Ground fault detection device

Abstract

The present application can detect a disconnection of a ground fault detection circuit generated during output operation of an output circuit. A ground fault detection device connected to an output circuit insulated from the ground, the ground fault detection device comprising: a midpoint resistor provided between a pair of output lines of the output circuit; a ground fault detection resistor provided between the midpoint resistor and the ground; an amplifier having a + input terminal connected to one end of the ground fault detection resistor and a - input terminal connected to the other end of the ground fault detection resistor; a pull-up resistor provided between the one end of the ground fault detection resistor and the + input terminal of the amplifier and connected to a positive power supply voltage; a pull-down resistor provided between the other end of the ground fault detection resistor and the - input terminal of the amplifier and connected to a negative power supply voltage; and a disconnection detection unit that detects a disconnection of the ground fault detection resistor.

Description

Technical Field

[0001] This invention relates to a grounding fault detection device. Background Technology

[0002] Patent Document 1 discloses a technique in which, in the event that a closed loop is formed between a ground fault detection unit and a short circuit detection unit, and the combination of an alternating current flowing through the closed loop may lead to false detection of a ground fault or a short circuit, one of the ground fault detection unit and the short circuit detection unit is disconnected from the ground wire to prevent the formation of a closed loop.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2010-239773 Summary of the Invention

[0004] However, in the technology of Patent Document 1, if the ground fault detection circuit is disconnected during charging (when no ground fault occurs), the ground fault current will not flow through the ground fault detection circuit, so the disconnection of the ground fault detection circuit cannot be detected. Therefore, in the technology of Patent Document 1, in order to detect the disconnection of the ground fault detection circuit, a ground fault needs to be deliberately generated before charging to diagnose whether the ground fault detection unit is working properly.

[0005] To address the aforementioned issues, one embodiment of the ground fault detection device is connected to an output circuit insulated relative to the ground. This ground fault detection device includes: a midpoint resistor disposed between a pair of output lines in the output circuit; a ground fault detection resistor disposed between the midpoint resistor and the ground; an amplifier having a + input terminal connected to one end of the ground fault detection resistor and a - input terminal connected to the other end of the ground fault detection resistor; a pull-up resistor disposed between one end of the ground fault detection resistor and the + input terminal of the amplifier, and connected to a positive power supply voltage; a pull-down resistor disposed between the other end of the ground fault detection resistor and the - input terminal of the amplifier, and connected to a negative power supply voltage; and a disconnection detection unit that detects a disconnection in the ground fault detection resistor by detecting the positive and negative power supply voltages input to the input terminals of the amplifier via the pull-up and pull-down resistors.

[0006] Therefore, the ground fault detection device according to one embodiment can easily and reliably detect the break in the ground fault detection circuit even during the output operation of the output circuit by increasing the voltage between the input terminals of the amplifier.

[0007] In one embodiment of the ground fault detection device, the open circuit detection unit can detect an open circuit in the ground fault detection resistor when the voltage of the amplifier's output signal is above a predetermined threshold.

[0008] Therefore, the ground fault detection device according to one embodiment can easily and reliably detect the open circuit of the ground fault detection circuit that occurs during the output operation of the output circuit by simply comparing the voltage of the amplifier's output signal with a predetermined threshold.

[0009] Furthermore, the ground fault detection device according to one embodiment may also include: an A / D converter that performs A / D conversion on the output signal of the amplifier, and a disconnection detection unit that can detect the disconnection of the ground fault detection resistor when the voltage of the output signal of the amplifier is higher than the allowable voltage range of the A / D converter.

[0010] Therefore, the ground fault detection device according to one embodiment can easily and reliably detect the open circuit of the ground fault detection circuit that occurs during the output operation of the output circuit by significantly increasing the detection voltage of the A / D converter.

[0011] Furthermore, in one embodiment, the ground fault detection device may also include an A / D converter that performs A / D conversion on the output signal of an amplifier, and the disconnection detection unit can determine multiple states of the ground fault detection device, including the disconnection of the ground fault detection resistor, based on the detection voltage of the amplifier output based on the A / D converter.

[0012] Therefore, the ground fault detection device according to one embodiment can easily distinguish multiple faults based on the detection voltage of the amplifier output based on the A / D converter.

