JP2018121453A - Power source device for electric vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To disclose a technology that detects an abnormality in a voltage sensor of a DC-DC converter.SOLUTION: A power source device for an electric vehicle comprises: a switch inserted between a battery and a power conversion device; a capacitor inserted further on an electric conversion device side than the switch; a DC-DC converter that inputs charge current into the capacitor from the battery; and a control device. During an ending procedure in which the control device stops respective operations of the DC-DC converter and power conversion device (S12, S14) and then a switch is changed from a conduction state to a non-conduction state (S22), the operations of the DC-DC converter and power conversion device are stopped and when the absolute value of a difference between a detection value Vc of a first voltage sensor of the DC-DC converter and a detection value Vb of a second voltage sensor of the battery, which are detected during the conduction state of the switch, is equal to or larger than a predetermined value, an occurrence of abnormality in the first voltage sensor is detected (YES in S16).SELECTED DRAWING: Figure 3

Description

  In this specification, the power supply device of an electric vehicle is disclosed. The electric vehicle referred to in this specification includes a hybrid vehicle including a traveling motor and an engine, and an electric vehicle and a fuel cell vehicle including a traveling motor but not including an engine.

Patent Document 1 discloses a power supply device for an electric vehicle including a battery and a power conversion device that converts power supplied from the battery and supplies the converted power to a motor. The battery and the power converter are connected by a high voltage power line and a low voltage power line.
A switch is inserted in each of the high-voltage power supply line and the low-voltage power supply line so that the battery and the power conversion device can be switched to a non-conductive state. In addition, a smoothing capacitor is inserted between the high-voltage power supply line and the low-voltage power supply line closer to the power converter than the switch so that the voltage input to the power converter is smoothed.

  When the electric vehicle stops traveling, the switch control device switches the switch from the conductive state to the non-conductive state. When the electric vehicle starts running, the switch control device switches the switch from the non-conductive state to the conductive state. If the battery voltage and the charging voltage of the smoothing capacitor are significantly different before the start of running, a large inrush current flows through the switch at the moment when the switch is switched from the non-conductive state to the conductive state, and the switch may be damaged.

  The power supply device of Patent Document 1 includes a DC-DC converter. The DC-DC converter includes a high voltage power line on the battery side from the switch and a high voltage power line on the power converter side from the switch, a low voltage power line on the battery side from the switch, and a low voltage power line on the power converter side from the switch. It is inserted between them, and the battery voltage can be stepped down and supplied to the auxiliary equipment, or the auxiliary equipment driving voltage can be stepped up and supplied to the power converter. When the DC-DC converter is provided, a charging current can be supplied from the DC-DC converter to the capacitor even if the switch is in a non-conductive state. In the power supply device of Patent Document 1, this DC-DC converter is used to prevent a large inrush current from flowing through the switch. That is, prior to switching the switch from the non-conductive state to the conductive state, the controller for the DC-DC converter starts operation of the DC-DC converter and charges the capacitor. Since the switch is switched to the introduction state after the battery voltage and the capacitor voltage substantially coincide with each other, it is possible to prevent a large inrush current from flowing through the switch. The DC-DC converter incorporates an internal inductor, a transformer, and the like, and a large inrush current does not flow through the DC-DC converter.

JP, 2006-101057, A

The DC-DC converter incorporates a first voltage sensor that detects a voltage between the high-voltage power supply line and the low-voltage power supply line on the power converter side of the switch, and is controlled based on the detected value.
If the first voltage sensor is normal, the first voltage sensor can detect the timing at which the battery voltage and the capacitor voltage substantially coincide with each other, and can prevent a large inrush current from flowing through the switch. However, if an abnormality occurs in the first voltage sensor, it may be erroneously determined that the battery voltage and the capacitor voltage are almost the same even though the battery voltage and the capacitor voltage are actually greatly shifted. Inrush current may flow.
In the present specification, a technique for detecting an abnormality of the first voltage sensor is disclosed. If an abnormality can be detected, processing for coping with the abnormality of the first voltage sensor can be executed.

