JP6836411B2 - Ground fault detector, power supply system - Google Patents

Description

The present invention relates to a ground fault detection device using a flying capacitor and a power supply system including a ground fault detection device.

In a hybrid vehicle equipped with an engine and an electric motor as a drive source, or in a vehicle such as an electric vehicle, a battery mounted on the vehicle body is charged and electric energy supplied from the battery is used to generate propulsive force. Generally, a battery-related power supply circuit is configured as a high-voltage circuit that handles a high voltage of 200 V or more, and in order to ensure safety, the high-voltage circuit including the battery is electrically insulated from the vehicle body that serves as a reference potential point for grounding. It has a non-grounded configuration.

In a vehicle equipped with a non-grounded high-voltage battery, the system provided with the high-voltage battery, specifically, the insulation state (ground fault) between the main power supply system from the high-voltage battery to the motor and the vehicle body is monitored. Therefore, a ground fault detection device is provided. As the ground fault detection device, a method using a capacitor called a flying capacitor is widely used.

FIG. 5 is a diagram showing an example of a circuit of a power supply system including a flying capacitor type ground fault detection device. As shown in this figure, the ground fault detection device 400 is connected to the ungrounded high voltage battery 300 via the positive electrode side power supply line 301 and the negative electrode side power supply line 302, and the ground fault of the system provided with the high voltage battery 300. It is a device that detects.

The high-voltage battery 300 supplies power to the load 360 via the positive electrode side power supply line 301 and the negative electrode side power supply line 302, and the connection state with the positive electrode side load 360 is switched by the positive electrode side main relay 321. The connection state with the load 360 on the negative electrode side is switched by the main relay 322 on the negative electrode side. Switching between the positive electrode side main relay 321 and the negative electrode side main relay 322 is performed in conjunction with the external control device 200, which is a higher-level device.

Here, the insulation resistance between the positive electrode side and the ground of the high voltage battery 300 is represented by RLp1, and the insulation resistance between the negative electrode side and the ground is represented by RLn1. Further, the terminating resistance between the positive electrode and the ground on the load 360 side is represented by RLp2, and the terminating resistance between the negative electrode and the ground is represented by RLn2. In a normal state where no ground fault has occurred, generally, the insulation resistors RLp1 and RLn1 on the high voltage battery 300 side are the terminating resistors RLp2 and RLn2 on the load 360 side, and RLp1 and RLn1 are combined when the main relay is on. It is clearly larger than the resistors RLp1 // RLp2 and RLn1 // RLn2.

Between the positive electrode side power supply line 301 and the ground of the high voltage battery 300 and between the negative electrode side power supply line 302 and the ground, Y capacitors (lines) are used to remove high frequency noise of the power supply and stabilize the operation, respectively. -Bypass capacitors) capacitors CYp1 and CYn1 are connected. Further, CYp2 and CYn2 are connected as Y capacitors between the positive electrode on the load 360 side and the ground and between the negative electrode on the load 360 side and the ground, respectively.

However, the Y capacitor may be omitted. Even in this case, due to the parasitic capacitance, there are capacitors CYp1, CYn1, CYp2, and CYn2 between the capacitors and the ground. Generally, YCp1 = YCn1 << YCp2 = YCn2, but these relationships may not hold depending on the design, situation, and the like.

As shown in this figure, the ground fault detection device 400 includes a detection capacitor C1 that operates as a flying capacitor. Further, four switching elements S1 to S4 are provided around the detection capacitor C1 in order to switch the measurement path and control the charging and discharging of the detection capacitor C1.

In the ground fault detection device 400, in order to grasp the insulation resistances RLp1 and RLn1 on the high voltage battery 300 side, the measurement operation is repeated with the V0 measurement period → Vc1n measurement period → V0 measurement period → Vc1p measurement period as one cycle. However, the V0 measurement period → Vc1n measurement period → Vc1p measurement period may be set as one cycle. In each measurement period, the detection capacitor C1 is charged with the voltage to be measured, and then the charging voltage of the detection capacitor C1 is measured. Then, the detection capacitor C1 is discharged for the next measurement.

