Low cost optional ac pole grounding detection circuit

Abstract

The utility model relates to a low -cost optional AC stake grounding detection circuit, including the grounding function control circuit, half wave rectifier circuit, voltage division circuit, grounding detection circuit, TVS protection circuit and MCU processing unit grounding function control circuit, the grounding function control circuit is used for controlling the opening and closing of detection function, and its output is connected with the power supply loop of half wave rectifier circuit, the input of half wave rectifier circuit is connected with the fire line L_in of AC stake, and the output of half wave rectifier circuit is connected with the input of voltage division circuit, is used for carrying out half wave rectification processing to 220V AC, the output of voltage division circuit is connected with the input of TVS protection circuit, grounding detection circuit respectively, is used for reducing the voltage after rectification to the identifiable range of grounding detection circuit, can significantly reduce the overall circuit cost. Avoid the damage of power supply voltage fluctuation to the circuit, realize the dual effect of low -cost design and basic current -limiting protection.

Description

Technical Field

[0001] This utility model relates to a grounding detection circuit, and more particularly to a low-cost optional grounding detection circuit for AC piles. Background Technology

[0002] In the safe operation system of AC charging piles for new energy vehicles, grounding status detection is a core link to ensure the safety of personnel and equipment. It must comply with industry standards such as GB / T 18487.1. By monitoring the integrity of the grounding circuit in real time, risks such as leakage and electric shock can be avoided. Therefore, the research and optimization of related detection circuits has become a technical hotspot.

[0003] Several grounding detection schemes have been disclosed in the prior art. For example, an AC charging pile isolation grounding detection circuit uses a dual-diode rectification and voltage divider resistor network to obtain the voltage signal. After TVS diode protection, the signal is transmitted to the control unit through a differential comparator and optocoupler isolation, realizing synchronous detection of grounding status and live / neutral reverse connection. Another charging pile grounding detection device uses a solid-state relay to output leakage current, combined with a leakage current detection unit and an amplification unit to realize grounding detection, emphasizing fast response characteristics.

[0004] However, existing solutions still have the following drawbacks: they all rely on devices such as optocouplers and differential comparators, which not only increases the cost of component procurement but also requires supporting drive circuits, resulting in a complex overall structure that is difficult to adapt to low-cost AC charging pile scenarios. Furthermore, they are prone to energy consumption redundancy in temporary debugging or multiple grounding protection scenarios. In addition, most solutions lack dedicated filtering mechanisms for virtual voltages caused by grid fluctuations, and the application of full-wave rectification and voltage transformers results in a large circuit size, which is not conducive to miniaturized PCB layout.

[0005] In view of the above-mentioned shortcomings, the designer actively researched and innovated to create a low-cost optional AC pile grounding detection circuit, making it more valuable for industrial use. Utility Model Content

[0006] To address the aforementioned technical problems, the purpose of this utility model is to provide a low-cost, optional grounding detection circuit for AC piles.

[0007] This utility model discloses a low-cost, optional grounding detection circuit for AC charging piles, comprising a grounding function control circuit, a half-wave rectifier circuit, a voltage divider circuit, a grounding detection circuit, a TVS protection circuit, and an MCU processing unit grounding function control circuit. Its features include: the grounding function control circuit controls the activation and deactivation of the detection function, and its output is connected to the power supply circuit of the half-wave rectifier circuit; the input of the half-wave rectifier circuit is connected to the live wire L_in of the AC charging pile, and its output is connected to the input of the voltage divider circuit for half-wave rectification of the 220V AC power; the output of the voltage divider circuit is connected to the inputs of the TVS protection circuit and the grounding detection circuit, respectively, to reduce the rectified voltage to a range detectable by the grounding detection circuit; the output of the grounding detection circuit is connected to the MCU processing unit to output a corresponding detection signal based on the voltage signal after voltage division; and the TVS protection circuit absorbs interference signals and protects downstream circuit components.