  A power supply device for an electric vehicle disclosed in the present specification includes a battery, a power conversion device that converts power supplied from the battery and supplies the motor, a high-voltage power supply line and a low-voltage power supply line that connect the battery and the power conversion device, A switch inserted in each of the high-voltage power line and the low-voltage power line, a capacitor inserted between the high-voltage power line and the low-voltage power line on the power converter side from the switch, and a high-voltage power line on the battery side from the switch Between the switch and the high-voltage power line on the power converter side from the switch, and between the low-voltage power line on the battery side from the switch and the low-voltage power line on the power converter side from the switch. A DC-DC converter having a first voltage sensor for detecting a voltage between the power line and the low voltage power line, and a high voltage power line and a low voltage power line on the battery side from the switch A second voltage sensor for detecting a voltage between, and a control device for controlling the switch and the DC-DC converter and the power converter. The control device stops the operation of the DC-DC converter and the power converter, and then starts the operation of the DC-DC converter after finishing the switching procedure from the conductive state to the non-conductive state, and then the switch is non-conductive. And a detection value of the first voltage sensor detected while the switch is in the conductive state by stopping the operation of the DC-DC converter and the power converter when executing the end procedure. When the absolute value of the difference between the detection values of the second voltage sensor is greater than or equal to a predetermined value, it is detected that an abnormality has occurred in the first voltage sensor.

In order to detect an abnormality in the first voltage sensor, it is assumed that the detection value of the first voltage sensor is compared with the detection value of the second voltage sensor. However, the detection value of the first voltage sensor and the detection value of the second voltage sensor are not guaranteed to coincide with each other due to wiring resistance or the like, and are usually difficult to compare.
According to the above configuration, the control device stops the operation of the DC-DC converter and the power converter when executing the termination procedure, and the detected value of the first voltage sensor and the second voltage sensor detected while the switch is in the conductive state. Compare the detected values. During this period, it is guaranteed that the detection value of the first voltage sensor and the detection value of the second voltage sensor match because they are not affected by the wiring resistance or the like. If they do not match, an abnormality occurs in the first voltage sensor. It can be determined that it is. Thereby, the control device can detect an abnormality of the first voltage sensor and execute a process for dealing with the abnormality of the first voltage sensor. The abnormality handling process includes, for example, a process for notifying the user of an abnormality of the first voltage sensor, a process for prohibiting execution of the subsequent start procedure, and a start procedure based on a detection value of a voltage sensor different from the first voltage sensor. The process etc. which perform are illustrated. When the switch is on, or when the DC-DC converter or the power conversion device is operating, the detection value of the first voltage sensor and the detection value of the second voltage sensor must match due to the wiring resistance. Is not guaranteed, and abnormalities cannot be detected even when compared under the conditions.
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 power supply device of the electric vehicle of an Example. It is a figure which shows the mode of the starting procedure in a power supply device. It is a flowchart figure which shows the process of the completion | finish procedure in a power supply device.

  FIG. 1 is a block diagram of a power supply device 2 for an electric automobile. The power supply device 2 is mounted on the electric automobile and drives the traveling motor 6. In the present embodiment, an embodiment of the power supply device 2 mounted on an electric vehicle will be described.

  The power supply device 2 includes a main battery 4, a traveling motor 6, a high voltage power supply line 8, a low voltage power supply line 9, a system main relay 10, a power conversion device 18, a sub battery 20, and a first DC-DC converter. 22, a second DC-DC converter 24, an auxiliary machine 26, a main voltage sensor 28, a control device 32, and an ignition switch 34.

The main battery 4 is a secondary 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 volts (V). The main battery 4 supplies power to the motor 6 via the power converter 18. Thereby, the motor 6 is driven and the electric vehicle runs. Moreover, the main battery 4 can also be charged with the electric power generated by the motor 6 when the running electric vehicle decelerates.

  The high voltage power line 8 connects the high voltage side terminal of the main battery 4 and the high voltage side terminal of the power converter 18. The low voltage power line 9 connects the low voltage side terminal of the main battery 4 and the low voltage side terminal of the power converter 18. The power of the main battery 4 is supplied to the power converter 18 through the high voltage power line 8 and the low voltage power line 9. Further, when the traveling electric vehicle decelerates, the electric power generated by the motor 6 is supplied to the main battery 4 via the high voltage power line 8 and the low voltage power line 9.

