JP6831362B2 - Leakage detector, earth leakage detection system, and diagnostic method - Google Patents

Description

The disclosed embodiments relate to earth leakage detection devices, earth leakage detection systems, and diagnostic methods.

Conventionally, an earth leakage detection device includes an earth leakage detection circuit that detects an earth leakage from a power source based on the resistance value of an insulating resistor that insulates between the power source and the ground. Such an earth leakage detection device includes a constant voltage element such as a Zener diode connected in parallel with the power supply in order to protect the circuit element from a sudden high voltage such as a surge voltage exceeding the power supply voltage (for example,). See Patent Document 1).

Japanese Unexamined Patent Publication No. 2014-125168

However, the earth leakage detection device may not be able to accurately detect the earth leakage when the constant voltage element is short-circuited.

One aspect of the embodiment is made in view of the above, and provides an earth leakage detection device, an earth leakage detection system, and a diagnosis method capable of diagnosing a short-circuit failure of a constant voltage element with a simple configuration. The purpose.

The earth leakage detection device according to one aspect of the embodiment includes an earth leakage detection circuit, a plurality of constant voltage elements, a plurality of switches, and a diagnostic unit. The leakage detection circuit is a circuit for detecting leakage from the power supply based on the resistance value of the insulation resistance that insulates between the power supply and the ground. A plurality of constant voltage elements connected in series are connected in parallel between the earth leakage detection circuit and the power supply, and hold the voltage applied from the power supply to the earth leakage detection circuit at a predetermined voltage. The plurality of switches are connected in parallel to the constant voltage element to bypass the constant voltage element. When the diagnosis unit turns on the switch connected in parallel to the constant voltage element not to be diagnosed and turns off the switch connected in parallel to the constant voltage element to be diagnosed, the diagnostic unit turns off the constant voltage to be diagnosed. A short-circuit failure diagnosis of the constant voltage element is performed based on the voltage held by the element.

According to the earth leakage detection device, the earth leakage detection system, and the diagnosis method according to one aspect of the embodiment, it is possible to diagnose a short-circuit failure of a constant voltage element with a simple configuration.

FIG. 1 is an explanatory diagram showing an example of a configuration of an earth leakage detection system according to an embodiment. FIG. 2 is an explanatory diagram of an earth leakage detection operation performed by the earth leakage detection device according to the embodiment. FIG. 3 is an explanatory diagram of an earth leakage detection operation performed by the earth leakage detection device according to the embodiment. FIG. 4 is an explanatory diagram of an earth leakage detection operation performed by the earth leakage detection device according to the embodiment. FIG. 5 is an explanatory diagram showing a state in which the first diode according to the embodiment has a short-circuit failure. FIG. 6 is an explanatory diagram of a diagnostic operation of a constant voltage element performed by the leakage detection device according to the embodiment. FIG. 7 is an explanatory diagram of the diagnostic operation of the constant voltage element performed by the leakage detection device according to the embodiment. FIG. 8 is an explanatory diagram of an open failure diagnosis operation of the first diagnostic switch and the second diagnostic switch performed by the leakage detection device according to the embodiment.

Hereinafter, embodiments of an earth leakage detection device, an earth leakage detection system, and a diagnostic method will be described in detail with reference to the accompanying drawings. The present invention is not limited to the embodiments shown below.

In the following, an earth leakage detection system for detecting an electric leakage from a high-voltage battery (hereinafter, simply referred to as a battery), which is an example of a power source of an electric vehicle, to the ground of a vehicle will be described as an example. The earth leakage detection system according to the embodiment can be applied not only to the battery of an electric vehicle but also to the earth leakage detection from any battery.

FIG. 1 is an explanatory diagram showing an example of the configuration of the earth leakage detection system 100 according to the embodiment. As shown in FIG. 1, the earth leakage detection system 100 includes a battery BT, a first insulation resistance Ra, a second insulation resistance Rb, and an earth leakage detection device 1.

The battery BT is a rechargeable secondary battery such as a lithium ion battery. The battery BT is charged by, for example, a quick charging device or the regenerative energy of the vehicle, and supplies electric power to a load such as a motor that runs the vehicle. Here, a case where the rated voltage of the battery BT is 240V to 400V and the ground of the vehicle (hereinafter, referred to as the vehicle ground) is 360V will be described.

