Relay adhesion detection circuit

Abstract

The utility model discloses a relay adhesion detection circuit, which is used for an alternating current charging pile and comprises a relay output control circuit, a mutual inductor sampling circuit, a subtracter and a voltage follower. Wherein the relay output control circuit comprises a live wire relay and a null line relay, the live wire relay is connected with the live wire input end of the mutual inductor sampling circuit, the null line relay is connected with the null line input end of the mutual inductor sampling circuit, and the first output end of the mutual inductor sampling circuit is connected with the first input end of the subtractor; the second output end of the mutual inductor sampling circuit is connected with the second input end of the subtractor, the third input end of the subtractor is connected to the first voltage source through the voltage follower, and the voltage output end of the subtractor outputs voltage signals used for adhesion detection. According to the relay adhesion detection circuit, the relay is low in cost, and the reliability, stability and efficiency of relay adhesion detection are improved.

Description

Technical Field

[0001] The utility model relates to the technical field of relay connection detection, in particular to a relay adhesion detection circuit. Background Art

[0002] AC charging piles are widely used to charge electric vehicles. When an AC charging pile is operating, if a relay adhesion fault occurs and cannot be detected in a timely and accurate manner, it will cause damage to the charging circuit and pose a potential safety hazard for electricity use.

[0003] Currently, there are mainly two schemes for detecting the adhesion of relays in AC charging piles: The first scheme is to judge whether a relay adhesion fault occurs by detecting the auxiliary contact signal of the relay. This type of relay with auxiliary contacts is large in size and high in cost; the second scheme is to set up an optocoupler circuit between the output terminals of two relays to detect whether a relay adhesion fault occurs. As a key component in the optocoupler circuit, the performance of the optocoupler is greatly affected by temperature, and the current changes with the ambient temperature, which will cause the output signal of the optocoupler circuit to be distorted. Especially in a hot environment, the stability of relay adhesion detection cannot be guaranteed. At the same time, during the process of the optocoupler converting optical signals, it is easily affected by optical noise, thereby introducing a certain degree of electrical signal noise. This noise will interfere with the output signal of the optocoupler circuit, resulting in a reduction in the reliability of relay adhesion detection. Summary of the Utility Model

[0004] The main purpose of the utility model is to provide a relay adhesion detection circuit, aiming to solve the technical problems of high cost, poor stability or low reliability of the existing relay adhesion detection circuit for AC charging piles.

[0005] To achieve the above object, the utility model provides a relay adhesion detection circuit for an AC charging pile, including a relay output control circuit, a current transformer sampling circuit, a subtractor and a voltage follower; wherein, the relay output control circuit includes a live wire relay and a neutral wire relay. The live wire relay is connected to the live wire input terminal of the current transformer sampling circuit, and the neutral wire relay is connected to the neutral wire input terminal of the current transformer sampling circuit. The first output terminal of the current transformer sampling circuit is connected to the first input terminal of the subtractor, and the second output terminal of the current transformer sampling circuit is connected to the second input terminal of the subtractor. The third input terminal of the subtractor is connected to a first voltage source through the voltage follower, and the voltage output terminal of the subtractor outputs a voltage signal for adhesion detection.

[0006] Preferably, the transformer sampling circuit includes a voltage transformer, a first resistor, a second resistor, a third resistor, and a fourth resistor; wherein, a first terminal of the primary side of the voltage transformer is sequentially connected to one end of the first resistor through the third resistor and the second resistor; a first terminal of the secondary side of the voltage transformer is connected to a second terminal of the secondary side of the voltage transformer through the fourth resistor.

[0007] Preferably, the transformer sampling circuit further includes a thirteenth resistor and a fourteenth resistor; wherein, a second terminal of the primary side of the voltage transformer is connected to one end of the thirteenth resistor through the fourteenth resistor; the other end of the first resistor is the neutral input terminal of the transformer sampling circuit, the other end of the thirteenth resistor is the live input terminal of the transformer sampling circuit, the first terminal of the secondary side of the voltage transformer is the first output terminal, and the second terminal of the secondary side of the voltage transformer is the second output terminal.

