Residual current acquisition circuit for charging pile

Abstract

The utility model provides a residual current acquisition circuit for a charging pile, which relates to the technical field of electric vehicle charging pile equipment and comprises a residual current transformer, a first field effect transistor, a second field effect transistor and an operational amplifier. An S pole and a G pole of the first field effect transistor are connected, and a first resistor is arranged between the S pole and the G pole; a D pole of the first field effect transistor is connected with an N4 end of the residual current transformer; the S pole and the G pole of the second field effect transistor are connected, and a second resistor is arranged between the S pole and the G pole; the D pole of the second field effect transistor is connected with the N3 end of the residual current transformer; a third resistor and a fourth resistor are sequentially arranged between the positive input end of the operational amplifier and the L1 end of the residual current transformer, one end, close to the fourth resistor, of the third resistor is connected with the L2 end of the residual current transformer, a first capacitor is arranged between the third resistor and the L2 end of the residual current transformer, and one end of the third resistor is connected with a fifth resistor. The residual current detection device can effectively detect the residual current of the electric vehicle charging pile.

Description

Technical Field

[0001] The utility model relates to the technical field of electric vehicle charging pile equipment, and particularly relates to a residual current acquisition circuit for a charging pile. Background Art

[0002] In the new national standard GB / T18487.1-2003 for charging piles, it is required to support DC6mA residual current detection. Therefore, a new type of residual current sensor that supports both AC and DC is needed to collect the residual power in real time, so as to meet the requirements of the new national standard.

[0003] Therefore, there is an urgent need for a residual current acquisition circuit for a charging pile to solve the problem that the residual current of the charging pile needs to be collected in real time. Summary of the Utility Model

[0004] The utility model provides a residual current acquisition circuit for a charging pile to solve the problem that the residual current of the charging pile needs to be collected in real time.

[0005] In order to achieve the above purpose, the technical scheme adopted by the utility model is as follows:

[0006] A residual current acquisition circuit for a charging pile includes a residual current transformer, a first field effect transistor, a second field effect transistor and an operational amplifier;

[0007] The S pole and G pole of the first field effect transistor are connected and a first resistor is arranged therebetween, and the D pole of the first field effect transistor is connected to the N4 end of the residual current transformer;

[0008] The S pole and G pole of the second field effect transistor are connected and a second resistor is arranged therebetween, and the D pole of the second field effect transistor is connected to the N3 end of the residual current transformer;

[0009] The positive input end of the operational amplifier is connected to the L1 end of the residual current transformer, and a third resistor and a fourth resistor are arranged in sequence therebetween. One end of the third resistor close to the fourth resistor is connected to the L2 end of the residual current transformer and a first capacitor is arranged therebetween. One end of the third resistor is connected to a fifth resistor, one end of the fifth resistor is connected to the L2 end of the residual current transformer, one end of the fourth resistor is connected to a second capacitor, and the second capacitor is grounded;

[0010] The negative input end of the operational amplifier is connected to the output end, the output end of the operational amplifier is connected to a sixth resistor, and the sixth resistor is connected to a third capacitor, and the third capacitor is grounded.

[0011] In summary, due to adopting the above technical scheme, the beneficial effect of the utility model is:

[0012] The structure of the utility model is simple and can effectively collect the remaining power, so as to know the usage status of the current, and provide a judgment basis for the later DC 6 mA detection and the realization of Class A AC residual current protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic circuit diagram of the utility model. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0014] The following will describe the utility model in detail with reference to the drawings.

[0015] In order to make the purpose, technical solutions and advantages of the utility model more clear, the following will further describe the utility model in detail with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the utility model and are not used to limit the utility model.

