Grounding detection circuit for AC power supply

Abstract

The utility model relates to the technical field of grounding detection, and discloses an AC power supply grounding detection circuit comprising a safety capacitor CY1, a safety capacitor CY2, a first resistor branch, a second resistor branch and an operational amplification unit. One end of the safety capacitor CY1 is electrically connected with the input end of the first resistor branch and one end of the safety capacitor CY2, and the other end of the safety capacitor CY2 is electrically connected with the input end of the second resistor branch and the ground wire PE; the output end of the first resistor branch is electrically connected with the positive input end of the operational amplification unit, the output end of the second resistor branch is electrically connected with the negative input end of the operational amplification unit, and the output end of the operational amplification unit is used for outputting a detection signal; during use, when the positions of the live wire and the zero wire connected to the two ends of the safety capacitor CY1 are different and the grounding of the ground wire PE is unreliable, the operational amplification unit can output peak voltages of different magnitudes, so that reliable grounding detection can be realized, and the whole circuit only uses one operational amplification unit, so that the number of components is small, and the circuit structure is simple.

Description

Technical Field

[0001] This utility model relates to the field of grounding detection technology, specifically to a grounding detection circuit powered by AC. Background Technology

[0002] With the rapid development of new energy vehicle technology, the application of AC charging piles for electric vehicles is also increasing. Because the charging process of AC charging piles involves high voltage and high current, ensuring safety has become the primary and core task of AC charging piles.

[0003] In power supply networks, the correct detection of the protective earth (PE) conductor is extremely important. If a fault occurs in the grounding line and grounding abnormalities cannot be detected in time, it may lead to leakage accidents, which will seriously threaten the lives of users.

[0004] Existing grounding detection circuits use a lot of electronic components in the circuit, which introduces more unstable factors and increases the risk of failure. For example, the grounding detection circuit of an AC charging pile disclosed in patent publication number CN219392246U uses two detection branches to detect the live wire and the neutral wire respectively. The circuit has many components and a complex structure. Utility Model Content

[0005] In view of the shortcomings of the prior art, the present invention provides a grounding detection circuit for AC power supply. The technical problem to be solved is that the existing grounding detection circuit for AC power supply detects the live wire and the neutral wire separately through corresponding detection circuits. It has many components and a complex structure, which increases the risk of grounding failure.

[0006] To solve the above technical problems, this utility model provides the following technical solution: a grounding detection circuit for AC power supply, including a safety capacitor CY1, a safety capacitor CY2, a first resistor branch, a second resistor branch, and an operational amplifier unit;

[0007] The two ends of the safety capacitor CY1 are used to connect to the live wire and the neutral wire. One end of the safety capacitor CY1 is connected to the input terminal of the first resistor branch and one end of the safety capacitor CY2, respectively. The other end of the safety capacitor CY2 is connected to the input terminal of the second resistor branch and the ground wire PE, respectively.

[0008] The output terminal of the first resistor branch is electrically connected to the positive input terminal of the operational amplifier unit, and the output terminal of the second resistor branch is electrically connected to the negative input terminal of the operational amplifier unit. The output terminal of the operational amplifier unit is used to output the detection signal.

[0009] In one embodiment, the first resistor branch includes M resistors connected in series, where M is a positive integer greater than 1.

[0010] In one embodiment, the second resistor branch includes N resistors connected in series, where N is a positive integer greater than 1.

[0011] In one implementation, both M and N are three.

[0012] In one embodiment, the three resistors of the first resistor branch are resistors R2, R3 and R4 in series, and the three resistors of the second resistor branch are resistors R8, R9 and R10 in series.

[0013] The resistors R2, R3, R8, and R9 have the same resistance value, and the resistors R4 and R10 have the same resistance value, which is half the resistance value of resistor R2.

[0014] In one embodiment, the operational amplifier unit includes an operational amplifier chip U1 of model LM2904DR;

[0015] Pin 3 of the operational amplifier chip U1 is the positive input terminal of the operational amplifier unit. It is electrically connected to one end of resistor R1, one end of resistor R6, one end of capacitor C1, and the output terminal of the first resistor branch. The other end of resistor R1 is used to input the working voltage, and the other ends of resistor R6 and capacitor C1 are both grounded.

[0016] The first pin of the operational amplifier chip U1 is electrically connected to one end of resistor R5, one end of resistor R7 and one end of capacitor C2, respectively. The other end of resistor R5 is used to output the detection signal. The other end of resistor R7 is electrically connected to the other end of capacitor C2, the second pin of operational amplifier chip U1, and the output end of the second resistor branch, respectively.

[0017] In one embodiment, the resistance values ​​of resistor R1 and resistor R6 are the same.

[0018] In one embodiment, the resistance of resistor R7 is half the resistance of resistor R1.

[0019] In one embodiment, the capacitance values ​​of capacitor C1 and capacitor C2 are the same.