[0008] Preferably, the turns ratio of the voltage transformer is 1:1.

[0009] Preferably, the subtractor includes: a first operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, and a first capacitor; wherein, the inverting input terminal of the first operational amplifier is connected to the second terminal of the sixth resistor, and is respectively connected to the output terminal of the first operational amplifier through the fifth resistor and the first capacitor; the non-inverting input terminal of the first operational amplifier is simultaneously connected to the second terminal of the eighth resistor and the second terminal of the ninth resistor; the output terminal of the first operational amplifier is connected to the first terminal of the seventh resistor; the first terminal of the sixth resistor is the first input terminal, the first terminal of the eighth resistor is the second input terminal, the first terminal of the ninth resistor is the third input terminal, and the second terminal of the seventh resistor is the voltage output terminal.

[0010] Preferably, the subtractor further includes: a first filter circuit; wherein, the first filter circuit includes a tenth resistor and a second capacitor connected in parallel; the second terminal of the seventh resistor is grounded through the first filter circuit.

[0011] Preferably, the voltage follower includes: a second operational amplifier, an eleventh resistor, a twelfth resistor, and a fifth capacitor; wherein, the non-inverting input terminal of the second operational amplifier is connected to a first voltage source through the eleventh resistor, and is grounded through a second filter circuit formed by the twelfth resistor and the fifth capacitor; the inverting input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier; the output terminal of the second operational amplifier is connected to the third input terminal of the subtractor.

[0012] Preferably, the first operational amplifier and the second operational amplifier adopt an integrated dual operational amplifier.

[0013] Preferably, the relay adhesion detection circuit further includes a control unit; the control unit is connected to the voltage output terminal of the subtractor, and when the control unit determines that the live wire relay and / or the neutral wire relay is adhered according to the voltage signal, it disconnects the connection with the charging pile.

[0014] Preferably, the relay adhesion detection circuit further includes a power management circuit, and the power management circuit is used to output a first voltage source and supply power to the relay output control circuit, the current transformer sampling circuit, the subtractor, the voltage follower and the control unit.

[0015] The relay adhesion detection circuit provided by the present invention includes a relay output control circuit, a current transformer sampling circuit, a subtractor and a voltage follower. The relay output control circuit includes a live wire relay and a neutral wire relay. After the live wire relay and the neutral wire relay are closed, the output terminal of the relay output control circuit is conducted with the input terminal of the current transformer sampling circuit, and the high-voltage signal of the power grid is transmitted to the current transformer sampling circuit. After the current transformer sampling circuit converts the high-voltage signal into a low-voltage AC signal, it is input to the subtractor. The subtractor reprocesses the low-voltage AC signal, and at the same time adjusts the DC bias of the subtractor through the voltage follower, so that the subtractor outputs a positive voltage signal with a complete waveform to detect relay adhesion according to the positive voltage signal. The relay adhesion detection circuit of the present invention does not need to set auxiliary contacts or a circuit to replace the auxiliary contacts, and the cost of the relay is low. Compared with using an optocoupler circuit for relay adhesion detection, the present invention uses a subtractor and cooperates with a voltage follower to reprocess the low-voltage AC signal output by the current transformer sampling circuit, which can avoid the interference of optical noise and waveform distortion of the output voltage signal, and improve the reliability and stability of relay adhesion detection; secondly, the high-voltage signal of the power grid is step-down sampled through the current transformer sampling circuit without being converted into a DC signal, and the response speed is faster, which is beneficial to improving the efficiency of relay adhesion detection. Description of the Drawings

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a connection block diagram of the relay adhesion detection circuit in an embodiment of the present invention;

[0018] Figure 2 This is the circuit diagram of the current transformer sampling circuit of the relay adhesion detection circuit in an embodiment of the present utility model;

[0019] Figure 3 This is the circuit diagram of the subtractor of the current transformer sampling circuit of the relay adhesion detection circuit in an embodiment of the present utility model;