In the V0 measurement period, the voltage corresponding to the high voltage battery 300 voltage is measured. Therefore, the switching elements S1 and S2 are turned on, the switching elements S3 and S4 are turned off, and the detection capacitor C1 is charged. That is, as shown in FIG. 6A, the high voltage battery 300, the resistor R1, and the detection capacitor C1 serve as measurement paths.

When measuring the charging voltage of the detection capacitor C1, the switching elements S1 and S2 are turned off, the switching elements S3 and S4 are turned on, sampling is performed by the control device 420, and the detection capacitor C1 is further measured for the next measurement. Discharge. The operation at the time of measuring the charging voltage of the detection capacitor C1 and at the time of discharging the detection capacitor C1 is the same in other measurement periods.

In the Vc1n measurement period, the voltage reflecting the influence of the insulation resistance RLn1 is measured. Therefore, the switching elements S1 and S4 are turned on, the switching elements S2 and S3 are turned off, and the detection capacitor C1 is charged. That is, as shown in FIG. 6B, the high-voltage battery 300, the resistor R1, the detection capacitor C1, the resistor R4, the ground, and the insulation resistor RLn1 serve as measurement paths.

In the Vc1p measurement period, the voltage reflecting the influence of the insulation resistance RLp1 is measured. Therefore, the switching elements S2 and S3 are turned on, the switching elements S1 and S4 are turned off, and the detection capacitor C1 is charged. That is, as shown in FIG. 6C, the high-voltage battery 300, the insulation resistance RLp1, the ground, the resistance R3, the resistance R1, and the detection capacitor C1 serve as measurement paths.

It is known that (RLp1 × RLn1) / (RLp1 + RLn1) can be obtained based on (Vc1p + Vc1n) / V0 calculated from V0, Vc1n, and Vc1p obtained in these measurement periods. Therefore, the control device 420 in the ground fault detection device 400 can grasp the insulation resistances RLp1 and RLn1 by measuring V0, Vc1n, and Vc1p. Then, when the insulation resistances RLp1 and RLn1 are equal to or lower than the predetermined determination reference level, it is determined that a ground fault has occurred and an alarm is output.

FIG. 7 shows general voltage waveforms across the detection capacitor C1 in one cycle of the V0 measurement period, the Vc1n measurement period, the V0 measurement period, and the Vc1p measurement period. Here, FIG. 7A shows a general waveform when both the main relays 321 on the positive electrode side and the main relay 322 on the negative electrode side are turned off, and FIG. 7B shows both main relays. This is a general waveform when is turned on.

As described above, the insulation resistors RLp1 and RLn1 on the high voltage battery 300 side> the terminating resistors RLp2 and RLn2 on the load 360 side. Therefore, when the main relay is on, the insulation resistance and the terminating resistance are combined, and the current flowing during the Vc1n measurement period and the Vc1p measurement period becomes large. As a result, the voltage charged during the Vc1n measurement period and the Vc1p measurement period increases.

Therefore, when only one main relay is turned on, as shown in FIG. 7 (c), only one of the Vc1n measurement period and the Vc1p measurement period has a larger charging voltage than when both main relays are turned off. Become. In the example of this figure, only the negative electrode side main relay 322 is turned on, and only the charging voltage during the Vc1n measurement period is large.

From this, as shown in FIG. 8A, when switching control is performed from the state where both main relays are on to the state where both main relays are off, the detection capacitor C1 is used for both the Vc1n measurement period and the Vc1p measurement period. If the charging voltage is significantly reduced, it can be detected that both main relays have normally switched from on to off, that is, no sticking has occurred.

