Fault detection circuit for a gfi and an inverter

Abstract

The application discloses a fault detection circuit and an inverter of a GFCI. The GFCI comprises an oscillation circuit, and the oscillation circuit outputs an oscillation signal when the GFCI is in operation. The fault detection circuit of the GFCI comprises a frequency selection circuit and a controller. The frequency selection circuit outputs the oscillation signal when the frequency of the oscillation signal is in a first preset frequency range, or stops outputting the oscillation signal when the frequency of the oscillation signal is not in the first preset frequency range. The controller determines that the GFCI is not faulty when the oscillation signal is received, and determines that the GFCI is faulty when the oscillation signal is not received. In this way, whether the GFCI is faulty can be accurately detected.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a fault detection circuit and inverter for GFCI. Background Technology

[0002] For non-isolated grid-connected inverters, continuous grounding leakage current detection is required to protect product safety and personal safety.

[0003] Currently, two main technical solutions are used to achieve leakage current detection: the first is based on a dedicated integrated leakage current detection chip in conjunction with peripheral circuits. This solution has high integration and fast response, but the chip cost is high and the supply of some components is limited, which is not conducive to the overall cost control. The second is to use a self-designed flux transformer in conjunction with discrete components to build a detection circuit. Although it has certain advantages in material cost, it lacks a complete fault self-checking mechanism. Summary of the Invention

[0004] This application provides a fault detection circuit and inverter for a GFCI, which can accurately detect whether a fault has occurred in the GFCI.

[0005] In a first aspect, embodiments of this application provide a fault detection circuit for a GFCI (GFine Cycle Interchange). The GFCI includes an oscillation circuit that outputs an oscillation signal during operation. The fault detection circuit for the GFCI includes: a frequency selection circuit that receives the oscillation signal and is configured to output the oscillation signal when the frequency of the oscillation signal is within a first preset frequency range, or to stop outputting the oscillation signal when the frequency of the oscillation signal is not within the first preset frequency range; and a controller electrically connected to the frequency selection circuit and configured to determine that the GFCI is not faulty when the oscillation signal is received, and to determine that the GFCI is faulty when the oscillation signal is not received.

[0006] In one or more embodiments, the fault detection circuit of the GFCI further includes a level generation circuit electrically connected to the frequency selection circuit. The level generation circuit is configured to output a first level signal when an oscillation signal is received, or to output a second level signal when no oscillation signal is received. A controller is electrically connected to the level generation circuit and is configured to determine that the GFCI is not faulty when the first level signal is received, and to determine that the GFCI is faulty when the second level signal is received.

[0007] In one or more embodiments, the level generation circuit includes: a shaping circuit electrically connected to a frequency selection circuit, a first power supply, and ground, configured to output a third level signal based on the first power supply when an oscillation signal is received, and to output a fourth level signal based on ground when no oscillation signal is received; and a level conversion circuit electrically connected to the shaping circuit, a controller, and a second power supply, configured to output a first level signal based on the second power supply when the third level signal is received, and to output a second level signal based on the fourth level signal when the fourth level signal is received, wherein the voltage of the second power supply is the same as the supply voltage of the controller.

[0008] In one or more embodiments, the shaping circuit includes a first switching circuit and a second switching circuit; the first switching circuit is electrically connected to a frequency selection circuit, a third power supply, and ground, and is configured to turn on when an oscillation signal is received, so that the connection node between the first switching circuit and the second switching circuit is electrically connected to ground, or to turn off when no oscillation signal is received, so that the connection node is electrically connected to the third power supply; the second switching circuit is electrically connected to the first switching circuit, the first power supply, ground, and a level conversion circuit, and is configured to turn off when the connection node is electrically connected to ground, so as to output a third level signal to the level conversion circuit based on the first power supply, or to turn on when the connection node is electrically connected to the third power supply, so as to output a fourth level signal to the level conversion circuit based on ground.

[0009] In one or more embodiments, the level conversion circuit includes a unidirectional conductive circuit, a pull-up circuit, and a filter circuit; the unidirectional conductive circuit is electrically connected to the shaping circuit, the pull-up circuit, and the filter circuit, and is configured to be turned off when a third level signal is received, or to be turned on when a fourth level signal is received, so as to output a second level signal based on the fourth level signal; the pull-up circuit is electrically connected to a second power supply, and is configured to output a first level signal based on the second power supply when the unidirectional conductive circuit is turned off; the filter circuit is electrically connected to a controller, and is configured to filter the first level signal or the second level signal and then output it to the controller.