[0013] Invention Effects

[0014] According to one embodiment of the ground fault detection device, a ground fault detection circuit breakage that occurs during the output operation of the output circuit can be detected. Attached Figure Description

[0015] Figure 1 This is a diagram illustrating the structure of a power supply system according to one embodiment. Detailed Implementation

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0017] (Structure of power supply system 1)

[0018] Figure 1 This is a diagram illustrating the structure of a power supply system 1 according to one embodiment. (See diagram for example.) Figure 1 As shown, the power supply system 1 includes an output circuit 10 and a ground fault detection device 100.

[0019] The output circuit 10 includes a power converter 11, an insulation resistor 12, a + power supply line 13, a - power supply line 14, an output terminal Positive, and an output terminal Negative. The output circuit 10 supplies the power output from the power converter 11 to the target device (not shown) connected to the output terminal Positive and the output terminal Negative via the + power supply line 13 and the - power supply line 14.

[0020] As an example, output circuit 10 is a charging circuit that charges the target device by supplying power to the target device. In this case, the target device can be, for example, various electric vehicles (Hybrid Electric Vehicle (HEV), Plug-in Hybrid Electric Vehicle (PHEV), Fuel Cell Electric Vehicle (FCEV), Battery Electric Vehicle (BEV), etc.) or batteries used in various electric vehicles.

[0021] + Power supply line 13 is the output line (power supply line) connecting the power converter 11 and the output terminal Positive. - Power supply line 14 is the output line (power supply line) connecting the power converter 11 and the output terminal Negative.

[0022] Insulation resistor 12 is connected between power converter 11 and the two output terminals. Insulation resistor 12 has a resistance rp and a resistance rn. One end of insulation resistor rp is connected to the positive power supply line 13 between power converter 11 and the output terminal Positive, and the other end is grounded. One end of insulation resistor rn is connected to the negative power supply line 14 between power converter 11 and the output terminal Negative, and the other end is grounded. The output circuit 10 is insulated from ground, but small leakage currents may occur. Insulation resistor 12 insulates against such leakage currents and other currents inherent to the device.

[0023] In addition, such as Figure 1 As shown, when a ground fault occurs, the output circuit 10 forms a ground fault path with a ground fault resistance Rfault between the + power supply line 13 and the ground.

[0024] like Figure 1 As shown, the ground fault detection device 100 is connected to the output circuit 10 (between the power converter 11 and the two output terminals).

[0025] The ground fault detection device 100 includes, in sequence from the output circuit 10 side, a midpoint resistor 101, a ground fault detection resistor Rs, a filter unit 102, a pull-up resistor Rpu, a pull-down resistor Rpd, an amplifier AMP, a protection circuit 103, an A / D converter 104, an insulation unit 105, and a control unit 106.

[0026] A midpoint resistor 101 is positioned between the positive power supply line 13 and the negative power supply line 14 of the output circuit 10 (i.e., between a pair of output lines). The midpoint resistor 101 has a structure where resistors Rp and Rn are connected in series. One end of resistor Rp is connected to the positive power supply line 13. One end of resistor Rn is connected to the negative power supply line 14. The other ends of resistors Rp and Rn are connected to each other.

[0027] The ground fault detection resistor Rs is a shunt resistor placed between the midpoint resistor 101 (the connection point between the other end of resistor Rp and the other end of resistor Rn) and the ground. The ground fault detection resistor Rs is configured to detect ground fault current. In the event of a ground fault in the output circuit 10, most of the ground fault current flows through the ground fault detection resistor Rs. Therefore, the ground fault detection device 100 can detect the ground fault current by measuring the voltage across the ground fault detection resistor.

[0028] Furthermore, the ground fault current Ileak is represented by the following equation (1). Here, R is assumed to be resistance Rp = resistance Rn. Also, the insulation resistances rp and rn are assumed to be sufficiently large and negligible.

[0029] Ileak=E / (R+2Rs+2Rfault) · · · (1)

[0030] In addition, Figure 1 In the example shown, the ground fault detection resistor Rs has a structure of two resistors connected in series, but it is not limited to this. For example, the ground fault detection resistor Rs can be a ground fault detection resistor with one resistor, or a ground fault detection resistor with a structure of three or more resistors connected in series. Furthermore, for example, the ground fault detection resistor Rs can be a structure of multiple resistors connected in series and then connected in parallel.