The first insulation resistance Ra and the second insulation resistance Rb are connected in series, and are connected in parallel between the battery BT and the leakage detection device 1. Specifically, one end of the first insulation resistance Ra is connected to the positive electrode of the battery BT, and the other end is connected to one end of the second insulation resistance Rb and the vehicle ground. The other end of the second insulation resistor Rb is connected to the negative electrode of the battery BT.

The first insulation resistor Ra and the second insulation resistor Rb have a resistance value of several megaΩ, but if the resistance value drops for some reason, electric leakage from the battery BT to the vehicle ground will occur. It occurs, for example, there is a risk of electric shock when performing quick charging.

Therefore, in order to prevent electric shock, the electric leakage detection device 1 detects electric leakage from the battery BT, for example, while charging the battery BT. The leakage detection device 1 includes a leakage detection circuit 10 for detecting leakage from the battery BT based on the resistance values of the first insulation resistance Ra and the second insulation resistance Rb, and a microcomputer (hereinafter, referred to as a microcomputer 3). ) And.

The leakage detection circuit 10 includes a flying capacitor C and a differential amplifier 2. The flying capacitor C is connected in parallel between the battery BT and the differential amplifier 2. Of the pair of electrodes included in the flying capacitor C, one electrode is connected to the positive electrode of the battery BT via the first switch Sw1, the first protection resistor R1, and the high-voltage side connection terminal B.

Further, the other electrode of the flying capacitor C is connected to the negative electrode of the battery BT via the second switch Sw2, the second protection resistor R2, and the low voltage side connection terminal G. As a result, the flying capacitor C is disconnected from the battery BT by turning off both the first switch Sw1 and the second switch Sw2.

Further, one of the pair of electrodes included in the flying capacitor C is connected to one of the two input terminals of the differential amplifier 2 via the third switch Sw3. Further, the other electrode of the flying capacitor C is connected to the other input terminal of the differential amplifier 2 via the fourth switch Sw4.

Further, the wiring connecting the third switch Sw3 and the differential amplifier 2 is connected to the vehicle ground via the third protection resistor R3. The wiring connecting the fourth switch Sw4 and the differential amplifier 2 is connected to the vehicle ground via the fourth protection resistor R4.

Further, one electrode of the flying capacitor C is connected to the wiring connecting the second switch Sw2 and the fourth switch Sw4 via the fifth switch Sw5 and the fifth protection resistor R5.

The differential amplifier 2 detects the charging voltage of the flying capacitor C. Specifically, the differential amplifier 2 amplifies the potential difference (voltage) between the pair of electrodes of the flying capacitor C and outputs the voltage to the microcomputer 3.

The microcomputer 3 includes a microcomputer having a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and various circuits. The microcomputer 3 may be partially or wholly composed of hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

The microcomputer 3 executes the program stored in the ROM by the CPU using the RAM as a work area, controls the operation of the first to fourth switches Sw1 to Sw4, and obtains the voltage input from the differential amplifier 2. Based on this, it functions as a determination unit for determining whether or not an electric leakage has occurred.

An example of the leakage detection operation performed by the leakage detection device 1 will be described later with reference to FIGS. 2 to 4. Further, the microcomputer 3 also controls to discharge and reset the flying capacitor C by turning on the fifth switch Sw5 and the second switch Sw2.

Further, the leakage detection device 1 has a plurality of (here, four) constant voltages connected in series to protect the circuit elements of the leakage detection circuit 10 from sudden high voltages such as a surge voltage exceeding the rated voltage of the power supply voltage. The elements D1 to D4 are provided.

The constant voltage elements D1 to D4 are, for example, Zener diodes. If the constant voltage elements D1 to D4 are circuit elements that can hold (fix) the output voltage at a predetermined voltage when a voltage equal to or higher than a predetermined voltage is applied, for example, a fixed output voltage type 3-terminal regulator or the like. , Any constant voltage element may be used.

In the following, in order to distinguish the constant voltage elements D1 to D4, the constant voltage element D1 is referred to as the first diode D1, the constant voltage element D2 is referred to as the second diode D2, the constant voltage element D3 is referred to as the third diode D3, and the constant voltage element D4 is referred to. It will be referred to as a fourth diode D4. Further, here, a case where each Zener voltage of the first to fourth diodes D1 to D4 is 110V will be described.

The first to fourth diodes D1 to D4 connected in series are connected in parallel between the battery BT and the leakage detection circuit 10. Specifically, in the first diode D1, the cathode is connected to the positive electrode of the battery BT via the first protection resistor R1 and the high-voltage side connection terminal B, and the anode is connected to the cathode of the second diode D2.