[0010] In one or more embodiments, the frequency selection circuit includes a first resistor, a second resistor, a first capacitor, and a second capacitor; the first terminal of the first capacitor receives an oscillation signal, the second terminal of the first capacitor is electrically connected to the first terminal of the first resistor and the first terminal of the second resistor, the second terminal of the second resistor is electrically connected to the level generation circuit and the first terminal of the second capacitor, and the second terminals of the first resistor and the second terminal of the second capacitor are both electrically connected to ground.

[0011] In one or more embodiments, the first switching circuit includes a first switching transistor, a first diode, a third resistor, a fourth resistor, a fifth resistor, a third capacitor, and a fourth capacitor; the anode of the first diode is electrically connected to a frequency selection circuit, the cathode of the first diode is electrically connected to a first terminal of the third resistor, the second terminal of the third resistor is electrically connected to a first terminal of the fourth resistor, a first terminal of the third capacitor, and a first terminal of the first switching transistor, the third terminal of the first switching transistor is electrically connected to a first terminal of the fifth resistor, a first terminal of the fourth capacitor, and a second switching circuit, the second terminal of the fifth resistor is electrically connected to a third power supply, and the second terminals of the fourth resistor, the third capacitor, the first switching transistor, and the fourth capacitor are all electrically connected to ground.

[0012] In one or more embodiments, the second switching circuit includes a second switching transistor, a sixth resistor, a seventh resistor, an eighth resistor, a fifth capacitor, and a sixth capacitor; the first terminal of the sixth resistor is electrically connected to the first switching circuit, the second terminal of the sixth resistor is electrically connected to the first terminal of the seventh resistor, the first terminal of the fifth capacitor, and the first terminal of the second switching transistor, the third terminal of the second switching transistor is electrically connected to the first terminal of the eighth resistor, the first terminal of the sixth capacitor, and a level conversion circuit, the second terminal of the eighth resistor is electrically connected to the first power supply, and the second terminals of the seventh resistor, the fifth capacitor, the second switching transistor, and the sixth capacitor are all electrically connected to ground.

[0013] In one or more embodiments, the unidirectional conductive circuit includes a second diode; the anode of the second diode is electrically connected to a pull-up circuit and a filter circuit, and the cathode of the second diode is electrically connected to a shaping circuit.

[0014] In one or more embodiments, the pull-up circuit includes a ninth resistor; the first end of the ninth resistor is electrically connected to a second power supply, and the second end of the ninth resistor is electrically connected to a unidirectional conductive circuit and a filter circuit.

[0015] In one or more embodiments, the filter circuit includes a tenth resistor and a seventh capacitor; the first end of the tenth resistor is electrically connected to a unidirectional conductive circuit and a pull-up circuit, the second end of the tenth resistor is electrically connected to the first end of the seventh capacitor and a controller, and the second end of the seventh capacitor is electrically connected to ground.

[0016] Secondly, embodiments of this application provide an inverter including a GFCI and a fault detection circuit for the GFCI as described in the first aspect.

[0017] The beneficial effects of this application are as follows: The fault detection circuit of the GFCI in this embodiment includes a frequency selection circuit and a controller. When the target circuit is not faulty, the frequency of the oscillation signal is within a first preset frequency range. The frequency selection circuit outputs the oscillation signal to the controller, which receives the oscillation signal and determines that the target circuit is not faulty. When the target circuit is faulty, the frequency of the oscillation signal is not within the first preset frequency range. The frequency selection circuit stops outputting the oscillation signal to the controller, and the controller does not receive the oscillation signal and determines that the target circuit is faulty. In this way, accurate detection of whether the GFCI is faulty is achieved. Attached Figure Description

[0018] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are not intended to limit the embodiments, and elements having the same reference numerals in the drawings are designated as similar elements.

[0019] Figure 1 This is a schematic diagram of the GFCI fault detection circuit provided in the embodiments of this application. Figure 1 ;

[0020] Figure 2 This is a schematic diagram of the GFCI fault detection circuit provided in the embodiments of this application. Figure 2 ;

[0021] Figure 3 This is a schematic diagram of the GFCI fault detection circuit provided in the embodiments of this application. Figure 3 ;

[0022] Figure 4 This is a schematic diagram of the GFCI fault detection circuit provided in the embodiments of this application. Figure 4 ;

[0023] Figure 5 This is a schematic diagram of the GFCI fault detection circuit provided in the embodiments of this application. Figure 5 ;

[0024] Figure 6 This is a schematic diagram of the circuit structure of the GFCI fault detection circuit provided in the embodiments of this application;

[0025] Figure 7 This is a schematic diagram of the oscillation signal and the first level signal provided in the embodiments of this application;

[0026] Figure 8 This is a schematic diagram of the oscillation signal and the second-level signal provided in the embodiments of this application. Figure 1 ;

[0027] Figure 9 This is a schematic diagram of the oscillation signal and the second-level signal provided in the embodiments of this application. Figure 2 . Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be described clearly and in detail below with reference to the accompanying drawings. Obviously, the embodiments in this application are only some embodiments, not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0029] It should be noted that when an element is described as "connected" to another element, it can be directly connected to the other element, or there can be one or more intermediate elements between them.

