An alternating current charging pile and mode two cable on-box controller ground detection method

Abstract

The application belongs to the field of grounding detection, and relates to an AC charging pile and a mode two cable upper box controller grounding detection method, which comprises the following steps: setting a normal threshold value of grounding resistance and an abnormal threshold value of grounding resistance; collecting the voltage of an AC voltage collection circuit by an MCU to obtain a single-phase AC voltage, and the voltage peak value corresponding to the single-phase AC voltage is a single-phase AC voltage peak value; collecting the voltage of a PE collection circuit by the MCU to obtain a PE voltage, and the peak value sampled by the PE collection circuit is a PE voltage peak value; when the grounding resistance value is equal to the normal threshold value of grounding resistance, the peak value sampled by the PE collection circuit is a normal PE voltage peak value; when the grounding resistance value is equal to the abnormal threshold value of grounding resistance, the peak value sampled by the PE collection circuit is an abnormal PE voltage peak value; an index table is established according to the single-phase AC voltage or the single-phase AC voltage peak value, and whether the grounding is good is judged according to the PE voltage peak value obtained according to the index table. Reliable grounding detection can be performed.

Description

Technical Field

[0001] This invention relates to the field of grounding detection technology, and more specifically, to a grounding detection method for an AC charging pile and a mode 2 cable-on-box controller. Background Technology

[0002] For safety reasons, single-phase AC charging piles and Mode 2 cable-mounted box controllers must have good grounding. Poor grounding must be detected and addressed promptly; otherwise, leakage will occur. If subsequent leakage detection also fails to function reliably, it will inevitably lead to personal safety accidents.

[0003] The existing grounding detection circuits for single-phase AC charging piles and mode 2 cable-on-box controllers have the following problems: within a certain range, they can reliably detect poor grounding, but when the voltage exceeds a certain range, the detection becomes unstable or even fails, which can cause safety hazards. Summary of the Invention

[0004] The technical problem this invention aims to solve is that existing grounding detection circuits for single-phase AC charging piles and mode 2 cable-on-box controllers become unstable or even fail to detect voltage when it exceeds a certain range, posing a safety hazard. To address these deficiencies, this invention provides a grounding detection method for AC charging piles and mode 2 cable-on-box controllers, comprising:

[0005] Set the normal grounding resistance threshold and the abnormal grounding resistance threshold;

[0006] The MCU acquires the voltage of the AC voltage acquisition circuit to obtain the single-phase AC voltage. The peak value of the single-phase AC voltage is called the single-phase AC voltage peak value. The MCU acquires the voltage of the PE acquisition circuit to obtain the PE voltage. The peak value sampled by the PE acquisition circuit is called the PE voltage peak value.

[0007] When the grounding resistance value is equal to the normal grounding resistance threshold, the peak value sampled by the PE acquisition circuit is the normal peak value of the PE voltage. When the grounding resistance value is equal to the abnormal grounding resistance threshold, the peak value sampled by the PE acquisition circuit is the abnormal peak value of the PE voltage.

[0008] An index table is established based on the single-phase AC voltage or the peak value of the single-phase AC voltage, with the normal peak value of the PE voltage and the abnormal peak value of the PE voltage as index items.

[0009] Based on the peak value of the single-phase AC voltage, find the corresponding serial number in the index table to obtain the peak value of the PE voltage;

[0010] If the peak value of the PE voltage is greater than the normal peak value of the PE voltage, the grounding is considered good. If the peak value of the PE voltage is less than the abnormal peak value of the PE voltage, the grounding is considered poor.

[0011] Preferably, before the step of setting the normal grounding resistance threshold and the abnormal grounding resistance threshold, the method further includes the step of:

[0012] The AC voltage acquisition circuit is connected to the ADC port of the MCU through a voltage divider conversion. The L and N terminals of the PE acquisition circuit are isolated by a capacitor, and the voltage is divided by a resistor and connected to the ADC port of the MCU through EC. The PE terminal is connected to the ground through a grounding resistor.

[0013] Preferably, the step of obtaining a single-phase AC voltage by acquiring the voltage of the AC voltage acquisition circuit using the MCU specifically includes:

[0014] The voltage of the AC voltage acquisition circuit is acquired by the MCU;

[0015] Determine whether the voltage collected by the MCU is within the effective voltage range; if so, retain it; otherwise, discard it.

