Ground fault detection device
The ground fault detection device addresses the challenge of detecting circuit disconnections by using a resistor network and amplifier to monitor voltage changes, ensuring reliable fault detection without requiring intentional ground faults.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TOYOTA JIDOSHA KK
- Filing Date
- 2024-12-23
- Publication Date
- 2026-07-03
AI Technical Summary
Existing ground fault detection technologies fail to detect disconnections in the ground fault detection circuit during charging operations due to the absence of ground fault current flow, necessitating intentional ground faults for diagnosis.
A ground fault detection device with a midpoint resistor, ground fault detection resistor, pull-up and pull-down resistors, amplifier, and disconnection detection unit, which detects disconnections by monitoring voltage changes at the amplifier inputs, even during normal operation.
The device reliably detects breaks in the ground fault detection circuit by identifying voltage increases at the amplifier terminals, eliminating the need for intentional ground faults and enabling real-time fault detection.
Smart Images
Figure 2026111223000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a ground fault detection device.
Background Art
[0002] In Patent Document 1 below, when a closed loop is formed between a ground fault detection unit and a short circuit detection unit and there is a combination that may erroneously detect a ground fault or a short circuit from the alternating current flowing therethrough, one of the ground fault detection unit and the short circuit detection unit is disconnected from the ground to prevent the formation of a closed loop.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] However, in the technology of Patent Document 1, when the ground fault detection circuit is disconnected during the charging operation (when no ground fault occurs), since the ground fault current does not flow through the ground fault detection circuit, it is impossible to detect the disconnection of the ground fault detection circuit. For this reason, in order to detect the disconnection of the ground fault detection circuit in the technology of Patent Document 1, it was necessary to intentionally cause a ground fault before the charging operation to diagnose whether the ground fault detection unit operates normally.
Means for Solving the Problems
[0005] [[ID=4第1]] To solve the above-mentioned problems, a ground fault detection device according to one embodiment is a ground fault detection device connected to an output circuit insulated from the earth, and comprises 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 earth, 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 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 the disconnection of the ground fault detection resistor by detecting that the ground fault detection resistor is disconnected and that the positive power supply voltage and the negative power supply voltage are input to the input terminal of the amplifier via the pull-up resistor and the pull-down resistor.
[0006] As a result, the ground fault detection device according to one embodiment can easily and reliably detect a break in the ground fault detection circuit by detecting an increase in the voltage between the input terminals of the amplifier, even while the output circuit is operating.
[0007] In one embodiment of the ground fault detection device, the wire break detection unit may detect a wire break in the ground fault detection resistor when the voltage of the output signal of the amplifier is above a predetermined threshold.
[0008] As a result, the ground fault detection device according to one embodiment can easily and reliably detect a break in the ground fault detection circuit that occurred 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, in a ground fault detection device according to one embodiment, an A / D converter is further provided to perform A / D conversion of the output signal of the amplifier, and the wire break detection unit may detect a wire break in 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] As a result, the ground fault detection device according to one embodiment can easily and reliably detect a break in the ground fault detection circuit that occurred during the output operation of the output circuit by noticing a clear increase in the detection voltage of the A / D converter.
[0011] Furthermore, in a ground fault detection device according to one embodiment, an A / D converter is further provided to perform A / D conversion of the output signal of the amplifier, and the wire break detection unit may determine a plurality of states of the ground fault detection device, including a wire break in the ground fault detection resistor, according to the detected voltage of the output of the amplifier by the A / D converter.
[0012] As a result, the ground fault detection device according to one embodiment can easily differentiate between multiple faults based on the detection voltage of the output of the amplifier by the A / D converter. [Effects of the Invention]
[0013] According to one embodiment of the ground fault detection device, it is possible to detect a break in the ground fault detection circuit that occurs during the output operation of the output circuit. [Brief explanation of the drawing]
[0014] [Figure 1] A diagram showing the configuration of a power supply system according to one embodiment. [Modes for carrying out the invention]
[0015] One embodiment of the present invention will be described below with reference to the drawings.
[0016] (Configuration of power supply system 1) Figure 1 shows the configuration of a power supply system 1 according to one embodiment. As shown in Figure 1, the power supply system 1 includes an output circuit 10 and a ground fault detection device 100.
[0017] The output circuit 10 comprises 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 equipment (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.
[0018] As an example, the output circuit 10 is a charging circuit that charges a target device by supplying power to the target device. In this case, examples of the target device include various electric vehicles (such as HEV (Hybrid Electric Vehicle), PHEV (Plug-in Hybrid Electric Vehicle), FCEV (Fuel Cell Electric Vehicle), BEV (Battery Electric Vehicle), etc.), or batteries used in various electric vehicles, and the like.
[0019] The + power supply line 13 is an output line (power supply line) that connects between the power converter 11 and the output terminal Positive. The - power supply line 14 is an output line (power supply line) that connects between the power converter 11 and the output terminal Negative.
