Grounding detection circuit with double live wire input

Abstract

The utility model provides a double-live-wire input grounding detection circuit. The double-live-wire input grounding detection circuit comprises an MCU, a voltage access assembly, a voltage acquisition member, a bias resistance assembly and a signal acquisition assembly. The two input ends IN1 and IN2 of the voltage access assembly are connected with the two input ends of the charging pile, the two output ends of the voltage access assembly are connected through the first capacitor C and the second capacitor which are connected in series, the common end of the first capacitor and the common end of the second capacitor are connected with the grounding end PE of the charging pile, and the voltage access assembly is symmetrically designed. The voltage acquisition components are respectively connected in series with the two output ends of the voltage access component, and the output ends of the voltage acquisition component are also connected with an AC / DC converter, so that voltage signals can be converted into direct current to provide power for other modules. One end of the bias resistance component is connected with one of the input ends of the charging pile, the other end of the bias resistance component is connected with the grounding end of the charging pile, the output end of the voltage acquisition component is connected with the input end of the signal acquisition component, and the signal acquisition component is used for receiving a voltage signal, amplifying the voltage signal and outputting the amplified voltage signal to the ADC sampling end of the MCU.

Description

Technical Field

[0001] This utility model relates to the field of detection circuit technology, and in particular to a grounding detection circuit with dual live wire inputs. Background Technology

[0002] With the rapid development of the electric vehicle industry, charging piles, as a key infrastructure for electric vehicle energy replenishment, are receiving increasing attention for their safety and stability. Traditionally, grounding testing of charging piles is mainly based on the Y-type power grid structure of national or European standards, namely a three-phase four-wire power supply system including a live wire (L), a neutral wire (N), and a ground wire (PE). In this system, the purpose of grounding testing is to ensure a good electrical connection between the charging pile and the ground to prevent electric shock accidents and ensure equipment safety.

[0003] However, in specific regions or application scenarios, such as industrial applications or certain special power grid structures, charging piles may face a power supply environment with dual live wire input. This means that there is no neutral wire in the traditional sense; instead, the power supply consists of two live wires (L1, L2) and a ground wire (PE). This structure is similar to a simplified form of a delta grid. For such non-standard power grid structures, traditional grounding detection methods have significant limitations.

[0004] First, the traditional voltage divider detection method, which involves connecting a large resistor in series with the live wire or neutral wire to the ground wire (PE), using the voltage divider principle to obtain the L / N voltage value against PE, and then sampling and analyzing it through the analog-to-digital converter (ADC) of a microcontroller (MCU) to evaluate the grounding quality, cannot be directly applied in dual-live-wire input or delta-connected power grids because there is no neutral wire (N) as a reference point.

[0005] Secondly, while the optocoupler-based detection method can overcome some limitations of the voltage divider method by detecting the electrical connection between the live / neutral wire (or one of the live wires in the case of two live wires) and the ground wire, this method may be subject to electromagnetic interference from the Y capacitor of the electric vehicle's power supply during charging pile operation, especially during high-current charging. This interference may cause the optocoupler to misjudge, thus affecting the accuracy of grounding detection. This could result in the charging pile misjudging a good ground connection even when the ground wire is actually disconnected. Utility Model Content

[0006] To address the aforementioned issues, the purpose of this invention is to provide a grounding detection circuit with dual live wire input. By connecting a pull-off resistor component to the circuit, when the grounding terminal of the charging pile is poorly grounded, the voltage values ​​at the first and second detection points will be different, thereby identifying whether the grounding is good. This solves the problem in traditional detection methods where dual live wire input cannot accurately detect whether the grounding is good due to the lack of a neutral wire as a reference point.

[0007] This utility model is achieved through the following technical solution:

[0008] A grounding detection circuit with dual live wire inputs, comprising:

[0009] MCU;

[0010] The voltage access component has two input terminals connected to the two input terminals of the charging pile. The two output terminals of the voltage access component are connected in series through a first capacitor and a second capacitor, respectively. The common terminal of the first capacitor and the second capacitor is connected to the ground terminal of the charging pile. The voltage access component is symmetrically designed, and the capacitance values ​​of the first capacitor and the second capacitor are equal.

[0011] A voltage acquisition device is connected in series at the two output terminals of the voltage input component, serving as a first detection point and a second detection point, for acquiring voltage signals from the two output terminals; the output terminal of the voltage acquisition component is also connected to an AC / DC converter.

[0012] A biasing resistor assembly, one end of which is connected to one of the input terminals of the charging pile and the other end of which is connected to the ground terminal of the charging pile;

[0013] The signal acquisition component has the first detection point and the second detection point connected to the input terminal of the signal acquisition component, which is used to receive the voltage signal, amplify it and output it to the ADC sampling terminal of the MCU.