[0008] Furthermore, in the aforementioned low-cost optional AC pile grounding detection circuit, the grounding function control circuit includes a 2P pin header J1 and a current-limiting resistor R9. One end of the current-limiting resistor R9 is connected to the 3.3V operating power supply terminal of the circuit, and the other end is connected to one pin of the 2P pin header J1. The other pin of the 2P pin header J1 is connected to the power supply input terminal of the half-wave rectifier circuit. The 2P pin header J1 controls the start and stop of the detection function by whether a jumper cap is connected. When the jumper cap is connected, the current-limiting resistor R9 is short-circuited, and the grounding function control circuit is disconnected. When the jumper cap is not connected, the current-limiting resistor R9 is connected to the power supply circuit of the half-wave rectifier circuit.

[0009] Furthermore, in the aforementioned low-cost optional AC pile grounding detection circuit, when the detection function is enabled, the 2P pin J1 is not connected to the jumper cap, and the 2P pin J2 is connected to the jumper cap. At this time, the current-limiting resistor R9 is conducting, the half-wave rectifier circuit receives power, the voltage divider circuit is grounded through the 2P pin J2, and the circuit is connected to a 3.3V operating voltage. When the detection function is disabled, the 2P pin J1 is connected to the jumper cap, and the 2P pin J2 is not connected to the jumper cap. At this time, the current-limiting resistor R9 is short-circuited, the power supply to the half-wave rectifier circuit is disconnected, the voltage divider circuit cannot be grounded, and the entire detection circuit is disconnected.

[0010] Furthermore, in the aforementioned low-cost optional AC charging pile grounding detection circuit, the half-wave rectifier circuit includes a rectifier diode D1. The anode of the rectifier diode D1 is connected to the live wire L_in of the AC charging pile via a wire, and the cathode of the rectifier diode D1 is connected to the input terminal of the voltage divider circuit. The rectifier diode D1 only allows the positive half-axis sine wave of 220V AC power to pass through, converting the AC power into unidirectional pulsating DC power before transmitting it to the voltage divider circuit.

[0011] Furthermore, in the aforementioned low-cost optional AC pile grounding detection circuit, the voltage divider circuit includes a front-end current-limiting resistor R1, a voltage divider resistor R2, a voltage divider resistor R3, a voltage divider resistor R4, an end voltage divider resistor R5, and a 2P pin header J2; one end of the front-end current-limiting resistor R1 is connected to the cathode of the rectifier diode D1 in the half-wave rectifier circuit, and the other end is connected to one end of the voltage divider resistor R2; the other end of the voltage divider resistor R2 is connected to one end of the voltage divider resistor R3, and the other end of the voltage divider resistor R3 is connected to one end of the voltage divider resistor R4. The voltage divider is connected to the terminal, with one end of the voltage divider resistor R4 connected to one end of the terminal voltage divider resistor R5; the other end of the terminal voltage divider resistor R5 is connected to one pin of the 2P pin header J2, and the other pin of the 2P pin header J2 is grounded; the voltage division ratio of the voltage divider circuit is set such that when the voltage of the live wire L_in to ground is ≥185V, the peak voltage output to the TVS protection circuit after voltage division can trigger the grounding detection circuit to operate; when the voltage of the live wire L_in to ground is <185V, the peak voltage output after voltage division cannot trigger the grounding detection circuit to operate.

[0012] Furthermore, in the aforementioned low-cost optional AC grounding detection circuit, an RC filter circuit is connected between the output of the voltage divider circuit and the input of the TVS protection circuit. The RC filter circuit includes a filter resistor R10 and a filter capacitor C1. One end of the filter resistor R10 is connected to the non-grounded pin of the 2P header J2 in the voltage divider circuit, and the other end is connected to the non-grounded terminal of the TVS transistor ESD1 in the TVS protection circuit. One end of the filter capacitor C1 is connected to the common connection terminal of the filter resistor R10 and the TVS transistor ESD1, and the other end is grounded. This is used to filter out high-frequency noise in the voltage divider signal and avoid high-frequency interference causing false triggering of the MOSFET.

