JP6348456B2 - Vehicle power supply system - Google Patents

Description

  The present invention relates to a power supply system for a vehicle.

  Hybrid vehicles and electric vehicles that use a rotating electrical machine as a drive source are equipped with a battery (DC power supply) and a boost converter that boosts the battery voltage.

  In order to insulate high-voltage devices such as a battery and a boost converter from the vehicle body (body), these high-voltage devices are supported on the vehicle body via an insulation resistor. In order to prevent conduction between a high-voltage device and a vehicle body due to insulation deterioration, Patent Document 1 discloses a detection device that detects deterioration of insulation resistance. Patent Document 2 discloses a measuring device that detects battery voltage in addition to detection of insulation deterioration.

  In these detection devices and measurement devices, a so-called flying capacitor method is measured. That is, a capacitor and a voltage sensor are connected in parallel to the battery, and a relay is provided on each of a positive electrode wiring and a negative electrode wiring connecting the battery and the capacitor. Further, relays are provided respectively on the positive electrode wiring and the negative electrode wiring connecting the capacitor and the voltage sensor.

  In measuring the battery voltage, a set of relays between the battery and the capacitor is turned on to charge (accumulate) the charge of the battery in the capacitor. Next, the set of relays is turned off, and the set of relays between the capacitor and the voltage sensor is turned on to cause the voltage sensor to measure the capacitor voltage. Thus, the battery voltage is detected via the capacitor. In addition, since it is necessary to empty the charge of the capacitor between the voltage detection and the next voltage detection, the capacitor is connected to the discharge resistor. The discharge resistor is connected (grounded) to the vehicle body.

  In detecting the deterioration of the insulation resistance, one of a set of relays between the battery and the capacitor and one of the set of relays between the capacitor and the voltage sensor are turned on. At this time, if the insulation resistances RHp and RHn are deteriorated, a loop through the vehicle body as shown in FIG. 10 is formed, and the capacitor SSC is charged. By measuring the terminal voltage of the capacitor SSC with the voltage sensor, it is possible to determine the deterioration status of the insulation resistances RHp and RHn.

JP-A-8-226950 JP 2009-281986 A

  By the way, when the insulation resistances RHp and RHn are deteriorated to cause a short circuit and the boost converter is in operation, the potential of the vehicle body becomes equal to the boost voltage by the boost converter. At this time, as shown in FIG. 11, a high voltage exceeding the withstand voltage is applied to both ends of the relay in the off state (SSR 4 in FIG. 11), which may lead to a so-called on-failure. Although it is conceivable to increase the withstand voltage of the relay and prevent the discharge resistors R1 and R2 from having a high resistance in order to prevent an on-failure, a high withstand voltage relay generally has a high on-state resistance (on-resistance). It is known that the discharge resistances R1 and R2 are high resistances, so that the time constant in the RC circuit increases and it takes time to charge and discharge the capacitor SSC, leading to a prolonged detection time. Another problem arises. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a vehicle power supply system that can suppress a relay ON failure without prolonging the detection time.

  The present invention relates to a vehicle power supply system. The system includes a battery, a boost converter supported by a vehicle body via an insulation resistor and boosting the voltage of the battery, a capacitor connected in parallel to the battery, and a voltage sensor connected in parallel to the battery and the capacitor. And a first positive electrode side relay and a first negative electrode side relay respectively provided on a positive electrode wiring and a negative electrode wiring connecting the battery and the capacitor, and a positive electrode wiring and a negative electrode wiring connecting the capacitor and the voltage sensor, respectively. The second positive side relay and the second negative side relay and the positive and negative wires connecting the capacitor and the voltage sensor branch from between the second positive side relay and the second negative side relay and the voltage sensor. And a ground wiring connected to the vehicle body via a discharge resistor. Furthermore, the vehicle power supply system is provided in a first bypass wiring connected to the negative electrode of the battery by bypassing the first and second negative relays from the ground wiring, and the first and second negative relays A first Zener diode having a breakdown voltage that is less than the withstand voltage is provided. In addition, the first positive electrode side and the negative electrode side relay and the second positive electrode side and the negative electrode side relay closer to the capacitor are provided in a second bypass wiring connected in parallel with the capacitor and have a predetermined relay protection voltage or less. And a second Zener diode having a breakdown voltage.

  According to the present invention, it is possible to suppress relay ON failure without prolonging the detection time.

