Charging pile relay contact adhesion detection circuit

Abstract

The utility model discloses a charging pile relay contact adhesion detection circuit, which is characterized in that an input end of a resistance current limiting circuit is connected with a third pin of a relay K1, a fourth pin of the relay K1 is connected with a live wire L1IN, a half-wave rectification circuit comprises a diode D2, a negative electrode end of the diode D2 is connected with a null wire NIN, and a negative electrode end of the diode D2 is connected with a positive electrode end of the relay K1. The positive electrode end of the diode D2 and the output end of the resistance current limiting circuit are respectively connected with an optical coupling isolation circuit, and the optical coupling isolation circuit is connected with a post-stage MCU. According to the utility model, current limiting is carried out on the whole circuit through the resistor current limiting circuit, rectification is carried out through the half-wave rectification circuit, electrical isolation of high voltage and low voltage is realized through the optical coupler isolation circuit, and voltage signals between the output end live wire L1OUT of the relay and the power supply input null line NIN are detected. The relay output contact adhesion fault detection circuit has the advantages of being simple in circuit design, high in practicability, high in response speed and high in reliability.

Description

Technical Field

[0001] The utility model belongs to the technical field of AC charging pile detection, and particularly relates to a detection circuit for adhesion of relay contacts of a charging pile. Background Technique

[0002] With the popularization of new energy vehicles, the demand for charging piles has gradually increased, and the safety and reliability of the design of charging pile products have attracted much attention from consumers. In the charging control application of AC charging piles, the problem of adhesion of on-board relays is a common electrical fault, which will seriously affect the safety of charging pile charging.

[0003] At present, most of the traditional detection circuits for adhesion of relay contacts of charging piles have problems such as complex circuit design, high use cost, and high failure rate of the detection circuit itself; therefore, there is an urgent need for a detection circuit for adhesion of relay contacts of charging piles with simple circuit design, fast response speed, and high reliability. Content of the Utility Model

[0004] To solve the problems raised in the above background technique. The utility model provides a detection circuit for adhesion of relay contacts of a charging pile, which has the characteristics of simple circuit design, fast response speed, and high reliability.

[0005] To achieve the above object, the utility model provides the following technical solution: A detection circuit for adhesion of relay contacts of a charging pile, including a resistor current-limiting circuit, a half-wave rectification circuit, and an optocoupler isolation circuit. Among them, the input end of the resistor current-limiting circuit is connected to the 3rd pin of the relay K1, the 4th pin of the relay K1 is connected to the live wire L1_IN, the half-wave rectification circuit includes a diode D2, the negative end of the diode D2 is connected to the neutral wire N_IN, and the positive end of the diode D2 and the output end of the resistor current-limiting circuit are respectively connected to the optocoupler isolation circuit, and the optocoupler isolation circuit is connected to the subsequent MCU.

[0006] To perform current limiting, further, the resistor current-limiting circuit includes resistors R1, R2, R3, R4, R5, and R6 connected in series in sequence.

[0007] To play the role of reverse clamping protection for the optocoupler U1 and avoid breakdown of the primary diode of the optocoupler U1 due to too high reverse voltage, and clamp the reverse voltage at 0.7V. Further, the half-wave rectification circuit also includes a diode D1, the positive end of the diode D1 is connected to the positive end of the diode D2, and the negative end of the diode D1 is connected to the output end of the resistor current-limiting circuit.

[0008] In order to convert the primary current conduction signal into a secondary low-voltage level signal, further, the optocoupler isolation circuit includes an optocoupler U1. Among them, the pin 1 of the optocoupler U1 is connected to the output end of the resistor current-limiting circuit, the pin 2 of the optocoupler U1 is connected to the positive extreme of the diode D2, the pin 3 of the optocoupler U1 is connected to the ground terminal, and the pin 4 of the optocoupler U1 is connected to the subsequent MCU.

[0009] Further, the optocoupler isolation circuit further includes a resistor R7. Among them, one end of the resistor R7 is connected to the pin 4 of the optocoupler U1, and the other end of the resistor R7 is connected to the +5V power supply.

[0010] In order to provide impedance matching, further, the optocoupler isolation circuit further includes a resistor R8. Among them, one end of the resistor R8 is connected to the pin 4 of the optocoupler U1, and the other end of the resistor R8 is connected to the subsequent MCU.

[0011] In order to filter out high-frequency interference pulse signals and improve the signal output stability, further, the optocoupler isolation circuit further includes a capacitor C1, and the capacitor C1 is connected in parallel between the pin 3 and the pin 4 of the optocoupler U1.

