Alternating current grounding detection circuit compatible with multiple power supply types

Abstract

The utility model relates to the technical field of grounding detection, and discloses an AC grounding detection circuit compatible with various power supply types, which comprises a safety capacitor CY1, a safety capacitor CY2, a safety capacitor CY3, a switch, a first resistor branch, a second resistor branch, an operational amplifier U1, a voltage following unit and an MCU main control unit. In actual use, by controlling the on-off of the switch, the voltage difference between the bottom line PE and the live wire L2 can be detected through the operational amplifier U1 when the switch is on and recorded as a first voltage difference, and the voltage difference between the bottom line PE and the live wire L2 can be detected through the operational amplifier U1 when the switch is off and recorded as a second voltage difference. The MCU main control unit can detect whether grounding is reliable or not by comparing the difference value of the first voltage difference and the second voltage difference, due to the fact that the circuit is provided with the two live wire connecting points and the grounding point, the circuit can be suitable for various power supply types, the operational amplifier U1 is used for difference value detection, and it is not needed to worry that the detection reliability is affected by circuit parameter changes.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of grounding detection, and particularly relates to an alternating current grounding detection circuit compatible with multiple power supply types. BACKGROUND

[0002] With the vigorous development of new energy, especially electric new energy vehicles, the existing vehicle production scale presents explosive growth, and alternating current charging piles matched with electric vehicles are also produced. Because of charging, it is strong current and large current, so safety is the top priority. In the power system, the detection of the grounding PE line is very important. If the grounding line is abnormal and is not discovered in time, once the electric leakage occurs, it will cause personal harm to the related users and endanger life.

[0003] In the existing product, because the product is applied in different countries and different regions, the power supply types of these countries and regions are also different, which leads to various collection methods of the grounding circuit, and all types of use scenarios cannot be simultaneously compatible. In the prior art, for the grounding detection of the charging pile, many use optical coupling detection. The performance of the optical coupling related circuit parameters changes with power supply fluctuation, environmental temperature and the like, and the grounding fault is often detected to fail or misreported, which greatly reduces safety or causes product quality problems. UTILITY MODEL CONTENT

[0004] In view of the deficiencies in the background art, the utility model provides an alternating current grounding detection circuit compatible with multiple power supply types, and the technical problem to be solved is that the existing alternating current grounding detection circuit has poor compatibility and poor reliability.

[0005] To solve the above technical problems, the utility model provides the following technical scheme: an alternating current grounding detection circuit compatible with multiple power supply types, comprising a safety capacitor CY1, a safety capacitor CY2, a safety capacitor CY3, a switch, a first resistance branch, a second resistance branch, an operational amplifier U1, a voltage follower unit and an MCU main control unit.

[0006] One end of the safety capacitor CY1 is used for electrical connection with a live wire L1. The other end of the safety capacitor CY1 is electrically connected with the one end of the safety capacitor CY1 and the one end of the safety capacitor CY3, and is used for electrical connection with a ground wire PE. The other end of the safety capacitor CY2 is electrically connected with the other end of the safety capacitor CY3 through the switch, and is used for electrical connection with a live wire L2.

[0007] One end of the safety capacitor CY2 is electrically connected with the input end of the second resistance branch. The output end of the second resistance branch is electrically connected with the output end of the operational amplifier U1. One intermediate node of the second resistance branch is electrically connected with the negative input end of the operational amplifier U1.

[0008] The other end of the safety capacitor CY2 is electrically connected with the input end of the first resistance branch, the output end of the first resistance branch is grounded, and one intermediate node of the first resistance branch is electrically connected with the positive input end of the operational amplifier U1.

[0009] The output end of the operational amplifier U1 is electrically connected with the input end of the voltage follower unit, and the output end of the voltage follower unit is electrically connected with the MCU master control unit.

[0010] In some embodiments, the MCU master control unit is electrically connected with the switch to control the on-off of the switch.

[0011] In some embodiments, the switch is a pair of normally open contacts of a relay.

[0012] In some embodiments, the first resistance branch comprises resistors R2, R3, R4 and R1 connected in series, one end of the resistor R2 is the input end of the first resistance branch, one end of the resistor R1 is one intermediate node of the first resistance branch, and the other end of the resistor R1 is the output end of the first resistance branch.

[0013] In some embodiments, the resistor R1 is connected in parallel with a capacitor C1 at both ends.

[0014] In some embodiments, the second resistance branch comprises resistors R6, R7, R8 and R11 connected in series, one end of the resistor R6 is the input end of the second resistance branch, one end of the resistor R11 is one intermediate node of the second resistance branch, and the other end of the resistor R11 is the output end of the second resistance branch.