Further, the anode of the second diode D2 is connected to the cathode of the third diode D3. The anode of the third diode D3 is connected to the cathode of the fourth diode D4. The anode of the fourth diode D4 is connected to the negative electrode of the battery BT via the second protection resistor R2 and the low voltage side connection terminal G.

As a result, in the earth leakage detection device 1, when the voltage applied from the battery BT to the earth leakage detection circuit 10 becomes 440 V or more, a current flows from the cathode of the first to fourth diodes D1 to D4 to the anode, resulting in an earth leakage. The voltage applied to the detection circuit 10 is maintained at 440V. Therefore, when a sudden high voltage such as a surge voltage exceeding the rated voltage of the power supply voltage is applied, the leakage detection device 1 uses the first to fourth diodes D1 to D4 to detect the circuit element of the leakage detection circuit 10. It can be protected from high voltage.

However, the leakage detection device 1 may not be able to accurately detect the occurrence of leakage when any of the constant voltage elements of the first to fourth diodes D1 to D4 causes a short-circuit failure.

Therefore, the leakage detection device 1 is a first diagnostic switch that is connected in parallel to the first to fourth diodes D1 to D4 and bypass-connected to the first to fourth diodes D1 to D4 in order to diagnose a short-circuit failure of the constant voltage element. It includes Sw6 and a second diagnostic switch Sw7.

Specifically, the first diagnostic switch Sw6 connects a current path that bypasses the first diode D1 and the second diode D2. Further, the second diagnostic switch Sw7 connects a current path that bypasses the third diode D3 and the fourth diode D4.

Then, the microcomputer 3 controls the operation of the first diagnostic switch Sw6 and the second diagnostic switch Sw7 with the first switch Sw1 and the second switch Sw2 connected, and based on the charging voltage of the flying capacitor C at that time. Diagnose a short circuit failure of a constant voltage element.

At this time, the microcomputer 3 functions as a diagnostic unit for diagnosing a short-circuit failure of the constant voltage element. As described above, the leakage detection device 1 includes first and second diagnostic switches Sw6 and Sw7 that are connected in parallel to the first to fourth diodes D1 to D4 and bypass-connect the first to fourth diodes D1 to D4. A short circuit failure of a constant voltage element can be diagnosed with a simple configuration. An example of the operation when the leakage detection device 1 diagnoses a short-circuit failure of the constant voltage element will be described later with reference to FIG.

Next, the operation of the leakage detection device 1 will be described with reference to FIGS. 2 to 8. In the following, the leakage detection operation when the constant voltage element is normal, the leakage detection operation when the constant voltage element has a short failure, the short failure diagnosis operation of the constant voltage element, the first diagnostic switch Sw6 and the second diagnostic switch Sw7. The open fault diagnosis operation will be described in this order.

First, the leakage detection operation in a normal state of the constant voltage element will be described with reference to FIGS. 2 to 4. 2 to 4 are explanatory views of an earth leakage detection operation performed by the earth leakage detection device 1 according to the embodiment. The leakage detection device 1 determines, for example, the presence or absence of leakage from the battery BT during rapid charging of the battery BT.

As shown in FIG. 2, when the leakage detection device 1 detects the leakage due to the decrease in the resistance value of the first insulation resistor Ra, the microcomputer 3 switches the second switch Sw2 and the third switch Sw3 for a predetermined time. Turn on and turn off the first switch Sw1 and the fourth switch Sw4.

Then, the earth leakage detection device 1 turns off the second switch Sw2 and the third switch Sw3 after a predetermined time has elapsed. During this time, the microcomputer 3 keeps the fifth switch Sw5 off. As a result, the current flows along the path indicated by the thick arrow in FIG. 2 while the second switch Sw2 and the third switch Sw3 are on.

Specifically, the current is the positive electrode of the battery BT, the first insulation resistance Ra, the vehicle ground, the third protection resistance R3, the third switch Sw3, the flying capacitor C, the second switch Sw2, the second protection resistance R2, and the low voltage side. The connection terminal G and the negative electrode of the battery BT flow in this order.