[0020] Figure 4 This is the circuit diagram of the voltage follower of the current transformer sampling circuit of the relay adhesion detection circuit in an embodiment of the present utility model;

[0021] Figure 5 This is the overall circuit diagram of the relay adhesion detection circuit in an embodiment of the present utility model;

[0022] Figure 6 This is the connection block diagram of the relay adhesion detection circuit in another embodiment of the present utility model. Detailed implementation manners

[0023] In order to better understand the above technical solutions, the exemplary embodiments of the present utility model will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present utility model are shown in the drawings, it should be understood that the present utility model can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided so that the present utility model can be more thoroughly understood and the scope of the present utility model can be fully conveyed to those skilled in the art.

[0024] It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0025] The present utility model provides a relay adhesion detection circuit for an AC charging pile. Referring to Figure 1 and Figure 5 , in one embodiment, the relay adhesion detection circuit includes a relay output control circuit 1, a current transformer sampling circuit 2, a subtractor 3, and a voltage follower 4; wherein, the relay output control circuit 1 includes a live wire relay KA1 and a neutral wire relay KA2. The live wire relay KA1 is connected to the live wire input terminal Lout of the current transformer sampling circuit 2, and the neutral wire relay KA2 is connected to the neutral wire input terminal Nout of the current transformer sampling circuit 2. The first output terminal of the current transformer sampling circuit 2 is connected to the first input terminal Vsen1 of the subtractor 3, and the second output terminal of the current transformer sampling circuit 2 is connected to the second input terminal Vsen2 of the subtractor 3. The third input terminal Vref of the subtractor 3 is connected to the first voltage source VCC1 through the voltage follower 4, and the voltage output terminal of the subtractor 3 outputs a voltage signal RELAY_DA for adhesion detection.

[0026] In this embodiment, the relay output control circuit 1 includes a live wire relay KA1 and a neutral wire relay KA2. Both the live wire relay KA1 and the neutral wire relay KA2 include normally open contacts and coils. Among them, one end of the normally open contact in the live wire relay KA1 is connected to the live wire L1in, and the other end is connected to the live wire input terminal Lout of the mutual inductor sampling circuit 2. One end of the coil in the live wire relay KA1 is connected to the second voltage source VCC2, and the other end serves as the control terminal L-O of the live wire relay KA1. That is to say, the live wire relay KA1 is connected to the live wire and conducts or disconnects according to the first control signal obtained at the control terminal L-O. One end of the normally open contact in the neutral wire relay KA2 is connected to the neutral wire N1in, and the other end is connected to the neutral wire input terminal Nout of the mutual inductor sampling circuit 2. One end of the coil in the neutral wire relay KA2 is connected to the second voltage source VCC2, and the other end serves as the control terminal N-O of the neutral wire relay KA2. That is to say, the neutral wire relay KA2 is connected to the neutral wire and conducts or disconnects according to the second control signal obtained at the control terminal N-O. It should be noted that the first control signal and the second control signal can be output by a controller that is simultaneously connected to the live wire relay KA1 and the neutral wire relay KA2. Preferably, the second voltage source VCC2 is a 12V DC power supply.

[0027] The mutual inductor sampling circuit 2 includes a live wire input terminal Lout, a neutral wire input terminal Nout, a first output terminal, and a second output terminal. The mutual inductor sampling circuit 2 can convert the high voltage between the live wire input terminal Lout and the neutral wire input terminal Nout into a low-voltage AC signal and transmit it to the subtractor 3 for further processing.

[0028] The subtractor 3 includes a first input terminal Vsen1, a second input terminal Vsen2, a third input terminal Vref, and a voltage output terminal. Among them, the first input terminal Vsen1 of the subtractor 3 is connected to the first output terminal of the mutual inductor sampling circuit 2, the second input terminal Vsen2 of the subtractor 3 is connected to the second output terminal of the mutual inductor sampling circuit 2, and the third input terminal Vref of the subtractor 3 is connected to the output terminal of the voltage follower 4. The subtractor 3 is used to perform a subtraction operation on the low-voltage AC signal output by the mutual inductor sampling circuit 2, reduce the voltage value of the AC signal, and output the voltage signal RELAY_AD after the subtraction operation through the voltage output terminal for relay adhesion detection. It should be noted that the voltage signal RELAY_AD can be detected by a controller connected to the subtractor 3. At this time, it is possible to determine whether the live wire relay KA1 and / or the neutral wire relay KA2 is adhered by detecting the waveform characteristics or peak value of the voltage signal RELAY_AD.

