AC charging system grounding detection circuit

Abstract

The utility model discloses an AC charging system grounding detection circuit, and belongs to the technical field of AC charging. The circuit comprises a signal sampling module, a signal processing module and a processor. The signal sampling module comprises a primary resistance voltage dividing unit, a half-wave rectifying unit, a secondary resistance voltage dividing unit and a resistance sampling unit; each live wire or live wire and zero wire of an AC power supply is provided with a resistance voltage dividing unit, and the voltage dividing signal output end of the resistance voltage dividing unit is connected with a half-wave rectification unit. The output end of the half-wave rectification unit is connected to a signal ground GND and a protection ground wire PE after passing through the secondary resistance voltage dividing unit and the resistance sampling unit in sequence; the resistance sampling unit outputs a resistance sampling signal on a protection ground wire PE to the signal processing module, and the signal processing module processes the resistance sampling signal and then transmits the processed resistance sampling signal to the processor. According to the utility model, accurate function detection can be carried out on the protection ground wire so as to deal with abnormal conditions of the ground wire in time and avoid charging safety accidents caused by the abnormal conditions.

Description

Technical Field

[0001] The utility model relates to the technical field of electric vehicle charging, in particular to a grounding detection circuit for an AC charging system. Background Art

[0002] The charging standard for new energy electric vehicles requires the detection of ground wire function, that is, the charging product needs to confirm that the ground wire is in good condition before charging, during charging, and after charging. If the ground wire is detected to be disconnected, the charging circuit needs to be disconnected and an alarm needs to be issued to remind the user to avoid charging safety accidents.

[0003] The grounding detection method currently used in new energy vehicle charging products mainly uses a live wire to ground loop to detect whether the ground wire access is good. However, when the ground wire contact is poor, that is, there is a certain resistance between the ground wire and the real earth, the actual function of the ground wire cannot be detected, which may cause accident risks during the charging process. Summary of the invention

[0004] The utility model aims to provide an AC charging system grounding detection circuit, which can accurately detect the function of the protective ground wire and promptly respond to abnormal ground wire conditions to avoid charging safety accidents caused thereby.

[0005] The technical solution adopted by the utility model is: an AC charging system grounding detection circuit, including a signal sampling module, a signal processing module and a processor;

[0006] The signal sampling module includes a primary resistor voltage divider unit, a half-wave rectifier unit, a secondary resistor voltage divider unit and a resistor sampling unit; the primary resistor voltage divider unit is respectively arranged on each live wire or the live wire and the neutral wire of the AC power supply, and the output end of the primary resistor voltage divider unit is connected to one of the half-wave rectifier units; the output end of the half-wave rectifier unit is connected to the signal ground GND and the protective ground wire PE after passing through the secondary resistor voltage divider unit and the resistor sampling unit in sequence;

[0007] The resistance sampling unit outputs a resistance sampling signal on the protective ground wire PE to the signal processing module, and the signal processing module processes the resistance sampling signal and transmits it to the processor.

[0008] Optionally, the signal processing module includes a primary filtering unit, a primary signal amplifying unit, a secondary filtering unit and a secondary signal amplifying unit which are sequentially connected between the output end of the resistance sampling unit and the input end of the processor;

[0009] Among them, the amplification factor of the first-level signal amplification unit is less than 10 times, and less than the amplification factor of the second-level signal amplification unit. That is, the signal amplification amplitude of the utility model is small when passing through the first signal amplification unit, and the signal amplitude is low, thereby avoiding the coupling interference of the external EMC signal, and then the signal is amplified again when passing through the second-level signal amplification unit, so that the signal and the AC source maintain the same frequency AC half-wave signal.

[0010] Optionally, the signal processing module further includes a signal rectification unit and a signal holding unit;

[0011] The output end of the secondary signal amplification unit is connected to the signal rectification unit, the DC output end of the signal rectification unit is connected to the signal holding unit, and the output end of the signal holding unit is connected to the processor. The signal rectification unit can convert the ground detection signal from a pulse signal into a DC signal, so that it is no longer affected by the input power grid frequency, has a higher resolution, and can be better compatible with 50Hz and 60Hz power grids.