[0012] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0013] 1. The present utility model limits the current of the entire circuit through the resistor current-limiting circuit, rectifies through the half-wave rectification circuit, realizes the electrical isolation between high voltage and low voltage through the optocoupler isolation circuit, and realizes the fault judgment of the adhesion of the relay output contact by detecting the voltage signal between the live wire L1_OUT of the relay output end and the power supply input neutral wire N_IN. It has the characteristics of simple circuit design, strong practicability, fast response speed and high reliability;

[0014] 2. The present utility model uses the diode D2 to reversely block the current flowing from the power supply input neutral wire N_IN to the live wire L1_OUT of the relay output end, adopts the half-wave conduction mode, effectively avoids the conduction of the neutral wire flowing to the live wire of the relay output end in the negative half cycle of the power supply, and effectively improves the safety of the charging pile during charging;

[0015] 3. The half-wave rectification circuit of the present utility model further includes a diode D1. The positive extreme of the diode D1 is connected to the positive extreme of the diode D2, and the negative extreme of the diode D1 is connected to one end of the resistor R6. The diode D1 plays a role of reverse clamping protection for the optocoupler U1, avoids the breakdown of the optocoupler U1 primary diode due to too high reverse voltage, and clamps the reverse voltage at 0.7V. Description of the Drawings

[0016] The drawings are used to provide a further understanding of the present utility model, and constitute a part of the specification. Together with the embodiments of the present utility model, they are used to explain the present utility model and do not constitute a limitation to the present utility model. In the drawings:

[0017] Figure 1 is the circuit diagram of the present utility model; Specific embodiments

[0018] The technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0019] Embodiment 1

[0020] Please refer to Figure 1 , the present utility model provides the following technical solutions: A charging pile relay contact adhesion detection circuit, including a resistor current limiting circuit, a half-wave rectification circuit, and an optocoupler isolation circuit. Among them, the resistor current limiting circuit includes resistors R1, R2, R3, R4, R5, and R6 connected in series in sequence. The optocoupler isolation circuit includes optocoupler U1, resistor R7, resistor R8, and capacitor C1. The half-wave rectification circuit includes diode D2. One end of resistor R1 is connected to pin 3 of relay K1. Pin 4 of relay K1 is connected to live wire L1_IN. The negative terminal of diode D2 is connected to neutral wire N_IN. The positive terminal of diode D2 and one end of resistor R6 are respectively connected to pin 1 of optocoupler U1. Pin 4 of optocoupler U1 is respectively connected to one end of resistor R7, resistor R8, and capacitor C1. The other end of resistor R7 is connected to the +5V power supply. The other end of capacitor C1 and pin 3 of optocoupler U1 are respectively connected to the ground terminal. The other end of resistor R8 is connected to the pin of the subsequent MCU.

[0021] In this embodiment, the resistance values of resistors R1, R2, R3, R4, R5, and R6 are all 20K; the models of diodes D1 and D2 are M7; optocoupler U1 is a level conversion isolation device that converts the primary current conduction signal into a secondary low-voltage level signal. The model of optocoupler U1 is PC817. Resistor R7 is the pull-up resistor of the secondary output port of optocoupler U1. Resistor R8 is an impedance matching resistor. Capacitor C1 is the signal anti-jitter filtering capacitor at the output port of optocoupler U1, which filters out high-frequency interference pulse signals and improves the signal output stability.

[0022] By adopting the above technical solutions, the utility model limits the current of the whole circuit through a resistance current-limiting circuit, rectifies the current through a half-wave rectification circuit, realizes the electrical isolation between high voltage and low voltage through an optocoupler isolation circuit, and judges the fault of the adhesion of the relay output contact by detecting the voltage signal between the live wire L1_OUT of the relay output terminal and the neutral wire N_IN of the power supply input. It has the characteristics of simple circuit design, strong practicability, fast response speed and high reliability; the utility model uses the diode D2 to reversely block the current flowing from the neutral wire N_IN of the power supply input to the live wire L1_OUT of the relay output terminal, adopts a half-wave conduction mode, effectively avoids the conduction of the neutral wire in the negative half cycle of the power supply flowing to the live wire L1_OUT of the relay output terminal, and effectively improves the safety of the charging pile during charging.

[0023] In the utility model, resistors R1, R2, R3, R4, R5 and R6 are connected in series in the primary circuit of the optocoupler U1 to form a current-limiting circuit, which plays the role of limiting the input current of AC220V and protecting the primary of the optocoupler element from overcurrent. The primary conduction coupling control current of the optocoupler U1 is in the range of 1.5 mA to 3 mA. The current-limiting resistor is packaged in the 1206 specification, and its maximum power is 0.25W. In this embodiment, resistors R1, R2, R3, R4, R5 and R6 are connected in series to reduce the power consumption of a single current-limiting resistor and improve the reliability of the circuit. The combination of 6 resistors is 120K, and the current-limiting current for AC200V is 1.83 mA, meeting the conduction requirements of the optocoupler, thereby improving the reliability of the output voltage detection.

[0024] Embodiment 2

[0025] The difference between this embodiment and Embodiment 1 is that: specifically, the half-wave rectification circuit further includes a diode D1. The positive end of the diode D1 is connected to the positive end of the diode D2, and the negative end of the diode D1 is connected to one end of the resistor R6.

[0026] By adopting the above technical solutions, the diode D1 plays a role of reverse clamping protection for the optocoupler U1, avoiding the breakdown of the primary diode of the optocoupler U1 due to too high reverse voltage, and clamping the reverse voltage at 0.7V.