  The system main relay (SMR) 10 includes a switch 10 a inserted into the high voltage power line 8 and a switch 10 b inserted into the low voltage power line 9. The SMR 10 switches between the high voltage power supply line 8 and the low voltage power supply line 9 between conduction and non-conduction. Of the high-voltage power supply line 8, reference numeral 8 a is assigned to the high-voltage power supply wiring on the main battery 4 side from the SMR 10, and reference numeral 8 b is assigned to the high-voltage power supply wiring on the power converter 18 side from the SMR 10. Among the low-voltage power supply lines 9, reference numeral 9a is assigned to the low-voltage power supply wiring on the main battery 4 side from the SMR 10, and reference numeral 9b is assigned to the low-voltage power supply wiring on the power converter 18 side from the SMR 10.

  The power conversion device 18 is connected between the main battery 4 and the motor 6. The power conversion device 18 includes a smoothing capacitor 12, a converter 14, and an inverter 16. The smoothing capacitor 12 smoothes the voltage between the high voltage power supply line 8b and the low voltage power supply line 9b. The smoothing capacitor 12 is inserted between the high voltage power supply line 8b and the low voltage power supply line 9b.

  Converter 14 boosts the voltage of main battery 4 to a voltage suitable for driving motor 6. Converter 14 steps down the voltage of the electric power generated by motor 6 to a voltage suitable for charging main battery 4. The converter 14 includes a battery-side terminal 14c that connects the converter 14 to the main battery 4 via the high-voltage power line 8b and the low-voltage power line 9b, an inverter-side terminal 14d that connects the converter 14 to the inverter 16, and a battery-side terminal 14c. The battery side voltage sensor 14a which detects the voltage between terminals, and the inverter side voltage sensor 14b which detects the voltage between terminals of the inverter side terminal 14d are provided. The converter 14 uses the detection value of the battery side voltage sensor 14a and the detection value of the inverter side voltage sensor 14b to increase the power supplied from the main battery 4 and decrease the power generated by the motor 6.

  The inverter 16 converts the DC power supplied from the main battery 4 into three-phase AC power for driving the motor 6. The inverter 16 converts the three-phase AC power generated by the motor 6 into DC power for charging the main battery 4.

  The sub battery 20 is a secondary battery such as a lead battery. In the present embodiment, the voltage of the sub battery 20 is about 13V to 14.5V. The sub battery 20 is connected to an auxiliary machine 26 such as a power steering or an air conditioner.

  The first DC-DC converter 22 includes a high voltage power supply line 8a on the main battery 4 side from the SMR 10 and a high voltage side terminal of the sub battery 20, and a low voltage power supply line 9a on the main battery 4 side from the SMR 10 and a low voltage side terminal of the sub battery 20. Is inserted between. The first DC-DC converter 22 can step down the power of the main battery 4 and supply it to the sub battery 20 to charge the sub battery 20. The first DC-DC converter 22 can also step down the power of the main battery 4 and supply it to the second DC-DC converter 24 and the auxiliary device 26.

  The second DC-DC converter 24 includes a DC-DC converter circuit 24a and a converter voltage sensor 24b. The DC-DC converter circuit 24a is provided between the high voltage power supply line 8b on the power converter 18 side of the SMR 10 and the high voltage side terminal of the sub battery 20, and on the low voltage power line 9b on the power converter 18 side of the SMR 10 and the low voltage of the sub battery 20. It is inserted between the side terminals. Converter voltage sensor 24b detects the voltage between high voltage power supply line 8b and low voltage power supply line 9b. Hereinafter, the voltage detected by the converter voltage sensor 24b is referred to as a capacitor voltage Vc.

  The DC-DC converter circuit 24a steps down the electric power generated by the motor 6 and supplies it to the sub battery 20 when the electric vehicle that is running decelerates. Thereby, not only the electric power of the main battery 4 but also the electric power generated by the motor 6 can be used to rapidly charge the sub-battery 20. The DC-DC converter circuit 24a can boost the power supplied from the first DC-DC converter 22 and the sub-battery 20 and supply the boosted power to the high-voltage power supply line 8b and the low-voltage power supply line 9a. Thereby, the start procedure mentioned later can be performed.