[0012] Optionally, the first-stage filtering unit includes a first signal filtering unit and a second signal filtering unit connected in parallel to the output end of the resistance sampling unit, and the output ends of the first-stage filtering unit are respectively connected to the first-stage signal amplifying unit.

[0013] Optionally, the processor uses a single-chip microcomputer, and the output end of the signal holding unit is connected to the ADC pin of the single-chip microcomputer. When the ground line is disconnected, there is no current on the resistance sampling unit, and there is no signal on the ADC port of the single-chip microcomputer; when the ground line is well grounded or poorly contacted, current flows through the resistance sampling unit, but because the ground resistance to ground is not zero only when the contact is poor, the signals that can be collected by the ADC port of the single-chip microcomputer in the two cases are different. Therefore, it is only necessary to determine whether the converted digital signal is within the design range to determine whether the ground line has poor contact.

[0014] Optionally, the primary resistor voltage divider unit includes a primary voltage divider resistor connected in series to the live wire and the neutral wire of the AC power supply, the secondary resistor voltage divider unit includes a secondary voltage divider resistor R4, the half-wave rectifier unit includes a rectifier diode, a cathode of which is connected to the primary voltage divider resistor, an anode of which is connected to the secondary voltage divider resistor R4, and a bidirectional voltage regulator diode is connected in parallel to the rectifier diode;

[0015] The resistance sampling unit includes a sampling resistor R10 connected in series between the secondary voltage-dividing resistor R4 and the GND terminal and connected in series with the protective ground wire PE, and the two ends of the sampling resistor R10 serve as the output ends of the resistance sampling unit. R10, as the last series resistance to the ground, can use a high-precision resistor to improve the accuracy of the ground impedance value detection.

[0016] Optionally, the first signal filtering unit and the second signal filtering unit respectively adopt parallel resistor-capacitor filtering circuits; the first-stage signal amplifying unit includes an operational amplifier U1A and a resistor R1 connected in parallel to the inverting input terminal and the output terminal of U1A;

[0017] The two ends of the sampling resistor R10 are connected to the input ends of the first signal filter unit and the second signal filter unit respectively; the output ends of the first signal filter unit and the second signal filter unit are connected to the reverse input end and the same direction input end of U1A respectively. In the negative half cycle of the AC power supply, the potential at both ends of the sampling resistor R10 is higher than the ground end at the other end. Therefore, the second signal filter unit corresponding to the high potential output is connected to the same direction input end of U1A, and the first signal filter unit corresponding to the low potential output is connected to the reverse input end of U1A.

[0018] Optionally, the secondary signal amplification unit includes an operational amplifier U1B, a resistor R16 and a resistor R17; the two ends of the resistor R16 are respectively connected to the same-direction input end and the output end of U1B, one end of the resistor R17 is connected to the reverse input end of U1B, and the other end is grounded; the output end of U1B serves as the output end of the secondary signal amplification unit.

[0019] Optionally, the signal rectification unit includes a resistor R9 and a diode D3, and a capacitor C6 with one end connected between R9 and D3 and the other end grounded; the anode of the diode D3 is connected to R9, and the cathode serves as the output end of the signal rectification unit.

[0020] Optionally, the signal holding unit includes a capacitor C7 and a resistor R11 connected in parallel, one end of which is grounded and the other end is connected between the output end of the signal rectifying unit and an ADC pin of the single chip microcomputer. Beneficial Effects

[0021] Compared with the prior art, the utility model has the following advantages and progress:

[0022] (1) The resistance to ground of the AC power line is collected through a resistor divider circuit, which can detect situations such as good grounding, broken grounding, and poor contact, and can detect changes in ground impedance, which can effectively avoid the risk of charging accidents when the ground cannot be measured due to poor contact. The involvement of two resistor divider units can reduce the leakage of the input end to the ground, and avoid the reduction of the accuracy of ground resistance detection due to excessive sampling signals.