[0013] Furthermore, in the aforementioned low-cost optional AC pile grounding detection circuit, the TVS protection circuit includes a TVS diode ESD1. One end of the TVS diode ESD1 is connected to the non-grounded pin of the 2P header J2 in the voltage divider circuit, and the other end is grounded. The TVS diode ESD1 is used to absorb surge interference in the output signal of the voltage divider circuit, preventing interference signals from damaging the devices in the grounding detection circuit. The TVS protection circuit also includes a safety capacitor C2. One end of the safety capacitor C2 is connected to the non-grounded end of the TVS diode ESD1, and the other end is grounded, forming a parallel structure with the TVS diode ESD1 to withstand instantaneous high-voltage surges.

[0014] Furthermore, the aforementioned low-cost optional AC pile grounding detection circuit includes a two-stage MOSFET detection unit, a gate current-limiting resistor R6, a voltage divider bias resistor R7, and a pull-up resistor R8. The two-stage MOSFET detection unit includes MOSFETs Q1 and Q2. One end of the gate current-limiting resistor R6 is connected to the non-grounded terminal of the TVS transistor ESD1 in the TVS protection circuit, and the other end is connected to the gate of MOSFET Q1. The source of MOSFET Q1 is grounded, and its drain is connected to one end of the voltage divider bias resistor R7. The other end of the voltage divider bias resistor R7 is connected to the 3.3V operating power supply terminal of the circuit. The gate of MOSFET Q2 is connected to the drain of MOSFET Q1, its source is grounded, and its drain is connected to one end of the pull-up resistor R8. The other end of the pull-up resistor R8 is connected to the 3.3V operating power supply terminal of the circuit, and the drain of MOSFET Q2 is connected to the signal input terminal of the MCU processing unit through a signal line.

[0015] Furthermore, in the aforementioned low-cost optional AC pile grounding detection circuit, the grounding detection circuit further includes a status indication module, which is an LED indicator or a buzzer. The control terminal of the status indication module is connected to the signal output terminal of the MCU processing unit. When the MCU processing unit receives a square wave signal from the grounding detection circuit that alternates between a 3.3V high level and a 0V low level, it controls the status indication module to output a normal operation signal. When the MCU processing unit continuously receives a 0V low level signal from the grounding detection circuit, it controls the status indication module to output a fault alarm signal.

[0016] By means of the above solution, this utility model has at least the following advantages: 1. The grounding function control circuit adopts a combination of a 2P header J1 and a resistor R9, replacing the high-cost components such as relays and switching chips commonly used in existing technologies. The procurement cost of the 2P header and resistor is only 1 / 5 to 1 / 10 of that of a conventional relay, and no additional drive circuit is required, significantly reducing the overall circuit cost. At the same time, resistor R9 can limit the current flowing into the half-wave rectifier circuit when the detection function is enabled, avoiding damage to the circuit caused by power supply voltage fluctuations, achieving the dual effect of low-cost design and basic current limiting protection.

[0017] 2. In the signal preprocessing stage, the half-wave rectifier circuit extracts the positive half-axis sine wave of 220V AC power using only a single rectifier diode D1. Compared to the multiple diodes and transformers required by existing full-wave rectifier circuits, the structure is significantly simplified, further reducing hardware costs. Simultaneously, it effectively filters out transient low voltages and induced voltages caused by grid fluctuations, preventing the grounding detection circuit from misjudging the grounding status due to virtual voltages, significantly improving the circuit's anti-interference capability and ensuring detection accuracy.

[0018] 3. It can discharge interference signals such as grid surge voltage and electrostatic discharge within nanoseconds, stabilizing the voltage divider output voltage within a safe range. The two-stage MOSFET forms signal isolation, effectively isolating the MCU and back-end devices from high voltage impact, significantly improving the circuit's operational reliability and safety.

