Control method for power supply system and power supply system

Abstract

To provide a method for controlling a power supply system capable of sufficiently discharging electric charges of a Y capacitor.SOLUTION: A power supply system includes: a power supply unit 11 for outputting power to a load 20; a set of Y capacitors 15B, 15C interposed between a positive electrode and a ground potential 30 and a negative electrode and the ground potential 30, respectively; a set of a positive electrode switch 14P and a negative electrode switch 14N interposed between the power supply unit 11 and the load 20 and connecting and disconnecting the positive electrode and the negative electrode, respectively; and an insulation detection circuit 35 having a capacitor 36 connected between a power supply line 13 between the power supply unit 11 and the negative switch 14N and the ground potential 30, and detecting an insulation degree between the power supply unit 11 and the ground potential 30. When shutting down a power supply system 1, a control device 40 controls the positive electrode switch 14P to be turned off and the negative electrode switch 14N to be turned on to discharge electric charges of the Y capacitors 15B, 15C, and after a voltage applied to the load 20 becomes equal to or lower than a predetermined voltage, controls the negative electrode switch 14N to be turned off.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control method for a power supply system and a power supply system.

Background Art

[0002] As a noise countermeasure for a power supply system that supplies power to a load, it is widely practiced to provide a Y capacitor in the power line. In such a power supply system, when shutting down the power supply system for maintenance or the like, it is necessary to discharge the charge of the Y capacitor.

[0003] Patent Document 1 discloses a configuration including a Y capacitor discharge circuit provided with a discharge switch and a discharge resistor, and executing the discharge of the Y capacitor by turning on the discharge switch when discharge is necessary.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] In the prior art, even when a discharge circuit for a Y capacitor is provided, if an imbalance occurs in the charges charged in the Y capacitors on the positive electrode side and the negative electrode side, a sufficient discharge time is required to eliminate this imbalance and discharge the charges. Further, depending on the circuit configuration, there is a problem that even after a sufficient discharge time has elapsed, the imbalance is not eliminated and charges remain in the Y capacitor.

[0006] An object of the present invention is to provide a control technique for a power supply system that can sufficiently discharge the charge of a Y capacitor.

Means for Solving the Problems

[0007] According to one aspect of the present invention, it is applied to a method for controlling a power supply system. The power supply system comprises a power supply unit that outputs power to a load via a power line consisting of a positive electrode and a negative electrode, a pair of Y capacitors interposed between the positive electrode and the negative electrode and the housing, a pair of positive electrode switches and negative electrode switches interposed between the power supply unit and the load to disconnect and reconnect the positive electrode and the negative electrode, respectively, an insulation detection circuit having a capacitor connected between the power line between the power supply unit and the negative electrode switch and the ground potential, for detecting the degree of insulation between the power supply unit and the ground potential, and a control device for controlling the positive electrode switch and the negative electrode switch. In this power supply system control method, when shutting down the power supply system, the positive electrode switch is controlled to turn off and the negative electrode switch is controlled to turn on to discharge the charge of the pair of Y capacitors, and after the voltage applied to the load falls below a predetermined voltage, the negative electrode switch is controlled to turn off. [Effects of the Invention]

[0008] According to the present invention, when the power supply system is shut down, the positive switch is controlled to turn off, and then the negative switch is controlled to turn on until the voltage applied to the load falls below a predetermined voltage. With this control, even if the charge of the positive and negative Y capacitors is not uniform, the charge of the Y capacitor can be sufficiently discharged by controlling the negative switch to turn on in accordance with the voltage applied to the load. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an explanatory diagram of a power supply system according to an embodiment of the present invention. [Figure 2] Figure 2 is a flowchart of the actions performed by the control unit. [Figure 3] Figure 3 shows the flowchart executed by the vehicle controller. [Figure 4] Figure 4 is an explanatory diagram for setting the off-timer. [Figure 5] Figure 5 shows the time chart executed by the vehicle controller. [Modes for carrying out the invention]

[0010] Embodiments of the present invention will be described below with reference to the drawings and other documents.

[0011] Figure 1 is an explanatory diagram of a power supply system 1 according to an embodiment of the present invention.

[0012] The power supply system 1 comprises a power supply unit 11, a main relay 14, a filter circuit 15, a load 20, a ground potential 30, a control device 40, and a vehicle controller 50.