[0030] Furthermore, the technical features involved in the various embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0031] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the block diagram of the GFCI fault detection circuit provided in the embodiments of this application. The GFCI fault detection circuit 100 is used to determine whether the GFCI 200 is faulty. The GFCI 200 includes an oscillation circuit 210, which outputs an oscillation signal when the GFCI 200 is running. Specifically, the frequency of the oscillation signal output by the oscillation circuit 210 can characterize whether the GFCI 200 has failed. Therefore, the GFCI fault detection circuit 100 can determine whether the GFCI 200 has failed based on the oscillation signal.

[0032] The GFCI (Ground Fault Circuit Interrupter) 200 is used to detect current leakage (i.e., ground faults) and automatically disconnect the circuit power supply within a short time when a ground fault is detected. The GFCI 200 includes a flux transformer and an oscillation circuit 210. The flux transformer includes a main winding and an auxiliary winding. The auxiliary winding is used as an inductor in the oscillation circuit 210. Thus, both the flux transformer and the oscillation circuit 210 can directly affect the frequency of the oscillation signal output by the oscillation circuit 210. When GFCI200 is in normal condition, GFCI200 is not faulty, the inductance of the auxiliary winding is normal, and the frequency f0 of the oscillation signal is within the first preset frequency range, i.e., f0∈(f1, f2), where (f1, f2) is the first preset frequency range. When GFCI200 is in an open circuit state (the flux transformer and / or the oscillation circuit 210 is open), GFCI200 is faulty, the inductance of the auxiliary winding is infinitely large or the circuit is broken, the oscillation stops or the frequency of the oscillation signal is low. At this time, f0<f1, and the frequency f0 of the oscillation signal is not within the first preset frequency range. When GFCI200 is in a short circuit state, the ground leakage current detection circuit is faulty, and the inter-turn short circuit of the auxiliary winding causes the effective inductance to decrease, which leads to an increase in the frequency of the oscillation signal. At this time, f0>f2, and the frequency f0 of the oscillation signal is not within the first preset frequency range. Therefore, the frequency of the oscillation signal output by the oscillation circuit 210 can characterize whether the GFCI200 has malfunctioned. Subsequently, the GFCI fault detection circuit 100 can determine whether the GFCI200 has malfunctioned based on the oscillation signal.

[0033] like Figure 1 As shown, the fault detection circuit 100 of GFCI includes a frequency selection circuit 110 and a controller 120. The frequency selection circuit 110 is electrically connected to the controller 120.

[0034] Specifically, the frequency selection circuit 110 receives an oscillation signal OSC. The frequency selection circuit 110 is configured to output the oscillation signal when the frequency of the oscillation signal OSC is within a first preset frequency range (f1, f2), or to stop outputting the oscillation signal OSC when the frequency of the oscillation signal OSC is not within the first preset frequency range (f1, f2). The controller 120 is configured to determine that the GFCI200 is not faulty when it receives the oscillation signal OSV, and to determine that the GFCI200 is faulty when it does not receive the oscillation signal OSV.

[0035] Thus, when GFCI200 is not faulty, the frequency of the oscillation signal OSC is within the first preset frequency range (f1, f2). The frequency selection circuit 110 outputs the oscillation signal OSC to the controller 120. The controller 120 receives the oscillation signal OSC and determines that GFCI200 is not faulty.

[0036] When GFCI200 malfunctions, the frequency of the oscillation signal OSC is not within the first preset frequency (f1, f2) range. The frequency selection circuit 110 stops outputting the oscillation signal OSC to the controller 120. The controller 120 does not receive the oscillation signal OSC and determines that GFCI200 has malfunctioned.

[0037] In summary, this method accurately detects whether the GFCI200 has malfunctioned, thereby preventing adverse effects caused by GFCI200 failure, such as protection function failure. Secondly, the above process requires no manual intervention and can automatically complete a closed-loop self-test, demonstrating high practicality and reliability. Furthermore, the final judgment is based on a binary level signal (high / low level signal), exhibiting strong anti-interference capability and high accuracy and reliability.