[0014] The resistance of the pull-off resistor component is greater than the equivalent resistance of the second capacitor.

[0015] The grounding detection circuit also includes a control component, which is connected to the MCU. The MCU controls whether the pull-off resistor component is connected to the circuit through the control component.

[0016] Furthermore, the control component includes a switching transistor and an optocoupler; the control terminal of the switching transistor is connected to the MCU, one of the two terminals of the switching transistor is grounded, the other of the two electrodes of the switching transistor is connected to the light emitter of the optocoupler, and the other end of the light emitter is connected to the power supply; the light receiver of the optocoupler is connected between the bias resistor assembly and the grounding terminal of the charging pile.

[0017] Furthermore, the biasing resistor assembly includes one resistor or multiple resistors connected in series.

[0018] Furthermore, the resistance value of the pull-off resistor component is ten times or more greater than the equivalent resistance value of the second capacitor.

[0019] Furthermore, the voltage acquisition device is an inductor.

[0020] Furthermore, the signal acquisition component includes two operational amplifiers. The first acquisition point is connected to the input terminal of one of the operational amplifiers through a first voltage divider resistor group, and the second acquisition point is connected to the input terminal of the other operational amplifier through a second voltage divider resistor group. The output terminals of both operational amplifiers are connected to the MCU. The resistance values ​​of the first voltage divider resistor group and the second voltage divider resistor group are the same.

[0021] Furthermore, a reference voltage is connected between the first voltage divider resistor group and the input terminal of the operational amplifier; a reference voltage is also connected between the second voltage divider resistor group and the input terminal of the operational amplifier.

[0022] Furthermore, the voltage access component includes a common-mode inductor connected in series, a fuse connected to the two windings of the common-mode inductor respectively, an X capacitor provided on both sides of the common-mode inductor, the X capacitor being connected across the two electric field lines, and the other end of the fuse being the two input terminals of the voltage access component.

[0023] Compared with the prior art, the technical solution of this utility model and its beneficial effects are as follows:

[0024] (1) By connecting the bias resistor assembly into the circuit, the two voltage acquisition devices are biased asymmetrically to the resistance of the grounding terminal. Thus, when the grounding terminal is not grounded, the voltage difference between the first detection point and the second detection point is large, so that they can be accurately identified.

[0025] (2) By connecting the appropriate resistance value of the pull-off resistor component and controlling the on and off time of the optocoupler by the MCU, the effective value of current leakage caused by incomplete insulation material or other reasons can be controlled within the safety requirements.

[0026] (3) The resistance of the bias resistor assembly is much greater than the equivalent resistance of the second capacitor, which makes the voltage difference between the first detection point and the grounding terminal PE and the second detection point and the grounding terminal PE quite large. This can better solve the problem of inaccurate detection caused by the interference of the Y capacitor of the vehicle power supply during charging. Attached Figure Description

[0027] Figure 1 This is a module block diagram of a grounding detection circuit with dual live wire input provided in an embodiment of this utility model;

[0028] Figure 2 This is a circuit diagram of the pressure input component, the pull-off resistor component, and the control component provided in this embodiment of the utility model;

[0029] Figure 3 This is a circuit diagram of the signal acquisition component provided in this embodiment of the utility model;

[0030] Figure 4 This is a block diagram of the MCU provided in this embodiment of the utility model.

[0031] Illustration:

[0032] Voltage input component-10; bias resistor component-20; control component-30; signal acquisition component-40; first voltage divider resistor group-41; second voltage divider resistor group-42. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this utility model and are not intended to limit this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0034] See Figure 1 A grounding detection circuit with dual live wire inputs includes an MCU, a voltage input component, a voltage acquisition component, a pull-bias resistor component, and a signal acquisition component. The two input terminals IN1 and IN2 of the voltage input component are connected to the two input terminals of the charging pile. The two output terminals of the voltage input component are connected in series via a first capacitor CY1 and a second capacitor CY2, respectively. The common terminal of the first capacitor CY1 and the second capacitor CY2 is connected to the grounding terminal PE of the charging pile. The voltage input component has a symmetrical design. The voltage acquisition components are connected in series to the two output terminals of the voltage input component. The output terminal of the voltage acquisition component is also connected to an AC / DC converter to convert the voltage signal into DC power to provide power to other modules. One end of the pull-bias resistor component is connected to one of the input terminals of the charging pile, and the other end is connected to the grounding terminal of the charging pile. The output terminal of the voltage acquisition component is connected to the input terminal of the signal acquisition component. The signal acquisition component receives the voltage signal, amplifies it, and outputs it to the ADC sampling terminal of the MCU.