At this time, if the resistance value of the first insulation resistor Ra is normal, the flying capacitor C is charged with the normal charging voltage obtained by subtracting the voltage drop due to the third protection resistor R3 and the second protection resistor R2 from 360V. To. However, when the resistance value of the first insulation resistor Ra decreases and the electric leakage occurs, the flying capacitor C is charged at a voltage higher than the normal charging voltage.

Therefore, as shown in FIG. 3, the microcomputer 3 turns on the third switch Sw3 and the fourth switch Sw4, and refers to the voltage corresponding to the charging voltage of the flying capacitor C input from the differential amplifier 2.

Then, when the voltage input from the differential amplifier 2 is equal to or higher than a predetermined threshold value, the microcomputer 3 determines that an electric leakage has occurred due to a decrease in the resistance value of the first insulation resistor Ra. After that, the microcomputer 3 turns on the fifth switch Sw5 to reset the flying capacitor C.

Further, as shown in FIG. 4, when the leakage detection device 1 detects the leakage due to the decrease in the resistance value of the second insulation resistor Rb, the microcomputer 3 causes the first switch Sw1 and the fourth switch for a predetermined time. Sw4 is turned on, and the third switch Sw3 and the second switch Sw2 are turned off.

Then, the earth leakage detection device 1 turns off the first switch Sw1 and the fourth switch Sw4 after a predetermined time has elapsed. During this time, the microcomputer 3 keeps the fifth switch Sw5 off. As a result, the current flows along the path indicated by the thick arrow in FIG. 4 while the first switch Sw1 and the fourth switch Sw4 are on.

Specifically, the current is the positive electrode of the battery BT, the high-voltage side connection terminal B, the first protection resistor R1, the first switch Sw1, the flying capacitor C, the fourth switch Sw4, the fourth protection resistor R4, the vehicle ground, and the second. The insulation resistance Rb and the negative electrode of the battery BT flow in this order.

At this time, if the resistance value of the second insulation resistor Rb is normal, the flying capacitor C is charged with the normal charging voltage obtained by subtracting the voltage drop due to the first protection resistor R1 and the fourth protection resistor R4 from 40V. To. However, when the resistance value of the second insulation resistor Rb is lowered and the electric leakage occurs, the flying capacitor C is charged at a voltage higher than the normal charging voltage.

Therefore, as shown in FIG. 3, the microcomputer 3 turns on the third switch Sw3 and the fourth switch Sw4, and refers to the voltage corresponding to the charging voltage of the flying capacitor C input from the differential amplifier 2.

Then, when the voltage input from the differential amplifier 2 is equal to or higher than a predetermined threshold value, the microcomputer 3 determines that an electric leakage has occurred due to a decrease in the resistance value of the second insulation resistor Rb. After that, the microcomputer 3 turns on the fifth switch Sw5 to reset the flying capacitor C.

Next, with reference to FIG. 5, the leakage detection operation in the state where the constant voltage element has a short-circuit failure will be described. FIG. 5 is an explanatory diagram showing a state in which the first diode D1 according to the embodiment has a short-circuit failure.

For example, when the leakage detection device 1 performs an operation of detecting leakage due to a decrease in the resistance value of the second insulation resistor Rb in a state where the first diode D1 is short-circuited, the thick line arrow and the thick dotted arrow are shown in FIG. A current flows through the path indicated by.

Specifically, as described above, the microcomputer 3 turns on the first switch Sw1 and the fourth switch Sw4 when detecting an electric leakage due to a decrease in the resistance value of the second insulation resistor Rb. As a result, the current flows through the path shown by the thick arrow in FIG. 4 unless the first diode D1 is short-circuited, and in the flying capacitor C, the upper electrode shown in FIG. 4 is positive and the lower electrode is negative. Is charged.

However, when the first diode D1 is short-circuited, the current flows along the path indicated by the thick line arrow and the thick dotted line arrow in FIG. Specifically, when the first diode D1 has a short-circuit failure, the second to fourth diodes D2 to D4 connected in series pass a current from the cathode to the anode when the potential difference between both ends exceeds 330 V, and the voltage at both ends. Is held at 330V. As a result, the potential on the cathode side of the first diode D1 becomes 330V.

Therefore, for example, when the voltage of the battery BT is 400 V, as shown by the thick dotted arrow in FIG. 5, the current flows from the positive electrode of the battery BT to the high voltage side connection terminal B, the first protection resistor R1, and the first to first. The four diodes D1 to D4, the second protection resistor R2, the low voltage side connection terminal G, and the negative electrode of the battery BT flow in this order.