[0015] In some embodiments, the resistor R11 is connected in parallel with a capacitor C3 at both ends.

[0016] In some embodiments, the voltage follower unit comprises a resistor R5, an operational amplifier U2, a capacitor C2 and a resistor R10, one end of the resistor R5 is electrically connected with the output end of the operational amplifier U1, and is the input end of the voltage follower unit, the other end of the resistor R5 is electrically connected with the positive input end of the operational amplifier U2, the negative input end of the operational amplifier U2 is electrically connected with the output end of the operational amplifier U2 and one end of the resistor R10 respectively, the other end of the resistor R10 is electrically connected with the MCU master control unit, and is the output end of the voltage follower unit, and is grounded through the capacitor C2.

[0017] In some embodiments, the output end of the operational amplifier U1 is electrically connected with the input end of the voltage follower unit through a diode D2, and the negative electrode of the diode D2 is also grounded through a resistor R9; and the input end of the second resistance branch is also grounded through a resistor R21.

[0018] In certain embodiments, the output end of the voltage follower unit is further electrically connected with a clamping unit.

[0019] The utility model has the beneficial effect compared with prior art: in actual use, the utility model can pass through the on-off of control switch, detects the voltage difference between bottom line PE and firewire L2 through operational amplifier U1 when switch is on, and is recorded as first pressure difference, detects the voltage difference between bottom line PE and firewire L2 through operational amplifier U1 when switch is off, and is recorded as second pressure difference, and the difference between first pressure difference and second pressure difference can be detected by MCU master control unit whether ground is reliable, since the circuit sets two firewire connection points and a grounding point, can be suitable for multiple power supply types, and uses operational amplifier U1 to detect difference, need not worry about that circuit parameter change influences detection reliability. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is the circuit diagram of the utility model in the embodiment. DETAILED DESCRIPTION

[0021] The utility model will be explained further in detail now in combination with the drawings. These drawings are all simplified schematic diagrams, and only illustrate the basic structure of the utility model in a schematic way, therefore it only shows the structure related to the utility model.

[0022] As Figure 1 Shown, a kind of AC ground detection circuit of compatible multiple power supply types, including safety capacitor CY1, safety capacitor CY2, safety capacitor CY3, switch, first resistance branch 1, second resistance branch 2, operational amplifier U1, voltage follower unit 3 and MCU master control unit 4;

[0023] Safety capacitor CY1 one end is used to and firewire L1 electrically connected;Safety capacitor CY1 other end is respectively connected with safety capacitor CY1 one end and safety capacitor CY3 one end, and is used to and ground PE electrically connected;Safety capacitor CY2 other end is connected with safety capacitor CY3 other end by switch, and is used to and firewire L2 electrically connected;

[0024] Safety capacitor CY2 one end is connected with the input end of second resistance branch 2, and the output end of second resistance branch 2 is connected with the output end of operational amplifier U1, and one intermediate node of second resistance branch 2 is connected with the negative input end of operational amplifier U1;

[0025] Safety capacitor CY2 other end is connected with the input end of first resistance branch 1, and the output end of first resistance branch 1 is grounded, and one intermediate node of first resistance branch 1 is connected with the positive input end of operational amplifier U1;

[0026] The output end of the operational amplifier U1 is electrically connected with the input end of the voltage follower unit 3, and the output end of the voltage follower unit 3 is electrically connected with the MCU master control unit 4.

[0027] In actual use, the utility model can detect the voltage difference between the bottom line PE and the firewire L2 through the operational amplifier U1 when the switch is turned on, and the difference is recorded as the first voltage difference, and the utility model can detect the voltage difference between the bottom line PE and the firewire L2 through the operational amplifier U1 when the switch is turned off, and the difference is recorded as the second voltage difference, and the MCU master control unit 4 can detect whether the grounding is reliable by comparing the difference between the first voltage difference and the second voltage difference, and since two firewire connection points and one grounding point are arranged in the circuit, the circuit can be applied to various power supply types, and the difference is detected by using the operational amplifier U1, so that the detection reliability is not affected by the change of circuit parameters.

[0028] Specifically, in the embodiment, the MCU master control unit 4 is electrically connected with the switch, and the on-off of the switch is controlled. Figure 1 In the embodiment, the switch is a pair of normally open contacts of the relay K1.