[0038] In some embodiments, such as Figure 2 As shown, the fault detection circuit 100 of GFCI also includes a level generation circuit 130.

[0039] The level generation circuit 130 is electrically connected to the frequency selection circuit 110 and the controller 120, respectively. The level generation circuit 130 is configured to output a first level signal when an oscillation signal OSV is received, or to output a second level signal when an oscillation signal OSC is not received. The controller 120 is configured to determine that the GFCI200 is not faulty when the first level signal is received, and to determine that the GFCI200 is faulty when the second level signal is received.

[0040] Thus, when GFCI200 is not faulty, the frequency of the oscillation signal OSC is within the first preset frequency range (f1, f2). The frequency selection circuit 110 outputs the oscillation signal OSC to the level generation circuit 130. The level generation circuit 130 outputs the first level signal. The controller 120 receives the first level signal and determines that GFCI200 is not faulty.

[0041] When GFCI200 malfunctions, the frequency of the oscillation signal OSC is not within the first preset frequency (f1, f2) range. The frequency selection circuit 110 stops outputting the oscillation signal OSC to the level generation circuit 130. The level generation circuit 130 outputs a second level signal. The controller 120 receives the second level signal and determines that GFCI200 has malfunctioned.

[0042] In some embodiments, such as Figure 3 As shown, the level generation circuit 130 includes a shaping circuit 131 and a level conversion circuit 132.

[0043] The shaping circuit 131 is electrically connected to the frequency selection circuit 110, the first power supply V1, and ground GND. The shaping circuit 131 is configured to output a third-level signal based on the first power supply V1 when an oscillation signal OSC is received, and to output a fourth-level signal based on ground GND when no oscillation signal OSC is received. The level conversion circuit 132 is electrically connected to the shaping circuit 131, the controller 120, and the second power supply V2. The level conversion circuit 132 is configured to output a first-level signal based on the second power supply V2 when a third-level signal is received, and to output a second-level signal based on the fourth-level signal when a fourth-level signal is received.

[0044] The third level signal can be either a high or low level signal, and the fourth level signal can also be either a high or low level signal. Furthermore, when the third level signal is high, the fourth level signal is low; and when the third level signal is low, the fourth level signal is high. For both the third and fourth level signals, the logical high level is based on the voltage of the first power supply V1 (e.g., 12V).

[0045] The first level signal is either a high level signal or a low level signal, and the second level signal is either a high level signal or a low level signal. Furthermore, when the first level signal is high, the second level signal is low; and when the second level signal is low, the first level signal is high. For both the first and second level signals, the logical high value is based on the voltage of the second power supply V2 (e.g., 3.3V).

[0046] Thus, the level generation circuit 130 shapes the original oscillation signal OSC to obtain a more ideal high / low level signal, and then outputs a standard logic signal that matches the power supply voltage of the controller 120 through level conversion. On the one hand, the shaping circuit 131 can convert the non-standard waveform oscillation signal OSC into a clean digital square wave (high / low level), improving system reliability; on the other hand, the level conversion circuit can ensure that the signal received by the controller 120 meets the input level requirements of the controller 120, avoiding damage or misjudgment. Furthermore, since the oscillation circuit 210 and the controller 120 can use different power supplies, the system design flexibility can be enhanced.

[0047] In some embodiments, such as Figure 4 As shown, the shaping circuit 131 includes a first switching circuit 1311 and a second switching circuit 1312.

[0048] The first switching circuit 1311 is electrically connected to the frequency selection circuit 110, the third power supply V3, and ground GND. The first switching circuit 1311 is configured to turn on when an oscillation signal OSC is received, so that the connection node between the first switching circuit 1311 and the second switching circuit 1312 is electrically connected to ground GND; or, when no oscillation signal OSC is received, it is turned off, so that the connection node is electrically connected to the third power supply V3. The second switching circuit 1312 is electrically connected to the first switching circuit 1311, the first power supply V1, ground GND, and the level conversion circuit 132. The second switching circuit 1312 is configured to turn off when the connection node is electrically connected to ground GND, so as to output a third level signal to the level conversion circuit 132 based on the first power supply V1; or, when the connection node is electrically connected to the third power supply V3, it is configured to turn on, so as to output a fourth level signal to the level conversion circuit 132 based on ground GND.

[0049] Specifically, when the frequency selection circuit 110 outputs the oscillation signal OSC, the first switching circuit 1311 is turned on, the connection node between the first switching circuit 1311 and the second switching circuit 1312 is electrically connected to ground GND through the first switching circuit 1311, the second switching circuit 1312 is turned off, and a third level signal is output to the level conversion circuit 132 based on the first power supply V1.