On the other hand, as shown in FIG. 8B, even though the control was performed to turn off both main relays from the state where both main relays were on, the detection capacitor was detected during either the Vc1n measurement period or the Vc1n measurement period. If the charging voltage of C1 does not decrease, it can be detected that one of the main relays remains on, that is, the on-sticking occurs.

In this regard, Patent Document 1 states that when the main relay is turned off, the charging voltage value of the measurement path including the insulation resistance is substantially equal to the charging voltage value when the main relay is turned on. It is described that it is determined that the relay is on and stuck.

Japanese Unexamined Patent Publication No. 2015-214264

However, when the main relay is turned off, the ground fault detection device 100 determines that the on-stick occurrence occurs when the charging voltage value of the measurement path including the insulation resistance is substantially equal to the charging voltage value when it is on. Due to the design characteristics of the built-in power supply system, characteristic fluctuations, etc., it is determined that the on-stick is on even though the on-stick has not occurred, or the on-stick is on even though the on-stick has occurred. There may be a situation where it is not determined.

For example, when the insulation resistance RLp1 or RLn1 is lowered, a waveform as shown in FIG. 9A may be obtained. In this case, if it is determined that the charging voltage during the Vc1n measurement period when the main relay is on and the charging voltage during the Vc1n measurement period when the main relay is off are approximately equal, the on-sticking does not occur. Regardless, on-sticking is erroneously detected.

Further, regarding the Y capacitor, there is generally a relationship of YCp1 = YCn1 << YCp2 = YCn2, but when YCp1 and YCn1 are large due to design reasons, parasitic capacitance, etc., as shown in FIG. 9B. Waveforms may be obtained. In this case as well, if it is determined that the charging voltage during the Vc1n measurement period when the main relay is on and the charging voltage during the Vc1n measurement period when the main relay is off are approximately equal, on-sticking does not occur. Nevertheless, on-sticking is erroneously detected.

On the other hand, when YCp1, YCn1, YCp2, and YCn2 are almost equal, even when on-sticking occurs, as shown in FIG. 9C, the Vc1n measurement period when the main relay is on There may be a difference between the charging voltage and the charging voltage during the Vc1n measurement period when the main relay is off. If it is not determined that the two are substantially equal, the on-sticking will not be detected even though the on-sticking has occurred.

In this way, when the main relay is turned off and the charging voltage value of the measurement path including the insulation resistance is approximately equal to the charging voltage value when it is on, the on-sticking is erroneously detected. There may be a situation where the detection omission of the on-sticking occurs.

Therefore, an object of the present invention is to provide a new criterion for determining whether the main relay is fixed on.