[0013] The power supply unit 11 comprises a battery 12 and a power line 13 consisting of a positive electrode line 13P and a negative electrode line 13N. The power supply unit 11 outputs DC power supplied from the battery 12 to the load 20 via the power line 13. The battery 12 is composed of a DC high-voltage battery.

[0014] The main relay 14 is interposed in the power line 13 between the power supply unit 11 and the load 20, and switches the flow of power between the power supply unit 11 and the load 20 on and off. The main relay 14 consists of a positive relay 14P, which is provided on the positive line 13P and acts as a positive switch to switch the positive line 13P on and off, and a negative relay 14N, which is provided on the negative line 13N and acts as a negative switch to switch the negative line 13N on and off.

[0015] The filter circuit 15 is configured with capacitors that reduce normal mode noise and common mode noise contained in the DC current output from the power supply unit 11 to the load 20.

[0016] The filter circuit 15 includes an X capacitor 15A positioned between the positive electrode line 13P and the negative electrode line 13N, a Y capacitor 15B positioned between the positive electrode line 13P and the ground potential 30, and a Y capacitor 15C positioned between the negative electrode line 13N and the ground potential 30.

[0017] The X capacitor 15A reduces normal mode noise superimposed between the positive line 13P and the negative line 13N of the power supply line 13.

[0018] The Y capacitor 15B has its positive electrode connected to the positive electrode line 13P and its ground electrode connected to the ground potential 30 respectively. The Y capacitor 15C has its positive electrode connected to the negative electrode line 13N and its ground electrode connected to the ground potential 30 respectively. The Y capacitors 15B and 15C reduce the common mode noise of the power supply line 13. The capacitance values of the Y capacitor 15B and the Y capacitor 15C are set to the same value.

[0019] The load 20 includes a motor 2 and an inverter circuit 21 that supplies power to the motor 2.

[0020] The inverter circuit 21 includes a plurality of switching elements that are power modules, converts the direct current supplied from the battery 12 via the power supply line 13 into alternating current power, and outputs it to the motor 2. Also, the inverter circuit 21 converts the regenerative power of the motor 2 into direct current and outputs it to the battery 12 via the power supply line 13.

[0021] The ground potential 30 is constituted by, for example, the housing in which the power supply unit 11 and the load 20 are accommodated or the vehicle body. The ground potential 30 becomes the reference potential (ground potential) with respect to the power supply unit 11.

[0022] An insulation detection circuit 35 for detecting the insulation degree between these is provided between the negative electrode line 13N of the power supply line 13 and the ground potential 30. The insulation detection circuit 35 includes a capacitor 36 and a detection sensor 37, and detects the insulation degree between the negative electrode line 13N and the ground potential 30 by detecting the voltage between the terminals of the capacitor 36. When the insulation degree drops below a predetermined reference value, the insulation detection circuit 35 outputs a signal indicating that to the control device 40 or the vehicle controller 50.

[0023] The power supply system 1 of this embodiment is mounted on, for example, an electric vehicle and drives the vehicle by driving the motor 2 based on the control of the vehicle controller 50. Although the load 20 has been described as being composed of an inverter circuit 21 and a motor 2, it is not limited to this. Any load that is supplied with DC current from the power supply unit 11 may be used.

[0024] Next, we will describe the operation of power supply system 1, configured in this way, during shutdown.

[0025] Power supply system 1 may need to be shut down for maintenance or other reasons. In such cases, it is necessary to discharge the charge stored in the X capacitor 15A, Y capacitor 15B, and Y capacitor 15C of the filter circuit 15 before shutting down.

[0026] Generally, the X capacitor 15A and the Y capacitors 15B and 15C are controlled to turn off the main relay 14, forming a closed circuit with the inverter circuit 21, thereby discharging their charge and reducing it to a discharge termination voltage (e.g., 50[V]).

[0027] In this embodiment, when an isolation detection circuit 35 is provided between the negative electrode line 13N and the ground potential 30, the charge charged to the Y capacitor 15B and Y capacitor 15C may not be uniform. That is, assuming that the isolation detection circuit 35 does not have a capacitor 36, the capacitance of the Y capacitor 15B and the capacitance of the Y capacitor 15C are the same. On the other hand, when a capacitor 36 is connected between the negative electrode line 13N and the ground potential 30, the Y capacitor 15C and the capacitor 36 are in parallel with the ground potential 30. In this case, when the main relay 14 is ON, the capacitance on the negative electrode side (capacitance to ground) becomes larger than the capacitance of the positive electrode side Y capacitor 15B (for example, if the capacitance between the positive electrode line 13P and the ground potential 30 is 1, the capacitance between the negative electrode line 13N and the ground potential 30 becomes 40).