[0029] Specifically, in the embodiment, in the Figure 1 In the embodiment, the first resistance branch 1 comprises the resistance R2, the resistance R3, the resistance R4 and the resistance R1 which are connected in series, one end of the resistance R2 is the input end of the first resistance branch 1, one end of the resistance R1 is an intermediate node of the first resistance branch 1, and the other end of the resistance R1 is electrically connected with the positive input end of the operational amplifier U1, and the other end of the resistance R1 is the output end of the first resistance branch 1 and is grounded.

[0030] In actual use, the first resistance branch 1 inputs the voltage of the firewire L2 to the positive input end of the operational amplifier U1 according to a ratio, and the ratio is determined by the resistance values of the resistance R2, the resistance R3, the resistance R4 and the resistance R1.

[0031] Specifically, in the embodiment, in the Figure 1 In the embodiment, the capacitor C1 is connected in parallel across the resistance R1.

[0032] Specifically, in the embodiment, in the Figure 1 In the embodiment, the second resistance branch 2 comprises the resistance R6, the resistance R7, the resistance R8 and the resistance R11 which are connected in series, one end of the resistance R6 is the input end of the second resistance branch 2, one end of the resistance R11 is an intermediate node of the second resistance branch 2, and the other end of the resistance R11 is electrically connected with the negative input end of the operational amplifier U1, and the other end of the resistance R11 is the output end of the second resistance branch 2 and is electrically connected with the output end of the operational amplifier U1.

[0033] Specifically, in the embodiment, in the Figure 1 In the embodiment, the capacitor C3 is connected in parallel across the resistance R11.

[0034] Specifically, in the embodiment, in Figure 1 In the embodiment, the voltage follower unit 3 comprises a resistor R5, an operational amplifier U2, a capacitor C2 and a resistor R10, one end of the resistor R5 is electrically connected with the output end of the operational amplifier U1, serving as the input end of the voltage follower unit 3, the other end of the resistor R5 and the positive input end of the operational amplifier U2 are electrically connected, the negative input end of the operational amplifier U2 is electrically connected with the output end of the operational amplifier U2 and one end of the resistor R10 respectively, the other end of the resistor R10 is electrically connected with the MCU master unit 4, serving as the output end of the voltage follower unit 3, and is grounded through the capacitor C2.

[0035] Specifically, in the embodiment, in Figure 1 In the embodiment, the output end of the operational amplifier U1 is electrically connected with the input end of the voltage follower unit 3 through a diode D2, and the negative electrode of the diode D2 is further grounded through a resistor R9; the input end of the second resistor branch 2 is further grounded through a resistor R21.

[0036] Specifically, in the embodiment, in Figure 1 In the embodiment, the output end of the voltage follower unit 3 is further electrically connected with a clamping unit 5.

[0037] In actual use, the voltage input to the MCU master unit 4 can be prevented from being too high through the clamping unit 5, thereby protecting the MCU master unit, wherein the clamping unit 5 can be a clamping diode.

[0038] For Figure 1 The circuit shown in the figure is used for detecting the voltage between the firewire L2 and the ground wire PE. When normally grounded, under the national standard power supply, the voltage between N and the ground wire PE is 0V. Under the double firewire power supply, the voltage between the firewire L2 and the ground wire PE is a standard 120V, which is a fixed value. When not grounded, the voltage value detected by the firewire L2 (N line) and the ground wire PE point is affected by the external equivalent safety capacitor CY1 and the safety capacitor CY2, and an uncertain voltage value may appear, therefore, in the utility model, only the change amount of the voltage value between the firewire L2 (N line) and the ground wire PE is detected, the relay K1 is periodically switched, and the purpose is to parallel the safety capacitor CY3 and the safety capacitor CY2. When the voltage between the firewire L2 (N line) and the ground wire PE changes obviously before and after the relay K1 is switched, and reaches a certain threshold value, it is judged that the ground is not grounded.

[0039] For the North American single-phase power system, the standard double fire line L1 and L2 power supply, the fire line L1 to ground wire PE is 120V voltage, the fire line L2 to ground wire PE is 120V voltage, the fire line L1 to fire line L2 is 240V voltage; for the national standard and European standard, the power supply is L1, N and PE mode, the voltage between L1 and N is 220VAC-240VAC, the voltage between N and PE is 0V, in order to ensure the reliability, the voltage dividing capacitor capacity of fire line L1 and fire line L2 (N) should be equal;

[0040] The utility model discloses in actual application, for the power supply type that does not use, when relay K1 is not closed, the voltage between fire line L2 (N) and ground wire PE is measured as Vac1 by operational amplifier U1, when relay K1 is closed, the voltage between fire line L2 (N) and ground wire PE is measured as Vac2 by operational amplifier U1.