[0016] Preferably, the voltage sampling accuracy of the AC voltage acquisition circuit of the MCU is 0.1V, 1V, or 5V.

[0017] Preferably, the AC voltage acquisition circuit includes: a first amplifier circuit, a second amplifier circuit, and an isolation circuit connected in sequence by electrical connections. The first amplifier circuit is used to boost the L AC signal with a reference voltage of 2.5V, the second amplifier circuit is used to boost the N AC signal with a reference voltage of 2.5V, and the isolation circuit is used to isolate the L AC signal from the N AC signal before connecting them to the MCU.

[0018] Preferably, the PE acquisition circuit includes: an isolation circuit, a voltage divider circuit, and a PE voltage detection circuit connected in sequence by electrical connections; the isolation circuit is used to isolate the AC input L terminal and the AC input N terminal; the voltage divider circuit is used for resistive voltage division; and the PE voltage detection circuit is used to detect the voltage at one end of the sampling resistor R5 relative to the analog ground.

[0019] Preferably, the first amplification circuit includes: the non-inverting input terminal of amplifier U42A is connected to one end of capacitor C2; the inverting input terminal of amplifier U42A is connected to one end of resistor R3 and one end of resistor R4 respectively; the other end of resistor R3 is connected to one end of resistor R2; the other end of resistor R2 is connected to one end of resistor R1; the other end of resistor R1 is connected to one end of capacitor C1; the positive power supply terminal of amplifier U42A is connected to one end of capacitor C3; and the other end of resistor R4 is connected to the output terminal of amplifier U42A.

[0020] Preferably, the second amplification circuit includes: the non-inverting input terminal of amplifier U42B is connected to one end of capacitor C5 and one end of capacitor C4 respectively; the inverting input terminal of amplifier U42B is connected to one end of resistor R5, one end of resistor R8 and one end of resistor R9 respectively; the other end of resistor R8 is connected to one end of resistor R7; the other end of resistor R7 is connected to one end of resistor R6; and the other end of resistor R6 is connected to one end of capacitor C6.

[0021] Preferably, the isolation circuit includes: one end of resistor R10 is connected to one end of capacitor C6 and pin 3 of dual diode D1, and the other end of capacitor C6 is connected to pin 1 of dual diode D1.

[0022] Preferably, the voltage divider circuit includes resistors R1, R2, R3, and R4 connected in series.

[0023] The grounding detection method for AC charging piles and mode 2 cable-on-box controllers of the present invention has the following advantages: it can adapt to grounding detection over a wide voltage range, can reliably detect grounding within a single-phase AC voltage range of 30V-300V, and can set a good grounding resistance threshold of R within a single-phase AC voltage range of 30V-300V according to actual needs. Ok Set the grounding failure threshold to , and set R Ok R Err All values ​​are constant; the grounding resistance can be set to be less than a certain set resistance threshold (R). Ok The grounding is deemed good if the grounding resistance exceeds a certain set threshold value (R). Err The problem was determined to be due to poor grounding. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort. The present invention will be further described below in conjunction with the drawings and embodiments. In the drawings:

[0025] Figure 1 This is a flowchart of the grounding detection method for AC charging piles and mode 2 cable box controllers of the present invention;

[0026] Figure 2 This is a schematic diagram of the grounding detection circuit used in the grounding detection method of AC charging pile and mode 2 cable box controller of the present invention;

[0027] Figure 3This is a circuit diagram of the AC voltage acquisition circuit used in the AC charging pile and mode 2 cable box controller grounding detection method of the present invention.

[0028] Figure 4 This is a circuit diagram of the PE acquisition circuit used in the AC charging pile and mode 2 cable box controller grounding detection method of the present invention.