In order to solve the above problems, the ground fault detection device according to the first aspect of the present invention includes a non-grounded high-voltage battery in which the connection state with a load having a termination resistance between the ground and the ground is switched by a main relay. A ground fault detection device that is connected to detect a ground fault in a system provided with the high voltage battery, and is a detection capacitor that operates as a flying capacitor, the high voltage battery, and a positive electrode and ground of the high voltage battery. A positive voltage measurement path including the insulation resistance with and the detection capacitor, an insulation resistance between the high voltage battery, the negative voltage of the high voltage battery and the ground, and a negative voltage measurement path including the detection capacitor. The on-time voltage, which is the charging voltage of the detection capacitor when the main relay is switched on for each of the positive-side measurement path and the negative-position measurement path, and the on-time voltage. When the off voltage is larger than the on voltage in any of the measurement paths by comparing with the off voltage which is the charging voltage of the detection capacitor when the main relay is switched off. In addition, the main relay is provided with a control unit for determining that on-sticking has occurred.
Here, the control unit can determine that on-sticking has occurred in the main relay arranged on the pole side where the off voltage is larger than the on voltage.
Further, the switch group can be switched to a power supply measurement path that further includes the high voltage battery and the detection capacitor and does not include an insulation resistance, and the control unit uses the power supply measurement path as the main. The on power supply voltage, which is the charging voltage of the detection capacitor when the relay is switched on, and the off, which is the charging voltage of the detection capacitor when the main relay is switched off. If there is a fluctuation exceeding a predetermined reference with the current power supply voltage, the above comparison may not be performed.
The control unit can acquire switching control information of the main relay from an external control device which is a higher-level device.
In order to solve the above problems, the power supply system according to the second aspect of the present invention includes a non-grounded high-voltage battery, a load having a termination resistance between the grounded capacitors, and a connection between the high-voltage battery and the load. It is provided with a main relay for switching states, an external control device for switching control of the main relay, and a ground fault detecting device which is connected to the high-voltage battery and detects a ground fault in a system provided with the high-voltage battery. a power system, the ground fault detection device, a detection capacitor which operates as a flying capacitor, and the high-voltage battery, and the insulation resistance between the ground and the positive pole of the high voltage battery, and said detecting capacitor A switch group that switches between a positive voltage measurement path including the positive voltage battery, an insulation resistance between the negative voltage of the high voltage battery and the ground, and a negative voltage measurement path including the detection capacitor, and the positive voltage measurement path. And for each of the negative electrode measurement paths, when the main relay is switched on and controlled, the on voltage which is the charging voltage of the detection capacitor and when the main relay is switched off and controlled. Compared with the off voltage, which is the charging voltage of the detection capacitor, when the off voltage is larger than the on voltage in any of the measurement paths, the main relay is stuck on. It is characterized by including a control unit for determining.

According to the present invention, a new criterion for determining whether the main relay is stuck on is provided.

It is a figure which shows the circuit of the power-source system including the ground fault detection device which concerns on embodiment of this invention. It is a figure explaining the balance example of the step-down voltage between a positive electrode-ground and a negative electrode-ground. It is a figure explaining the presence / absence of on sticking and the voltage change at the time of turning on / off a main relay obtained in a Vc1 measurement period. It is a flowchart which shows the procedure of on sticking detection of a main relay. It is a figure which shows the circuit example of the power-source system including the ground fault detection device of a flying capacitor type. It is a figure which shows the measurement path of the V0 measurement period, the Vc1n measurement period, and the Vc1p measurement period. The general voltage waveforms across the detection capacitor in one cycle of V0 measurement period, Vc1n measurement period, V0 measurement period, and Vc1p measurement period are shown. It is a figure explaining the presence / absence of on sticking of a main relay, and the change of a waveform. It is a figure which shows the example of false detection and detection omission when the case where the charge voltage value is substantially equal is used as the determination criterion of on sticking.

Embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a circuit of a power supply system including a ground fault detection device 100 according to an embodiment of the present invention. As shown in this figure, the ground fault detection device 100 is connected to the ungrounded high voltage battery 300 via the positive electrode side power supply line 301 and the negative electrode side power supply line 302, and the ground fault of the system provided with the high voltage battery 300. It is a device that detects. The basic configuration of the circuit of the power supply system including the ground fault detection device 100 can be the same as the conventional one. Here, the high voltage means a voltage higher than the low voltage battery (generally 12V) for driving various devices (lamps, wipers, etc.) in the vehicle, and the high voltage battery 300 means the vehicle travels. It is a battery used for driving.

The high voltage battery 300 is composed of a rechargeable battery such as a lithium ion battery. The high-voltage battery 300 supplies power to the load 360 via the positive electrode side power supply line 301 and the negative electrode side power supply line 302, and the connection state with the positive electrode side load 360 is switched by the positive electrode side main relay 321. The connection state with the load 360 on the negative electrode side is switched by the main relay 322 on the negative electrode side. Switching between the positive electrode side main relay 321 and the negative electrode side main relay 322 is performed by the external control device 200, which is a higher-level device.

The load 360 can be, for example, an electric motor connected via an inverter or the like. Further, the high voltage battery 300 can be charged at the time of regeneration or at the time of connecting to the charging equipment.