[0020] In one embodiment, the present invention further includes an MCU main control unit, wherein the detection signal output by the operational amplifier unit is input to the MCU main control unit.

[0021] Compared with the prior art, the advantages of this utility model are as follows: In actual use, when the live wire and neutral wire of the AC power are connected to the two ends of the safety capacitor CY1 at different positions and the ground wire PE is not reliably grounded, the operational amplifier unit will output peak voltages of different magnitudes, thereby realizing reliable grounding detection. Moreover, the entire circuit only uses one operational amplifier unit, with fewer components and a simple circuit structure. Attached Figure Description

[0022] Figure 1 This is a circuit diagram of the present invention as shown in the embodiments. Detailed Implementation

[0023] The following specific embodiments illustrate the implementation of a grounding detection circuit for AC power supply disclosed in this utility model. Those skilled in the art can understand the advantages and effects of this utility model from the content disclosed in this specification. This utility model can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this utility model. Furthermore, the accompanying drawings of this utility model are for simple illustrative purposes only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this utility model in detail, but the disclosed content is not intended to limit the scope of protection of this utility model.

[0024] It should be understood that while terms such as "first," "second," and "third" may be used in this document to describe various components or features, these components or features should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one feature from another. Furthermore, the terms used in this document may, as appropriate, include any combination of one or more related items listed.

[0025] like Figure 1 As shown, an AC-powered grounding detection circuit includes a safety capacitor CY1, a safety capacitor CY2, a first resistor branch 1, a second resistor branch 2, and an operational amplifier unit 3.

[0026] Safety capacitor CY1 is used to connect the two ends of the live wire L and the neutral wire N. One end of safety capacitor CY1 is connected to the input terminal of the first resistor branch 1 and one end of safety capacitor CY2. The other end of safety capacitor CY2 is connected to the input terminal of the second resistor branch 2 and the ground wire PE.

[0027] The output terminal of the first resistor branch 1 is electrically connected to the positive input terminal of the operational amplifier unit 3, and the output terminal of the second resistor branch 2 is electrically connected to the negative input terminal of the operational amplifier unit 3. The output terminal of the operational amplifier unit 3 is used to output the detection signal.

[0028] In practical use, when the live wire L and neutral wire N of the AC power are connected to the two ends of the safety capacitor CY1 at different positions and the ground wire PE is unreliable, the operational amplifier unit 3 will output peak voltages of different magnitudes, thereby realizing reliable grounding detection. Moreover, the entire circuit only uses one operational amplifier unit 3, with fewer components and a simple circuit structure.

[0029] In this embodiment, the first resistor branch 1 includes M resistors connected in series, where M is a positive integer greater than 1. Additionally, the second resistor branch 2 includes N resistors connected in series, where N is a positive integer greater than 1.

[0030] In this embodiment, as Figure 1 As shown, both M and N are three. The three resistors in the first resistor branch 1 are resistors R2, R3 and R4 in series, and the three resistors in the second resistor branch 2 are resistors R8, R9 and R10 in series.

[0031] Among them, resistors R2, R3, R8 and R9 have the same resistance value, and resistors R4 and R10 have the same resistance value, which is half the resistance value of resistor R2.

[0032] In one implementation, M and N can be other equal values, such as 4, 5 or 6. There are no restrictions here, and they can be set according to actual needs.

[0033] like Figure 1 As shown, the operational amplifier unit 3 includes an operational amplifier chip U1 of model LM2904DR;

[0034] Pin 3 of the operational amplifier chip U1 is the positive input terminal of the operational amplifier unit. It is electrically connected to one end of resistor R1, one end of resistor R6, one end of capacitor C1, and the output terminal of the first resistor branch. The other end of resistor R1 is used to input the working voltage, which is a DC voltage of 3.3V. The other ends of resistor R6 and capacitor C1 are both grounded.

[0035] Pin 1 of the operational amplifier chip U1 is electrically connected to one end of resistor R5, one end of resistor R7, and one end of capacitor C2. The other end of resistor R5 is used to output the detection signal. The other end of resistor R7 is electrically connected to the other end of capacitor C2, pin 2 of the operational amplifier chip U1, and the output end of the second resistor branch.

[0036] Among them, resistors R1 and R6 have the same resistance value, and resistor R7 has half the resistance value of resistor R1. Additionally, capacitors C1 and C2 have the same capacitance value.

[0037] In addition, in this embodiment, the present invention also includes an MCU main control unit, and the detection signal output by the operational amplifier unit 3 is input to the MCU main control unit.

[0038] Taking a working voltage of 3.3V, a resistor R2 with a resistance of 510KΩ, a resistor R1 with a resistance of 10.2KΩ, and a capacitor C1 with a capacitance of 220pF as an example, for... Figure 1 The working process of the circuit shown is analyzed as follows:

[0039] When the ground wire PE of the charging pile is not properly connected, a voltage waveform will be generated between the neutral wire N and the ground wire PE. The voltage waveform is a sine wave with a reference voltage of 0V. This voltage serves as an important reference standard for whether the ground is connected. Considering the grid voltage error, the peak voltage of this voltage at this time is denoted as Vac.