Further, at this time, since the potential of the cathode of the first diode D1 is 330 V, which is lower than the potential of 360 V of the vehicle ground, a current flow from the vehicle ground to the cathode of the first diode D1 is formed.

Therefore, as shown by the thick arrow in FIG. 5, the current is applied from the positive electrode of the battery BT to the first insulation resistor Ra, the vehicle ground, the fourth protection resistor R4, the fourth switch Sw4, the flying capacitor C, and the first switch Sw1. The first to fourth diodes D1 to D4, the second protection resistor R2, the low voltage side connection terminal G, and the negative electrode of the battery BT flow in this order.

As a result, in the flying capacitor C, the upper electrode shown in FIG. 5 is negatively charged, the lower electrode is positively charged, and the positive and negative electrodes are opposite to those in the case where the first diode D1 shown in FIG. 4 is not short-circuited. Become.

In this state, when the first switch Sw1 and the fourth switch Sw4 are turned off and then the third switch Sw3 and the fourth switch Sw4 are turned on, the microcomputer 3 receives a voltage opposite to the original polarity from the flying capacitor C. Refer to the input output of the differential amplifier 2. Therefore, the microcomputer 3 cannot normally determine the presence or absence of electric leakage.

Therefore, the earth leakage detection device 1 diagnoses the short-circuit failure of the first to fourth diodes D1 to D4 before detecting the leakage, detects the leakage if there is no short-circuit failure, and if there is no leakage, the battery. Allows fast charging of the BT. Further, the electric leakage detection device 1 prohibits quick charging of the battery BT when any of the first to fourth diodes D1 to D4 has a short-circuit failure or when there is an electric leakage.

Next, with reference to FIGS. 6 and 7, the diagnostic operation of the constant voltage element performed by the leakage detection device 1 according to the embodiment will be described. 6 and 7 are explanatory views of the diagnostic operation of the constant voltage element performed by the leakage detection device 1 according to the embodiment.

When performing a short-circuit failure diagnosis of a constant voltage element, the microcomputer 3 turns on a switch connected in parallel to a constant voltage element not to be diagnosed and turns off a switch connected in parallel to the constant voltage element to be diagnosed. Then, the microcomputer 3 performs a short-circuit failure diagnosis of the constant voltage element to be diagnosed based on the voltage held by the constant voltage element to be diagnosed.

For example, as shown in FIG. 6, the microcomputer 3 turns on the second diagnostic switch Sw7 and turns off the first diagnostic switch Sw6 when performing short-circuit failure diagnosis of the first diode D1 and the second diode D2. At this time, the current flows along the path indicated by the thick arrow in FIG. 6 unless both the first diode D1 and the second diode D2 are short-circuited.

Specifically, the current is connected from the positive electrode of the battery BT to the high voltage side connection terminal B, the first protection resistor R1, the first diode D1, the second diode D2, the second diagnostic switch Sw7, the second protection resistor R2, and the low voltage side connection. It flows to the negative electrode of the terminal G and the battery BT.

After that, the microcomputer 3 turns on the first switch Sw1 and the second switch Sw2. As a result, the current also flows in the path indicated by the thick dotted arrow in FIG. Specifically, the current branches from the cathode of the first diode D1 and flows through the first switch Sw1, the flying capacitor C, and the second switch Sw2 to the second protection resistor R2.

At this time, the charging voltage of the flying capacitor C is, for example, when the voltage of the battery BT is 400 V, the Zener voltage of the first diode D1 and the second diode D2 unless the first diode D1 and the second diode D2 have failed. It is held at (220V).

Therefore, the microcomputer 3 turns off the first switch Sw1 and the second switch Sw2, then turns off the third switch Sw3 and the fourth switch Sw4, and sets the voltage corresponding to the charging voltage of the flying capacitor C to the differential amplifier 2 Get from.

At this time, when the charging voltage of the flying capacitor C is 220V and the microcomputer 3 acquires the voltage output from the differential amplifier 2, both the first diode D1 and the second diode D2 are short-circuited. Diagnose no.

On the other hand, of the first diode D1 and the second diode D2, for example, when the first diode D1 has a short-circuit failure, the current is the path indicated by the thick arrow and the path indicated by the thick arrow in FIG. Flows to.

In such a case, the charging voltage of the flying capacitor C is held at the Zener voltage (110V) of the second diode D2. Therefore, when the third switch Sw3 and the fourth switch Sw4 are turned on, the microcomputer 3 acquires the voltage output from the differential amplifier 2 when the charging voltage of the flying capacitor C is 110V.