Here, the insulation resistance between the positive electrode side and the ground of the high voltage battery 300 is represented by RLp1, and the insulation resistance between the negative electrode side and the ground is represented by RLn1. Further, the terminating resistance between the positive electrode and the ground on the load 360 side is represented by RLp2, and the terminating resistance between the negative electrode and the ground is represented by RLn2.

Between the positive electrode side power supply line 301 and the ground of the high voltage battery 300 and between the negative electrode side power supply line 302 and the ground, Y capacitors (lines) are used to remove high frequency noise of the power supply and stabilize the operation, respectively. -Bypass capacitors) capacitors CYp1 and CYn1 are connected. Further, CYp2 and CYn2 are connected as Y capacitors between the positive electrode on the load 360 side and the ground and between the negative electrode on the load 360 side and the ground, respectively. However, the Y capacitor may be omitted. Even in this case, due to the parasitic capacitance, there are capacitors CYp1, CYn1, CYp2, and CYn2 between the capacitors and the ground.

As shown in this figure, the ground fault detection device 100 includes a detection capacitor C1 that operates as a flying capacitor, a control device 120, and four switching elements S1 to S4. The switching elements S1 to S4 are arranged around the detection capacitor C1 in order to switch the measurement path and control the charging and discharging of the detection capacitor C1.

The switching elements S1 to S4 can be configured by an isolated switching element such as an optical MOSFET. The control device 120 executes various controls required for the ground fault detection device 100, such as a switch switching process, by executing a program incorporated in advance.

One end of the switching element S1 is connected to the positive electrode side power supply line 301, and the other end is connected to the anode side of the diode D1. The cathode side of the diode D1 is connected to the resistor R1, and the other end of the resistor R1 is connected to the positive electrode side terminal of the detection capacitor C1.

One end of the switching element S2 is connected to the negative electrode side power supply line 302, and the other end is connected to the resistor R5. The other end of the resistor R5 is connected to the negative electrode side terminal of the detection capacitor C1.

One end of the switching element S3 is connected to the anode side of the resistor R2 and the diode D3, and the other end is connected to the resistor R3 and the analog input terminal of the control device 120. The cathode side of the diode D3 is connected to the positive electrode side terminal of the detection capacitor C1, the other end of the resistor R2 is connected to the cathode side of the diode D2, and the anode side of the diode D2 is connected to the positive electrode side terminal of the detection capacitor C1. ing. The other end of the resistor R3 is grounded.

One end of the switching element S4 is connected to the negative electrode side terminal of the detection capacitor C1, and the other end is connected to the resistor R4. The other end of the resistor R4 is grounded.

In the ground fault detection device 100, in order to grasp the insulation resistances RLp1 and RLn1 on the high voltage battery 300 side, the measurement operation is repeated with the V0 measurement period → Vc1n measurement period → V0 measurement period → Vc1p measurement period as one cycle. However, the V0 measurement period → Vc1n measurement period → Vc1p measurement period may be set as one cycle. The ground fault determination based on the measured values obtained in each measurement period is the same as before. The V0 measurement period is a period for measuring the voltage corresponding to the voltage of the high voltage battery 300, and the Vc1n measurement period and the Vc1p measurement period are periods for measuring the voltage of the path including the insulation resistance.

Further, the ground fault detection device 100 has a Vc1n measurement period and a Vc1p measurement period (“Vc1”) when the positive electrode side main relay 321 and the negative electrode side main relay 322 (collectively referred to as “main relay”) are switched from on to off. Based on the change in the charging waveform of the detection capacitor C1 obtained in the "measurement period"), the on-sticking (welding) of the main relay is determined. Of course, the determination may be made based on the change in the charging waveform when the main relay is switched from off to on.

As described above, in determining whether the charging voltage value during the Vc1 measurement period is approximately the same when the main relay is on and off, erroneous detection of on-sticking may occur depending on the state of the insulation resistance, the state of the Y capacitor, etc. Detection omission may occur.