[0029] In the diagram, 1 - the L terminal of the AC input line of the AC terminal block or cable box controller; 2 - the N terminal of the AC input line of the AC terminal block or cable box controller; 3 - the PE terminal of the AC input line of the AC terminal block or cable box controller; 4 - the grounding resistance R between the PE terminal of the AC input line of the AC terminal block or cable box controller and the earth. x 5 - Ground; 6 - AC voltage sampled into the ADC port of the MCU, the ADC sample value corresponding to the voltage sample is denoted as ACV_ADC; 7 - PE voltage sampled into the ADC port of the MCU, the ADC sample value corresponding to the sample is denoted as PE_ADC; 8 - AC voltage acquisition circuit; 9 - PE acquisition circuit; 10 - MCU; 11 - First amplifier circuit; 12 - Second amplifier circuit; 13 - Isolation circuit; 14 - Isolation circuit; 15 - Voltage divider circuit; 16 - PE voltage detection circuit. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] It should be noted that if the embodiments of the present invention involve directional indicators (such as up, down, left, right, front, back, etc.), the directional indicators are only used to explain the relative positional relationship and movement of the components in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indicators will also change accordingly.

[0032] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0033] Please see Figure 1 This is a flowchart of the grounding detection method for the AC charging pile and the mode two cable box controller of the present invention. Figure 1 As shown, the AC charging pile and mode 2 cable box controller grounding detection method provided in the first embodiment of the present invention includes the following steps:

[0034] S1. Set the normal threshold and abnormal threshold for grounding resistance.

[0035] The purpose of setting normal and abnormal grounding resistance thresholds is to provide a basis for comparison between the grounding resistance and the normal grounding resistance threshold. When the actual measured grounding resistance is less than the normal grounding resistance threshold, it indicates that the current working circuit is operating normally; when the actual measured grounding resistance is greater than the abnormal grounding resistance threshold, it indicates that the current working circuit is operating abnormally and requires attention.

[0036] In practice, the normal and abnormal grounding resistance thresholds can be set according to the actual situation. For example, for customers with sensitive grounding alarm requirements, a grounding threshold of 350kΩ is recommended for high sensitivity. For customers with high fault tolerance requirements, a grounding threshold of 1.2mΩ is recommended, so that an alarm for poor grounding will only be triggered when the grounding condition is very poor. The smaller the grounding resistance threshold, the more sensitive and easier the grounding alarm will be; the larger the grounding resistance threshold, the more difficult it is to trigger an alarm for poor grounding. The normal grounding resistance threshold is generally set to less than 50kΩ, and the abnormal grounding resistance threshold is generally set to greater than 750kΩ. The area between the normal and abnormal thresholds is the hysteresis range. If the grounding resistance falls within the hysteresis range, the original alarm or non-alarm state will not change.

[0037] In some optional implementations of this embodiment, the following steps may be included before step S1:

[0038] The AC voltage acquisition circuit is connected to the ADC port of the MCU through a voltage divider conversion method. The L and N terminals of the PE acquisition circuit are isolated by capacitors and voltage divided by resistors before being connected to the ADC port of the MCU.

[0039] The MCU can be CMS32F035LQ48, or other models that meet the actual needs can be selected according to actual requirements.

[0040] S2. The MCU samples the voltage between L and N through its built-in ADC (Analog-to-Digital Converter) circuit. The voltage acquisition uses the root mean square (RMS) value of 200 ADC samples within one AC voltage cycle (20ms) to calculate the effective value of the single-phase AC voltage. The multiple represents the peak voltage. The MCU acquires the AC voltage from the PE circuit to ground using its built-in ADC. The PE-to-ground voltage is calculated by taking the root mean square (RMS) value of 200 ADC samples within one AC voltage cycle (20ms) to determine the effective value of the PE-to-ground voltage. The multiple is the peak value of the PE-to-ground voltage.

[0041] In some optional implementations of this embodiment, step S2, which involves the MCU acquiring the voltage of the AC voltage acquisition circuit to obtain the single-phase AC voltage, may further include:

[0042] The voltage of the AC voltage acquisition circuit is acquired by the MCU;

[0043] Determine whether the voltage collected by the MCU is within the effective voltage range. If it is, retain the single-phase AC voltage; otherwise, discard the single-phase AC voltage and retain the effective value of the single-phase AC voltage.

[0044] For example, a single-phase AC voltage value between 30V and 300V is considered a valid voltage. A single-phase AC voltage less than 30V or greater than 300V is considered an invalid voltage and is discarded.

[0045] Single-phase AC voltage is denoted as V. For the effective value of AC voltage V (30V, 300V), it is denoted as V. i .