[0019] 4. The state can be switched simply by plugging and unplugging the jumper cap, without the need for complex circuit modifications or program settings, making it easy to operate. This design can be adapted to different usage scenarios of AC terminals. For example, in temporary debugging scenarios where grounding detection is not required or in scenarios where grounding protection has been implemented through other means, this detection function can be turned off to reduce energy consumption and improve the flexibility of circuit use.

[0020] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, the preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the framework structure of a low-cost optional AC grounding detection circuit; Figure 2 This is a schematic diagram of the overall structure of a low-cost optional AC pile grounding detection circuit. Detailed Implementation

[0022] The specific embodiments of this utility model will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this utility model, but are not intended to limit its scope.

[0023] like Figure 1 , Figure 2The low-cost, optional AC grounding detection circuit shown includes a grounding function control circuit, a half-wave rectifier circuit, a voltage divider circuit, a grounding detection circuit, a TVS protection circuit, and an MCU processing unit grounding function control circuit. Its unique feature is that the grounding function control circuit consists of a 2P header J1 and a resistor R9. One end of resistor R9 is directly connected to the circuit's 3.3V operating power supply, and the other end is soldered to the "first pin" of the 2P header J1. The second pin of the 2P header J1 is connected to the power input terminal of the half-wave rectifier circuit via a wire. This ensures that the power supply node between the cathode of the rectifier diode D1 and the voltage divider circuit ensures that the half-wave rectifier circuit receives power only when the detection function is enabled. Meanwhile, the 2P header J1 is a conventional pluggable header, and the circuit is switched on and off by whether a jumper cap is inserted. When the jumper cap is inserted, the first and second pins of the 2P header J1 are shorted. When the jumper cap is not inserted, the first and second pins of J1 are disconnected, and current flows through resistor R9. Therefore, relying on the combination of 2P header J1 and resistor R9, relays, switching chips, and other components are not required. The procurement cost of the 2P header and resistor is only 1 / 5 to 1 / 10 of that of a conventional relay, and no additional drive circuit is needed. Furthermore, resistor R9 also provides current limiting protection. When the jumper cap is not inserted into 2P header J1, resistor R9 can limit the current flowing into the half-wave rectifier circuit, preventing circuit damage caused by power supply voltage fluctuations.

[0024] The half-wave rectifier circuit used in this invention includes a rectifier diode D1. The anode of the rectifier diode D1 is directly connected to the live wire L_in of the AC terminal via an insulated wire, corresponding to the 220VAC live wire of the AC terminal. The cathode of the rectifier diode D1 is connected to the front-end current-limiting resistor R1 of the voltage divider circuit via a wire, forming an effective signal path. Simultaneously, the ground signal of the half-wave rectifier circuit is connected to the common ground through the grounding terminal of the subsequent voltage divider circuit.

[0025] During implementation, when L_in receives 220VAC AC power, during the positive half-cycle (when the voltage is positive), rectifier diode D1 conducts in the forward direction, and current flows through diode D1 to the voltage divider circuit. During the negative half-cycle (when the voltage is negative), diode D1 is reverse-biased and no current flows to the voltage divider circuit. Ultimately, the half-wave rectifier circuit outputs only pulsating DC power containing the positive half-axis, rather than the continuous DC power of full-wave rectification. Therefore, compared to full-wave rectification which requires more than two diodes and a transformer, half-wave rectification requires only one diode, further reducing costs and meeting the requirement that grounding detection does not require a continuous DC signal, but only periodically detects voltage peaks.