[0041] If Vac1=Vac2, it is judged that the normal grounding, if the voltage difference between Vac1 and Vac2 is greater than a certain value, it is judged that the grounding is abnormal.

[0042] The above is according to the utility model for the inspiration, through the above description, the relevant staff can make various changes and modifications without deviating from the technical idea of the utility model. The technical scope of the utility model is not limited to the content of the specification, and the technical scope must be determined according to the scope of claims.

Claims

1. An AC grounding detection circuit compatible with multiple power supply types, characterized in that: It includes safety capacitor CY1, safety capacitor CY2, safety capacitor CY3, a switch, a first resistance branch, a second resistance branch, an operational amplifier U1, a voltage follower unit and an MCU main control unit; One end of the safety capacitor CY1 is used to be electrically connected to the live wire L1; the other end of the safety capacitor CY1 is electrically connected to one end of the safety capacitor CY1 and one end of the safety capacitor CY3 respectively, and is used to be electrically connected to the ground wire PE; the other end of the safety capacitor CY2 is electrically connected to the other end of the safety capacitor CY3 through the switch, and is used to be electrically connected to the live wire L2; One end of the safety capacitor CY2 is electrically connected to the input end of the second resistance branch, the output end of the second resistance branch is electrically connected to the output end of the operational amplifier U1, and an intermediate node of the second resistance branch is electrically connected to the negative input end of the operational amplifier U1; The other end of the safety capacitor CY2 is electrically connected to the input end of the first resistance branch, the output end of the first resistance branch is grounded, and an intermediate node of the first resistance branch is electrically connected to the positive input end of the operational amplifier U1; The output end of the operational amplifier U1 is electrically connected to the input end of the voltage follower unit, and the output end of the voltage follower unit is electrically connected to the MCU main control unit.

2. The AC grounding detection circuit compatible with multiple power supply types according to claim 1, characterized in that: The MCU main control unit is electrically connected to the switch to control the on and off of the switch.

3. The AC grounding detection circuit compatible with multiple power supply types according to claim 1 or 2, characterized in that: The switch is a pair of normally open contacts of a relay.

4. The AC grounding detection circuit compatible with multiple power supply types according to claim 1, characterized in that: The first resistance branch includes a resistor R2, a resistor R3, a resistor R4 and a resistor R1 connected in series in sequence, one end of the resistor R2 is the input end of the first resistance branch, one end of the resistor R1 is an intermediate node of the first resistance branch, and the other end of the resistor R1 is the output end of the first resistance branch.

5. The AC grounding detection circuit compatible with multiple power supply types according to claim 4, characterized in that: A capacitor C1 is connected in parallel to both ends of the resistor R1.

6. The AC grounding detection circuit compatible with multiple power supply types according to claim 1, 4 or 5, characterized in that: The second resistance branch includes a resistor R6, a resistor R7, a resistor R8 and a resistor R11 connected in series in sequence, one end of the resistor R6 is the input end of the second resistance branch, one end of the resistor R11 is an intermediate node of the second resistance branch, and the other end of the resistor R11 is the output end of the second resistance branch.

7. The AC grounding detection circuit compatible with multiple power supply types according to claim 6, characterized in that: A capacitor C3 is connected in parallel to both ends of the resistor R11.

8. The AC grounding detection circuit compatible with multiple power supply types according to claim 1, characterized in that: The voltage follower unit includes a resistor R5, an operational amplifier U2, a capacitor C2 and a resistor R10. One end of the resistor R5 is electrically connected to the output end of the operational amplifier U1 and is the input end of the voltage follower unit. The other end of the resistor R5 is electrically connected to the positive input end of the operational amplifier U2. The negative input end of the operational amplifier U2 is electrically connected to the output end of the operational amplifier U2 and one end of the resistor R10, respectively. The other end of the resistor R10 is electrically connected to the MCU main control unit and is the output end of the voltage follower unit, and is grounded through the capacitor C2.

9. The AC grounding detection circuit compatible with multiple power supply types according to claim 1, characterized in that: The output end of the operational amplifier U1 is electrically connected to the input end of the voltage follower unit through a diode D2 , and the cathode of the diode D2 is also grounded through a resistor R9 ; the input end of the second resistor branch is also grounded through a resistor R21 .

10. The AC grounding detection circuit compatible with multiple power supply types according to claim 1, characterized in that: The output end of the voltage follower unit is also electrically connected to a clamping unit.

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