[0023] (2) Strong compatibility. It can be used in single-phase (L, N, PE) and three-phase (L1, L2, L3, N, PE) power grid charging systems of national and European standards, as well as single-phase TN-C (L, N, PE) and two-phase TN-S (L1, L2, PE) power grids of American and Japanese standards.

[0024] (3) By setting up multi-stage signal amplification and filtering, the circuit's anti-interference ability is improved;

[0025] (4) By setting up a signal rectification unit and a signal holding unit, the AC ground detection signal is converted into a DC detection signal, which can adapt to ground detection under different grid frequencies;

[0026] (5) The circuit is small and easy to implement. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The figure shows a schematic diagram of a circuit module architecture of an embodiment of the utility model in a single-phase AC power grid charging system;

[0028] Figure 2 The figure shows a schematic diagram of a circuit module architecture of an embodiment of the utility model in a two-phase AC power grid charging system;

[0029] Figure 3 Shown is a schematic diagram of the circuit principle of a signal sampling module in an embodiment of the utility model. Implementation

[0030] The invention is further described below with reference to the accompanying drawings and specific embodiments.

[0031] In the description of the present utility model, it should be understood that the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features, and those skilled in the art can understand the specific meanings of the above terms in the present utility model according to specific circumstances.

[0032] The technical concept of the utility model is: using the AC live wire and neutral wire to ground loop to detect the ground line, and detecting the ground line impedance change according to the ground voltage divider resistance signal change. Considering the characteristics of the AC signal, a half-wave rectifier unit is added to the ground series resistance loop to avoid the crosstalk of the AC loop to the ground sampling signal in the timing.

[0033] Combination Figure 1 and Figure 2 ,The technical solution adopted by the utility model is: an AC charging system grounding detection circuit, including a signal sampling module, a signal processing module and a processor;

[0034] The signal sampling module includes a primary resistor voltage divider unit, a half-wave rectifier unit, a secondary resistor voltage divider unit and a resistor sampling unit; the primary resistor voltage divider unit is respectively arranged on each live wire or the live wire and the neutral wire of the AC power supply, and the output end of the primary resistor voltage divider unit is connected to one of the half-wave rectifier units; the output end of the half-wave rectifier unit is connected to the signal ground GND and the protective ground wire PE after passing through the secondary resistor voltage divider unit and the resistor sampling unit in sequence;

[0035] The resistance sampling unit outputs a resistance sampling signal on the protective ground wire PE to the signal processing module, and the signal processing module processes the resistance sampling signal and transmits it to the processor.

[0036] The AC charging system detection circuit of this embodiment has strong compatibility, and its application in single-phase TN-C (L, N, PE) and two-phase power grid TN-S (L1, L2, PE) are used as examples to illustrate the invention.

[0037] Example 1

[0038] like Figure 1 As shown, when the AC charging system grounding detection circuit of this embodiment is applied to a single-phase TN-C (L, N, PE):

[0039] In the signal sampling module, a primary resistor voltage divider unit and a half-wave rectifier unit are respectively arranged on the live wire and the neutral wire of the AC power supply; the output ends of the two half-wave rectifier units are connected to the signal ground GND and the protective ground wire PE after passing through the secondary resistor voltage divider unit and the resistor sampling unit in sequence;

[0040] The signal processing module includes a primary filtering unit, a primary signal amplifying unit, a secondary filtering unit, a secondary signal amplifying unit, a signal rectifying unit and a signal holding unit which are sequentially connected between the output end of the resistance sampling unit and the input end of the processor; wherein,

[0041] The first-stage filtering unit comprises a first signal filtering unit and a second signal filtering unit connected in parallel to the output end of the resistance sampling unit, and the output ends of the first-stage filtering unit and the second signal filtering unit are connected to the first-stage signal amplifying unit respectively;

[0042] The processor adopts a single-chip microcomputer, and the output end of the signal holding unit is connected to an ADC pin of the single-chip microcomputer.