[0028] If the capacitance to ground and the charge charged by Y capacitors 15B and 15C are not uniform, and the main relay 14 is controlled to turn off to form a closed circuit with the inverter circuit 21, the charge on the positive terminal Y capacitor 15B may discharge first, while the charge on the negative terminal Y capacitor 15C may not be sufficiently discharged and may remain. In this case, the charge on Y capacitor 15C may remain undischarged even after a sufficiently long period of time has elapsed. If the charge on Y capacitor 15C is not sufficiently discharged, it will affect the maintenance of the power supply system 1.

[0029] Therefore, in this embodiment, as will be explained below, the device is configured to discharge the charge sufficiently within a specified time even if the charge charged to Y capacitor 15B and Y capacitor 15C is not uniform.

[0030] Figure 2 is a flowchart of the control performed by the control device 40 of this embodiment.

[0031] The control shown in Figure 2 is executed when the power supply system 1 detects that a shutdown has been requested, such as when the ignition key (start switch) is turned off.

[0032] If the control device 40 detects that a shutdown has been requested for the power supply system 1, in step S10, it first controls only the positive relay 14P of the main relay 14 to turn off, while keeping the negative relay 14N controlled to be on.

[0033] By controlling the main relay 14 in this manner, the charge in the X capacitor 15A is discharged through the closed circuit formed between it and the inverter circuit 21.

[0034] The Y capacitors 15B and 15C are discharged by the closed circuit formed between them and the inverter circuit 21. Furthermore, in the case of the Y capacitor 15C, a closed circuit is formed between it and the capacitor 36 via the negative relay 14N, so more charge is discharged from the Y capacitor 15C compared to the Y capacitor 15B.

[0035] Next, in step S20, the control device 40 acquires the inverter circuit voltage via the vehicle controller 50 using a voltage sensor provided in the inverter circuit 21. The control device 40 determines whether the acquired inverter circuit voltage has fallen below a predetermined voltage, that is, whether it has fallen below the discharge termination voltage at which it can be determined that the charge of the Y capacitor 15C, which has the largest charge and takes the longest to discharge, has been sufficiently discharged.

[0036] If the inverter circuit voltage is not below a predetermined voltage, step S20 is repeated to keep the negative relay 14N ON.

[0037] If the inverter circuit voltage falls below a predetermined voltage, the process proceeds to step S30, and the negative relay 14N is controlled to turn off. After that, the flowchart shown in Figure 2 is completed.

[0038] Thus, in this embodiment, when the power supply system 1 is shut down, the control device 40 controls the positive relay 14P to turn off and the negative relay 14N to turn on, thereby discharging more charge from the negative Y capacitor 15C. Then, after the inverter voltage falls below a predetermined voltage, the control device 40 controls the negative relay 14N to turn off.

[0039] With this control, even if the charge between the positive Y capacitor 15B and the negative Y capacitor 15C is not uniform, the negative relay 14N can be kept ON in accordance with the inverter circuit voltage, thereby allowing the charge on the negative Y capacitor 15C to be sufficiently discharged.

[0040] Next, we will explain the operation of the inverter circuit 21 in the event of a malfunction.

[0041] When the vehicle controller 50 detects a fault when the power supply system 1 requests a shutdown, or when the vehicle controller 50 itself detects a fault and shuts down the power supply system 1 as a result, the following control is performed.

[0042] Figure 3 is a flowchart of the control performed by the vehicle controller 50 in this embodiment when a failure occurs.

[0043] If the vehicle controller 50 detects that a shutdown request has been made to the power supply system 1, it first determines in step S110 that the power supply system 1 is faulty.

[0044] There are several failure modes for the power supply system 1. The vehicle controller 50 determines the failure mode based on the detection values ​​of various sensors provided in the inverter circuit 21.

[0045] Now, let's discuss failure modes.

[0046] If the vehicle controller 50 determines that it cannot correctly acquire the voltage of the inverter circuit 21 due to factors such as its own malfunction, abnormal communication with the inverter circuit 21, or an abnormality in the voltage sensor provided in the inverter circuit 21, it determines that the malfunction mode is a voltage detection abnormality.