  The main voltage sensor 28 detects the voltage between the terminals of the main battery 4. The main battery 4 is a main component indispensable for running an electric vehicle. For this reason, a highly accurate sensor is used as the main voltage sensor 28. The main voltage sensor 28 is provided with multiple means for detecting an abnormality. On the other hand, the battery side voltage sensor 14 a, the inverter side voltage sensor 14 b, and the converter voltage sensor 24 b are sensors that are less accurate than the main voltage sensor 28. Further, these sensors 14a, 14b, 24b are not provided with means for detecting an abnormality. Hereinafter, the voltage detected by the main voltage sensor 28 is referred to as a battery voltage Vb.

  The control device 32 controls the SMR 10, the power conversion device 18, the first DC-DC converter 22, and the second DC-DC converter 24. Specifically, the control device 32 executes a start procedure (see FIG. 2) when the ignition (IG) switch 34 is depressed while the SMR 20 is in a non-conducting state. In the start procedure, the control device 32 starts the operation of the first DC-DC converter 22 and the second DC-DC converter 24, then switches the SMR 10 from the non-conductive state to the conductive state, and then operates the power converter 18. Start. As a result, the electric vehicle is activated (that is, the vehicle can be driven). On the other hand, when the IG switch 34 is pushed down while the SMR 20 is in the conductive state, the control device 32 executes the termination procedure (see FIG. 3). In the termination procedure, the control device 32 stops the operation of the power conversion device 18, the first DC-DC converter 22, and the second DC-DC converter 24, and then switches the SMR 10 from the conductive state to the non-conductive state. As a result, the electric vehicle stops (i.e., cannot be driven). Although details will be described later, when the control device 32 detects an abnormality in the converter voltage sensor 24b during execution of the termination procedure, the control device 32 executes a countermeasure process for coping with the abnormality.

  With reference to FIG. 2, processing in the start procedure will be described. When the SMR 10 is switched from the non-conductive state to the conductive state, if the charging voltage of the main battery 4 and the smoothing capacitor 12 is greatly different, the SMR 10 enters the SMR 10 at the moment when the SMR 10 is switched from the non-conductive state to the conductive state. Current flows. This inrush current causes damage to the SMR 10. The control device 32 performs a start procedure to prevent a large inrush current from flowing through the SMR 10.

  When the IG switch 34 is depressed, a signal (S1 in FIG. 2) is input from the IG switch 34 to the control device 32. Thereby, the control device 32 executes the start procedure. In the start procedure, first, the operation of the first DC-DC converter 22 and the second DC-DC converter 24 is started (S2). That is, the control device 32 causes the second DC-DC converter 24 to perform a boost operation that boosts the voltage stepped down by the first DC-DC converter 22 and the power of the sub-battery 20. As a result, a charging current is input to the smoothing capacitor 12 and the capacitor voltage starts to increase. The control device 32 compares the detection value of the main voltage sensor 28 with the detection value (S3) of the converter voltage sensor 24b, detects the timing when they match, and switches the SMR 10 from the non-conductive state to the conductive state at this timing ( S4).

  The thick line in FIG. 2 indicates the charging current of the smoothing capacitor 12 in the starting procedure. Before the SMR 10 is turned on, the current I1 + I2 obtained by adding the current I1 supplied by the first DC-DC converter 22 and the current I2 supplied by the sub-battery 20 passes through the second DC-DC converter 24, as indicated by the thick line. The smoothing capacitor 12 is supplied. Since the charging current includes both the current I1 from the first DC-DC converter 22 and the current I2 from the sub-battery 20, the first DC-DC converter 22 is not provided and only the power from the sub-battery 20 is smoothed. Compared with the configuration in which the capacitor 12 is charged, the time required for charging the smoothing capacitor 12 can be shortened.

  The charging current described above eliminates the difference in charging voltage between the main battery 4 and the smoothing capacitor 12 before the SMR 10 is turned on, and a large inrush current flows through the SMR 10 at the moment when the SMR 10 is switched from the non-conductive state to the conductive state. It is prevented.

  With reference to FIG. 3, the process in the termination procedure will be described. The process of FIG. 3 is executed when the electric vehicle stops.

  In S10, the control device 32 monitors whether or not the IG switch 34 is pushed down (that is, turned off) while the SMR 10 is in the conductive state. When the IG switch 34 is turned off (YES in S10), the control device 32 proceeds to S12.