[0050] When the frequency selection circuit 110 does not output the oscillation signal OSC, the first switching circuit 1311 is turned off, the connection node between the first switching circuit 1311 and the second switching circuit 1312 is electrically connected to the third power supply V3, the second switching circuit 1312 is turned on, and the level conversion circuit 132 is electrically connected to ground GND through the second switching circuit 1312, corresponding to the output of the fourth level signal to the level conversion circuit 132 based on ground GND.

[0051] In this way, a linkage mechanism based on a dual-switch circuit is realized, which reliably converts the physical state of "whether the oscillation signal exists" into a standard digital level signal (i.e., a third level signal or a fourth level signal).

[0052] The first power supply V1 and the third power supply V3 can be the same power supply or different power supplies. In a specific embodiment, the first power supply V1 and the third power supply V3 are set to be the same power supply to simplify the circuit structure.

[0053] In some embodiments, such as Figure 5 As shown, the level conversion circuit 132 includes a unidirectional conductive circuit 1321, a pull-up circuit 1322, and a filter circuit 1323.

[0054] The unidirectional conductive circuit 1321 is electrically connected to the shaping circuit 131, the pull-up circuit 1322, and the filter circuit 1323. The unidirectional conductive circuit 1321 is an electronic circuit structure that allows current to flow in only one direction and blocks reverse current. The unidirectional conductive circuit 1321 is configured to be cut off when a third-level signal is received, or to be turned on when a fourth-level signal is received, so as to output a second-level signal based on the fourth-level signal. The pull-up circuit 1322 is electrically connected to the second power supply V2, and is configured to output a first-level signal based on the second power supply V2 when the unidirectional conductive circuit 1321 is cut off. The filter circuit 1323 is electrically connected to the controller 120, and is configured to filter the first-level signal or the second-level signal before outputting it to the controller 120.

[0055] Specifically, when the shaping circuit 131 outputs the third level signal, the unidirectional conductive circuit 1321 is reverse-cut off, and the pull-up circuit 1322 outputs the first level signal based on the second power supply V2. The first level signal is then filtered by the filter circuit 1323 and input to the controller 120.

[0056] When the shaping circuit 131 outputs the fourth-level signal, the unidirectional conductive circuit 1321 is forward-biased. The controller 120 is grounded to GND through the filter circuit 1323, the unidirectional conductive circuit 1321, and the second switching circuit 1321. The fourth-level signal is received at the end of the unidirectional conductive circuit 1321 that is electrically connected to the second switching circuit 1312, thereby generating a second-level signal at the end of the unidirectional conductive circuit 1321 that is electrically connected to the filter circuit 1323. The second-level signal is then filtered by the filter circuit 1323 and input to the controller 120.

[0057] Thus, on the one hand, the combination of the unidirectional conductive circuit 1321 and the pull-up circuit 1322 can ensure that the high level received by the controller 120 is strictly equal to the power supply voltage of the controller 120, avoiding overvoltage damage or logic misjudgment; on the other hand, by setting the filter circuit 1323, noise and glitches (such as jitter caused by unstable oscillation signals) can be effectively suppressed.

[0058] Please refer to Figure 6 , Figure 6 The embodiments provided in this application are related to Figure 5 The block diagram shown corresponds to the circuit structure schematic of the GFCI fault detection circuit. For example... Figure 6 As shown, the frequency selection circuit 110 includes a first resistor R1, a second resistor R2, a first capacitor C1, and a second capacitor C2.

[0059] The first terminal of the first capacitor C1 is input with the oscillation signal OSC. The second terminal of the first capacitor C1 is electrically connected to the first terminal of the first resistor R1 and the first terminal of the second resistor R2. The second terminal of the second resistor R2 is electrically connected to the level generation circuit 130 and the first terminal of the second capacitor C2. The second terminals of the first resistor R1 and the second terminal of the second capacitor C2 are both electrically connected to ground GND.

[0060] Specifically, the first capacitor C1 and the first resistor R1 form a first filter to determine the frequency f2; the second resistor R2 and the second capacitor C2 form a second filter to determine the frequency f1. By adjusting the parameters of the first resistor R1, the second resistor R2, the first capacitor C1, and the second capacitor C2, the first preset frequency range (f1, f2) can be set.

[0061] In some embodiments, please continue to refer to Figure 6 The first switching circuit 1311 includes a first switching transistor Q1, a first diode D1, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a third capacitor C3, and a fourth capacitor C4.