[0047] Furthermore, if the vehicle controller 50 determines that the voltage obtained from the voltage sensor of the inverter circuit 21 is lower than the voltage range in which the inverter circuit 21 normally operates, it determines that the failure mode is a low voltage abnormality.

[0048] Furthermore, the vehicle controller 50 determines the failure mode to be an overcurrent / overvoltage abnormality if the current value obtained from the current sensor of the inverter circuit 21 indicates an overcurrent, if the current sensor itself is abnormal, if the temperature obtained from the temperature sensor of the inverter circuit 21 is determined to be higher than the normal operating temperature range of the inverter circuit 21, and if the voltage obtained from the voltage sensor of the inverter circuit 21 is determined to be higher than the normal operating voltage range of the inverter circuit 21.

[0049] Returning to Figure 3, in step S120, the vehicle controller 50 instructs the control device 40 to turn off only the positive relay 14P, while keeping the negative relay 14N controlled to be ON.

[0050] Next, the vehicle controller 50 sets the off timer for the negative relay 14N as follows, according to the fault mode determined in step S110.

[0051] If the failure mode is a voltage detection anomaly, it means that the voltage applied to the inverter circuit 21 cannot be correctly obtained. In other words, it is unknown how much charge is stored in the Y capacitor 15C. In this case, the vehicle controller 50 assumes that the charge stored in the Y capacitor 15C is at its maximum and sets the off-timer to a maximum time that is sufficient to discharge the assumed maximum charge. The maximum time (e.g., 300 sec.) is determined in advance by experimentation or simulation based on the characteristics of the Y capacitor 15C and the circuit configuration of the power supply system 1.

[0052] If the failure mode is a low-voltage anomaly, the voltage applied to the inverter circuit 21 is lower than the expected voltage. In this case, the vehicle controller 50 assumes that the charge stored in the Y capacitor 15C is at its minimum and sets the off-timer to a minimum time sufficient to discharge the assumed minimum charge. The minimum time (e.g., 5 sec.) is determined in advance by experiment or simulation based on the characteristics of the Y capacitor 15C and the circuit configuration of the power supply system 1, similar to the maximum time.

[0053] If the failure mode is an overcurrent anomaly, it means that the voltage applied to the inverter circuit 21 is being obtained correctly, but the state of the inverter circuit 21 indicates an overcurrent. In this case, the vehicle controller 50 sets the off timer according to the voltage based on the charge charged in the Y capacitor 15C, that is, the voltage obtained from the inverter circuit 21.

[0054] Figure 4 is an explanatory diagram showing the off-timer time set when the failure mode is an overcurrent / overvoltage anomaly.

[0055] The off-timer is determined in accordance with the voltage value on the inverter circuit side. In this case, the off-timer is determined in advance through experiments or simulations based on the characteristics of the Y capacitor 15C and the circuit configuration of power supply system 1.

[0056] If the vehicle controller 50 detects a high-voltage abnormality in the failure mode, it sets the off-timer by referring to a pre-set correspondence table as shown in Figure 4, according to the voltage obtained from the inverter circuit 21. For example, if the obtained voltage is 500[V], the off-timer is set to 250[sec.] by referring to Figure 4.

[0057] Next, in step S140 of Figure 3, the vehicle controller 50 determines whether the off-timer count set in step S130 has expired. If the off-timer is greater than 0 and the count has not expired, the vehicle controller 50 proceeds to step S150. In step S150, the value of the off-timer is subtracted and the system returns to step S140.

[0058] If the off-timer becomes less than 0 and it is determined that the count has expired, the process proceeds to step S160, and the vehicle controller 50 instructs the control device 40 to turn off the negative relay 14N. After that, the flowchart shown in Figure 3 ends.

[0059] Figure 5 is a time chart of the control performed by the vehicle controller 50 in this embodiment during a failure.

[0060] In Figure 5, the inverter circuit voltage, the on / off state of the positive relay 14P, and the on / negative state of the negative relay 14N are shown from top to bottom, respectively.

[0061] First, at timing T1, if a shutdown of the power supply system 1 is requested, and the vehicle controller 50 determines that the failure mode is a low voltage anomaly (shown by the solid line), then in step S120 of Figure 4, it controls only the positive relay 14P to turn off and controls the negative relay 14N to turn on. After a minimum time has elapsed (timing T2), it controls the negative relay 14N to turn off.

[0062] In this way, at timing T2, the inverter circuit voltage falls below the discharge termination voltage, and the discharge is completed.