[0046] AC voltage peak value: The voltage sampling circuit (VAC_ADC) marks the peak voltage value of the AC sine wave sampled by the ADC during the sampling period as V. m For each voltage peak (V) of the effective value of the AC voltage V (30V, 300V) m The value is denoted as V. m_i .

[0047] Resistance of the PE terminal to ground: R x The resistance of the PE terminal of the AC pile or cable box controller to the ground, such as Figure 1 As shown; the grounding resistance threshold value set when the grounding is good is denoted as R. Ok The grounding resistance threshold value set for poor grounding is denoted as R. Err .

[0048] The peak AC voltage sampling at any given time corresponds to the peak PE voltage sampling: at any given time, for each peak voltage V corresponding to the effective value V(30V, 300V) of the AC voltage sampled by the AC voltage sampling loop (VAC_ADC). m_i Simultaneously, the peak value of each PE_ADC sampled by the PE acquisition loop (PE_ADC) is denoted as V. PE_V_m_i .

[0049] When the AC pile or cable box controller is running, at a certain moment, the AC voltage sampling circuit samples the AC voltage (VAC_ADC) between the AC input lines LN (e.g., Figure 3 V m_i The voltage value and the peak voltage V relative to ground are the sum of the voltages sampled by the PE voltage acquisition circuit (PE_ADC) after voltage division by capacitor C1 and voltage division by capacitor C2 of L and N. PE_V_m_i .

[0050] S3. When the grounding resistance value is equal to the normal grounding resistance threshold, the peak value sampled by the corresponding PE acquisition circuit is the normal peak value of the PE voltage; when the grounding resistance value is equal to the abnormal grounding resistance threshold, the peak value sampled by the corresponding PE acquisition circuit is the abnormal peak value of the PE voltage.

[0051] When the grounding is good, the corresponding peak AC voltage sampling and the corresponding peak PE voltage sampling are: when R x =R Ok At that time, for each voltage peak V corresponding to the effective value V(30V, 300V) of the AC voltage sampled by the AC voltage sampling loop (VAC_ADC) m_i The peak value of each PE_ADC sampled by the corresponding PE acquisition loop (PE_ADC) is denoted as V. Ok_ PE _ V _ m_i. V m_i With V Ok_ PE _ V _ The acquisition of m_i allows adjustment of the actual effective value of the AC voltage V (30V, 300V), which is read from the program.

[0052] When there is poor grounding, the corresponding peak AC voltage sampling and the corresponding peak PE voltage sampling are obtained: when R x =R Err At that time, for each voltage peak V corresponding to the effective value V(30V, 300V) of the AC voltage sampled by the AC voltage sampling loop (VAC_ADC) m_i The peak value of each PE_ADC sampled by the corresponding PE acquisition loop (PE_ADC) is denoted as V. Err_ PE_ V _ m_i. V m_i With V Err_ PE _ V _m_i The actual effective value of the AC voltage V (30V, 300V) can be obtained by adjusting the value of the AC voltage and reading it from the program.

[0053] The initial value is measured based on the pre-set grounding resistance R when the grounding is good. Ok For the effective value of AC voltage V (30V, 300V), record the V value of the AC voltage sampling circuit (VAC_ADC). m_i And the peak value V sampled by the corresponding PE acquisition loop (PE_ADC) Ok_ PE _ V _ m_i; based on the pre-set grounding resistance R when grounding is faulty. Err For the effective value of AC voltage V (30V, 300V), record the V value of the AC voltage sampling circuit (VAC_ADC). m_i And the peak value V sampled by the corresponding PE acquisition loop (PE_ADC) Err_PE_V_m_i .

[0054] S4. Establish an index table based on the effective value or peak value of single-phase AC voltage, and use the normal peak value of PE voltage and the abnormal peak value of PE voltage as index items.

[0055] because There is a linear transformation relationship between the peak value and the effective value of a single-phase AC voltage. This is based on the effective voltage value (V... i ) or peak voltage (V m_i Create an index table to record the peak value (V) sampled by the PE acquisition loop (PE_ADC) when the grounding is good. Ok_PE_V_m_i ) and the peak value (V) sampled by the PE acquisition circuit (PE_ADC) when grounding is poor. Err_PE_V_m_i As shown in Table 1, ) are used as index items.