[0031] The filter unit 102 is arbitrarily disposed between the ground fault detection resistor Rs and the amplifier AMP. For example, a low-pass filter (LPF) for removing high-frequency noise and common-mode noise is used as the filter unit 102.

[0032] The amplifier AMP is connected to the ground fault detection resistor Rs via the filter section 102, amplifying the ground fault current detected by the ground fault detection resistor Rs (the ground fault current after filtering by the filter section 102). The amplifier AMP has a + input terminal connected to one end of the ground fault detection resistor Rs via the filter section 102 and a - input terminal connected to the other end of the ground fault detection resistor Rs via the filter section 102.

[0033] One end of the pull-up resistor Rpu is connected between the + output terminal of the filter section 102 and the + input terminal of the amplifier AMP, and the other end is connected to the positive power supply voltage Vcc.

[0034] One end of the pull-down resistor Rpd is connected between the -output terminal of the filter section 102 and the -input terminal of the amplifier AMP, and the other end is connected to the negative power supply voltage Vee.

[0035] Protection circuit 103 is located after amplifier AMP. When the output signal of amplifier AMP is input to A / D converter 104, protection circuit 103 protects the output signal of amplifier AMP to prevent A / D converter 104 from being damaged due to overvoltage. As protection circuit 103, for example, a clamping circuit with resistors and diodes is used.

[0036] The A / D converter 104 is located after the protection circuit 103. The A / D converter 104 converts the analog signal output from the amplifier AMP (the analog signal after protection processing by the protection circuit 103) into a digital signal.

[0037] The insulating part 105 is arbitrarily provided at the front end of the control part 106. For example, the insulating part 105 insulates the control part 106 from the protection circuit 103.

[0038] The control unit 106 is located at the rear of the insulation unit 105. It performs various controls within the ground fault detection device 100. For example, the control unit 106 performs a disconnection detection process to detect a break in the ground fault detection resistor Rs based on the output signal of the amplifier AMP. In other words, the control unit 106 functions as a "disconnection detection unit." The control unit 106 may be, for example, a microcontroller or a field-programmable gate array (FPGA).

[0039] (Operation of the ground fault detection device 100)

[0040] The operation of the ground fault detection device 100 will be explained below.

[0041] When no ground fault occurs in the output circuit 10, the ground fault resistance Rfault = ∞, so the ground fault current Ileak in the ground fault detection device 100 is almost zero according to the above equation (1). Therefore, in this case, even in the pull-up resistor Rpu and the pull-down resistor Rpd, the voltage between the two ends of the ground fault detection resistor Rs and the voltage between the two input terminals of the amplifier AMP are almost zero in the ground fault detection device 100.

[0042] In the ground fault detection device 100, when no ground fault occurs to the ground in the output circuit 10, when the ground fault detection resistor Rs is disconnected, the positive power supply voltage Vcc and the negative power supply voltage Vee are input to the two input terminals of the amplifier AMP via the pull-up resistor Rpu and the pull-down resistor Rpd. In this case, the voltage between the input terminals of the amplifier AMP becomes the positive power supply voltage Vcc minus the negative power supply voltage Vee, therefore the output voltage of the amplifier AMP is greater than when it is stable (i.e., when the ground fault detection resistor Rs is disconnected).

[0043] Therefore, in the ground fault detection device 100 according to one embodiment, the control unit 106 can detect the ground fault detection resistor Rs being disconnected when the output voltage of the detection amplifier AMP increases (i.e., becomes higher than a predetermined threshold).

[0044] Therefore, the ground fault detection device 100 according to one embodiment can detect the break in the ground fault detection resistor R generated during the output operation of the output circuit 10 (i.e., when the output circuit 10 does not have a ground fault with the earth).

[0045] Therefore, in the ground fault detection device 100 according to one embodiment, it is not necessary to diagnose the ground fault detection resistor Rs by intentionally causing a ground fault to the ground in the output circuit 10 before the output of the output circuit 10 is turned on.

[0046] In addition, in one embodiment of the ground fault detection device 100, not only when the ground fault detection resistor Rs is broken, but also when the peripheral part of the ground fault detection resistor Rs is broken (the break between the ground fault detection resistor Rs and the pull-up resistor Rpu and the elasticity between the ground fault detection resistor Rs and the pull-down resistor Rpd), the positive power supply voltage Vcc and the negative power supply voltage Vee are input to the two input terminals of the amplifier AMP, and the output voltage of the amplifier AMP increases compared to when it is stable. Therefore, the break can be detected by the control unit 106.