  In S <b> 12, the control device 32 stops the operation of the power conversion device 18. Further, the control device 32 stops the operation of the first DC-DC converter 22 and the second DC-DC converter 24 in S14.

  In S16, the control device 32 compares the detected value of the main voltage sensor 28 (that is, the battery voltage Vb) detected while the SMR 10 is in the conductive state and the detected value (that is, the capacitor voltage Vc) detected by the converter voltage sensor 24b. It is determined whether or not the absolute value of the difference is greater than or equal to a predetermined value. The predetermined value is set at the time of designing from the tolerance of the main voltage sensor 28 and the tolerance of the converter voltage sensor 24b. When it is determined that the absolute value of the difference between the battery voltage Vb and the capacitor voltage Vc is equal to or greater than the predetermined value (YES in S16), the control device 32 proceeds to S18. On the other hand, when determining that the absolute value of the difference between the battery voltage Vb and the capacitor voltage Vc is less than the predetermined value (NO in S16), the control device 32 skips S18 and S20 and proceeds to S22.

  In S18, the control device 32 outputs an abnormality signal indicating that an abnormality has occurred in the converter voltage sensor 24b to a notification device (not shown). The notification device is a device for notifying the user of the abnormality of the converter voltage sensor 24b, and is, for example, a warning light of an instrument panel, a diagnosis memory, or the like.

  In S20, the control device 32 executes a coping process for coping with the abnormality of the converter voltage sensor 24b. The coping process is, for example, a process of switching the state of the control device 32 from a state of executing the above start procedure to a state of executing the alternative start procedure, or a state of the control device 32 starting from the state of executing the start procedure. Is a process of switching to a state of prohibiting. In the alternative start procedure, for example, instead of S3 in FIG. 2, a process of detecting a timing at which the detected value of the main voltage sensor 28 matches the detected value of the battery side voltage sensor 14a in the power conversion device 18 is executed. Further, in the alternative start procedure, instead of the comparison process of the battery voltage and the capacitor voltage, the first DC-DC converter 22 and the first DC-DC converter 22 only for a predetermined time (a time when it is assumed that the difference between the charging voltages of the main battery 4 and the smoothing capacitor 12 is eliminated). A process of continuing the operation of the second DC-DC converter 24 may be executed. By executing the coping process, it is possible to prevent a large inrush current from flowing through the SMR 10 even if an abnormality occurs in the converter voltage sensor 24b.

  In S22, control device 32 switches SMR 10 from the conductive state to the non-conductive state. When S22 ends, the process of FIG. 3 ends.

  The effect of the present embodiment will be described. The detection value of the main voltage sensor 28 and the detection value of the converter voltage sensor 24b are determined when the SMR 10 is in a non-conductive state or when the power converter 18, the first DC-DC converter 22, and the second DC-DC converter 24 are operating. In case, it is not guaranteed to match. For this reason, it is usually difficult to compare the detected value of the main voltage sensor 28 with the detected value of the converter voltage sensor 24b to determine abnormality of the converter voltage sensor 24b.

  On the other hand, according to the present embodiment, the control device 32 stops the operation of the power conversion device 18, the first DC-DC converter 22, and the second DC-DC converter 24 when the termination procedure is executed, and the SMR 10 is in the conductive state. Meanwhile, the detected value of the main voltage sensor 28 is compared with the detected value of the converter voltage sensor 24b (S16). During this period, it is guaranteed that the detected value of the main voltage sensor 28 and the detected value of the converter voltage sensor 24b match. If they do not match, it is possible to determine that an abnormality has occurred in the converter voltage sensor 24b. When it is determined that the absolute value of the difference between the detection value of the main voltage sensor 28 and the detection value of the converter voltage sensor 24b is equal to or greater than a predetermined value, that is, the control device 32 detects an abnormal signal. Output (S18) and coping process (S18) are executed. Thereby, it is possible to appropriately cope with the abnormality of converter voltage sensor 24b.

