from ON to OFF after the occurrence of the communication failure, the HV-ECU 45 executes the process of FIG. The HV-ECU 45 monitors the operation of each low voltage device 41 and grasps the total power consumption of all the low voltage devices 41 in operation. The HV-ECU 45 checks whether or not the total power consumption of the low voltage device 41 is equal to or greater than the maximum output power of the second DDC 30 (S3). The HV-ECU 45 stores a value of the maximum output power of the second DDC 30 in advance. When the total power consumption of the low voltage device 41 is equal to or greater than the maximum output power of the second DDC 30 (S3: YES), the HV-ECU 45 lowers one specific output of the operating low voltage device 41 (S4). For example, the HV-ECU 45 lowers the set temperature of the heater, which is one of the low voltage devices 41, and lowers the output of the heater. If it does so, the power consumption of a heater will fall. Accordingly, the total power consumption of the low voltage device 41 is reduced. When step S4 is executed, the process returns to step S3, and the HV-ECU 45 checks again whether or not the total power consumption is equal to or greater than the maximum output power of the second DDC 30 (S3).

  When the total power consumption of the low voltage device 41 is still equal to or greater than the maximum output power of the second DDC 30 (S3: YES), the HV-ECU 45 lowers another output of the operating low voltage device 41 (S4). For example, the HV-ECU 45 lowers the audio output. If it does so, the power consumption of an audio | voice will fall and the total power consumption of the low voltage apparatus 41 will fall. The HV-ECU 45 repeats the process of step S4 until the total power consumption falls below the maximum output power of the second DDC 30. In the HV-ECU 45, the order of the low-voltage devices 41 for lowering the output is set, and the low-voltage devices 41 are selected along the order and the output is lowered.

  When the total power consumption falls below the maximum output power of the second DDC 30 (S3: NO), the HV-ECU 45 opens the SMR 20 (S5). When the total power consumption is lower than the maximum output power of the second DDC 30, the output voltage of the second DDC 30 is held at the voltage V2 as described in the description of FIG. 2A, and power is output from the first DDC 28. Not. That is, when the HV-ECU 45 opens the SMR 20 in step S5, no current flows through the SMR 20. When the SMR 20 is opened, no arc discharge or spike-like noise current occurs, so that the SMR 20 and surrounding devices are not damaged. That is, the power supply system 2 can open the SMR 20 safely.

  2A is executed by the DDC-ECU 43, and the process of FIG. 2B is executed by the HV-ECU 45. Since a communication failure has occurred between the DDC-ECU 43 and the HV-ECU 45, the DDC-ECU 43 and the HV-ECU 45 cannot cooperate with each other, and the processing in FIG. 2A and the processing in FIG. Each process is executed independently. The power supply system 2 according to the embodiment can supply sufficient power to the low-voltage device 41 during traveling, and the vehicle main switch 46, even if the DDC-ECU 43 and the HV-ECU 45 cannot operate in cooperation. SMR 20 can be safely opened when is turned off.

  Points to be noted regarding the technology described in the embodiments will be described. The SMR 20 of the embodiment corresponds to an example of “system switch” in the claims. The first DDC 28 corresponds to an example of a “first DC-DC converter” in the claims. The second DDC 30 corresponds to an example of a “second DC-DC converter” in the claims. The DDC-ECU 43 in the embodiment corresponds to an example of “DDC controller” in the claims, and the HV-ECU 45 in the embodiment corresponds to an example of “main controller” in the claims.

  The second DDC 30 is a bidirectional DC-DC capable of performing a step-up operation in which the power of the sub power line 24 is boosted and supplied to the main power line 10 in addition to the step-down operation in which the power of the main power line 10 is stepped down and supplied to the sub power line 24. It may be a converter. The power supply system 2 of an Example is applied to the hybrid vehicle provided with both an engine and a motor for driving | running | working. The power supply system disclosed in this specification can also be applied to an electric vehicle that does not include an engine.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Power supply system 4: Main battery 6: First motor 8: Second motor 10: Main power line 12: Power control unit (PCU)
14, 15: Smoothing capacitor 16: Converter 17: Inverter 20: System main relay (SMR)
22: Sub battery 24: Sub power line 28: First DC-DC converter (first DDC)
30: Second DC-DC converter (second DDC)
41: Low voltage device 43: DDC control unit (DDC-ECU)
45: HV control unit (HV-ECU)
46: Vehicle main switch 50: Air conditioner 61: Engine 62: Power distribution mechanism 100: Hybrid vehicle

Claims (1)

A main battery,
A power control unit that converts electric power supplied from the main battery into electric power for driving the motor, and a main power line that connects the main battery;
A system switch provided on the main power line, for switching between conduction and non-conduction between the main battery and the power control unit;
A sub power line for transmitting power to a low voltage device operating at a lower voltage than the main battery;
A first DC-DC connected between the main power line and the sub power line closer to the power control unit than the system switch, and capable of stepping down the power of the main power line and supplying it to the sub power line. A converter,
A second DC-DC converter connected between the main power line and the sub power line closer to the main battery than the system switch, and capable of performing a step-down operation for stepping down the power of the main power line and supplying it to the sub power line When,
A DDC controller for controlling the first and second DC-DC converters;
A main controller for transmitting a stop command signal for stopping the first DC-DC converter to the DDC controller when the vehicle main switch is switched from ON to OFF, and then opening the system switch;
With
The DDC controller controls the first DC-DC converter by setting an output target voltage of the first DC-DC converter to a first voltage when communication failure occurs with the main controller. Setting the output target voltage of the 2DC-DC converter to a second voltage higher than the first voltage to control the second DC-DC converter;
When the vehicle main switch is switched from ON to OFF while the communication failure occurs, the main controller does not transmit the stop command signal, and the total power consumption of the plurality of low-voltage devices is A power supply system for an electric vehicle that controls the low-voltage device so as not to exceed a maximum output power of a second DC-DC converter and opens the system switch.

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