[0035] The two input terminals of the voltage input component are connected to the live wire, i.e., dual live wire input. When the grounding terminal of the charging pile is well grounded, since the voltage input component is symmetrically designed, the capacitance values ​​of the first capacitor CY1 and the second capacitor CY2 are equal. Therefore, the voltages at the two output terminals of the voltage input component are equal. The voltage signals transmitted to the signal acquisition component through the voltage acquisition device are also the same. Similarly, the signals acquired by the ADC sampling terminal of the MCU after being processed by the signal acquisition component are also equal.

[0036] When the charging pile's grounding terminal is faulty, the pull-off resistor component is connected to the circuit, causing the voltage values ​​at the first and second detection points to be different. The voltage signals transmitted to the signal acquisition component via the voltage acquisition device are also different. Similarly, the signals acquired by the MCU's ADC sampling terminal after processing by the signal acquisition component are also unequal, thus identifying whether the grounding is good or not. In this embodiment, the resistance value of the pull-off resistor component is set to be much larger than the equivalent resistance value of the second capacitor, typically more than ten times. This ensures that when the grounding terminal is not grounded, the voltage difference between the two voltage acquisition devices and the grounding terminal is large, allowing for accurate identification.

[0037] Continue reading Figure 1 The grounding detection circuit also includes a control component 30, which is connected to the MCU. The MCU controls whether the pull-up resistor component 20 is connected to the circuit through the control component 30. Specifically, as Figure 2 As shown, the control component 30 includes a switching transistor Q9 and an optocoupler U2. Switch Q9 is an NPN transistor. The base of Q9 is connected to the MCU, the emitter of Q9 is grounded, and the collector of Q9 is connected to the emitter of optocoupler U2. The other end of the emitter is connected to the 3.3V power supply. The receiver of optocoupler U2 is connected between the pull-bias resistor assembly 20 and the ground terminal PE of the charging pile. When the MCU sends a high-level signal to switch Q9, Q9 conducts, thus creating a path between the 3.3V power supply, the emitter, switch Q9, and ground. The emitter of optocoupler U2 emits light, thereby turning on the receiver, which in turn connects the pull-bias resistor assembly 20 between the input terminal IN2 of the voltage input assembly and the ground terminal PE. The biasing resistor assembly includes one or more resistors connected in series. In this embodiment, it includes resistors R15, R16, R17 and R18 connected in series. The photodetector of the optocoupler U2 is connected in series between two adjacent resistors, such as resistors R17 and R18.

[0038] The voltage acquisition components are inductors L1 and L2. Inductor L1 is connected to the first output terminal of the voltage input component, and the other end of inductor L1 is the first detection point AC_N, which is also connected to the AC / DC converter. Inductor L2 is connected to the second output terminal of the voltage input component, and the other end of inductor L2 is the second detection point AC_L, which is also connected to the AC / DC converter. It is understood that inductors L1 and L2 have the same inductance value.

[0039] The voltage access component includes a common-mode inductor CL2 connected in series, and fuses F1 and F2 connected to the two windings of the common-mode inductor CL2 respectively. Capacitors CX2 and CX3 are provided on both sides of the common-mode inductor. CX2 and CX3 are connected across the two electric field lines. The other end of fuse F1 is the input terminal IN1 of the voltage access component, and the other end of fuse F1 is the input terminal IN2 of the voltage access component.

[0040] See Figure 3 and Figure 4 The signal acquisition component includes two operational amplifiers. In this embodiment, a dual operational amplifier U3 is used. The first acquisition point AC_N is connected to the input terminal IN1+ of the dual operational amplifier U3 through the first voltage divider resistor group 41, and the second acquisition point AC_L is connected to the input terminal IN2+ of the dual operational amplifier U3 through the second voltage divider resistor group 42. The two output terminals OUT1 and OUT2 of the dual operational amplifier U3 are both connected to the MCU. The resistance values ​​of the first voltage divider resistor group 41 and the second voltage divider resistor group 42 are the same. The voltages of inductor L1 to ground terminal PE and inductor L2 to ground terminal PE are divided by the first voltage divider resistor group 41 and the second voltage divider resistor group 42 to obtain a low-voltage AC signal. The obtained low-voltage AC signal is amplified by the amplifier circuit to enhance the driving capability and then sent to the ADC port of the MCU for effective value acquisition. If a high level is detected, it indicates that the grounding is good; if a low level is detected, it indicates that there is no grounding. It is worth noting that the high level and low level here are not 1 or 0 in digital circuits, but refer to the voltage above a certain threshold as a high level and the voltage below a certain threshold as a low level.