[0026] According to a more optimized embodiment of the present invention, the voltage divider circuit consists of a front-end current-limiting resistor R1, voltage-dividing resistors R2, R3, and R4, a rear-end voltage-dividing resistor R5, and a 2P header J2. One end of the front-end current-limiting resistor R1 is connected to the cathode of the half-wave rectifier circuit D1, and the other end is connected to one end of the voltage-dividing resistor R2. The other end of the voltage-dividing resistor R2 is connected to one end of the voltage-dividing resistor R3, the other end of the voltage-dividing resistor R3 is connected to one end of the voltage-dividing resistor R4, and the other end of the voltage-dividing resistor R4 is connected to one end of the rear-end voltage-dividing resistor R5. Simultaneously, the other end of the rear-end voltage-dividing resistor R5 is connected to the corresponding pin of the 2P header J2. Furthermore, one pin of the 2P header J2 is connected to the circuit's common ground GND. The output of the voltage divider circuit is the connection point between the rear-end voltage-dividing resistor R5 and pin A of J2. This connection point is connected to one end of the TVS diode ESD1 in the TVS protection circuit via a wire, forming a signal path from voltage division to protection.

[0027] During implementation, the voltage divider can be adjusted so that the grounding detection circuit can only detect a grounding signal when the voltage between the live wire and ground is higher than 185V. Specifically, the voltage between the live wire L_in and ground (i.e., the voltage between L_in and GND) is U_in. A threshold target is set: when U_in ≥ 185V, U_out needs to reach the gate conduction threshold voltage of MOSFET Q1 in the grounding detection circuit. The threshold voltage for a typical N-channel MOSFET is 2V~4V. When U_in < 185V, U_out < the gate conduction threshold, and MOSFET Q1 cannot conduct. This design can filter out "phantom voltages," such as instantaneous low voltage caused by grid fluctuations or induced voltages. If a phantom voltage causes U_in < 185V, the voltage divider's U_out will be insufficient to trigger MOSFET Q1, preventing the grounding detection circuit from falsely identifying a normal grounding.

[0028] Looking at the grounding control circuit, when the 2P header J1 is not plugged in, resistor R9 is conducting, and the half-wave rectifier circuit is powered. Simultaneously, when the 2P header J2 is plugged in, pins A and B are shorted, and the voltage divider circuit is grounded through 2P header J2, forming a complete voltage divider loop and outputting U_out. When the 2P header J1 is plugged in, R9 is short-circuited, the half-wave rectifier circuit is de-powered, and when the 2P header J2 is not plugged in, the voltage divider circuit is not grounded, cannot form a voltage divider loop, has no U_out output, and the grounding detection circuit has no signal input, thus its function is disabled.

[0029] Furthermore, in the TVS protection circuit used in this invention, the positive terminal (or low-potential end) of the TVS diode ESD1 is soldered to the output terminal of the voltage divider circuit. The negative terminal (or high-potential end) of the TVS diode ESD1 is directly soldered to the circuit's common ground GND. The TVS diode ESD1 is connected in parallel with the output terminal of the voltage divider circuit and the input terminal of the ground detection circuit, meaning that the U_out output of the voltage divider circuit is simultaneously transmitted to the TVS diode ESD1 and resistor R6, ensuring that interference signals are preferentially absorbed by the TVS diode ESD1.

[0030] When interference signals such as surge voltage or electrostatic discharge occur in the power grid, the output U_out of the voltage divider circuit will spike momentarily (far exceeding the normal voltage division value). At this time, the TVS diode ESD1 will conduct within nanoseconds, discharging the instantaneous high voltage to ground (GND) through ESD1, causing U_out to quickly drop to a safe voltage range (≤ the maximum gate withstand voltage of MOSFET Q1). After the interference signal disappears, ESD1 returns to the off state, without affecting the normal transmission of U_out. This prevents interference signals from damaging the downstream MOSFETs Q1 and Q2, as well as the MCU.