[0040] In addition, the voltage value is amplified to 17 / 4320 times the original value by the amplification unit. By dividing the voltage equally between resistors R1 and R6, the reference voltage of the acquired waveform can be raised to 1.65V. At this time, the acquired data is a sine waveform with a reference voltage of 1.65V. This waveform can be directly acquired and processed by the MCU main control unit with a reference voltage of 3.3V.

[0041] The MCU main control unit takes n peak values ​​of the acquired waveform data, i.e., 1 / 50Hz*n seconds, and records the peak voltage as Vac2;

[0042] If Vac2 = 1.65V, then the PE ground wire is considered to be properly grounded.

[0043] If 1.65 < Vac2 < (Vac*17) / 4320, then the grounding of the PE wire is determined to be abnormal;

[0044] If Vac2 = (Vac*17) / 4320, it is determined that the live wire L and the neutral wire N are reversed, and the wiring sequence needs to be adjusted and retested.

[0045] In this embodiment, the MCU main control unit can be selected from an existing microcontroller-based finished module, wherein the microcontroller can be an STM32 series microcontroller.

[0046] In one implementation, the MCU main control unit can also be electrically connected to the communication unit to transmit grounding detection data. The communication unit can be a wired communication unit or a wireless communication unit. When it is a wired communication unit, it can be an RS232 communication unit, an RS485 communication unit, a USB communication unit, or a CAN bus communication unit. When it is a wireless communication unit, it can be a Bluetooth communication unit, a WiFi communication unit, a 4G communication unit, or a 5G communication unit.

[0047] In one implementation, the MCU main control unit can also be electrically connected to the alarm unit, which can then issue a light alarm signal or an audible alarm signal.

[0048] Based on the above description and inspired by this utility model, those skilled in the art can make various changes and modifications without departing from the technical concept of this utility model. The technical scope of this utility model is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. An AC powered ground detection circuit, characterized by, The safety capacitor CY1, the safety capacitor CY2, the first resistance branch, the second resistance branch and the operational amplifier unit are included. The safety capacitor CY1 is electrically connected with the live wire and the neutral wire, and one end of the safety capacitor CY1 is electrically connected with the input end of the first resistance branch and one end of the safety capacitor CY2. The output end of the first resistance branch is electrically connected with the positive input end of the operational amplifier unit, the output end of the second resistance branch is electrically connected with the negative input end of the operational amplifier unit, and the output end of the operational amplifier unit is used for outputting a detection signal.

2. An AC powered ground detection circuit according to claim 1, wherein, The first resistance branch includes M resistors connected in series, and M is a positive integer greater than 1.

3. An AC powered ground detection circuit according to claim 2, wherein, The second resistance branch includes N resistors connected in series, and N is a positive integer greater than 1.

4. An AC powered ground detection circuit according to claim 3, wherein, M and N are both three.

5. An AC powered ground detection circuit according to claim 4, wherein, The three resistors of the first resistance branch are the resistor R2, the resistor R3 and the resistor R4 connected in series, and the three resistors of the second resistance branch are the resistor R8, the resistor R9 and the resistor R10 connected in series. The resistor R2, the resistor R3, the resistor R8 and the resistor R9 have the same resistance value, and the resistor R4 and the resistor R10 have the same resistance value which is half of the resistance value of the resistor R2.

6. An AC powered earth detection circuit as claimed in any one of claims 1 to 5, wherein, The operational amplifier unit includes an operational amplifier chip U1 with the model of LM2904DR. The No. 3 pin of the operational amplifier chip U1 is the positive input end of the operational amplifier unit, and is electrically connected with one end of the resistor R1, one end of the resistor R6, one end of the capacitor C1 and the output end of the first resistance branch. The No. 1 pin of the operational amplifier chip U1 is electrically connected with one end of the resistor R5, one end of the resistor R7 and one end of the capacitor C2, the other end of the resistor R5 is used for outputting the detection signal, the other end of the resistor R7 is electrically connected with the other end of the capacitor C2, the No. 2 pin of the operational amplifier chip U1 and the output end of the second resistance branch.

7. An AC powered ground detection circuit according to claim 6, wherein, The resistor R1 and the resistor R6 have the same resistance value.

8. An AC powered ground detection circuit according to claim 7, wherein, The resistance value of the resistor R7 is half of the resistance value of the resistor R1.

9. An AC powered ground detection circuit according to claim 6, wherein, The capacitor C1 and the capacitor C2 have the same capacitance value.

10. An AC powered ground detection circuit according to claim 1, wherein, The detection signal output by the operational amplifier unit is input to the MCU main control unit.

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