[0062] In this circuit, the anode of the first diode D1 is connected to the frequency selection circuit 110, the cathode of the first diode D1 is connected to the first end of the third resistor R3, the second end of the third resistor R3 is connected to the first end of the fourth resistor R4, the first end of the third capacitor C3 and the first end of the first switch Q1, the third end of the first switch Q1 is connected to the first end of the fifth resistor R5, the first end of the fourth capacitor C4 and the second switch circuit 1312, the second end of the fifth resistor R5 is connected to the third power supply V3, and the second ends of the fourth resistor R4, the third capacitor C3, the first switch Q1 and the fourth capacitor C4 are all connected to ground GND.

[0063] Specifically, the first diode D1 is used to prevent reverse current. The third resistor R3 and the fourth resistor R4 are used for voltage division; the fourth resistor R4 also acts as a discharge resistor when the first switch Q1 is turned off, ensuring that the first switch Q1 is reliably turned off. The third capacitor C3 and the fourth capacitor C4 are used for filtering. The fifth resistor R5 is a pull-up resistor.

[0064] In this embodiment, the first switching transistor Q1 is an NPN transistor. The base of the NPN transistor is the first terminal of the first switching transistor Q1, the emitter of the NPN transistor is the second terminal of the first switching transistor Q1, and the collector of the NPN transistor is the third terminal of the first switching transistor Q1.

[0065] In addition, the first switch Q1 can be any controllable switch, such as an insulated gate bipolar transistor (IGBT) device, an integrated gate commutated thyristor (IGCT) device, a gate turn-off thyristor (GTO) device, a silicon controlled rectifier (SCR) device, a junction gate field-effect transistor (JFET) device, a MOS controlled thyristor (MCT) device, etc.

[0066] In some embodiments, please continue to refer to Figure 6 The second switching circuit 1312 includes a second switching transistor Q2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a fifth capacitor C5, and a sixth capacitor C6.

[0067] Specifically, the first end of the sixth resistor R6 is electrically connected to the first switch circuit 1311, the second end of the sixth resistor R6 is electrically connected to the first end of the seventh resistor R7, the first end of the fifth capacitor C5 and the first end of the second switch Q2, the third end of the second switch Q2 is electrically connected to the first end of the eighth resistor R8, the first end of the sixth capacitor C6 and the level conversion circuit 132, the second end of the eighth resistor R8 is electrically connected to the first power supply V1, and the second ends of the seventh resistor R7, the fifth capacitor C5, the second switch Q2 and the sixth capacitor C6 are all electrically connected to ground GND.

[0068] Specifically, the sixth resistor R6 and the seventh resistor R7 are used for voltage division; the seventh resistor R7 also acts as a discharge resistor when the first switch Q1 is turned off, ensuring that the second switch Q2 is reliably turned off. The fifth capacitor C5 and the sixth capacitor C6 are used for filtering. The eighth resistor R8 is a pull-up resistor.

[0069] In this embodiment, the second switch Q2 is an NPN transistor. The base of the NPN transistor is the first terminal of the second switch Q2, the emitter of the NPN transistor is the second terminal of the second switch Q2, and the collector of the NPN transistor is the third terminal of the second switch Q2.

[0070] In addition, the second switch Q2 can be any controllable switch, such as an insulated gate bipolar transistor (IGBT) device, an integrated gate commutated thyristor (IGCT) device, a gate turn-off thyristor (GTO) device, a silicon controlled rectifier (SCR) device, a junction gate field-effect transistor (JFET) device, a MOS controlled thyristor (MCT) device, etc.

[0071] In some embodiments, please continue to refer to Figure 6 The unidirectional conductive circuit 1321 includes a second diode D2.

[0072] The anode of the second diode D2 is connected to the pull-up circuit 1322 and the filter circuit 1323, and the cathode of the second diode D2 is connected to the shaping circuit 131.

[0073] In some embodiments, please continue to refer to Figure 6 The pull-up circuit 1322 includes the ninth resistor R9.

[0074] Among them, the first end of the ninth resistor R9 is electrically connected to the second power supply V2, and the second end of the ninth resistor R9 is electrically connected to the unidirectional conductive circuit 1321 and the filter circuit 1323.

[0075] In some embodiments, please continue to refer to Figure 6 The filter circuit 1323 includes a tenth resistor R10 and a seventh capacitor C7.

[0076] In this circuit, the first terminal of the tenth resistor R10 is electrically connected to the unidirectional conductive circuit 1321 and the pull-up circuit 1322, the second terminal of the tenth resistor R10 is electrically connected to the first terminal of the seventh capacitor C7 and the controller 120, and the second terminal of the seventh capacitor C7 is electrically connected to ground GND. The tenth resistor R10 and the seventh capacitor C7 form an RC filter circuit.