It is a figure which illustrates the composition of the power supply system for vehicles concerning this embodiment. It is a figure explaining the process in which a capacitor is charged with a battery. It is a figure explaining the process in which the capacitor voltage after charge is measured. It is a figure explaining the degradation determination process of the insulation resistance RHp. It is a figure explaining the degradation determination process of insulation resistance RHn at the time of a buck-boost converter stop. It is a figure explaining the degradation determination process of the insulation resistance RHn at the time of buck-boost converter operation. It is a figure explaining the capacitor voltage measurement process at the time of insulation resistance RHp degradation. It is a figure explaining the setting of the breakdown voltage of a Zener diode. It is a figure which illustrates the composition of the power supply system for vehicles concerning another example of this embodiment. It is a figure explaining the deterioration determination process of the insulation resistance in the conventional detection circuit. It is a figure explaining the ON failure of a relay.

<Overall configuration>
FIG. 1 illustrates a power supply system 10 for a vehicle according to the present embodiment. The power supply system 10 includes a battery 12, a detection circuit 14, a system main relay 16, a buck-boost converter 18, and an inverter 20. The power supply system 10 is connected (grounded) to the vehicle bodies BD1 and BD2 via insulation resistances RHp and RHn.

  When the battery 12 and the step-up / down converter 18 are brought into conduction by the system main relay 16, the voltage of the battery 12 is boosted by the step-up / down converter 18. The boosted DC power is converted into AC power by the inverter 20 and supplied to a rotating electrical machine (not shown) that is a driving source of the vehicle.

  The detection circuit 14 measures the voltage of the battery 12 and determines deterioration of the insulation resistances RHp and RHn. In measuring the voltage of the battery 12, the first positive electrode side relay SSR1 and the first negative electrode side relay SSR2 are turned on (closed), so that the battery 12 charges the capacitor SSC. Thereafter, the voltage of the capacitor SSC is measured by the voltage sensor 22 by turning off the first positive relay SSR1 and the first negative relay SSR2 and turning on the second positive relay SSR3 and the second negative relay SSR4. Is done.

  In the determination of deterioration of the insulation resistances RHp and RHn, a circuit that connects the insulation resistance RHp or RHn and the capacitor SSC via the vehicle body is formed. For example, when the deterioration determination of the insulation resistance RHp is performed as shown in FIG. 4 described later, the first negative electrode side relay SSR2 and the second positive electrode side relay SSR3 are turned on. At this time, a circuit including the insulation resistance RHp and the capacitor SSC is formed via the vehicle body BD1 and the vehicle body BD3. By detecting the charge charged in the capacitor SSC at this time, it is possible to determine the deterioration state of the insulation resistance RHp.

  Furthermore, in the power supply system 10 according to the present embodiment, two bypass wirings are used to prevent a high voltage exceeding the withstand voltage from being applied to the relays SSR1 to SSR4 of the detection circuit 14 when the insulation resistances RHp and RHn are deteriorated. 24 and 26 (first bypass wiring and second bypass wiring) are provided.

  The bypass wiring 24 (first bypass wiring) is connected to the negative electrode of the battery 12 by bypassing the first negative electrode side relay SSR2 and the second negative electrode side relay SSR4 from the ground wiring 28 of the detection circuit 14. The bypass wiring 24 is provided with a Zener diode ZD1 (first Zener diode) whose forward direction is from the negative electrode to the positive electrode. The breakdown voltage of the Zener diode ZD1 is determined to be less than the withstand voltage of the first negative side relay SSR2 and the second negative side relay SSR4.

  When the insulation resistance RHp or RHn deteriorates and the potential of the vehicle bodies BD1 to BD3 becomes equal to the boosted voltage VH of the buck-boost converter 18, the voltage applied to the Zener diode ZD1 reaches the breakdown voltage and becomes conductive. . As a result, the voltage applied to the first negative side relay SSR2 and the second negative side relay SSR4 connected in parallel with the Zener diode ZD1 is equal to or lower than the breakdown voltage of the Zener diode ZD1, that is, the breakdown voltage or lower. ON failure of the side relay SSR2 and the second negative side relay SSR4 is avoided.

  The bypass wiring 26 (second bypass wiring) is connected in parallel to the capacitor SSC closer to the capacitor SSC than the first positive electrode side and negative electrode side relays SSR1, SSR2 and the second positive electrode side and negative electrode side relays SSR3, SSR4. The bypass wiring 26 is provided with two Zener diodes ZD21 and ZD22 (second Zener diode) so that the forward direction is the reverse direction.