[0029] The voltage follower 4 includes an input terminal and an output terminal. Among them, the input terminal of the voltage follower 4 is connected to the first voltage source VCC1, and the output terminal of the voltage follower 4 is connected to the third input terminal Vref of the subtractor 3. The voltage follower 4 is used to adjust the DC bias of the subtractor 3 so that the subtractor 3 can process the lower half cycle of the low-voltage AC signal, so that the subtractor 3 can output a positive voltage signal with a complete waveform and suitable for ADC sampling. Preferably, the first voltage source VCC1 is a 3.3V DC power supply. At this time, the subtractor 3 and the voltage follower 4 constitute a signal conditioning circuit, which can adjust the low-voltage AC signal output by the transformer sampling circuit 2 to obtain a positive voltage signal of 0 to 3.3V.

[0030] In summary, the relay adhesion detection circuit provided in this embodiment includes a relay output control circuit, a transformer sampling circuit, a subtractor, and a voltage follower. The relay output control circuit includes a live wire relay and a neutral wire relay. After the live wire relay and the neutral wire relay are closed, the output terminal of the relay output control circuit is conducted with the input terminal of the transformer sampling circuit, and the high-voltage signal of the power grid is transmitted to the transformer sampling circuit. After the transformer sampling circuit converts the high-voltage signal into a low-voltage AC signal, it is input to the subtractor. The subtractor processes the low-voltage AC signal again, and at the same time adjusts the DC bias of the subtractor through the voltage follower, so that the subtractor outputs a positive voltage signal with a complete waveform to detect relay adhesion according to the positive voltage signal. The relay adhesion detection circuit of this embodiment does not need to set auxiliary contacts or a circuit to replace auxiliary contacts, and the cost of the relay is low. Compared with using an optocoupler circuit to detect relay adhesion, this embodiment uses a subtractor, combined with a voltage follower to reprocess the low-voltage AC signal output by the transformer sampling circuit, which can avoid the interference of optical noise and waveform distortion of the output voltage signal, and improve the reliability and stability of relay adhesion detection; secondly, the high-voltage signal of the power grid is step-down sampled through the transformer sampling circuit without being converted into a DC signal, and the response speed is faster, which is beneficial to improving the efficiency of relay adhesion detection.

[0031] In a preferred embodiment, refer to Figure 2 , the transformer sampling circuit 2 includes a voltage transformer VS1, a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4; among them, the first wiring terminal on the primary side of the voltage transformer VS1 is sequentially connected to one end of the first resistor R1 through the third resistor R3 and the second resistor R2; the first wiring terminal on the secondary side of the voltage transformer VS1 is connected to the second wiring terminal on the secondary side of the voltage transformer VS1 through the fourth resistor R4.

[0032] In this embodiment, the resistance values of the first resistor R1, the second resistor R2, and the third resistor R3 are equal, and the ratio of the resistance value of the first resistor R1 to that of the fourth resistor R4 is 40:1; the turns ratio of the voltage transformer VS1 is 1:1.

[0033] In the transformer sampling circuit 2, after the alternating voltage is limited by the first resistor R1, the second resistor R2, and the third resistor R3, it enters the primary side of the voltage transformer VS1. Then, a current value proportional to the primary side is obtained at the secondary side of the voltage transformer VS1. After passing through the fourth resistor R4, a low-voltage alternating current signal is obtained. The transformer sampling circuit of this embodiment can realize the sampling of the low-voltage alternating current signal through the voltage transformer.