Further, the microcomputer 3 differentially transmits the same voltage as when the first diode D1 has a short-circuit failure even when the second diode D2 of the first diode D1 and the second diode D2 has a short-circuit failure. Obtained from amplifier 2.

Further, when both the first diode D1 and the second diode D2 are short-circuited, the microcomputer 3 acquires the voltage of 0V from the differential amplifier 2 because the charging voltage of the flying capacitor C becomes 0V.

Therefore, when the microcomputer 3 acquires the voltage output from the differential amplifier 2 when the charging voltage of the flying capacitor C is higher than 110 V, the first diode D1 and the second diode D2 are not short-circuited. Diagnose.

When the microcomputer 3 turns on the third switch Sw3 and the fourth switch Sw4 to acquire a voltage of 0 V from the differential amplifier 2, it is said that the first diode D1 and the second diode D2 are short-circuited. Diagnose.

Further, when performing short-circuit failure diagnosis of the third diode D3 and the fourth diode D4, the microcomputer 3 turns on the first diagnosis switch Sw6 and turns on the first switch Sw1 and the second switch Sw2. After that, the microcomputer 3 turns off the first switch Sw1 and the second switch Sw2, and turns on the third switch Sw3 and the fourth switch Sw4.

Then, when the charging voltage of the flying capacitor C is 220V and the microcomputer 3 acquires the voltage output from the differential amplifier 2, neither the third diode D3 nor the fourth diode D4 has a short-circuit failure. Diagnose.

Further, when the microcomputer 3 acquires the voltage output from the differential amplifier 2 when the charging voltage of the flying capacitor C is higher than 110 V, the third diode D3 and the fourth diode D4 are not short-circuited. Diagnose.

Further, when the microcomputer 3 turns on the third switch Sw3 and the fourth switch Sw4 to acquire a voltage of 0 V from the differential amplifier 2, it is said that the third diode D3 and the fourth diode D4 are short-circuited. Diagnose.

As described above, the leakage detection device 1 has a simple configuration in which the first diagnostic switch Sw6 and the second diagnostic switch Sw7 are provided in addition to the basic configuration for leakage detection, and short-circuits the first to fourth diodes D1 to D4. Failure diagnosis can be performed.

Further, the plurality of constant voltage elements connected in series of the leakage detection device 1 are Zener diodes, and the cathode is connected to the wiring connecting the positive electrode of the battery BT and the leakage detection circuit 10, and the negative electrode of the battery BT and the leakage are generated. The anode is connected to the wiring connecting the detection circuit 10.

As a result, the earth leakage detection device 1 switches on and off the first diagnostic switch Sw6 and the second diagnostic switch Sw7 that bypass the Zener diode, and refers to the charging voltage of the flying capacitor C. Short-circuit failure diagnosis of the 1st to 4th diodes D1 to D4 can be performed.

Further, the leakage detection device 1 diagnoses that the Zener diode has a short-circuit failure when the voltage held by the Zener diode is less than the Zener voltage. In this way, the earth leakage detection device 1 can perform short-circuit failure diagnosis of the first to fourth diodes D1 to D4 by a simple process of determining whether or not the voltage held by the Zener diode is less than the Zener voltage. it can.

Further, the leakage detection circuit 10 includes a flying capacitor C that is charged by a voltage applied from the battery BT via the first insulation resistance Ra or the second insulation resistance Rb, and causes an electric leakage based on the charging voltage of the flying capacitor C. To detect.

Further, in the microcomputer 3, when the charging voltage of the flying capacitor C charged by the voltage held by the constant voltage element to be diagnosed among the first to fourth diodes D1 to D4 is less than the Zener voltage of the constant voltage element. In addition, it is diagnosed that the constant voltage element to be diagnosed has a short-circuit failure.

As described above, the leakage detection device 1 can reduce the cost of the product by suppressing the increase in the number of circuit elements by using the flying capacitor C for both the leakage detection and the diagnosis of the constant voltage element. it can.

Even with an earth leakage detection device that does not have the first diagnostic switch Sw6 and the second diagnostic switch Sw7, if the voltage of the battery BT is sufficiently high, it is possible to diagnose a short-circuit failure of the constant voltage element, but the voltage of the battery BT. If is low, diagnosis may not be possible.