  By providing the Zener diodes ZD21 and ZD22, the voltage of the capacitor SSC connected in parallel with them is suppressed to be equal to or lower than the breakdown voltage of the Zener diodes ZD21 and ZD22. In the power supply system 10 according to the present embodiment, the breakdown voltage of the Zener diodes ZD21 and ZD22 is set to be equal to or lower than a predetermined relay protection voltage, and the peripheral relays SSR1 to SSR4 are controlled by suppressing the voltage of the capacitor SSC. It is possible to avoid applying an excessive voltage.

<Details of each configuration>
The battery 12 is composed of an assembled battery in which a plurality of single cells are connected in series. Each single cell is composed of a secondary battery such as a lithium ion battery or a nickel metal hydride battery.

  The system main relay 16 connects / disconnects the battery 12 and the step-up / step-down converter 18 (and an inverter or a rotating electrical machine in the subsequent stage). The system main relay 16 has a positive side relay SMRH connected to the positive side (positive side) and a negative side relay SMRL connected to the negative side (negative side). Further, a precharge relay SMRP is connected in parallel with the minus side relay SMRL. The precharge relay SMRP is connected to the resistor resistor RR. The precharge relay SMRP and the resistor resistor RR are used to prevent an inrush current when connecting the battery 12 and the buck-boost converter 18.

  The step-up / step-down converter 18 has two voltage conversion functions: a step-up converter that steps up the voltage of the battery 12 and a step-down converter that steps down the regenerative power from a rotating electrical machine (not shown). The step-up / step-down converter 18 includes, for example, a two-quadrant chopper circuit, and switching elements 36 and 42 such as IGBTs having forward directions from the positive electrode to the negative electrode, and diodes 38 and 44 connected in reverse parallel to this. Are connected in series. That is, the upper arm 40 and the lower arm 34 are connected in series. A reactor 32 connected in series with the battery 12 and a primary-side smoothing capacitor 30A connected in parallel with the battery 12 are provided between the upper arm 40 and the lower arm 34 on the primary side (battery 12 side). Further, a secondary smoothing capacitor 30 </ b> B is provided on the secondary side (rotary electric machine side) of the upper arm 40 and the lower arm 34 in parallel with the arms 34 and 40.

  The inverter 20 converts the DC power boosted by the step-up / down converter 18 into three-phase AC power and supplies it to the rotating electrical machine. Further, the three-phase AC power regenerated from the rotating electrical machine is converted to DC power and supplied to the step-up / down converter 18. The inverter 20 includes a plurality of switching elements (not shown), and power AC / DC conversion and orthogonal conversion are performed by turning these switching elements on and off.

  The detection circuit 14 is also called a battery ECU, and is configured as a part of a computer circuit. The detection circuit 14 is connected to both positive and negative ends of the battery 12.

  The detection circuit 14 is a so-called flying capacitor type voltage detection circuit, and a capacitor SSC is connected in parallel with the battery 12. The capacitor SSC is a so-called bipolar capacitor, and charge storage (charge) using the upper side of the drawing as a positive electrode and the lower side as a negative electrode, and charge storage using the upper side of the drawing as a negative electrode and the lower side as a positive electrode are possible. .

  A voltage sensor 22 is connected in parallel with the battery 12 and the capacitor SSC. An operational amplifier circuit or an A / D converter may be provided in the previous stage (capacitor SSC side) of the voltage sensor 22.

  The positive wiring 46 connecting the battery 12 and the capacitor SSC is provided with a first positive relay SSR1, and the negative wiring 48 is provided with a first negative relay SSR2. Further, the second positive electrode side relay SSR3 is provided in the positive electrode wiring 50 connecting the capacitor SSC and the voltage sensor 22, and the second negative electrode side relay SSR4 is provided in the negative electrode wiring 52.

  Further, the ground wiring 28 that branches from the positive electrode wiring 50 and the negative electrode wiring 52 between the second positive electrode side relay SSR3 and the second negative electrode side relay SSR4 and the voltage sensor 22 and is connected to the vehicle body BD3 is provided. The ground wiring 28 is led out from the positive electrode wiring 50 and the negative electrode wiring 52, and then joined and connected to the vehicle body BD3.

  The ground wiring 28 is provided with discharge resistors R1, R2 and an insulation resistor R3. The discharge resistor R1 is provided in a path from the negative electrode wiring 52 to the junction and the discharge resistance R2 is provided in a path from the positive electrode wiring 50 to the junction. The insulation resistance R3 is provided in the path from the merge to the vehicle body BD3.