[0034] In a preferred embodiment, the transformer sampling circuit 2 further includes a thirteenth resistor and a fourteenth resistor; wherein, the second terminal of the primary side of the voltage transformer VS1 is connected to one end of the thirteenth resistor through the fourteenth resistor; the other end of the first resistor is the neutral input terminal of the transformer sampling circuit 2, the other end of the thirteenth resistor is the live input terminal of the transformer sampling circuit 2, the first terminal of the secondary side of the voltage transformer is the first output terminal, and the second terminal of the secondary side of the voltage transformer is the second output terminal.

[0035] In this embodiment, the resistance values of the thirteenth resistor, the fourteenth resistor, and the first resistor R1 are equal. The thirteenth resistor and the fourteenth resistor are used to limit the alternating voltage entering the primary side of the voltage transformer VS1. At this time, the transformer sampling circuit 2 of this embodiment is provided with multiple current-limiting resistors on both access lines of the primary side of the voltage transformer VS1, which can greatly reduce the loss of the voltage transformer VS1 and has a better energy-saving effect.

[0036] In a preferred embodiment, referring to Figure 3 , the subtractor 3 includes: a first operational amplifier U1A, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, and a first capacitor C1; wherein, the inverting input terminal of the first operational amplifier U1A is connected to the second terminal of the sixth resistor R6, and is respectively connected to the output terminal of the first operational amplifier U1A through the fifth resistor R5 and the first capacitor C1; the non-inverting input terminal of the first operational amplifier U1A is simultaneously connected to the second terminal of the eighth resistor R8 and the second terminal of the ninth resistor R9; the output terminal of the first operational amplifier U1A is connected to the first terminal of the seventh resistor R7; the first terminal of the sixth resistor R6 is the first input terminal Vsen1, the first terminal of the eighth resistor R8 is the second input terminal Vsen2, the first terminal of the ninth resistor R9 is the third input terminal Vref, and the second terminal of the seventh resistor R7 is the voltage output terminal.

[0037] In this embodiment, the sixth resistor R6, the eighth resistor R8, and the ninth resistor R9 have equal resistance values, and the resistance ratio between the fifth resistor R5 and the sixth resistor R6 is 1:2; the first capacitor C1 is connected between the inverting input terminal and the output terminal of the first operational amplifier U1A for phase compensation of the first operational amplifier U1A; the seventh resistor R7 is connected to the output terminal of the first operational amplifier U1A for limiting the output current of the first operational amplifier U1A to protect the first operational amplifier U1A.

[0038] Based on Figure 3 the shown circuit diagram of the subtractor, the voltage expression of the subtractor 3 is specifically:

[0039]

[0040] When R 6 = 2R 5 , R 8 = R 9 , the above formula can be simplified to:

[0041]

[0042] Furthermore, since U 2 = U 3 , the above formula can be further simplified to:

[0043]

[0044] That is to say, for the subtractor 3 in this embodiment, under normal circumstances, when the relay does not stick, the live wire relay KA1 and / or the neutral wire relay KA2 are disconnected, and the voltages at the first output terminal and the second output terminal of the mutual inductor sampling circuit 2 are both 0. At this time, no current is input to the subtractor 3, and a DC voltage signal with a voltage of 3 / 4*V ref can be output through the subtractor 3. In abnormal circumstances, when the relay sticks and only one of the live wire relay KA1 and the neutral wire relay KA2 is disconnected, the voltages at the first output terminal and the second output terminal of the mutual inductor sampling circuit 2 are not equal. At this time, current is input to the subtractor 3, and an AC voltage signal with a voltage of 3 / 4*(V sen2 +V ref ) - V sen1 / 2 can be output through the subtractor 3. At this time, by detecting the waveform or peak value of the voltage signal, it can be determined whether the relay sticks.