[0043] When this embodiment is used, when a single-phase AC input grid is used, the live wire forms a loop with the ground wire through the primary resistor voltage divider unit, the half-wave rectifier unit, the secondary resistor voltage divider unit and the resistor sampling unit, and the neutral wire forms a loop with the ground wire through the secondary resistor voltage divider unit, the half-wave rectifier unit, the secondary resistor voltage divider unit and the resistor sampling unit.

[0044] When the grounding is good, only in the negative half cycle of the AC power supply, the current flows from PE, the first-level resistor sampling unit and the second-level resistor voltage divider unit to the AC source end, and a half-wave sampling signal is formed in the resistor sampling unit. The half-wave sampling signal passes through the first-level signal filtering unit, the first-level signal amplification unit, the second-level signal filtering unit, the second-level signal amplification unit, the signal rectification unit and the signal holding unit, and finally reaches the ADC pin of the single-chip microcomputer for sampling.

[0045] When the ground wire is disconnected, there is no current on the resistance sampling unit and there is no signal on the MCU ADC port; when the ground wire is well grounded or has poor contact, current flows through the resistance sampling unit, but the ground resistance to ground is not zero only when the contact is poor, that is, when the ground wire is well grounded and has poor contact, the voltage division at both ends of the resistance sampling unit is different due to the different ground resistance to ground. Therefore, the signals that can be collected by the MCU ADC port in the two cases are different. Therefore, it is only necessary to determine whether the converted digital signal is within the design range to determine whether the ground wire has poor contact.

[0046] refer to Figure 3 , which shows Figure 1 A specific implementation method, wherein:

[0047] The primary resistor voltage divider unit includes primary voltage divider resistors R2 and R14 respectively connected in series to the live wire and the neutral wire of the AC power supply, the secondary resistor voltage divider unit includes a secondary voltage divider resistor R4, the half-wave rectifier unit includes rectifier diodes D2 and D5, the cathode of which is connected to the primary voltage divider resistor, and the anode of which is connected to the secondary voltage divider resistor R4, and the rectifier diodes are connected in parallel with bidirectional voltage regulator diodes D1 and D4;

[0048] The resistance sampling unit includes a sampling resistor R10 connected in series between the secondary voltage-dividing resistor R4 and the GND terminal and connected in series with the protective ground wire PE, and the two ends of the sampling resistor R10 serve as the output ends of the resistance sampling unit. R10, as the last series resistance to the ground, can use a high-precision resistor to improve the accuracy of the ground impedance value detection.

[0049] The first signal filter unit and the second signal filter unit connected at both ends of R10 respectively use parallel resistor-capacitor filter circuits, such as Figure 3 R5 and C2 connected in parallel, and R12 and C5 connected in parallel; the first-level signal amplification unit includes an operational amplifier U1A and a resistor R1 connected in parallel to the reverse input terminal and the output terminal of U1A;

[0050] The two ends of the sampling resistor R10 are connected to the input ends of the first signal filter unit and the second signal filter unit respectively; the output ends of the first signal filter unit and the second signal filter unit are connected to the reverse input end and the same direction input end of U1A respectively. In the negative half cycle of the AC power supply, the potential at both ends of the sampling resistor R10 is higher than the ground end at the other end. Therefore, the second signal filter unit corresponding to the high potential output is connected to the same direction input end of U1A, and the first signal filter unit corresponding to the low potential output is connected to the reverse input end of U1A.

[0051] The secondary signal amplification unit includes an operational amplifier U1B, a resistor R16 and a resistor R17; the two ends of the resistor R16 are respectively connected to the same-direction input end and the output end of U1B, one end of the resistor R17 is connected to the reverse input end of U1B, and the other end is grounded; the output end of U1B serves as the output end of the secondary signal amplification unit.

[0052] In this embodiment, the amplification factor of the primary signal amplification unit is less than 10 times, and less than the amplification factor of the secondary signal amplification unit. That is, the signal amplification amplitude of the utility model is small when passing through the first signal amplification unit, and the signal amplitude is low, thereby avoiding the coupling interference of the external EMC signal, and then the signal is amplified again when passing through the secondary signal amplification unit, so that the signal and the AC source maintain the same frequency AC half-wave signal.