  The discharge resistors R1 and R2 are provided to empty the capacitor SSC after the voltage of the capacitor SSC is detected by the voltage sensor 22 (0 [C]). That is, the electric energy (electric power) accumulated in the capacitor SSC is consumed by the discharge resistors R1 and R2, and the charge of the capacitor SSC becomes empty.

  Note that, when charge is accumulated in the capacitor SSC at the time of determining deterioration of the insulation resistances RHp and RHn, which will be described later, a current passes through one of the discharge resistors R1 and R2. At this time, if the resistance values of the discharge resistors R1 and R2 are different, the time constant in the RC circuit is different, and the charge period of the capacitor SSC needs to be different for each deterioration determination of the insulation resistances RHp and RHn. From the viewpoint of simplification of time management, it is preferable that the resistance values of the discharge resistors R1 and R2 are equal.

  The detection circuit 14 according to the present embodiment is provided with two bypass wirings 24 and 26. The bypass wiring 24 (first bypass wiring) is connected to the negative electrode of the battery 12 by bypassing the first and second negative-side relays SSR2 and SSR4 from between the junction 54 of the ground wiring 28 and the insulation resistance R3. The bypass wiring 24 is provided with a Zener diode ZD1 whose forward direction is the direction from the negative electrode side to the positive electrode side, and a diode DD1 so as to face this. As will be described later, the breakdown voltage of the Zener diode ZD1 is less than the withstand voltage of the first and second negative side relays SSR2 and SSR4, and when a high voltage is applied from the vehicle body BD3, the first and second negative side Before reaching the withstand voltage of relays SSR2 and SSR4, Zener diode ZD1 reaches the breakdown voltage and becomes conductive. As a result, high voltage application to the first and second negative side relays SSR2 and SSR4 is avoided.

  The bypass wiring 26 (second bypass wiring) is connected in parallel to the capacitor SSC closer to the capacitor SSC than the first positive electrode side and negative electrode side relays SSR1, SSR2 and the second positive electrode side and negative electrode side relays SSR3, SSR4. Zener diodes ZD21 and ZD22 are provided opposite to the bypass wiring 26.

  Since the Zener diodes ZD21 and ZD22 are connected in parallel to the capacitor SSC, the upper limit voltage of the capacitor SSC is the breakdown voltage of the Zener diodes ZD21 and ZD22. In the power supply system 10 according to the present embodiment, the breakdown voltage of the Zener diodes ZD21 and ZD22 is set to be equal to or lower than a predetermined relay protection voltage, and the upper limit voltage during storage of the capacitor SSC is suppressed to be equal to or lower than this relay protection voltage. It is done. By suppressing the upper limit voltage of the capacitor SSC, it is possible to avoid applying an excessive voltage to the peripheral relays SSR1 to SSR4.

  Note that if the breakdown voltage differs between the Zener diodes ZD21 and ZD22, the upper limit value of the charge voltage of the capacitor SSC differs depending on the charge polarity. In this case, the process of determining the deterioration of the insulation resistance becomes complicated, for example, the determination value is varied according to the charge polarity. Therefore, it is preferable that the breakdown voltages of the Zener diodes ZD21 and ZD22 are equal.

<Normal detection circuit operation>
2 and 3 illustrate the operation when the detection circuit 14 detects the voltage of the battery 12. First, as shown in FIG. 2, the first positive electrode side relay SSR1 and the first negative electrode side relay SSR2 are turned on, and the second positive electrode side relay SSR3 and the second negative electrode side relay SSR4 are turned off. At this time, as indicated by a broken line in FIG. 2, a current flow is formed as follows: battery 12 → first positive relay SSR1 → capacitor SSC → first negative relay SSR2 → battery 12, and the battery 12 charges the capacitor SSC. Is charged.

  Next, as shown in FIG. 3, the first positive electrode side relay SSR1 and the first negative electrode side relay SSR2 are turned off, and the second positive electrode side relay SSR3 and the second negative electrode side relay SSR4 are turned on. At this time, as indicated by a broken line in FIG. 3, a current flow is formed as follows: capacitor SSC → second positive side relay SSR3 → voltage sensor 22 → second negative side relay SSR4 → capacitor SSC. Is measured. Further, in parallel with the flow of the broken line, a current flows from the capacitor SSC to the discharge resistors R1 and R2, so that the charge of the capacitor SSC becomes zero.