  Further, as described above, the main voltage sensor 28 is a sensor in which means for detecting an abnormality are prepared in multiple. That is, the abnormality of the main voltage sensor 28 is monitored by a process different from the process of FIG. Therefore, in S16 of FIG. 3, an abnormality occurs in the main voltage sensor 28, and the detected value of the main voltage sensor 28 and the detected value of the converter voltage sensor 24b become inconsistent even though the converter voltage sensor 24b is normal. There is nothing.

  In addition, in order to detect an abnormality in converter voltage sensor 24b, another configuration that compares the detected value of converter voltage sensor 24b with the detected value of battery-side voltage sensor 14a of power conversion device 18 is also assumed. In this configuration, the mismatch between the detected value of the converter voltage sensor 24b and the detected value of the battery-side voltage sensor 14a is due to the low accuracy of the battery-side voltage sensor 14a, or an abnormality has occurred in the battery-side voltage sensor 14a. Cannot determine whether it is a For this reason, the output of the abnormal signal and the coping process can be executed unnecessarily. On the other hand, according to the present embodiment, since the means for detecting an abnormality is compared with the high-precision main voltage sensor 28 prepared in a multiplex manner, the output of the abnormality signal and the countermeasure processing are executed unnecessarily. Is prevented.

  The main battery 4 is an embodiment of “battery”, the SMR 10 is an embodiment of “switch”, the smoothing capacitor 12 is an embodiment of “capacitor”, and the first DC-DC converter 22 and the second DC-DC converter 24 are. Is an example of a “DC-DC converter”. The combination of the first DC-DC converter 22 and the second DC-DC converter 24 includes a high-voltage power line on the battery side from the switch and a high-voltage power line on the power converter side from the switch, and a low-voltage power line and switch on the battery side from the switch. It is inserted between the low-voltage power lines on the power converter side. The converter voltage sensor 24b is an example of the “first voltage sensor”, and the main voltage sensor 28 is an example of the “second voltage sensor”.

  Hereinafter, points to be noted regarding the technology shown in the embodiments will be described. There is one DC-DC converter in which the first DC-DC converter 22 and the second DC-DC converter 24 are combined between the high-voltage power line 8a and the high-voltage power line 8b and between the low-voltage power line 9a and the low-voltage power line 9b. It may be inserted. In this modification, the one DC-DC converter is an example of a “DC-DC converter”.

  Further, the power conversion device 18 may include the smoothing capacitor 12 and the inverter 16 without including the converter 14.

  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 device 4: Main battery 6: Motor 8: High-voltage power supply line 9: Low-voltage power supply line 10: System main relay 12: Smoothing capacitor 14: Converter 16: Inverter 18: Power converter 20: Sub-battery 22: First DC- DC converter 24: 2nd DC-DC converter 24a: DC-DC converter circuit 24b: Converter voltage sensor 26: Auxiliary machine 28: Main voltage sensor 32: Controller 34: Ignition switch

Claims (1)

A power supply device for an electric vehicle,
Battery,
A power conversion device that converts the power supplied by the battery and supplies it to the motor;
A high voltage power line and a low voltage power line connecting the battery and the power converter,
A switch inserted in each of the high-voltage power line and the low-voltage power line;
A capacitor inserted between the high-voltage power line and the low-voltage power line on the power converter side from the switch;
Between the high-voltage power line on the battery side from the switch and the high-voltage power line on the power converter side from the switch, and on the low-voltage power line on the battery side from the switch and the power converter side from the switch. A DC-DC converter having a first voltage sensor inserted between the low-voltage power supply lines and detecting a voltage between the high-voltage power supply line and the low-voltage power supply line on the power converter side from the switch. When,
A second voltage sensor for detecting a voltage between the high-voltage power supply line and the low-voltage power supply line on the battery side from the switch;
A controller for controlling the switch, the DC-DC converter, and the power converter;
The control device stops the operation of the DC-DC converter and the power conversion device, and then starts the operation of the DC-DC converter after finishing the procedure for switching the switch from the conductive state to the non-conductive state. A start procedure for switching the switch from a non-conducting state to a conducting state, and during operation of the end procedure, the operation of the DC-DC converter and the power converter is stopped and the switch is in a conducting state. Detecting that an abnormality has occurred in the first voltage sensor when an absolute value of a difference between the detected value of the first voltage sensor and the detected value of the second voltage sensor is a predetermined value or more. Power supply.

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