[0053] The signal rectifying unit comprises a resistor R9 and a diode D3, and a capacitor C6 with one end connected between R9 and D3 and the other end grounded; the anode of the diode D3 is connected to R9, and the cathode serves as the output end of the signal rectifying unit.

[0054] The signal holding unit comprises a capacitor C7 and a resistor R11 connected in parallel, one end of which is grounded and the other end is connected between the output end of the signal rectifying unit and the ADC pin of the single chip microcomputer.

[0055] When the ground connection is poor and there is resistance to the ground, the current flows from PE to R10 and the resistance sampling unit during the negative half cycle of the AC. The secondary resistance voltage divider unit flows to the AC source end. At this time, a half-wave sampling signal is formed in the resistance sampling unit and changes with the resistance value of the ground resistance. When the ground connection is disconnected, there is no loop between the PE line and the AC power supply end, and the sampling signal is 0V.

[0056] Example 2

[0057] like Figure 2 As shown, different from Embodiment 1, when the AC charging system grounding detection circuit of this embodiment is applied to a two-phase power grid TN-S (L1, L2, PE):

[0058] In the signal sampling module, the two live wires L1 and L2 of the AC power supply are respectively provided with a primary resistor voltage divider unit and a half-wave rectifier unit; the output ends of the two half-wave rectifier units are connected to the signal ground GND and the protective ground wire PE after passing through the secondary resistor voltage divider unit and the resistor sampling unit in turn.

[0059] The working principle of this embodiment is: when two-phase AC is input into the power grid, the live wire L1 forms a loop with the ground wire through the primary resistor voltage divider unit, the half-wave rectifier unit, the secondary resistor voltage divider unit, the resistor sampling unit, and the live wire L2 forms a loop with the ground wire through the primary resistor voltage divider unit, the half-wave rectifier unit, the secondary resistor voltage divider unit, and the resistor sampling unit;

[0060] When the grounding is good, the current flows from PE, the first-level resistor sampling unit, and the second-level resistor voltage divider unit to the AC source end only during the negative half cycle of the AC power supply, and a half-wave sampling signal is formed in the resistor sampling unit.

[0061] The half-wave sampling signal passes through a primary signal filtering unit, a primary signal amplifying unit, a secondary signal filtering unit, a secondary signal amplifying unit, a signal rectifying unit and a signal holding unit, and finally reaches the single chip microcomputer for sampling.

[0062] When the signal passes through the first-level signal amplification unit, the signal amplification amplitude is small. The low signal amplitude can avoid the coupling interference of external EMC signals. When the signal passes through the second-level signal amplification unit, it is amplified again. At this time, the signal and the AC source maintain the same frequency of AC half-wave signal. After passing through the signal rectification unit and the signal holding unit, it is converted into a DC signal. The DC signal can effectively avoid the sampling difference caused by the grid frequency.

[0063] When the ground connection is poor and there is resistance to the ground, in the negative half cycle of the AC, the current flows from PE to R1, the first-level resistor sampling unit, and the second-level resistor voltage divider unit to the AC source end. At this time, a half-wave sampling signal is formed in the resistor sampling unit and changes with the resistance value of R1. When the ground connection is disconnected, there is no loop between the PE line and the AC power supply end, and the sampling signal is 0V. The purpose of detecting whether the ground wire is well grounded by detecting the resistor voltage divider signal to the ground in the negative half cycle of the AC can also be achieved.

[0064] In summary, the utility model can not only detect the continuity of the ground wire, but also detect the change of the ground resistance value, and has strong compatibility, good anti-interference characteristics, small size and low cost.

[0065] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the purpose of the present invention and the claims, which all fall within the protection of the present invention.