[0045] Based on Figure 5The overall circuit diagram of the relay adhesion detection circuit shown. The working principle of relay adhesion detection is as follows: First, close the live wire relay KA1 and open the neutral wire relay KA2. If the voltage signal output by the subtractor 3 is detected as an AC signal, it is determined that the neutral wire relay KA2 is adhered; otherwise, it is determined that the relay output control circuit 1 is working properly, indicating that the relay is in a normal state. Then, close the neutral wire relay KA2 and open the live wire relay KA1. If the voltage signal output by the subtractor 3 is detected as an AC signal, it is determined that the live wire relay KA1 is adhered; otherwise, it is determined that the relay output control circuit 1 is working properly, indicating that the relay is in a normal state. Finally, open both the live wire relay KA1 and the neutral wire relay KA2 simultaneously. If the voltage signal output by the subtractor 3 is detected as an AC signal, it is determined that both the live wire relay KA1 and the neutral wire relay KA2 are adhered. Further, when the live wire relay KA1 and / or the neutral wire relay KA2 is adhered, a adhesion warning is displayed, and the connection between the relay adhesion detection circuit and the AC charging pile is disconnected.

[0046] In a preferred embodiment, referring to Figure 3 , the subtractor 3 further includes: a first filter circuit; wherein, the first filter circuit includes a tenth resistor R10 and a second capacitor C2 connected in parallel; the second end of the seventh resistor R7 is grounded through the first filter circuit.

[0047] In this embodiment, the first filter circuit is a low-pass filter formed by the parallel connection of the tenth resistor R10 and the second capacitor C2, which can filter and reduce noise for the voltage signal output by the first operational amplifier U1A.

[0048] In a preferred embodiment, referring to Figure 4 , the voltage follower 4 includes: a second operational amplifier U1B, an eleventh resistor R11, a twelfth resistor R12, and a fifth capacitor C5; wherein, the non-inverting input terminal of the second operational amplifier U1B is connected to the first voltage source VCC1 through the eleventh resistor R11, and is grounded through a second filter circuit formed by the twelfth resistor R12 and the fifth capacitor C5; the inverting input terminal of the second operational amplifier U1B is connected to the output terminal of the second operational amplifier U1B; the output terminal of the second operational amplifier U1B is connected to the third input terminal Vref of the subtractor 3.

[0049] In this embodiment, the resistance values of the eleventh resistor R11 and the twelfth resistor R12 are equal. The twelfth resistor R12 and the fifth capacitor C5 are connected in parallel to form a second filter circuit, which is used to prevent high-frequency clutter from entering the input terminal of the voltage follower 4.

[0050] Based on the circuit diagram of the voltage follower as shown in Figure 4 , the voltage expression of the voltage follower 4 is specifically:

[0051]

[0052] When R 11 = R 12 , the above formula can be simplified to:

[0053]

[0054] Furthermore, when VCC1 = 3.3V, V ref = 1.65V.

[0055] That is to say, the voltage follower 4 of this embodiment can provide a low-impedance DC bias of 1.65V for the subtractor 3.

[0056] In a preferred embodiment, the first operational amplifier and the second operational amplifier adopt an integrated dual operational amplifier.

[0057] In this embodiment, the model of the dual operational amplifier can be LM2904, LM385 or other general dual operational amplifiers. Compared with the case where the first operational amplifier U1A and the second operational amplifier U1B both adopt single-channel operational amplifiers, the circuit is simpler and no additional power supply is required.

[0058] In a preferred embodiment, referring to Figure 6 , the relay adhesion detection circuit further includes a control unit; the control unit 5 is connected to the voltage output end of the subtractor 3, and when the control unit 5 determines that the live wire relay KA1 and / or the neutral wire relay KA2 are adhered according to the voltage signal, it disconnects the connection with the charging pile.

[0059] In this embodiment, the control unit 5 can be a single-chip microcomputer or a microcontroller containing a built-in ADC module (analog-to-digital converter), or an electronic circuit containing a controller and an analog-to-digital converter. Preferably, the control unit is an STM32F104 single-chip microcomputer. The AD input end of the STM32F104 single-chip microcomputer is connected to the voltage output end of the subtractor 3. At this time, after the STM32F104 single-chip microcomputer obtains the voltage signal RELAY_AD output from the voltage output end of the subtractor 3 through the AD input end, it detects the peak value of the voltage signal RELAY_AD through the built-in AD converter. When the peak value of the voltage signal RELAY_AD is greater than the preset voltage threshold, it is determined that the relay is adhered, a adhesion warning is issued, and the AC charging pile is prohibited from charging the electric vehicle.