Here, with reference to FIG. 1, a case where the leakage detection device 1 shown in FIG. 1 is not provided with the first diagnostic switch Sw6 and the second diagnostic switch Sw7 will be described. In such a case, in the leakage detection device 1, the charging voltage of the flying capacitor C becomes 400V unless the voltage of the battery BT is 400V and all the first to fourth diodes D1 to D4 are short-circuited.

At this time, for example, if any one of the first to fourth diodes D1 to D4 is short-circuited, the charging voltage of the flying capacitor C becomes 330V. Therefore, if the charging voltage of the flying capacitor C is higher than 330V, the microcomputer 3 can accurately diagnose that all the first to fourth diodes D1 to D4 are not short-circuited.

However, for example, when the voltage of the battery BT is 240V, one of the charging voltages of the flying capacitor C has a short failure even if all the first to fourth diodes D1 to D4 have not failed short. Even if it becomes 240V. Therefore, the microcomputer 3 cannot diagnose that any one of the first to fourth diodes D1 to D4 has a short-circuit failure.

On the other hand, the leakage detection device 1 including the first diagnostic switch Sw6 and the second diagnostic switch Sw7 can perform accurate short-circuit failure diagnosis even if the voltage of the battery BT drops to 240V.

For example, as shown in FIG. 7, in the microcomputer 3, when the voltage of the battery BT drops to 240V when the first diode D1 is short-circuited, the first diagnostic switch Sw6 is turned off and the second diagnostic switch is turned off. Turn on Sw7.

At this time, the charging voltage of the flying capacitor C is 220V unless the first diode D1 has a short-circuit failure, but since the first diode D1 has a short-circuit failure, it becomes 110V, which is the Zener voltage of the second diode D2. Be retained.

Therefore, the microcomputer 3 is accurate that if the charging voltage of the flying capacitor C is higher than 110V, the first diode D1 and the second diode D2 are not short-circuited, and if the charging voltage is not higher than 110V, the short-circuiting failure is occurring. Can be diagnosed.

As described above, according to the leakage detection device 1, for example, when the rated voltage of the battery BT is 240V to 400V, the first to first batteries BT have any voltage as long as they are within the rated voltage range. It is possible to accurately diagnose a short-circuit failure of the four diodes D1 to D4.

The earth leakage detection device 1 can also diagnose an open failure of the first diagnostic switch Sw6 and the second diagnostic switch Sw7. Next, with reference to FIG. 8, the open failure diagnosis operation of the first diagnostic switch Sw6 and the second diagnostic switch Sw7 performed by the leakage detection device 1 will be described.

As shown in FIG. 8, when performing open failure diagnosis of the first diagnostic switch Sw6 and the second diagnostic switch Sw7, the microcomputer 3 turns on both the first diagnostic switch Sw6 and the second diagnostic switch Sw7.

As a result, as shown by the thick arrow in FIG. 8, the current is transferred from the positive electrode of the battery BT to the high voltage side connection terminal B, the first protection resistor R1, the first diagnostic switch Sw6, the second diagnostic switch Sw7, and the second protective resistor. It flows in the order of R2, the low voltage side connection terminal G, and the negative electrode of the battery BT.

At this time, the current does not flow to the flying capacitor C unless the first diagnostic switch Sw6 and the second diagnostic switch Sw7 are open-failed. Therefore, the microcomputer 3 then turns off the first switch Sw1 and the second switch Sw2, and turns on the third switch Sw3 and the fourth switch Sw4.

Then, if the flying capacitor C is not charged, the microcomputer 3 diagnoses that the first diagnostic switch Sw6 and the second diagnostic switch Sw7 are not open-failed. Further, if the flying capacitor C is charged, the microcomputer 3 diagnoses that at least one of the first diagnostic switch Sw6 and the second diagnostic switch Sw7 is open-failed.

As described above, the leakage detection device 1 simply turns on the first diagnostic switch Sw6 and the second diagnostic switch Sw7 and refers to the charging voltage of the flying capacitor C, and the first diagnostic switch Sw6 and the second diagnostic switch Sw7. Can diagnose open faults.

Further effects and variations can be easily derived by those skilled in the art. For this reason, the broader aspects of the invention are not limited to the particular details and representative embodiments expressed and described as described above. Therefore, various modifications can be made without departing from the spirit or scope of the general concept of the invention as defined by the appended claims and their equivalents.