[0031] In practical implementation, the grounding detection circuit consists of MOSFETs Q1 and Q2, a gate current-limiting resistor R6, a voltage divider bias resistor R7, and a pull-up resistor R8. One end of the gate current-limiting resistor R6 is connected to the positive terminal of the TVS protection circuit ESD1, and the other end is connected to the gate (G) of MOSFET Q1. Simultaneously, the source (S) of MOSFET Q1 is directly connected to the common ground (GND), and its drain (D) is connected to one end of the voltage divider bias resistor R7. The other end of the voltage divider bias resistor R7 is connected to the 3.3V operating power supply. Furthermore, the gate (G) of MOSFET Q2 is connected to the drain (D) of MOSFET Q1, allowing the drain signal of Q1 to be directly input to the gate of Q2. Moreover, the source (S) of MOSFET Q2 is connected to the common ground (GND). One end of the pull-up resistor R8 is connected to the 3.3V operating power supply, and the other end is connected to the drain (D) of MOSFET Q2. During implementation, the drain D of MOSFET Q2 is connected to the PECheck signal input terminal of the MCU processing unit via a wire. At the same time, the PEControl signal terminal of the ground detection circuit is connected in parallel with the drain D of MOSFET Q2 to ensure that the MCU can receive both detection and control signals simultaneously.

[0032] When the grounding detection function is enabled, the grounding detection circuit begins to check whether the incoming line is grounded as soon as power is applied. If the grounding is normal, the circuit operates normally. If there is no grounding or a grounding abnormality is detected, a fault signal is transmitted to the microcontroller, specifically in two scenarios: Scenario 1: Normal grounding (U_in≥185V): When the output U_out of the voltage divider circuit is greater than or equal to the gate conduction threshold of the MOS tube Q1, the gate of MOS tube Q1 is powered on, and MOS tube Q1 is turned on. After MOS tube Q1 is turned on, the potential of its drain D is pulled down to close to the ground potential (≈0V), and the gate potential of Q2 is ≈0V, which is less than the conduction threshold of MOS tube Q2, so MOS tube Q2 is cut off. After MOS tube Q2 is cut off, its pull-up resistor R8 pulls the potential of the drain D of MOS tube Q2 up to 3.3V. As the half-wave rectifier circuit outputs the positive half-axis pulsating direct current, the output U_out of the voltage divider circuit changes periodically, MOS tube Q1 is periodically turned on / off → MOS tube Q2 is periodically cut off / on → the drain of MOS tube Q2 outputs a square wave signal alternating between 3.3V high level and 0V low level. Finally, the square wave signal is transmitted to the MCU through the PECheck interface, and the MCU determines that the grounding is normal.

[0033] Scenario 2, abnormal grounding (U_in<185V): The output U_out of the voltage divider circuit is less than the gate conduction threshold of MOS tube Q1, there is not enough voltage at the gate of MOS tube Q1, so MOS tube Q1 is cut off. After MOS tube Q1 is cut off, the voltage divider bias resistor R7 pulls the potential of the drain D of MOS tube Q1 up to 3.3V (power supply voltage). At this time, the gate potential of MOS tube Q2 is 3.3V, which is greater than or equal to the conduction threshold of MOS tube Q2, so that MOS tube Q2 remains continuously on. After MOS tube Q2 is turned on, the potential of its drain D is pulled down to ≈0V, and the drain of MOS tube Q2 continuously outputs a 0V low-level signal. At this time, the low-level signal is transmitted to the MCU through the PECheck interface, and the MCU determines that the grounding is abnormal.

[0034] The core function of the MCU processing unit adopted in the present invention is to receive detection signals and control status indication, which is specifically as follows: signal reception: the PECheck input port of the MCU is connected to the drain D of MOS tube Q2 to collect square wave / low level signals. status judgment: the internal program of the MCU presets a signal recognition logic, and continuously collects signals for 100ms~500ms (to avoid misjudgment of instantaneous signals). If the collected signal is a square wave, it is determined as normal; if it is a low level, it is determined as abnormal. status indication: the output port of the MCU is connected to the red indicator light of the device. When abnormal, the MCU outputs a high level to drive the red light to stay on / blink. When normal, the red light is off.