[0020] The insulation resistance 12 is connected between the power converter 11 and the two output terminals. The insulation resistance 12 has a resistance rp and a resistance rn. One end of the insulation resistance rp is connected to the + power supply line 13 between the power converter 11 and the output terminal Positive, and the other end is grounded to the ground. One end of the insulation resistance rn is connected to the - power supply line 14 between the power converter 11 and the output terminal Negative, and the other end is grounded to the ground. Although the output circuit 10 is insulated from the ground, there is a possibility that a slight leakage current or the like may occur. The insulation resistance 12 insulates such equipment-specific currents such as leakage current.
[0021] As shown in FIG. 1, when a ground fault occurs, the output circuit 10 forms a ground fault route having a ground fault resistance Rfault between the + power supply line 13 and the ground.
[0022] As shown in FIG. 1, the ground fault detection device 100 is connected to the output circuit 10 (between the power converter 11 and the two output terminals). The ground fault detection device 100 includes, in order from the output circuit 10 side, a midpoint resistor 101, a ground fault detection resistor Rs, a filter section 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 section 105, and a control section 106.
[0023] The midpoint resistor 101 is provided between the + power supply line 13 and the - power supply line 14 (i.e., between a pair of output lines) that the output circuit 10 has. The midpoint resistor 101 has a configuration in which a resistor Rp and a resistor Rn are connected in series. One end of the resistor Rp is connected to the + power supply line 13. One end of the resistor Rn is connected to the - power supply line 14. The other end of the resistor Rp and the other end of the resistor Rn are connected to each other.
[0024] The ground fault detection resistor Rs is a shunt resistor provided between the midpoint resistor 101 (the connection point of the other end of the resistor Rp and the other end of the resistor Rn) and the ground. The ground fault detection resistor Rs is provided to detect a ground fault current. When a ground fault occurs 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 between both ends of the ground fault detection resistor.
[0025] Note that the ground fault current Ileak is expressed by the following formula (1). However, let R = resistor Rp = resistor Rn. Also, assume that the insulation resistors rp and rn are sufficiently large and can be ignored.
[0026] Ileak = E / (R + 2Rs + 2Rfault) ··· (1)
[0027] In the example shown in FIG. 1, the ground fault detection resistor Rs has a configuration in which two resistors are connected in series, but it is not limited to this. For example, the ground fault detection resistor Rs may have one resistor or a configuration in which three or more resistors are connected in series. Also, for example, the ground fault detection resistor Rs may have a configuration in which a plurality of configurations in which a plurality of resistors are connected in series are connected in parallel.
[0028] The filter section 102 can be optionally provided between the ground fault detection resistor Rs and the amplifier AMP. For example, a low-pass filter (LPF) that removes high-frequency noise and common-mode noise may be used as the filter section 102.
[0029] The amplifier AMP is connected to the ground fault detection resistor Rs via the filter unit 102 and amplifies the ground fault current detected by the ground fault detection resistor Rs (the ground fault current after filtering by the filter unit 102). The amplifier AMP has a + input terminal connected to one end of the ground fault detection resistor Rs via the filter unit 102 and a - input terminal connected to the other end of the ground fault detection resistor Rs via the filter unit 102.
[0030] The pull-up resistor Rpu has one end connected between the + output terminal of the filter section 102 and the + input terminal of the amplifier AMP, and the other end connected to the positive power supply voltage Vcc.
[0031] The pull-down resistor Rpd has one end connected between the negative output terminal of the filter section 102 and the negative input terminal of the amplifier AMP, and the other end connected to the negative power supply voltage Vee.
[0032] The protection circuit 103 is located after the amplifier AMP. When the output signal of the amplifier AMP is input to the A / D converter 104, the protection circuit 103 performs protection processing on the output signal of the amplifier AMP to prevent the A / D converter 104 from being damaged by overvoltage. For example, a clamp circuit having a resistor and a diode can be used as the protection circuit 103.
[0033] 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.
[0034] The insulating section 105 can be optionally provided before the control unit 106. For example, the insulating section 105 isolates the control unit 106 from the protection circuit 103.
[0035] The control unit 106 is located downstream of the insulation unit 105. It performs various controls in the ground fault detection device 100. For example, the control unit 106 performs a disconnection detection process to detect when the ground fault detection resistor Rs is disconnected, based on the output signal of the amplifier AMP. In other words, the control unit 106 functions as a "disconnection detection unit". For example, a microcontroller, FPGA (Field Programmable Gate Array), etc., can be used as the control unit 106.
[0036] (Operation of ground fault detection device 100) The operation of the ground fault detection device 100 will be described below.
[0037] When the output circuit 10 is not grounded, the ground fault resistance Rfault = ∞, and therefore the ground fault current Ileak in the ground fault detection device 100 is approximately zero according to equation (1) above. Consequently, in this case, despite the presence of pull-up resistors Rpu and pull-down resistors Rpd in the ground fault detection device 100, the voltage across the ground fault detection resistor Rs and the voltage between the two input terminals of the amplifier AMP are approximately zero.