By the way, when on-sticking occurs on one side of the main relay, the insulation resistance of the pole on which on-sticking occurs apparently decreases during off-control. This is because the terminating resistance on the load side is combined with the insulation resistance when the main relay is fixed on. Here, this apparent insulation resistance is referred to as a ground fault resistance.

When the main relay is not stuck on, as shown in FIG. 2A, when the main relay is on-controlled, the ground fault resistance is equal to the combined resistance of the insulation resistance and the terminating resistance. Both the positive electrode side and the negative electrode side can be balanced with low values. Further, when the main relay is off-controlled, the ground fault resistance is equal to the insulation resistance, so that a high value can be balanced on both the positive electrode side and the negative electrode side. When the main relay is off-controlled, the ground fault resistance is large and there is no charge transfer from the stray capacitance on the load side, so the current flowing through the ground fault resistance is small. As a result, the voltage value obtained in the Vc1 measurement period becomes smaller on both the positive electrode side and the negative electrode side, as shown in FIG. 3A.

On the other hand, when on-stick occurs on one side of the main relay, as shown in FIG. 2B, when the main relay is on-controlled, the ground fault resistance is the combined resistance of the insulation resistance and the terminating resistance. Since it is equal to, both the positive electrode side and the negative electrode side can be balanced at a low value. However, when the main relay is off-controlled, the ground fault resistance of the pole where on-sticking does not occur becomes a value equal to the insulation resistance, but the terminating resistance of the pole where on-sticking occurs is insulated. It is a low value that is the combined resistance of the resistance and the terminating resistance.

Therefore, as shown in FIG. 3B, the voltage balance between the positive electrode and the ground and between the negative electrode and the ground, which is divided by the ground fault resistance, is lost, and the voltage in the Vc1 measurement period on the fixed electrode side is changed. , A peculiar phenomenon that it rises at the time of off control occurs. As described above, when the main relay is not stuck on during the off control, the voltage value obtained in the Vc1 measurement period becomes small on both the positive electrode side and the negative electrode side, so that when the voltage value rises, It can be determined that on-sticking has occurred.

Therefore, in the present invention, it is determined that on-sticking has occurred when either Vc1p or Vc1n rises during the off control of the main relay. At this time, the sticking point may be specified when the on-sticking occurs at the pole on the raised side.

For example, the control device 120 of the ground fault detection device 100 performs the on-stick detection of the main relay. FIG. 4 is a flowchart showing a procedure for detecting on-sticking of the main relay. Here, it is assumed that the control device 120 of the ground fault detection device 100 can acquire the on control information and the off control information of the main relay from the external control device 200.

The control device 120 of the ground fault detection device 100 executes a measurement cycle for ground fault detection while the main relay is on-controlled (S101), and measures V0, Vc1p, and Vc1n (S102). Further, while the main relay is off-controlled (S103), a measurement cycle for detecting a ground fault is executed, and V0, Vc1p, and Vc1n are measured (S104).

Then, it is determined whether or not the voltage of the high voltage battery 300 has fluctuated between the two measurements (S105). This is because if the voltage of the high voltage battery 300 fluctuates, it affects the measured value of Vc1. This determination can be made with reference to the measured value V0 corresponding to the voltage of the high voltage battery 300.

As a result, if the voltage of the high-voltage battery 300 fluctuates beyond a predetermined standard (S105: Yes), the accuracy of determining the increase / decrease of Vc1 is lowered, so the on-stick determination using the measured value this time is cancelled. (S106). However, the on-sticking determination may be performed this time by correcting the values of Vc1p and Vc1n using the voltage fluctuation amount of the high-voltage battery 300.

When there is no fluctuation in the voltage of the high-voltage battery 300 (S105: No), it is determined whether the off control time is small for both Vc1p and Vc1n (S107). As a result, when both Vc1p and Vc1n are small at the time of off control (S107: Yes), it is determined that on-sticking has not occurred (S108).