[0035] In addition, the indicated orientation or positional relationship described in the present utility model is all based on the orientation or positional relationship shown in the accompanying drawings, which is only for facilitating the description of the present utility model and simplifying the description, rather than indicating or implying that the referred device or structure must have a specific orientation, or be constructed and operated in a specific orientation, therefore it cannot be construed as a limitation to the present utility model.

[0036] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present utility model, and these improvements and modifications should also be considered within the protection scope of the present utility model.

Claims

1. A low-cost, selectable AC grounding detection circuit, comprising a grounding function control circuit, a half-wave rectifier circuit, a voltage divider circuit, a grounding detection circuit, a TVS protection circuit, and an MCU processing unit grounding function control circuit, characterized in that: The grounding function control circuit is used to control the activation and deactivation of the detection function, and its output terminal is connected to the power supply circuit of the half-wave rectifier circuit. The input terminal of the half-wave rectifier circuit is connected to the live wire L_in of the AC terminal, and the output terminal of the half-wave rectifier circuit is connected to the input terminal of the voltage divider circuit, which is used to perform half-wave rectification on 220V AC power. The output terminal of the voltage divider circuit is connected to the input terminal of the TVS protection circuit and the grounding detection circuit, respectively, to reduce the rectified voltage to the range that the grounding detection circuit can identify. The output of the grounding detection circuit is connected to the MCU processing unit and is used to output a corresponding detection signal based on the voltage signal after voltage division. The TVS protection circuit is used to absorb interference signals and protect downstream circuit components.

2. The low-cost optional AC pile grounding detection circuit according to claim 1, characterized in that: The grounding function control circuit includes a 2P header J1 and a current-limiting resistor R9. One end of the current-limiting resistor R9 is connected to the 3.3V operating power supply terminal of the circuit, and the other end is connected to one of the pins of the 2P header J1. The other pin of the 2P header J1 is connected to the power supply input terminal of the half-wave rectifier circuit. The 2P header J1 controls the start and stop of the detection function by whether a jumper cap is connected. When the jumper cap is connected, the current-limiting resistor R9 is short-circuited, and the grounding function control circuit is disconnected. When the jumper cap is not connected, the current-limiting resistor R9 is connected to the power supply circuit of the half-wave rectifier circuit.

3. The low-cost optional AC pile grounding detection circuit according to claim 2, characterized in that: When the detection function is enabled, pin J1 is not connected to the jumper cap, and pin J2 is connected to the jumper cap. At this time, the current limiting resistor R9 is conducting, the half-wave rectifier circuit receives power, the voltage divider circuit is grounded through pin J2, and the circuit is connected to a 3.3V operating voltage. When the detection function is disabled, pin J1 is connected to the jumper cap, and pin J2 is not connected to the jumper cap. At this time, the current limiting resistor R9 is short-circuited, the power supply to the half-wave rectifier circuit is disconnected, the voltage divider circuit cannot be grounded, and the entire detection circuit is disconnected.

4. The low-cost optional AC pile grounding detection circuit according to claim 1, characterized in that: The half-wave rectifier circuit includes a rectifier diode D1. The anode of the rectifier diode D1 is connected to the live wire L_in of the AC terminal through a wire, and the cathode of the rectifier diode D1 is connected to the input terminal of the voltage divider circuit. The rectifier diode D1 only allows the positive half-axis sine wave of 220V AC to pass through, converting the AC to unidirectional pulsating DC and then transmitting it to the voltage divider circuit.