[0038] In the ground fault detection device 100, when the output circuit 10 is not grounded, and a break occurs in the ground fault detection resistor Rs, 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 across the input terminals of the amplifier AMP becomes the positive power supply voltage Vcc minus the negative power supply voltage Vee, so the output voltage of the amplifier AMP increases compared to the steady state (i.e., when the ground fault detection resistor Rs is not broken).
[0039] Therefore, in one embodiment of the ground fault detection device 100, the control unit 106 can detect that the ground fault detection resistor Rs has been broken by detecting that the output voltage of the amplifier AMP has increased (i.e., has become higher than a predetermined threshold).
[0040] Therefore, according to the ground fault detection device 100 of one embodiment, it is possible to detect a break in the ground fault detection resistor R that occurs during the output operation of the output circuit 10 (i.e., when the output circuit 10 is not grounded).
[0041] Therefore, in one embodiment of the ground fault detection device 100, it is not necessary to diagnose the ground fault detection resistance Rs by intentionally causing a ground fault in the output circuit 10 to the ground before the output operation of the output circuit 10.
[0042] In one embodiment, the ground fault detection device 100 can detect not only a break in the ground fault detection resistor Rs, but also a break in the peripheral part of the ground fault detection resistor Rs (a break between the ground fault detection resistor Rs and the pull-up resistor Rpu, and a break in the elasticity between the ground fault detection resistor Rs and the pull-down resistor Rpd). In such cases, 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 above the steady state, allowing the control unit 106 to detect the break.
[0043] (modified version) In one embodiment of the ground fault detection device 100, the output voltage of the amplifier AMP when the ground fault detection resistor Rs is disconnected may be set higher than the allowable voltage range of the A / D converter 104 so that the control unit 106 can detect that the ground fault detection resistor Rs is disconnected.
[0044] Alternatively, in the ground fault detection device 100 according to one embodiment, the output voltage of the amplifier AMP when the ground fault detection resistor Rs is disconnected may be set to be within the allowable voltage range of the A / D converter 104 and above a predetermined threshold, so that the control unit 106 can detect that the ground fault detection resistor Rs is disconnected.
[0045] Furthermore, for example, in the ground fault detection device 100 according to one embodiment, the control unit 106 may be configured to determine a plurality of states of the ground fault detection device 100 (however, including at least a break in the ground fault detection resistor Rs) in accordance with the detection voltage of the output of the amplifier AMP by the A / D converter 104.
[0046] For example, the control unit 106 may be configured such that the detection voltage of the amplifier AMP by the A / D converter 104 when a ground fault occurs in the output circuit 10 is set to 50% or less of the maximum allowable voltage range of the A / D converter 104, the detection voltage of the amplifier AMP by the A / D converter 104 when the ground fault detection resistor Rs is broken is set to 80% of the maximum allowable voltage range of the A / D converter 104, and the detection voltage of the amplifier AMP by the A / D converter 104 when the A / D converter 104 fails is set to 100% of the maximum allowable voltage range of the A / D converter 104, thereby enabling the control unit 106 to distinguish between multiple states of the ground fault detection device 100 according to the detection voltage of the A / D converter 104.
[0047] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to these embodiments, and various modifications or changes are possible within the scope of the gist of the invention as described in the claims.
[0048] For example, the present invention can be suitably used in a charging device for electric vehicles, but is not limited to this. For example, the present invention can also be applied to charging devices for other target devices, devices other than charging devices (at least those that supply power to target devices), and so on. [Explanation of Symbols]
[0049] 1. Power supply system 10 Output Circuit 11 Power Converters 12. Insulation resistance rp resistance rn resistance 13 + power supply line 14 - Power supply line Positive output terminal Negative output terminal Rfault (Ground Fault Resistance) 100 Ground fault detection device 101 Midpoint Resistor Rp resistance Rn resistance 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 part 106 Control Unit
Claims
1. A ground fault detection device connected to an output circuit insulated from the earth, A midpoint resistor is provided between the pair of output lines of the output circuit, A ground fault detection resistor is provided between the aforementioned 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 negative input terminal of the amplifier, and is connected to the negative power supply voltage. A disconnection detection unit detects the disconnection of the ground fault detection resistor by detecting that the ground fault detection resistor is disconnected and that the positive power supply voltage and the negative power supply voltage are input to the input terminal of the amplifier via the pull-up resistor and the pull-down resistor. A ground fault detection device characterized by comprising the following features.
2. The wire break detection unit is, If the voltage of the output signal of the amplifier is above a predetermined threshold, the disconnection of the ground fault detection resistor is detected. The ground fault detection device according to claim 1.
3. The system further comprises an A / D converter for performing A / D conversion on the output signal of the amplifier, The wire break detection unit is, If the voltage of the output signal of the amplifier is higher than the allowable voltage range of the A / D converter, the ground fault detection resistor is detected to be open. The ground fault detection device according to claim 1.
4. The system further comprises an A / D converter for performing A / D conversion on the output signal of the amplifier, The wire break detection unit is, Depending on the detection voltage of the output of the amplifier by the A / D converter, the ground fault detection device determines a plurality of states, including the open circuit of the ground fault detection resistor. The ground fault detection device according to claim 1.