  FIG. 4 illustrates an operation when determining the deterioration of the insulation resistance RHp. The first positive relay SSR1 is turned off, and the first negative relay SSR2 is turned on. Further, the second positive side relay SSR3 is turned on, and the second negative side relay SSR4 is turned off. At this time, as indicated by a broken line, insulation resistance RHp → vehicle body BD1 → vehicle body BD3 → insulation resistance R3 → discharge resistance R2 → second positive relay SSR3 → capacitor SSC → first negative relay SSR2 → battery 12 → diode 44 → A current flow with the insulation resistance RHp is formed. As a result, charges are accumulated in the capacitor SSC. Thereafter, as shown in FIG. 3, the on / off states of the relays SSR1 to SSR4 are switched, the voltage of the capacitor SSC is measured, and the deterioration state of the insulation resistance RHp is determined.

  FIG. 5 illustrates an operation when determining the deterioration of the insulation resistance RHn. The first positive relay SSR1 is turned on, and the first negative relay SSR2 is turned off. Further, the second positive side relay SSR3 is turned off, and the second negative side relay SSR4 is turned on. At this time, as indicated by a broken line, the insulation resistance RHn → the battery 12 → the first positive relay SSR1 → the capacitor SSC → the second negative relay SSR4 → the discharge resistance R1 → the insulation resistance R3 → the vehicle body BD3 → the vehicle body BD2 → the insulation resistance RHn. And a current flow is formed. As a result, charges are accumulated in the capacitor SSC. Thereafter, as shown in FIG. 3, the on / off states of the relays SSR1 to SSR4 are switched to measure the voltage of the capacitor SSC, and the deterioration state of the insulation resistance RHn is determined.

  FIG. 5 shows the flow of current when the step-up / step-down converter 18 is not boosting and the voltage of the battery 12 is higher than the vehicle body BD2, such as when the switching elements 36 and 42 are off. . When the buck-boost converter 18 is boosting and the voltage of the battery 12 becomes lower than the vehicle body BD2, the current flow is reversed and the charge polarity of the capacitor SSC is reversed as shown in FIG.

<Operation of detection circuit when insulation resistance deteriorates>
FIG. 7 shows a current flow when the voltage sensor 22 measures the voltage of the capacitor SSC as shown in FIG. 3 when the insulation resistance RHp is deteriorated. The on / off states of the relays SSR1 to SSR4 are the same as in FIG. 3 (SSR1: off, SSR2: off, SSR3: on, SSR4: on). Further, it is assumed that the step-up / step-down converter 18 is in operation (during pressure increase).

  At this time, the boosted voltage of the step-up / down converter 18 is applied to the detection circuit 14 via the vehicle bodies BD1 and BD3. Since the potential of the vehicle body BD3 exceeds the breakdown voltage of the Zener diode ZD1, the Zener diode ZD1 becomes conductive. The voltage across the first negative side relay SSR2 in parallel with the zener diode ZD1 is equal to or lower than the breakdown voltage of the zener diode ZD1, and the application of the boosted voltage is avoided.

<Setting of Zener diode breakdown voltage>
The setting of the breakdown voltage of the Zener diode ZD1 and the Zener diode ZD21 (and ZD22) based on the operation state as shown in FIG. 7 will be described with reference to FIG. In this figure, as in FIG. 7, the second positive electrode side and negative electrode side relays SSR3, SSR4 are in the on state, and the first positive electrode side and negative electrode side relays SSR1, SSR2 are in the off state. Further, the Zener diode ZD22 is not shown.

  At this time, if the insulation resistance RHp or RHn is in a deteriorated state and the buck-boost converter 18 is in operation, the voltage of the vehicle body BD3 becomes equal to the boost voltage VH of the buck-boost converter 18. The potential at the connection point 56 between the ground wiring 28 and the bypass wiring 24 is equal to the breakdown voltage V1 (<VH) of the Zener diode ZD1.

  Further, when the capacitor SSC is charged, the upper limit voltage is the breakdown voltage V2 of the Zener diode ZD21. At this time, assuming that the resistance values of the discharge resistors R1 and R2 are equal, the terminal voltages of the discharge resistors R1 and R2 are both V2 / 2 (V2 × R2 / (R1 + R2) and V2 × R1 / (R1 + R2)).

  Taking these voltages into account, the voltage applied to both ends of the first negative-side relay SSR2 in the off state is (V1 + V2 / 2). If this voltage is less than the withstand voltage of the first negative relay SSR2, the on failure of the first negative relay SSR2 is avoided. That is, when the withstand voltage of the first negative relay SSR2 is Vu, the relay protection voltage for the Zener diode ZD21 (and ZD22) is less than 2 (Vu−V1).