[0063] If the vehicle controller 50 determines that the fault mode is an abnormal voltage value (indicated by a dashed line), in step S120 of Figure 4, it controls only the positive relay 14P to turn off and controls the negative relay 14N to turn on. After the maximum interval has elapsed (timing T4), it controls the negative relay 14N to turn off.

[0064] In this way, at timing T4, the inverter circuit voltage falls below the discharge termination voltage, and the discharge is completed.

[0065] If the vehicle controller 50 determines that the fault mode is a high voltage anomaly (indicated by the dotted line), in step S120 of Figure 4, it controls only the positive relay 14P to turn off and controls the negative relay 14N to turn on. Then, it sets the off timer by referring to the correspondence table in Figure 4 according to the voltage obtained from the inverter circuit 21. After that, when the off timer expires (timing T3), it controls the negative relay 14N to turn off.

[0066] In this way, if the inverter circuit voltage can be detected correctly, an off-timer corresponding to this voltage is set. When the off-timer expires at timing T3, the inverter circuit voltage will fall below the discharge termination voltage, and the discharge will be completed.

[0067] The embodiment of the present invention configured as described above is a control method for a power supply system 1, the power supply system 1 comprising: a power supply unit 11 that outputs power to a load 20 via a power line 13 consisting of a positive electrode and a negative electrode; a pair of Y capacitors 15B and 15C interposed between the positive electrode and the negative electrode and the ground potential 30, respectively; a pair of positive electrode switches (positive electrode relay 14P) and negative electrode switches (negative electrode relay 14N) interposed between the power supply unit 11 and the load 20 to intercept and disconnect the positive electrode and the negative electrode, respectively; and an insulation detection circuit 35 having a capacitor 36 connected between the power line 13 between the power supply unit 11 and the negative electrode relay 14N and the ground potential 30, and detecting the degree of insulation between the power supply unit 11 and the ground potential 30. When the power supply system 1 is shut down, the control device 40 controls the positive electrode relay 14P to turn off and the negative electrode relay 14N to turn on to discharge the charge of the Y capacitors 15B and 15C, and after the voltage applied to the load 20 falls below a predetermined voltage, controls the negative electrode relay 14N to turn off.

[0068] In this configuration, when the power supply system 1 is shut down, the positive relay 14P is controlled to turn off and the negative relay 14N is controlled to turn on, thereby controlling the discharge of more charge from the negative Y capacitor 15C. With this control, even if the charge between the positive Y capacitor 15B and the negative Y capacitor 15C is not uniform due to the presence of the isolation detection circuit 35, the negative relay 14N is kept on according to the inverter circuit voltage, allowing the charge between the Y capacitors 15B and 15C to be sufficiently discharged.

[0069] Furthermore, in this embodiment, a vehicle controller 50 is provided to control the operation of the load 20. When the vehicle controller 50 detects a fault related to the load 20, it determines the timing to control the negative relay 14N from on to off according to the detected fault, and at the determined timing, it causes the control device 40 to control the negative relay 14N on or off.

[0070] With this configuration, if the inverter circuit 21 is determined to be malfunctioning, an off-timer is set at a timing corresponding to the inverter circuit voltage. When the off-timer expires, the inverter circuit voltage will fall below the discharge termination voltage, allowing the discharge of the Y capacitors 15B and 15C to be completed.

[0071] Furthermore, in this embodiment, if the vehicle controller 50 detects a fault that prevents it from obtaining the voltage of the load 20, it controls the negative relay 14N to turn ON until a preset maximum time has elapsed.

[0072] With this configuration, if the voltage of the inverter circuit 21 cannot be obtained, the Y capacitors 15B and 15C are discharged until a predetermined maximum time has elapsed, so the charge of the negative terminal Y capacitor 15C can be discharged more reliably.

[0073] Furthermore, in this embodiment, if the vehicle controller 50 detects a fault in which the voltage of the load 20 becomes low, it controls the negative relay 14N to turn ON until a preset minimum time has elapsed.

[0074] With this configuration, when the voltage of the inverter circuit 21 is low, the charge stored in the negative terminal Y capacitor 15C is sufficiently small. By allowing the Y capacitors 15B and 15C to discharge until a predetermined minimum time has elapsed, the Y capacitors 15B and 15C can be discharged in the shortest possible time.