[0041] Furthermore, a reference voltage is connected between the first voltage divider resistor group 41 and the input terminal IN1+ of the dual operational amplifier U3; a reference voltage is also connected between the second voltage divider resistor group 42 and the input terminal IN12 of the dual operational amplifier U3. The AC signal obtained by voltage division by the first voltage divider resistor group 41 and the second voltage divider resistor group 42 is superimposed with the reference voltage so that the negative half-wave can also be sent to the back end for acquisition.

[0042] This invention employs a dual-wire input grounding detection circuit. By integrating a pull-bias resistor into the circuit, a voltage difference is achieved between the first and second detection points when the grounding terminal is not grounded. This solves the problem of traditional detection circuits failing to detect a lack of grounding when there is a dual-wire input but the grounding terminal is not grounded, as the first and second detection points are symmetrical with respect to ground. By using an appropriate pull-bias resistor and controlling the on / off time of the optocoupler with the MCU, the effective value of current leakage caused by incomplete insulation or other reasons can be controlled within safety regulations. Furthermore, the significant voltage difference between the first and second detection points relative to the grounding terminal PE effectively addresses the problem of inaccurate detection caused by interference from the Y capacitor of the vehicle-side power supply during charging.

[0043] The foregoing description illustrates and describes preferred embodiments of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the present invention through the foregoing teachings or related technical or knowledge. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A grounding detection circuit with dual live wire inputs, characterized in that, include: MCU; The voltage access component has two input terminals connected to the two input terminals of the charging pile. The two output terminals of the voltage access component are connected in series through a first capacitor and a second capacitor, respectively. The common terminal of the first capacitor and the second capacitor is connected to the ground terminal of the charging pile. The voltage access component is symmetrically designed, and the capacitance values ​​of the first capacitor and the second capacitor are equal. A voltage acquisition device is connected in series at the two output terminals of the voltage input component, serving as a first detection point and a second detection point, for acquiring voltage signals from the two output terminals; the output terminal of the voltage acquisition component is also connected to an AC / DC converter. A biasing resistor assembly, one end of which is connected to one of the input terminals of the charging pile and the other end of which is connected to the ground terminal of the charging pile; The signal acquisition component has the first detection point and the second detection point connected to the input terminal of the signal acquisition component, which is used to receive the voltage signal, amplify it and output it to the ADC sampling terminal of the MCU. The resistance of the pull-off resistor component is greater than the equivalent resistance of the second capacitor.

2. The grounding detection circuit with dual live wire input according to claim 1, characterized in that, It also includes a control component, which is connected to the MCU. The MCU controls whether the pull-up resistor component is connected to the circuit through the control component.

3. A grounding detection circuit with dual live wire inputs according to claim 2, characterized in that, The control component includes a switching transistor and an optocoupler; the control terminal of the switching transistor is connected to the MCU, one of the two terminals of the switching transistor is grounded, the other of the two electrodes of the switching transistor is connected to the light emitter of the optocoupler, and the other end of the light emitter is connected to the power supply; the light receiver of the optocoupler is connected between the bias resistor assembly and the ground terminal of the charging pile.

4. A grounding detection circuit with dual live wire inputs according to claim 1, characterized in that, The biasing resistor assembly includes one resistor or multiple resistors connected in series.

5. A grounding detection circuit with dual live wire inputs according to claim 1, characterized in that, The resistance of the pull-off resistor assembly is ten times or more the equivalent resistance of the second capacitor.

6. A grounding detection circuit with dual live wire inputs according to claim 1, characterized in that, The voltage acquisition device is an inductor.

7. A grounding detection circuit with dual live wire inputs according to claim 1, characterized in that, The signal acquisition component includes two operational amplifiers. The first acquisition point is connected to the input terminal of one of the operational amplifiers through a first voltage divider resistor group, and the second acquisition point is connected to the input terminal of the other operational amplifier through a second voltage divider resistor group. The output terminals of both operational amplifiers are connected to the MCU. The resistance values ​​of the first voltage divider resistor group and the second voltage divider resistor group are the same.

8. A grounding detection circuit with dual live wire inputs according to claim 7, characterized in that, A reference voltage is also connected between the first voltage divider resistor group and the input terminal of the operational amplifier; a reference voltage is also connected between the second voltage divider resistor group and the input terminal of the operational amplifier.

9. A grounding detection circuit with dual live wire inputs according to claim 1, characterized in that, The voltage access component includes a common-mode inductor connected in series, a fuse connected to the two windings of the common-mode inductor respectively, an X capacitor on both sides of the common-mode inductor, the X capacitor being connected across the two electric field lines, and the other end of the fuse being the two input terminals of the voltage access component.

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