[0056] Table 1

[0057]

[0058]

[0059] The header of such a table corresponds to a data structure in the program:

[0060]

[0061] The entire table corresponds to a structure array.

[0062] S5. Based on the peak value of the single-phase AC voltage, find the corresponding serial number in the index table and obtain the peak value of the PE voltage.

[0063] When the AC pile or cable box controller is running, at a certain moment, the V of the AC voltage sampling circuit (VAC_ADC) m_i The value and the peak value V sampled by the PE acquisition loop (PE_ADC) PE_V_m_i First, according to V m_i Find the corresponding index in the array, which is the array subscript, and thus find the corresponding item.

[0064] S6. If the peak value of PE voltage is greater than the normal peak value of PE voltage, the current grounding is considered good. If the peak value of PE voltage is less than the abnormal peak value of PE voltage, the current grounding is considered poor.

[0065] During actual operation of the device, at a certain moment, the V of the AC voltage sampling circuit (VAC_ADC) m_i The value and the peak value V sampled by the PE acquisition loop (PE_ADC) PE_V_m_i First, according to V m_i Find the corresponding index in the array, i.e., the array subscript, which is to find the corresponding item, and then use V. PE_V_m_i >V Ok_PE_V_m_i This indicates that the grounding is good; based on V PE_V_m_i <V Err_PE_V_m_i This can be determined to be a grounding problem.

[0066] The resistance R between the PE terminal of the charging pile or cable box controller and the ground. x When the signal changes, the signal in the PE acquisition loop (PE_ADC) will change accordingly: specifically, R x When the value increases, the signal amplitude of the PE acquisition circuit (PE_ADC) decreases; R x When the value decreases, the signal amplitude of the PE acquisition circuit (PE_ADC) increases.

[0067] Please see Figure 2 This is a schematic diagram of the grounding detection circuit used in the grounding detection method for AC charging piles and mode two cable box controllers of the present invention. Figure 2 As shown, it includes an MCU, an AC voltage acquisition circuit, a PE acquisition circuit, an AC input L terminal, an AC input N terminal, an AC input PE terminal, and a grounding resistor R. x The MCU is connected to the AC voltage acquisition circuit and the PE acquisition circuit respectively. The AC voltage acquisition circuit is connected to the AC input line L terminal, AC input line N terminal, and the PE acquisition circuit respectively. The AC input line PE terminal is connected to the grounding resistor R. x Connection, grounding resistance R xConnected to ground. The MCU is used to acquire the single-phase AC voltage (VAC_ADC) from the AC voltage acquisition circuit and the PE voltage (PE_ADC) from the PE acquisition circuit, and then perform single-phase AC voltage (VAC_ADC) and PE voltage (PE_ADC) analysis and processing.

[0068] Based on the AC voltage sampling (peak voltages at L and N), find the closest voltage V in Table 1. m_i This allows us to find the index i of the corresponding item table array, and then, under the corresponding item, based on V... PE_V_m_i >V Ok_PE_V_m_i This indicates that the grounding is good; based on V PE_V_m_i <V Err_PE_V_m_i This can be determined to be a grounding problem.

[0069] Please see Figure 3 This is a circuit diagram of the AC voltage acquisition circuit used in the AC charging pile and mode two cable box controller grounding detection method of the present invention. Figure 3 As shown, the AC voltage acquisition circuit includes a first amplifier circuit, a second amplifier circuit, and a first isolation circuit connected in sequence by electrical connections. The first amplifier circuit is used to boost the L AC signal using a reference voltage of 2.5V. The second amplifier circuit is used to boost the N AC signal using a reference voltage of 2.5V. The first isolation circuit is used to isolate the L AC signal from the N AC signal before connecting them to the MCU. The voltage sampling accuracy of the AC voltage acquisition circuit of the MCU can be, but is not limited to, 0.1V, 1V, or 5V. The sampling accuracy can be selected according to actual needs.

[0070] The first amplifier circuit includes: the non-inverting input terminal of amplifier U42A is connected to one end of capacitor C2; the inverting input terminal of amplifier U42A is connected to one end of resistor R3 and one end of resistor R4 respectively; the other end of resistor R3 is connected to one end of resistor R2; the other end of resistor R2 is connected to one end of resistor R1; the other end of resistor R1 is connected to one end of capacitor C1; the positive power supply terminal of amplifier U42A is connected to one end of capacitor C3; and the other end of resistor R4 is connected to the output terminal of amplifier U42A.