[0075] Furthermore, in this embodiment, if the vehicle controller 50 detects an overcurrent or overvoltage abnormality, it detects the inverter circuit voltage and sets an off timer to control the negative relay 14N from on to off according to the detected inverter circuit voltage, and keeps the negative relay 14N on until the set off timer expires.

[0076] With this configuration, the charge on the Y capacitors 15B and 15C can be discharged more reliably by allowing them to discharge until the off-timer corresponding to the inverter circuit voltage expires.

[0077] Although embodiments and modifications thereof of the present invention have been described above, these embodiments and modifications only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the embodiments described above.

[0078] In the embodiment described above, the positive relay 14P and negative relay 14N that switch the flow of power between the power supply unit 11 and the load 20 on and off are not necessarily limited to relays, but can be any semiconductor switch or contactor that functions as a switch to switch the flow of power on and off. [Explanation of Symbols]

[0079] 1: Power supply system, 11: Power supply unit, 13N: Negative line, 13P: Positive line, 14: Main relay, 14N: Negative relay, 14P: Positive relay, 15: Filter circuit, 15A: X capacitor, 15B: Y capacitor, 15C: Y capacitor, 20: Load, 21: Inverter circuit, 30: Ground potential, 35: Insulation detection circuit, 36: Capacitor, 40: Control device, 50: Vehicle controller

Claims

1. A method for controlling a power supply system, The power supply system comprises: a power supply unit that outputs power to a load via a power line consisting of a positive electrode and a negative electrode; a pair of Y capacitors interposed between the positive electrode and the negative electrode and the ground potential; a pair of positive electrode switches and negative electrode switches interposed between the power supply unit and the load to intermittently switch the positive electrode and the negative electrode, respectively; an insulation detection circuit having a capacitor connected between the power line between the power supply unit and the negative electrode switch and the ground potential, for detecting the degree of insulation between the power supply unit and the ground potential; and a control device for controlling the positive electrode switch and the negative electrode switch. When shutting down the power supply system, the control device controls the positive switch to turn off and the negative switch to turn on to discharge the charge from the pair of Y capacitors. After the voltage applied to the load falls below a predetermined voltage, the negative electrode switch is controlled to turn off. A method for controlling a power supply system.

2. A method for controlling a power supply system according to claim 1, The power supply system includes a vehicle controller that controls the operation of the load, When shutting down the power supply system, if the vehicle controller detects a fault related to the load, it determines the timing for switching the negative switch on and then off according to the detected fault, and at the determined timing, it instructs the control device to switch the negative switch on and off. A method for controlling a power supply system.

3. A method for controlling a power supply system according to claim 2, If the vehicle controller detects a fault that prevents it from obtaining the voltage of the load, The negative electrode switch is controlled to turn ON until a preset maximum time has elapsed. A method for controlling a power supply system.

4. A method for controlling a power supply system according to claim 2, If the vehicle controller detects a fault in which the voltage of the load becomes low, The negative electrode switch is controlled to turn ON until a preset minimum time has elapsed. A method for controlling a power supply system.

5. A method for controlling a power supply system according to claim 2, If the vehicle controller detects a fault in the load that causes overcurrent or overvoltage, The voltage of the load is detected, and an off-timer is set to control the negative switch from on to off according to the detected voltage of the load. The negative electrode switch is controlled to turn ON until the set off timer expires. A method for controlling a power supply system.

6. A power supply system, A power supply unit that outputs power to a load via a power line consisting of a positive electrode and a negative electrode, A pair of Y capacitors interposed between the positive electrode and the negative electrode and the ground potential, A set of positive and negative switches are interposed between the power supply unit and the load, and the positive and negative electrodes are respectively connected and disconnected. An insulation detection circuit having a capacitor connected between the power line between the power supply unit and the negative electrode switch and the ground potential, and detecting the degree of insulation between the power supply unit and the ground potential, A control device for controlling the on / off state of the positive switch and the negative switch, Equipped with, The control device is When shutting down the power supply system, the positive switch is controlled to turn off and the negative switch is controlled to turn on to discharge the charge from the pair of Y capacitors, and after the voltage applied to the load falls below a predetermined voltage, the negative switch is controlled to turn off. Power supply system.

7. A power supply system according to claim 6, The vehicle includes a vehicle controller that controls the operation of the aforementioned load, When the vehicle controller shuts down the power supply system, if it detects a fault related to the load, it determines the timing for turning the negative switch on and then off according to the detected fault, and at the determined timing, it instructs the control device to turn the negative switch on and off. Power supply system.

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