  For example, when the withstand voltage Vu of the first negative side relay SSR2 is 600V and the breakdown voltage of the Zener diode ZD1 is 450V, the breakdown voltage (relay protection voltage) of the Zener diode ZD21 is 300V because (450 + V2 / 2) <600. It becomes as follows.

  It is preferable that the Zener diodes ZD1, ZD21, and ZD22 have a breakdown voltage that is equal to or higher than a predetermined lower limit value (for example, 200 V) because the capacitor SSC cannot be sufficiently charged if the breakdown voltage is excessively low. is there.

  Further, since the capacitor SSC is connected in parallel with the Zener diodes ZD21 and ZD22, the voltage measurement of the battery 12 and the deterioration determination of the insulation resistances RHp and RHn can be performed within the range of the breakdown voltage of the Zener diodes ZD21 and ZD22. Is preferred. For example, the higher the voltage applied to the capacitor SSC, the higher the terminal voltage increase rate (dV / dt) of the capacitor SSC. Based on the terminal voltage, voltage measurement of the battery 12 and deterioration determination of the insulation resistances RHp and RHn may be performed. For example, when the capacitor SSC is charged by the fully charged battery 12, the predetermined charging time is from the empty state of the capacitor SSC until the terminal voltage of the capacitor SSC reaches the breakdown voltage of the Zener diodes ZD21 and ZD22. It may be time.

Second Embodiment
Although the detection circuit 14 shown in FIGS. 1-8 was connected only to the positive and negative ends of the battery 12, it is not restricted to this form. For example, as shown in FIG. 9, a plurality of single cells may be divided into several battery units 12A, 12B. In this case, the positive relay SSR1 is connected to the positive terminal of the battery unit 12A, and the negative relay SSR5 is connected to the negative terminal. Further, the positive side relay SSR6 is connected to the positive end of the battery unit 12B, and the negative side relay SSR2 is connected to the negative end. By turning on the positive side relay SSR1 and the negative side relay SSR5, charges are accumulated from the battery unit 12A to the capacitor SSC. Further, by turning on the positive side relay SSR6 and the negative side relay SSR2, charges are accumulated in the capacitor SSC from the battery unit 12B. Other relay operations are the same as those shown in FIGS.

  DESCRIPTION OF SYMBOLS 10 Power supply system, 12 Battery, 14 Detection circuit, 18 Buck-boost converter, 22 Voltage sensor, 24 1st bypass wiring, 26 2nd bypass wiring, 28 Ground wiring, 46 Battery-capacitor positive wiring, 48 Battery-capacitor negative electrode Wiring, 50 Capacitor-voltage sensor positive wiring, 52 Capacitor-voltage sensor negative wiring, BD1 to BD3 Car body, R1, R2 discharge resistance, RHp, RHn Insulation resistance, SSC capacitor, SSR1 Negative side relay, SSR3 second positive side relay, SSR4 second negative side relay, V1 first Zener diode breakdown voltage, V2 second Zener diode breakdown voltage, VH boost voltage, Vu first positive side relay withstand voltage, ZD1 first Zener diode, ZD2 , ZD22 the second Zener diode.

Claims (1)

A vehicle power supply system,
Battery,
A boost converter that is supported by the vehicle body via an insulation resistor and boosts the voltage of the battery;
A capacitor connected in parallel to the battery;
A voltage sensor connected in parallel to the battery and capacitor;
A first positive electrode side relay and a first negative electrode side relay respectively provided on a positive electrode wiring and a negative electrode wiring connecting the battery and the capacitor;
A second positive electrode side relay and a second negative electrode side relay provided respectively in the positive electrode wiring and the negative electrode wiring connecting the capacitor and the voltage sensor;
A ground wiring that branches from between the second positive side relay, the second negative side relay and the voltage sensor, and is connected to the vehicle body via a discharge resistor, in the positive and negative wirings connecting the capacitor and the voltage sensor. When,
With
A breakdown voltage that is provided in a first bypass wiring connected to the negative electrode of the battery by bypassing the first and second negative relays from the ground wiring and is less than a withstand voltage of the first and second negative relays A first Zener diode having:
A breakdown that is provided in a second bypass wiring connected in parallel to the capacitor closer to the capacitor than the first positive electrode side and negative electrode side relay and the second positive electrode side and negative electrode side relay, and is equal to or lower than a predetermined relay protection voltage. A second Zener diode having a voltage;
A vehicle power supply system comprising:

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