100 Leakage detection system 1 Leakage detection device 2 Differential amplifier 3 Microcomputer 10 Leakage detection circuit BT Battery Ra 1st insulation resistor Rb 2nd insulation resistor R1 1st protection resistor R2 2nd protection resistor R3 3rd protection resistor R4 4th protection resistor R5 5th protection resistor D1 1st diode D2 2nd diode D3 3rd diode D4 4th diode Sw1 1st switch Sw2 2nd switch Sw3 3rd switch Sw4 4th switch Sw5 5th switch Sw6 1st diagnostic switch Sw7 2nd diagnostic Switch B High-voltage side connection terminal G Low-voltage side connection terminal C Flying resistor

Claims (7)

A leakage detection circuit for detecting leakage from the power supply based on the resistance value of the insulation resistance that insulates between the power supply and ground, and
A plurality of series-connected constant voltage elements connected in parallel between the earth leakage detection circuit and the power supply and holding the voltage applied from the power supply to the earth leakage detection circuit at a predetermined voltage.
A plurality of switches connected in parallel to the constant voltage element to bypass the constant voltage element, and
When the switch connected in parallel to the constant voltage element not to be diagnosed is turned on and the switch connected in parallel to the constant voltage element to be diagnosed is turned off, the switch is held by the constant voltage element to be diagnosed. An electric leakage detection device including a diagnostic unit that diagnoses a short circuit failure of the constant voltage element based on the voltage. The constant voltage element is
It is a Zener diode, and is characterized in that a cathode is connected to a wiring connecting the positive electrode of the power supply and the leakage detection circuit, and an anode is connected to a wiring connecting the negative electrode of the power supply and the leakage detection circuit. The leakage detection device according to claim 1. The diagnostic unit
The second aspect of the present invention is characterized in that when the voltage held by the Zener diode to be diagnosed is less than the Zener voltage of the constant voltage element, it is diagnosed that the constant voltage element to be diagnosed has a short-circuit failure. The earth leakage detection device described. The earth leakage detection circuit is
A flying capacitor charged by a voltage applied from the power source through the insulation resistor is provided, and leakage is detected based on the charging voltage of the flying capacitor.
The diagnostic unit
When the charging voltage of the flying capacitor charged by the voltage held by the Zener diode to be diagnosed is less than the Zener voltage of the constant voltage element, it is diagnosed that the constant voltage element to be diagnosed has a short-circuit failure. The leakage detection device according to claim 3, wherein the leakage detection device is provided. The diagnostic unit
The earth leakage detection device according to claim 4, wherein when all the switches are controlled to be turned on and the flying capacitor is charged, it is diagnosed that one of the switches is open-failed. .. Power supply and
Insulation resistance that insulates between the power supply and ground,
It is equipped with an earth leakage detection device that detects an earth leakage from the power supply.
The earth leakage detection device is
An earth leakage detection circuit for detecting an earth leakage from the power source based on the resistance value of the insulation resistance, and an earth leakage detection circuit.
A plurality of series-connected constant voltage elements connected in parallel between the earth leakage detection circuit and the power supply and holding the voltage applied from the power supply to the earth leakage detection circuit at a predetermined voltage.
A plurality of switches connected in parallel to the constant voltage element to bypass the constant voltage element, and
When the switch connected in parallel to the constant voltage element not to be diagnosed is turned on and the switch connected in parallel to the constant voltage element to be diagnosed is turned off, the switch is held by the constant voltage element to be diagnosed. A leakage detection system including a diagnostic unit that diagnoses a short circuit failure of the constant voltage element based on the voltage. An earth leakage detection circuit for detecting an earth leakage from the power source based on the resistance value of the insulation resistance that insulates between the power source and the ground is connected in parallel between the earth leakage detection circuit and the power source, and from the power source. A method for diagnosing an earth leakage detection device including a plurality of series-connected constant voltage elements that hold a voltage applied to the earth leakage detection circuit at a predetermined voltage.
The diagnostic unit of the earth leakage detection device
Of the plurality of switches connected in parallel to the constant voltage element and bypass-connected to the constant voltage element, the switch connected in parallel to the constant voltage element not subject to diagnosis is turned on to connect the constant voltage element to be diagnosed. The process of turning off the switches connected in parallel and
A diagnostic method comprising a step of performing a short-circuit failure diagnosis of the constant voltage element based on a voltage held by the constant voltage element to be diagnosed.

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