Claims

1. An AC charging system grounding detection circuit, characterized in that: It includes a signal sampling module, a signal processing module and a processor; The signal sampling module includes a primary resistor voltage divider unit, a half-wave rectifier unit, a secondary resistor voltage divider unit and a resistor sampling unit; The first-level resistor voltage divider unit is respectively arranged on each live wire or the live wire and the neutral wire of the AC power supply, and the output end of the first-level resistor voltage divider unit is connected to one of the half-wave rectifier units; the output end of the half-wave rectifier unit is connected to the signal ground GND and the protective ground wire PE after passing through the second-level resistor voltage divider unit and the resistor sampling unit in sequence; The resistance sampling unit outputs a resistance sampling signal on the protective ground wire PE to the signal processing module, and the signal processing module processes the resistance sampling signal and transmits it to the processor.

2. The AC charging system grounding detection circuit according to claim 1, characterized in that: The signal processing module comprises a primary filtering unit, a primary signal amplifying unit, a secondary filtering unit and a secondary signal amplifying unit which are sequentially connected between the output end of the resistance sampling unit and the input end of the processor; The amplification factor of the first-stage signal amplification unit is less than 10 times, and less than the amplification factor of the second-stage signal amplification unit.

3. The AC charging system grounding detection circuit according to claim 2, characterized in that: The signal processing module also includes a signal rectification unit and a signal holding unit; The output end of the secondary signal amplifying unit is connected to the signal rectifying unit, the DC output end of the signal rectifying unit is connected to the signal holding unit, and the output end of the signal holding unit is connected to the processor.

4. The AC charging system grounding detection circuit according to claim 3, characterized in that: The primary filtering unit comprises a first signal filtering unit and a second signal filtering unit connected in parallel to the output end of the resistance sampling unit, and the output ends of the first signal filtering unit and the second signal filtering unit are connected to the primary signal amplifying unit respectively.

5. The AC charging system grounding detection circuit according to claim 4, characterized in that: The processor adopts a single-chip microcomputer, and the output end of the signal holding unit is connected to the ADC pin of the single-chip microcomputer.

6. The AC charging system grounding detection circuit according to claim 5, characterized in that: The primary resistor voltage divider unit includes a primary voltage divider resistor connected in series to the live wire and the neutral wire of the AC power supply, the secondary resistor voltage divider unit includes a secondary voltage divider resistor R4, the half-wave rectifier unit includes a rectifier diode, the cathode of which is connected to the primary voltage divider resistor, the anode of which is connected to the secondary voltage divider resistor R4, and the rectifier diode is connected in parallel with a bidirectional voltage regulator diode; The resistance sampling unit includes a sampling resistor R10 which is connected in series between the secondary voltage-dividing resistor R4 and the GND terminal and is connected in series to the protective ground line PE. Both ends of the sampling resistor R10 serve as output ends of the resistance sampling unit.

7. The AC charging system grounding detection circuit according to claim 6, characterized in that: The first signal filtering unit and the second signal filtering unit respectively adopt parallel resistor-capacitor filtering circuits; the first-stage signal amplification unit includes an operational amplifier U1A and a resistor R1 connected in parallel to the reverse input terminal and the output terminal of U1A; The two ends of the sampling resistor R10 are respectively connected to the input ends of the first signal filtering unit and the second signal filtering unit; the output ends of the first signal filtering unit and the second signal filtering unit are respectively connected to the reverse input end and the same direction input end of U1A.

8. The AC charging system grounding detection circuit according to claim 7, characterized in that: The secondary signal amplification unit includes an operational amplifier U1B, a resistor R16 and a resistor R17; the two ends of the resistor R16 are respectively connected to the same-direction input end and the output end of U1B, one end of the resistor R17 is connected to the reverse input end of U1B, and the other end is grounded; the output end of U1B serves as the output end of the secondary signal amplification unit.

9. The AC charging system grounding detection circuit according to claim 8, characterized in that: The signal rectification unit includes a resistor R9 and a diode D3, and a capacitor C6 having one end connected between R9 and D3 and the other end grounded; The anode of the diode D3 is connected to R9, and the cathode serves as the output end of the signal rectification unit.

10. The AC charging system grounding detection circuit according to claim 9, characterized in that: The signal holding unit comprises a capacitor C7 and a resistor R11 connected in parallel, one end of which is grounded and the other end is connected between the output end of the signal rectifying unit and the ADC pin of the single chip microcomputer.

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