[0016] In this embodiment, a residual current acquisition circuit for a charging pile is provided, as Figure 1 shown, which includes a residual current transformer CT1, a first field effect transistor Q8, a second field effect transistor Q9 and an operational amplifier U9B; the S pole and the G pole of the first field effect transistor Q8 are connected and a first resistor R7 is arranged therebetween, and the D pole of the first field effect transistor Q8 is connected to the N4 terminal of the residual current transformer CT1;

[0017] the S pole and the G pole of the second field effect transistor Q9 are connected and a second resistor R75 is arranged therebetween, and the D pole of the second field effect transistor Q9 is connected to the N3 terminal of the residual current transformer CT1;

[0018] the positive input terminal of the operational amplifier U9B is connected to the L1 terminal of the residual current transformer CT1 and a third resistor R58 and a fourth resistor R59 are arranged in sequence therebetween, one end of the third resistor R58 close to the fourth resistor R59 is connected to the L2 terminal of the residual current transformer CT1 and a first capacitor C34 is arranged therebetween, one end of the third resistor R58 is connected to a fifth resistor R57, one end of the fifth resistor R57 is connected to the L2 terminal of the residual current transformer CT1, one end of the fourth resistor R59 is connected to a second capacitor C36, and the second capacitor C36 is grounded;

[0019] the negative input terminal of the operational amplifier U9B is connected to the output terminal, the output terminal of the operational amplifier U9B is connected to a sixth resistor R79, and the sixth resistor R79 is connected to a third capacitor C47, and the third capacitor C47 is grounded.

[0020] In the utility model, a new combined current sensor specially designed for charging piles is used. CT1 in the above figure is a 500:1 residual current transformer CT1 and a 4-turn detection winding.

[0021] Figure 1 The circuit therein converts the current on the primary side into a proportional secondary side voltage, then filters out interference and adds a 1.65V bias voltage and sends it to the single-chip microcomputer (RCD_CRT). The single-chip microcomputer samples this signal to obtain the true effective value of the residual current, which is used to implement residual current protection and self-check of the residual current protection function.

[0022] The principle of self-check of the residual current protection function is as follows: by inputting 50Hz square waves with a 180-degree phase difference between CC_P and CC_N, this signal will generate a 50HZ alternating current on the detection winding. If the single-chip microcomputer measures this signal and the measured value is correct, it is considered that the residual current protection function is intact; otherwise, the self-check fails and charging is not allowed to be initiated.

[0023] To support DC6mA detection, another residual current sensor interface RCD for the 2023 new national standard is provided in the present utility model to implement Class A AC residual current protection and DC6mA residual current protection. As Figure 1 shown, the TEST pin comes from the single-chip microcomputer and is a 3.3V TTL signal, which is converted into a 5V signal through the U5 optocoupler to trigger sensor self-check. The sensor trip signal RCD_MC is connected to the single-chip microcomputer, and when the single-chip microcomputer detects that this signal is at a high level, the relay should be disconnected for protection.

[0024] The above are only the preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present utility model shall be included within the protection scope of the present utility model.

Claims

1. A residual current acquisition circuit for a charging pile, characterized in that: It includes a residual current transformer, a first field effect transistor, a second field effect transistor and an operational amplifier; The S pole and the G pole of the first field effect tube are connected with a first resistor arranged therebetween, and the D pole of the first field effect tube is connected to the N4 terminal of the residual current transformer; The S pole and the G pole of the second field effect tube are connected with a second resistor arranged therebetween, and the D pole of the second field effect tube is connected to the N3 terminal of the residual current transformer; The positive input terminal of the operational amplifier is connected to the L1 terminal of the residual current transformer, and a third resistor and a fourth resistor are sequentially arranged therebetween; one end of the third resistor close to the fourth resistor is connected to the L2 terminal of the residual current transformer, and a first capacitor is arranged therebetween; one end of the third resistor is connected to a fifth resistor, and one end of the fifth resistor is connected to the L2 terminal of the residual current transformer; one end of the fourth resistor is connected to a second capacitor, and the second capacitor is grounded; The negative input terminal of the operational amplifier is connected to the output terminal, the output terminal of the operational amplifier is connected to a sixth resistor, the sixth resistor is connected to a third capacitor, and the third capacitor is grounded.

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