[0060] It should be noted that it is common knowledge to detect the peak value of the voltage signal RELAY_AD through the AD converter of the STM32F104 single-chip microcomputer. By comparing the peak value of the voltage signal RELAY_AD with the preset voltage threshold to determine whether the relay is stuck is a simple logical judgment and can be thought of without the need for those skilled in the art to put in labor.

[0061] It can be understood that in other embodiments, the control unit can determine whether the voltage signal is an AC signal or a DC signal by detecting the waveform characteristics of the voltage signal RELAY_AD to determine whether the relay is stuck.

[0062] Further, referring to Figure 6 , the relay stuck detection circuit further includes a live wire relay drive circuit 6 and a neutral wire relay drive circuit 7; wherein, the input end of the live wire relay drive circuit 6 is connected to the control end L-O of the live wire relay KA1, and the output end is connected to the first control signal output end of the control unit 5; the input end of the neutral wire relay drive circuit 7 is connected to the control end N-O of the neutral wire relay KA2, and the output end is connected to the second control signal output end of the control unit 5.

[0063] In this embodiment, both the live wire relay drive circuit 6 and the neutral wire relay drive circuit 7 are triode switch circuits. The triode switch circuit includes a first triode, a first current limiting resistor, a first feedback resistor, and a first diode. One end of the first current limiting resistor is the control signal input end, and the other end is connected to the base of the first triode. The emitter of the first triode is grounded and is connected to the base of the first triode through the first feedback resistor. The collector of the first triode is respectively connected to the control end of the relay (i.e., the second end of the coil in the relay) and the anode of the first diode, and the cathode of the first diode is connected to the 12V second voltage source VCC2. It can be understood that in this embodiment, through the triode switch circuit, the purpose of driving the live wire relay KA1 and / or the neutral wire relay KA2 to conduct or disconnect can be achieved.

[0064] It can be understood that in other embodiments, the live wire relay KA1 and the neutral wire relay KA2 can be controlled by independent controllers. At this time, the maximum output current of the controller is consistent with the operating current of the relay, the control output end of the controller is directly connected to the second end of the coil in the relay, and the controller controls the relay to conduct or turn on and off through an internal program.

[0065] In a preferred embodiment, the relay stuck detection circuit further includes a power management circuit. The power management circuit is used to output the first voltage source VCC1 and supply power to the relay output control circuit 1, the current transformer sampling circuit 2, the subtractor 3, the voltage follower 4, and the control unit 5.

[0066] In this embodiment, the power management circuit can output a first voltage source VCC1, a second voltage source VCC2, and a third voltage source VCC3. The first voltage source VCC1 is connected to the input terminal of the voltage follower 4 to adjust the output voltage of the voltage follower 4. At the same time, the first voltage source VCC1 is connected to the power supply terminal of the control unit (preferably an STM32 single-chip microcomputer) to provide a working voltage for the control unit 5. The second voltage source VCC2 is connected to the first end of the coil in the relay to provide a working voltage for the relay. The third voltage source VCC3 is connected to the power supply terminal of the first operational amplifier U1A or the power supply terminal of the second operational amplifier U1B to provide a working voltage for the first operational amplifier U1A or the second operational amplifier U1B. Preferably, the power management circuit uses a power management chip.

[0067] It should be noted that in this utility model, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a circuit or unit including a series of elements not only includes those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such a circuit or unit. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the circuit or unit including the element.

[0068] Secondly, it should be noted that in this utility model, terms such as "connected" and "coupled" can be direct connections or indirect connections through intermediate elements or intermediate circuits, and all elements and all circuits are electrically connected.

[0069] The above are only the preferred embodiments of this utility model, and do not limit the patent scope of this utility model accordingly. Any equivalent connection block diagram or circuit diagram transformation made by using the content of the specification and drawings of this utility model, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of this utility model by the same token.