On the other hand, when either Vc1p or Vc1n is not reduced at the time of off control (S107: No), it is determined that on-sticking has occurred (S109). At this time, it may be determined that the main relay on the pole side of Vc1p and Vc1n, which is larger during the off control, is stuck on.

The external control device 300 may determine whether the main relay is stuck on. In this case, the main relay may be turned on and off, and the values of Vc1p and Vc1n in each state may be acquired from the control device 120 of the ground fault detection device 100. The voltage fluctuation of the high-voltage battery 300 may be determined by acquiring V0 from the control device 120 of the ground fault detection device 100, or by acquiring the voltage of the high-voltage battery 300 separately measured.

100 Ground fault detection device 120 Control device 200 External control device 300 High voltage battery 301 Positive electrode side power supply line 302 Negative electrode side power supply line 321 Positive electrode side main relay 322 Negative electrode side main relay 360 Load

Claims (5)

A ground fault detection device that detects a ground fault in a system provided with the high voltage battery by connecting to a non-grounded high voltage battery whose connection state with a load having a terminating resistor is switched by the main relay. And
A detection capacitor that operates as a flying capacitor,
Insulation of the high voltage battery, the positive electrode measurement path including the insulation resistance between the positive electrode and the ground of the high voltage battery, and the detection capacitor, the high voltage battery, and the negative electrode and the ground of the high voltage battery. A group of switches for switching between a resistor and a negative electrode measurement path including the detection capacitor, and
For each of the positive electrode measurement path and the negative electrode measurement path, the on-time voltage, which is the charging voltage of the detection capacitor when the main relay is switched on, and the main relay are switched off and controlled. When the off voltage, which is the charging voltage of the detection capacitor, is compared with the off voltage, and the off voltage is larger than the on voltage in any of the measurement paths, the main relay is fixed on. And the control unit that determines that
A ground fault detection device characterized by being equipped with. The ground fault detecting device according to claim 1, wherein the control unit determines that on-sticking has occurred in a main relay arranged on the pole side where the off voltage is larger than the on voltage. The switch group can be switched to a power supply measurement path that further includes the high voltage battery and the detection capacitor and does not include an insulation resistor.
The control unit switches and controls the on power supply voltage, which is the charging voltage of the detection capacitor when the main relay is switched on, with respect to the power supply measurement path, and the main relay is switched off. The place according to claim 1 or 2, wherein if the off-time power supply voltage, which is the charging voltage of the detection capacitor, fluctuates beyond a predetermined reference, the comparison is not performed. Entanglement detector. The ground fault detection device according to any one of claims 1 to 3, wherein the control unit acquires switching control information of the main relay from an external control device which is a higher-level device. With a non-grounded high voltage battery,
With a load that has a terminating resistor between ground and
A main relay that switches the connection state between the high-voltage battery and the load,
An external control device that controls switching of the main relay and
A power supply system including a ground fault detection device that is connected to the high voltage battery and detects a ground fault in a system provided with the high voltage battery.
The ground fault detection device,
A detection capacitor that operates as a flying capacitor,
Insulation of the high voltage battery, the positive electrode measurement path including the insulation resistance between the positive electrode and the ground of the high voltage battery, and the detection capacitor, the high voltage battery, and the negative electrode and the ground of the high voltage battery. A group of switches for switching between a resistor and a negative electrode measurement path including the detection capacitor, and
For each of the positive electrode measurement path and the negative electrode measurement path, the on-time voltage, which is the charging voltage of the detection capacitor when the main relay is switched on, and the main relay are switched off and controlled. When the off voltage, which is the charging voltage of the detection capacitor, is compared with the off voltage, and the off voltage is larger than the on voltage in any of the measurement paths, the main relay is fixed on. And the control unit that determines that
A power supply system characterized by being equipped with.

Images