[0071] The second amplifier circuit includes: the non-inverting input terminal of amplifier U42B is connected to one end of capacitor C5 and one end of capacitor C4 respectively; the inverting input terminal of amplifier U42B is connected to one end of resistor R5, one end of resistor R8 and one end of resistor R9 respectively; the other end of resistor R8 is connected to one end of resistor R7; the other end of resistor R7 is connected to one end of resistor R6; and the other end of resistor R6 is connected to one end of capacitor C6.

[0072] The first isolation circuit includes: one end of resistor R10 is connected to one end of capacitor C6 and pin 3 of dual diode D1, and the other end of capacitor C6 is connected to pin 1 of dual diode D1.

[0073] Please see Figure 4 This is a circuit diagram of the PE acquisition circuit used in the grounding detection method of the AC charging pile and mode two cable box controller of the present invention. The PE acquisition circuit includes: a second isolation circuit, a voltage divider circuit, and a PE circuit connected in sequence electrically. The second isolation circuit is used to isolate the AC input L terminal and the AC input N terminal. The voltage divider circuit is used for resistive voltage division. The PE circuit is used to provide the voltage between the PE circuit and the superimposed value of the AC signal L and the AC signal N after passing through the capacitor impedance. The isolation circuit includes: capacitor C1 and capacitor C2 connected in parallel. The capacitors isolate DC and pass AC. Here, capacitors C1 and C2 are equivalent to an impedance for AC. The AC signal L and the AC signal N are superimposed after passing through capacitors C1 and C2.

[0074] The voltage divider circuit includes resistors R1, R2, R3, and R4 connected in series. Resistors R1, R2, R3, and R4 are series voltage divider resistors. After R1, R2, R3, and R4 are connected in series, they are then connected in parallel with capacitors C1 and C2 to form a series voltage divider circuit.

[0075] The PE circuit includes: one end of resistor R5 is connected to pin 3 of dual diode D1 and one end of capacitor C3. The impedance of resistor R5 connected in parallel with capacitors C1 and C2, together with resistors R1, R2, R3, and R4, forms a series voltage divider circuit. One end of resistor R5 is grounded, and the other end, PE_ADC, is connected to the ADC port of the microcontroller to sample the voltage.

[0076] The AC voltage acquisition circuit is connected to the MCU's ADC port via a voltage divider. The PE acquisition circuit isolates L and N through capacitors C1 and C2, and then divides the voltage through resistors R1, R2, R3, R4, and R5 before connecting it to the MCU's ADC port via EC.

[0077] The beneficial effects of this invention, through the design of the above embodiments, are: it can adapt to grounding detection over a wide voltage range, reliably performing grounding detection within a single-phase AC voltage range of 30V-300V; and, according to actual needs, a good grounding resistance threshold of R can be set within the single-phase AC voltage range of 30V-300V. Ok Set the grounding failure threshold to , and set R Ok R Err All values ​​are constant; the grounding resistance can be set to be less than a certain set resistance threshold (R). OkThe grounding is deemed good if the grounding resistance exceeds a certain set threshold value (R). Err The problem was determined to be due to poor grounding.

[0078] This invention has been described with reference to specific embodiments, but those skilled in the art will understand that various changes and equivalent substitutions can be made without departing from the scope of the invention. Furthermore, numerous modifications can be made to this invention to suit specific applications without departing from its protection scope. Therefore, this invention is not limited to the specific embodiments disclosed herein, but includes all embodiments falling within the scope of the claims.