Claims

1. A relay adhesion detection circuit, characterized in that: Used for an AC charging pile, comprising a relay output control circuit, a transformer sampling circuit, a subtractor and a voltage follower; wherein the relay output control circuit comprises a live wire relay and a neutral wire relay, the live wire relay is connected to the live wire input end of the transformer sampling circuit, the neutral wire relay is connected to the neutral wire input end of the transformer sampling circuit, the first output end of the transformer sampling circuit is connected to the first input end of the subtractor, the second output end of the transformer sampling circuit is connected to the second input end of the subtractor, the third input end of the subtractor is connected to a first voltage source through the voltage follower, and the voltage output end of the subtractor outputs a voltage signal for adhesion detection.

2. The relay adhesion detection circuit according to claim 1, characterized in that: The transformer sampling circuit includes a voltage transformer, a first resistor, a second resistor, a third resistor and a fourth resistor; wherein the first terminal on the primary side of the voltage transformer is connected to one end of the first resistor through the third resistor and the second resistor in sequence; the first terminal on the secondary side of the voltage transformer is connected to the second terminal on the secondary side of the voltage transformer through the fourth resistor.

3. The relay adhesion detection circuit as claimed in claim 2, characterized in that: The transformer sampling circuit also includes a thirteenth resistor and a fourteenth resistor; wherein, the second terminal on the primary side of the voltage transformer is connected to one end of the thirteenth resistor through the fourteenth resistor; the other end of the first resistor is the neutral line input end of the transformer sampling circuit, the other end of the thirteenth resistor is the live line input end of the transformer sampling circuit, the first terminal on the secondary side of the voltage transformer is the first output end, and the second terminal on the secondary side of the voltage transformer is the second output end.

4. The relay adhesion detection circuit according to claim 2, characterized in that: The turns ratio of the voltage transformer is 1:

1.

5. The relay adhesion detection circuit according to any one of claims 1 to 4, characterized in that: The subtractor includes: a first operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor and a first capacitor; wherein the inverting input terminal of the first operational amplifier is connected to the second end of the sixth resistor, and is connected to the output terminal of the first operational amplifier through the fifth resistor and the first capacitor respectively; the non-inverting input terminal of the first operational amplifier is simultaneously connected to the second end of the eighth resistor and the second end of the ninth resistor; the output terminal of the first operational amplifier is connected to the first end of the seventh resistor; the first end of the sixth resistor is the first input terminal, the first end of the eighth resistor is the second input terminal, the first end of the ninth resistor is the third input terminal, and the second end of the seventh resistor is the voltage output terminal.

6. The relay adhesion detection circuit according to claim 5, characterized in that: The subtractor further includes: a first filtering circuit; wherein the first filtering circuit includes a tenth resistor and a second capacitor connected in parallel; and the second end of the seventh resistor is grounded through the first filtering circuit.

7. The relay adhesion detection circuit according to claim 6, characterized in that: The voltage follower includes: a second operational amplifier, an eleventh resistor, a twelfth resistor and a fifth capacitor; wherein the non-phase input terminal of the second operational amplifier is connected to the first voltage source through the eleventh resistor, and is grounded through a second filter circuit composed of the twelfth resistor and the fifth capacitor; the negative phase input terminal of the second operational amplifier is connected to the output terminal of the second operational amplifier; and the output terminal of the second operational amplifier is connected to the third input terminal of the subtractor.

8. The relay adhesion detection circuit according to claim 7, characterized in that: The first operational amplifier and the second operational amplifier are integrated dual operational amplifiers.

9. The relay adhesion detection circuit according to claim 1, characterized in that: The relay adhesion detection circuit also includes a control unit; the control unit is connected to the voltage output end of the subtractor, and when the control unit determines that the live wire relay and / or the neutral wire relay are adhered according to the voltage signal, the control unit disconnects the connection with the charging pile.

10. The relay adhesion detection circuit according to claim 9, characterized in that: The relay adhesion detection circuit also includes a power management circuit, which is used to output a first voltage source and supply power to the relay output control circuit, the transformer sampling circuit, the subtractor, the voltage follower and the control unit.

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