[0077] The following are Figure 6 The principle of the circuit shown will be explained.

[0078] When GFCI200 is not faulty, the frequency of the oscillation signal OSC is within the first preset frequency range (f1, f2), and the oscillation signal OSC is as follows: Figure 7 As shown in signal L11, the oscillation signal OSC is filtered by the first resistor R1, the second resistor R2, the first capacitor C1, and the second capacitor C2, and then output to the first switch Q1, causing the first switch Q1 to conduct (i.e., the first switch Q1 operates in the saturation region). The first terminal of the second switch Q2 is electrically connected to ground GND through the sixth resistor and the first switch Q1, turning off the second switch Q2. The first power supply V1 is output through the eighth resistor R8, corresponding to the output of the third level signal. The second diode D2 is reverse-biased and cut off. The second power supply V2 is input to the controller 120 through the ninth resistor R9 and the tenth resistor R10, corresponding to the controller 120 receiving the first level signal (in this embodiment, the first level signal is a high level signal, as shown in the image). Figure 7 (As shown in signal L12). Controller 120 determines that GFCI200 is not faulty.

[0079] When GFCI200 malfunctions, specifically when GFCI200 is in an open-circuit state, the oscillation stops or the frequency of the oscillation signal OSC is low. In this case, f0 < f1, and the frequency f0 of the oscillation signal OSC is not within the first preset frequency range. (The last sentence appears to be incomplete and possibly refers to a different context.) Figure 8 The signal L21 in the diagram is shown. When GFCI200 is in a short-circuit state, the frequency of the oscillation signal OSC increases. At this time, f0 > f2, and the frequency f0 of the oscillation signal is not within the first preset frequency range. The oscillation signal OSC is as follows: Figure 9 The signal L31 is shown in the diagram. The oscillation signal OSC cannot pass through the filter circuit composed of the first resistor R1, the second resistor R2, the first capacitor C1, and the second capacitor C2. The first switch Q1 is turned off. The third power supply V3 acts on the first terminal of the second switch Q2 through the fifth resistor R5 and the sixth resistor R6, so that the second switch Q2 is turned on (i.e., the second switch Q2 is working in the saturation region). The cathode of the second diode D2 is electrically connected to ground GND through the second switch Q2, corresponding to the fourth level signal acting on the cathode of the second diode D2. The second diode D2 is forward turned on, and the controller 120 is electrically connected to ground GND through the second diode D2 and the second switch Q2, corresponding to the controller 120 receiving the second level signal (in this embodiment, the second level signal is a low level signal, as shown in the diagram). Figure 8 Signal L22 or such Figure 9 (As shown in signal L32). Controller 120 determines that GFCI200 has malfunctioned.

[0080] This application also provides an inverter that includes a GFCI and a fault detection circuit for the grounded GFCI in any embodiment of this application.

[0081] The fault detection circuit of the GFCI is electrically connected to the GFCI to detect whether the GFCI is faulty. In this way, the combination of the GFCI and the GFCI fault self-test not only achieves protection against external electrical faults, but also monitors the health status of the protection system itself, forming a closed-loop, reliable protection mechanism that conforms to modern safety engineering concepts.

[0082] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

[0083] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A fault detection circuit for GFCI, characterized in that, The GFCI includes an oscillation circuit that outputs an oscillation signal during operation. The fault detection circuit of the GFCI includes: A frequency selection circuit is input to the oscillation signal and is configured to output the oscillation signal when the frequency of the oscillation signal is within a first preset frequency range, or to stop outputting the oscillation signal when the frequency of the oscillation signal is not within the first preset frequency range. A level generation circuit, electrically connected to the frequency selection circuit, is configured to output a first level signal when the oscillation signal is received, or to output a second level signal when the oscillation signal is not received. The controller, electrically connected to the level generation circuit, is configured to determine that the GFCI is not faulty when the first level signal is received, and to determine that the GFCI is faulty when the second level signal is received; The level generation circuit includes: The shaping circuit, electrically connected to the frequency selection circuit, the first power supply and ground, is configured to output a third-level signal based on the first power supply when the oscillation signal is received, and to output a fourth-level signal based on the ground when the oscillation signal is not received. A level conversion circuit, electrically connected to the shaping circuit, the controller, and the second power supply, is configured to output a first level signal based on the second power supply when the third level signal is received, and to output a second level signal based on the fourth level signal when the fourth level signal is received, wherein the voltage of the second power supply is the same as the power supply voltage of the controller; The shaping circuit includes a first switching circuit and a second switching circuit; The first switching circuit is electrically connected to the frequency selection circuit, the third power supply, and the ground. The first switching circuit is configured to turn on when the oscillation signal is received, so that the connection node between the first switching circuit and the second switching circuit is electrically connected to the ground, or to turn off when the oscillation signal is not received, so that the connection node is electrically connected to the third power supply. The second switching circuit is electrically connected to the first switching circuit, the first power supply, the ground, and the level conversion circuit. The second switching circuit is configured to turn off when the connection node is electrically connected to the ground in order to output the third level signal to the level conversion circuit based on the first power supply, or to turn on when the connection node is electrically connected to the third power supply in order to output the fourth level signal to the level conversion circuit based on the ground.