Claims

1. A grounding detection method for an AC charging pile and a mode 2 cable-on-box controller, characterized in that, include: Set the normal grounding resistance threshold and the abnormal grounding resistance threshold; The MCU acquires the voltage of the AC voltage acquisition circuit to obtain the single-phase AC voltage. The peak value of the single-phase AC voltage is called the single-phase AC voltage peak value. The MCU acquires the voltage of the PE acquisition circuit to obtain the PE voltage. The peak value sampled by the PE acquisition circuit is called the PE voltage peak value. When the grounding resistance value is equal to the normal grounding resistance threshold, the peak value sampled by the PE acquisition circuit is the normal peak value of the PE voltage. When the grounding resistance value is equal to the abnormal grounding resistance threshold, the peak value sampled by the PE acquisition circuit is the abnormal peak value of the PE voltage. An index table is established based on the single-phase AC voltage or the peak value of the single-phase AC voltage, with the normal peak value of the PE voltage and the abnormal peak value of the PE voltage as index items. Based on the peak value of the single-phase AC voltage, find the corresponding serial number in the index table to obtain the peak value of the PE voltage; If the peak value of the PE voltage is greater than the normal peak value of the PE voltage, the grounding is considered good. If the peak value of the PE voltage is less than the abnormal peak value of the PE voltage, the grounding is considered poor. Among them, PE voltage refers to the voltage between AC signal L and AC signal N after passing through the capacitor impedance.

2. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 1, characterized in that, Before the step of setting the normal threshold and abnormal threshold for grounding resistance, the following step is also included: The AC voltage acquisition circuit is connected to the ADC port of the MCU through a voltage divider conversion. The L and N terminals of the PE acquisition circuit are isolated by capacitors, voltage divided by resistors, filtered by capacitors, and then connected to the ADC port of the MCU through PE_ADC. The PE terminal is connected to the ground through a grounding resistor.

3. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 1, characterized in that, The step of obtaining a single-phase AC voltage by acquiring the voltage of the AC voltage acquisition circuit using the MCU specifically includes: The voltage of the AC voltage acquisition circuit is acquired by the MCU; Determine whether the voltage collected by the MCU is within the effective voltage range; if so, retain it; otherwise, discard it.

4. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 1, characterized in that, The AC voltage acquisition circuit includes a first amplifier circuit, a second amplifier circuit, and a first isolation circuit connected in sequence by electrical connections. The first amplifier circuit is used to boost the L AC signal with a reference voltage of 2.5V. The second amplifier circuit is used to boost the N AC signal with a reference voltage of 2.5V. The first isolation circuit is used to isolate the L AC signal and the N AC signal before connecting them to the ADC interface of the MCU.

5. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 1, characterized in that, The PE acquisition circuit includes: a second isolation circuit, a voltage divider circuit, and a PE voltage detection circuit connected in sequence by electrical connections. The second isolation circuit is used to isolate DC from the AC input L terminal and the AC input N terminal. The voltage divider circuit is used for resistive voltage division. The PE voltage detection circuit is used to detect the voltage at one end of the sampling resistor R5 relative to the analog ground.

6. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 4, characterized in that, The first amplifier circuit includes: the non-inverting input terminal of amplifier U42A is connected to one end of capacitor C2; the inverting input terminal of amplifier U42A is connected to one end of resistor R3 and one end of resistor R4 respectively; the other end of resistor R3 is connected to one end of resistor R2; the other end of resistor R2 is connected to one end of resistor R1; the other end of resistor R1 is connected to one end of capacitor C1; the positive power supply terminal of amplifier U42A is connected to one end of capacitor C3; and the other end of resistor R4 is connected to the output terminal of amplifier U42A.

7. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 4, characterized in that, The second amplifier circuit includes: the non-inverting input terminal of amplifier U42B is connected to one end of capacitor C5 and one end of capacitor C4 respectively; the inverting input terminal of amplifier U42B is connected to one end of resistor R5, one end of resistor R8 and one end of resistor R9 respectively; the other end of resistor R8 is connected to one end of resistor R7; the other end of resistor R7 is connected to one end of resistor R6; and the other end of resistor R6 is connected to one end of capacitor C6.

8. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 4, characterized in that, The first isolation circuit includes: one end of resistor R10 is connected to one end of capacitor C6 and pin 3 of dual diode D1, and the other end of capacitor C6 is connected to pin 1 of dual diode D1.

9. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 5, characterized in that, The voltage divider circuit includes resistors R1, R2, R3, and R4 connected in series.

10. The grounding detection method for AC charging piles and mode two cable box controllers according to claim 5, characterized in that, The PE voltage detection circuit includes: one end of resistor R5 is connected to pin 3 of dual diode D1 and one end of capacitor C3 respectively.

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