5. The low-cost optional AC pile grounding detection circuit according to claim 1, characterized in that: The voltage divider circuit includes a front-end current-limiting resistor R1, a voltage-dividing resistor R2, a voltage-dividing resistor R3, a voltage-dividing resistor R4, a terminal voltage-dividing resistor R5, and a 2P header J2. One end of the front-end current-limiting resistor R1 is connected to the cathode of the rectifier diode D1 in the half-wave rectifier circuit, and the other end is connected to one end of the voltage-dividing resistor R2. The other end of the voltage-dividing resistor R2 is connected to one end of the voltage-dividing resistor R3, the other end of the voltage-dividing resistor R3 is connected to one end of the voltage-dividing resistor R4, and the other end of the voltage-dividing resistor R4 is connected to one end of the terminal voltage-dividing resistor R5. The other end of the terminal voltage-dividing resistor R5 is connected to one pin of the 2P header J2, and the other pin of the 2P header J2 is grounded. The voltage division ratio of the voltage divider circuit is set such that when the voltage of the live wire L_in to ground is ≥185V, the peak voltage output to the TVS protection circuit after voltage division can trigger the grounding detection circuit; when the voltage of the live wire L_in to ground is <185V, the peak voltage output after voltage division cannot trigger the grounding detection circuit.

6. The low-cost optional AC pile grounding detection circuit according to claim 5, characterized in that: An RC filter circuit is connected between the output of the voltage divider circuit and the input of the TVS protection circuit. The RC filter circuit includes a filter resistor R10 and a filter capacitor C1. One end of the filter resistor R10 is connected to the non-grounded pin of the 2P header J2 in the voltage divider circuit, and the other end is connected to the non-grounded terminal of the TVS transistor ESD1 in the TVS protection circuit. One end of the filter capacitor C1 is connected to the common connection terminal of the filter resistor R10 and the TVS transistor ESD1, and the other end is grounded. It is used to filter out high-frequency noise in the voltage divider signal and avoid high-frequency interference causing the MOSFET to be falsely triggered.

7. The low-cost optional AC pile grounding detection circuit according to claim 1, characterized in that: The TVS protection circuit includes a TVS diode ESD1. One end of the TVS diode ESD1 is connected to the non-grounded pin of the 2P header J2 in the voltage divider circuit, and the other end is grounded. The TVS diode ESD1 is used to absorb surge interference in the output signal of the voltage divider circuit to prevent interference signals from damaging the devices in the grounding detection circuit. The TVS protection circuit also includes a safety capacitor C2. One end of the safety capacitor C2 is connected to the non-grounded end of the TVS diode ESD1, and the other end is grounded, forming a parallel structure with the TVS diode ESD1 to withstand instantaneous high voltage surges.

8. The low-cost optional AC pile grounding detection circuit according to claim 1, characterized in that: The grounding detection circuit includes a two-stage MOSFET detection unit, a gate current-limiting resistor R6, a voltage divider bias resistor R7, and a pull-up resistor R8. The two-stage MOSFET detection unit includes MOSFET Q1 and MOSFET Q2. One end of the gate current-limiting resistor R6 is connected to the non-grounded terminal of the TVS transistor ESD1 in the TVS protection circuit, and the other end is connected to the gate of MOSFET Q1. The source of MOSFET Q1 is grounded, and its drain is connected to one end of the voltage divider bias resistor R7. The other end of the voltage divider bias resistor R7 is connected to the 3.3V operating power supply terminal of the circuit. The gate of MOSFET Q2 is connected to the drain of MOSFET Q1, its source is grounded, and its drain is connected to one end of the pull-up resistor R8. The other end of the pull-up resistor R8 is connected to the 3.3V operating power supply terminal of the circuit, and the drain of MOSFET Q2 is connected to the signal input terminal of the MCU processing unit through a signal line.

9. The low-cost optional AC pile grounding detection circuit according to claim 8, characterized in that: The grounding detection circuit also includes a status indicator module, which is an LED indicator or a buzzer. The control terminal of the status indicator module is connected to the signal output terminal of the MCU processing unit. When the MCU processing unit receives a square wave signal with alternating 3.3V high level and 0V low level output from the grounding detection circuit, it controls the status indicator module to output a normal operation signal. When the MCU processing unit continuously receives the 0V low level signal output from the grounding detection circuit, it controls the status indicator module to output a fault alarm signal.

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