2. The fault detection circuit of GFCI according to claim 1, characterized in that, The level conversion circuit includes a unidirectional conductive circuit, a pull-up circuit, and a filter circuit. The unidirectional conductive circuit is electrically connected to the shaping circuit, the pull-up circuit, and the filtering circuit. The unidirectional conductive circuit is configured to be turned off when the third level signal is received, or to be turned on when the fourth level signal is received, so as to output the second level signal based on the fourth level signal. The pull-up circuit is electrically connected to the second power supply, and the pull-up circuit is configured to output the first level signal based on the second power supply when the unidirectional conductive circuit is turned off. The filtering circuit is electrically connected to the controller, and the filtering circuit is configured to filter the first level signal or the second level signal and then output it to the controller.

3. The fault detection circuit for GFCI according to claim 1 or 2, characterized in that, The frequency selection circuit includes a first resistor, a second resistor, a first capacitor, and a second capacitor; The first terminal of the first capacitor receives the oscillation signal, the second terminal of the first capacitor is electrically connected to the first terminal of the first resistor and the first terminal of the second resistor, the second terminal of the second resistor is electrically connected to the level generation circuit and the first terminal of the second capacitor, and the second terminals of the first resistor and the second capacitor are both electrically connected to ground.

4. The fault detection circuit of GFCI according to claim 1, characterized in that, The first switching circuit includes a first switching transistor, a first diode, a third resistor, a fourth resistor, a fifth resistor, a third capacitor, and a fourth capacitor; The anode of the first diode is electrically connected to the frequency selection circuit, and the cathode of the first diode is electrically connected to the first terminal of the third resistor. The second terminal of the third resistor is electrically connected to the first terminal of the fourth resistor, the first terminal of the third capacitor, and the first terminal of the first switching transistor. The third terminal of the first switching transistor is electrically connected to the first terminal of the fifth resistor, the first terminal of the fourth capacitor, and the second switching circuit. The second terminal of the fifth resistor is electrically connected to the third power supply. The second terminals of the fourth resistor, the third capacitor, the first switching transistor, and the fourth capacitor are all electrically connected to ground.

5. The fault detection circuit for GFCI according to claim 1, characterized in that, The second switching circuit includes a second switching transistor, a sixth resistor, a seventh resistor, an eighth resistor, a fifth capacitor, and a sixth capacitor; The first end of the sixth resistor is electrically connected to the first switching circuit. The second end of the sixth resistor is electrically connected to the first end of the seventh resistor, the first end of the fifth capacitor, and the first end of the second switching transistor. The third end of the second switching transistor is electrically connected to the first end of the eighth resistor, the first end of the sixth capacitor, and the level conversion circuit. The second end of the eighth resistor is electrically connected to the first power supply. The second ends of the seventh resistor, the fifth capacitor, the second switching transistor, and the sixth capacitor are all electrically connected to ground.

6. The fault detection circuit for GFCI according to claim 2, characterized in that, The unidirectional conductive circuit includes a second diode; The anode of the second diode is electrically connected to the pull-up circuit and the filter circuit, and the cathode of the second diode is electrically connected to the shaping circuit.

7. The fault detection circuit for GFCI according to claim 2, characterized in that, The pull-up circuit includes a ninth resistor; The first end of the ninth resistor is electrically connected to the second power supply, and the second end of the ninth resistor is electrically connected to the unidirectional conductive circuit and the filter circuit.

8. The fault detection circuit for GFCI according to claim 2, characterized in that, The filter circuit includes a tenth resistor and a seventh capacitor; The first end of the tenth resistor is electrically connected to the unidirectional conductive circuit and the pull-up circuit, the second end of the tenth resistor is electrically connected to the first end of the seventh capacitor and the controller, and the second end of the seventh capacitor is electrically connected to ground.

9. An inverter, characterized in that, Includes GFCI and the fault detection circuit of GFCI as described in any one of claims 1-8.

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