[0027] The working principle of the utility model is as follows:

[0028] (1). When the relay K1 has a fault of contact burning and adhesion, it cannot perform normal contact opening / closing actions. At this time, the L1_OUT end of the relay contact is still energized, and the live wire L1_IN of the power supply input outputs L1_OUT through the normally open contact of the relay K1;

[0029] (2) After the live wire output L1_OUT is current-limited through the series connection of resistors R1, R2, R3, R4, R5, and R6, it flows through the primary of optocoupler U1 and diode D2 to the power supply neutral wire N_IN terminal;

[0030] (3) During the positive half-cycle of the AC power supply of the live wire output L1_OUT and N_IN, the primary light-emitting diode of optocoupler U1 conducts, and the secondary of optocoupler U1 is also in the conducting state, clamped at a level voltage of 0.3V, and a low level is output through resistor R8;

[0031] (4) During the negative half-cycle of the AC power supply of the live wire output L1_OUT and N_IN, due to the reverse series connection of diode D2, no current passes through the primary light-emitting diode of optocoupler U1, the secondary of optocoupler U1 is in the cut-off state, and a high level of 5V is output through resistor R8; in this case, a pulse signal of 50HZ consistent with the power grid supply frequency will be generated at the secondary of optocoupler U1.

[0032] The judgment logic is as follows:

[0033] After the relay K1 performs the contact release action, when a 50HZ pulse signal is detected at the secondary of optocoupler U1, it is judged as a relay contact adhesion fault, and when no signal is output, it is judged as a normal working state, so as to judge the working state of the relay and improve the reliability of the system operation.

[0034] In summary, the utility model limits the current of the entire circuit through a resistor current-limiting circuit, rectifies through a half-wave rectification circuit, realizes electrical isolation between high voltage and low voltage through an optocoupler isolation circuit, and realizes the fault judgment of the relay output contact adhesion through the detection of the voltage signal between the live wire L1_OUT of the relay output end and the power supply input neutral wire N_IN, with the characteristics of simple circuit design, strong practicability, fast response speed, and high reliability; the utility model uses diode D2 to reversely block the current flowing from the power supply input neutral wire N_IN to the live wire L1_OUT of the relay output end, adopts a half-wave conduction mode, effectively avoids the conduction of the neutral wire flowing to the live wire of the relay output end during the negative half-cycle of the power supply, and effectively improves the safety of the charging pile during charging; the half-wave rectification circuit of the utility model further includes diode D1, the positive terminal of diode D1 is connected to the positive terminal of diode D2, the negative terminal of diode D1 is connected to one end of resistor R6, and diode D1 plays an anti-phase clamping protection role for optocoupler U1, avoiding the breakdown of the primary diode of optocoupler U1 due to too high reverse voltage, and clamping the reverse voltage at 0.7V.

[0035] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A charging pile relay contact adhesion detection circuit, characterized in that: It includes a resistor current limiting circuit, a half-wave rectifier circuit and an optocoupler isolation circuit, wherein the input end of the resistor current limiting circuit is connected to the 3rd pin of the relay K1, the 4th pin of the relay K1 is connected to the live wire L1_IN, the half-wave rectifier circuit includes a diode D2, the negative end of the diode D2 is connected to the neutral wire N_IN, the positive end of the diode D2 and the output end of the resistor current limiting circuit are respectively connected to the optocoupler isolation circuit, and the optocoupler isolation circuit is connected to the post-stage MCU.

2. A charging pile relay contact adhesion detection circuit according to claim 1, characterized in that: The resistor current limiting circuit comprises a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5 and a resistor R6 which are connected in series in sequence.

3. A charging pile relay contact adhesion detection circuit according to claim 1, characterized in that: The half-wave rectifier circuit further includes a diode D1, a positive terminal of the diode D1 is connected to a positive terminal of the diode D2, and a negative terminal of the diode D1 is connected to an output terminal of the resistor current limiting circuit.

4. A charging pile relay contact adhesion detection circuit according to claim 1, characterized in that: The optocoupler isolation circuit includes an optocoupler U1, wherein pin 1 of the optocoupler U1 is connected to the output end of the resistor current limiting circuit, pin 2 of the optocoupler U1 is connected to the positive end of the diode D2, pin 3 of the optocoupler U1 is connected to the ground end, and pin 4 of the optocoupler U1 is connected to the post-stage MCU.

5. A charging pile relay contact adhesion detection circuit according to claim 1, characterized in that: The optocoupler isolation circuit further includes a resistor R7, wherein one end of the resistor R7 is connected to pin 4 of the optocoupler U1, and the other end of the resistor R7 is connected to a +5V power supply.

6. A charging pile relay contact adhesion detection circuit according to claim 1, characterized in that: The optocoupler isolation circuit further includes a resistor R8, wherein one end of the resistor R8 is connected to the 4th pin of the optocoupler U1, and the other end of the resistor R8 is connected to the subsequent MCU.

7. A charging pile relay contact adhesion detection circuit according to claim 1, characterized in that: The optocoupler isolation circuit further includes a capacitor C1, which is connected in parallel to pins 3 and 4 of the optocoupler U1.

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