[0047] (Modified Example)

[0048] In one embodiment of the ground fault detection device 100, the control unit 106 can detect the ground fault detection resistor Rs being disconnected by setting the output voltage of the amplifier AMP when the ground fault detection resistor Rs is disconnected to be higher than the allowable voltage range of the A / D converter 104.

[0049] Alternatively, in one embodiment of the ground fault detection device 100, the control unit 106 can detect the ground fault detection resistor Rs being disconnected by setting the output voltage of the amplifier AMP when the ground fault detection resistor Rs is disconnected to be within the allowable voltage range of the A / D converter 104 and above a predetermined threshold.

[0050] Furthermore, for example, in the ground fault detection device 100 according to one embodiment, the control unit 106 can also determine multiple states of the ground fault detection device 100 (including at least the disconnection of the ground fault detection resistor Rs) based on the detection voltage of the amplifier AMP based on the A / D converter 104.

[0051] For example, it can be configured such that the detection voltage of the amplifier AMP based on the A / D converter 104 when a ground fault occurs in the output circuit 10 is set to 50% or less of the maximum value of the allowable voltage range of the A / D converter 104; the detection voltage of the amplifier AMP based on the A / D converter 104 when the ground fault detection resistor Rs is disconnected is set to 80% of the maximum value of the allowable voltage range of the A / D converter 104; and the detection voltage of the amplifier AMP based on the A / D converter 104 when a fault occurs is set to 100% of the maximum value of the allowable voltage range of the A / D converter 104. In this way, the control unit 106 can determine multiple states of the ground fault detection device 100 based on the detection voltage of the A / D converter 104.

[0052] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to these embodiments. Various modifications or alterations can be made within the scope of the spirit of the present invention as set forth in the claims.

[0053] For example, the present invention can be preferably used in charging devices for charging electric vehicles, but is not limited thereto. For example, the present invention can also be applied to charging devices for charging other target devices, devices other than charging devices (at least devices that supply power to the target devices), etc.

[0054] Symbol Explanation

[0055] 1-Power supply system, 10-Output circuit, 11-Power converter, 12-Insulation resistance, rp-Resistor, rn-Resistor, 13-+Power supply line, 14--Power supply line, Positive-Output terminal, Negative-Output terminal, Rfault-Ground fault resistor, 100-Ground fault detection device, 101-Midpoint resistor, Rp-Resistor, Rn-Resistor, Rs-Ground fault detection resistor, 102-Filter section, Rpu-Pull-up resistor, Rpd-Pull-down resistor, AMP-Amplifier, 103-Protection circuit, 104-A / D converter, 105-Insulation section, 106-Control section.

Claims

1. A ground fault detection device connected to an output circuit insulated relative to the earth, characterized in that it comprises: A midpoint resistor is provided between a pair of output lines of the output circuit; A ground fault detection resistor is provided between the midpoint resistor and the ground; An amplifier having a + input terminal connected to one end of the ground fault detection resistor and a - input terminal connected to the other end of the ground fault detection resistor; A pull-up resistor is provided between one end of the ground fault detection resistor and the + input terminal of the amplifier, and is connected to the positive power supply voltage; A pull-down resistor is provided between the other end of the ground fault detection resistor and the -input terminal of the amplifier, and is connected to the negative power supply voltage; and The open circuit detection unit detects the open circuit of the ground fault detection resistor by detecting the positive power supply voltage and the negative power supply voltage input to the input terminal of the amplifier via the pull-up resistor and the pull-down resistor.

2. The grounding fault detection device according to claim 1, characterized in that, The open circuit detection unit detects the open circuit in the ground fault detection resistor when the voltage of the amplifier's output signal is above a predetermined threshold.

3. The ground fault detection device of claim 1, wherein, It also has: An A / D converter performs A / D conversion on the output signal of the amplifier. The open circuit detection unit detects the open circuit in the ground fault detection resistor when the voltage of the amplifier's output signal is higher than the allowable voltage range of the A / D converter.

4. The ground fault detection device of claim 1, wherein, It also has: An A / D converter performs A / D conversion on the output signal of the amplifier. The open circuit detection unit determines multiple states of the ground fault detection device, including the open circuit detection resistor, based on the detection voltage of the amplifier output from the A / D converter.

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