Relay adhesion detection circuit in alternating current circuit
Through the detection circuit of resistive voltage division, capacitive isolation and waveform processing, the problems of resource occupation and high power consumption in relay adhesion detection are solved, and the relay adhesion detection with low cost and low power consumption is realized, which improves the reliability and safety of the system.
Patent Information
- Application Number
- CN202421367070.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-17
- Publication Date
- 2025-09-02
- Estimated Expiration
- 2034-06-17
AI Technical Summary
In the prior art, the relay adhesion detection scheme occupies CPU ADC resources or costs high, consumes a large power, affects the reliability and security of the system.
The detection circuit of resistive voltage division, capacitive isolation and waveform processing is adopted to capture the relay adhesion state in real time through the GPIO port of the MCU, and the waveform is processed using the comparator and voltage division circuit to achieve signal isolation and low power consumption detection.
It reduces power consumption to tens of microamperes, saves ADC resources, is low in cost, and improves the reliability and security of the system.
Smart Images
Figure CN223296101U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the field of relay adhesion detection, and in particular relates to a relay adhesion detection circuit in an AC circuit. Background Art
[0002] In existing AC systems, such as photovoltaic and inverter systems, relays are crucial electrical devices for rapidly disconnecting and closing the AC main circuit. Relay sticking can be caused by a variety of factors, including current overload, insufficient contact area (heating), excessive operating frequency, and excessive sparking during operation. This can prevent the main circuit from being disconnected, seriously impacting system safety. Therefore, AC systems like photovoltaic and inverter systems require relay sticking detection to improve system reliability and safety.
[0003] There are two main schemes for relay adhesion detection: the first scheme uses an analog circuit to collect the relay midpoint voltage through ADC. The disadvantage of this scheme is that it must occupy CPU ADC resources. At the same time, some circuits use an isolated ADC scheme, which is relatively expensive. The second scheme collects the bus voltage and achieves signal isolation through an optocoupler circuit. The advantage of this scheme is low cost, but the disadvantage is relatively high power consumption.
[0004] The utility model is proposed to solve the defects of analog circuits occupying ADC resources and having high costs or achieving isolation through optical coupling but with high power consumption, and its purpose is to provide a relay adhesion detection circuit in an AC circuit.
[0005] The utility model is realized through the following technical solutions:
[0006] A relay adhesion detection circuit in an AC circuit comprises a resistor voltage-dividing branch, a capacitor isolation branch and a waveform processing branch connected in sequence; the resistor voltage-dividing branch comprises two voltage-dividing resistors connected in series, and the free ends of the two voltage-dividing resistors are respectively connected to connection points on adjacent busbars; the capacitor isolation branch comprises an isolation resistor connected in parallel with the second voltage-dividing resistor and two isolation capacitors, and the two isolation capacitors are respectively arranged in a parallel circuit between the isolation resistor and the voltage-dividing resistor; one end of the isolation resistor is grounded, and the other end is connected to the waveform processing branch; the waveform processing branch comprises a comparator and a waveform resistor group connected to the output end of the comparator, the non-phase input end of the comparator is connected to the capacitor isolation branch, and the inverting input end is connected to a reference voltage; the waveform resistor group comprises a first waveform resistor connected to the output end of the comparator, and a second waveform resistor, a third waveform resistor and a waveform capacitor connected to the other end of the first waveform resistor, and the connection end of the first waveform resistor and the remaining resistors is connected to the GPIO port of an MCU.
[0007] In the above technical solution, the connection point is set between two adjacent relays on the busbar.
[0008] In the above technical solution, the positive and negative power supply terminals of the comparator are connected to the positive and negative electrodes of the power supply and are grounded through capacitors.
[0009] In the above technical solution, the other ends of the second waveform resistor and the third waveform resistor are respectively connected to the positive and negative electrodes of the comparator power supply, and the other end of the waveform capacitor is grounded.
[0010] The beneficial effects of the utility model are:
[0011] This utility model provides a relay sticking detection circuit in an AC circuit. This circuit utilizes a "resistance divider + capacitor isolation + pulse detection" approach. Even with relatively low currents, the capacitor can still transmit the AC waveform normally. By increasing the divider resistor, the current in the loop is reduced, lowering power consumption to as low as tens of microamperes. The waveform is processed using a comparator and a voltage divider circuit, and captured in real time via a standard GPIO port on an MCU, thereby determining whether the relay is sticking. This utility model offers low cost, low power consumption, and the ability to conserve ADC resources. By utilizing capacitor isolation to achieve signal isolation detection, it represents a pioneering practical application with significant application value. BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Figure 1 This is a schematic diagram of the assembly structure of the relay adhesion detection circuit of Example 1 of the present utility model;
[0013] Figure 2 This is a schematic diagram of the bus sampling point setting position of Example 1 of the present utility model;
[0014] Figure 3 This is a relay adhesion detection circuit diagram of Example 1 of the present utility model.
[0015] in:
[0016] For ordinary technicians in this field, other relevant drawings can be obtained based on the above drawings without any creative work. DETAILED DESCRIPTION
[0017] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific implementation methods.
[0018] Example 1
[0019] In this embodiment, the AC signal takes three-phase electricity as an example. The phase voltage of A, B, and C is 220V, 50HZ AC signal. Two relays are connected in series to the A, B, and C busbars respectively. The sampling point is taken at the connection between the two relays, such as Figure 2As shown, the connection point between relay K1 and relay K2 on bus A is marked as A_Relay_node, the connection point between relay K3 and relay K4 on bus B is marked as B_Relay_node, and the connection point between relay K5 and relay K6 on bus C is marked as C_Relay_node; Figure 1 As described above, detection circuits are connected between A_Relay_node and B_Relay_node, and between B_Relay_node and C_Relay_node;
[0020] A_Relay_node, B_Relay_node, and C_Relay_node collect the sampling signals on the AB and BC buses respectively. The relay adhesion detection circuit in the specific AC circuit is as follows:
[0021] The resistor divider branch of the AB bus includes a first voltage divider resistor R1 and a second voltage divider resistor R9 connected in series. The other end of the first voltage divider resistor R1 is connected to the A_Relay_node between the relay K1 and the relay K2 on the A bus; the other end of the second voltage divider resistor R9 is connected to the B_Relay_node between the relay K3 and the relay K4 on the B bus. The signals of the A_Relay_node and the B_Relay_node are divided by the first voltage divider resistor R1 and the second voltage divider resistor R9.
[0022] The resistance divider branch of the BC bus includes a first voltage divider resistor R12 and a second voltage divider resistor R20 connected in series. The other end of the first voltage divider resistor R12 is connected to the B_Relay_node between relay K3 and relay K4 on the B bus; the other end of the second voltage divider resistor R20 is connected to the C_Relay_node between relay K5 and relay K6 on the C bus. The signals of B_Relay_node and C_Relay_node are divided by the first voltage divider resistor R12 and the second voltage divider resistor R20.
[0023] The resistance values of the first voltage-dividing resistors R1 and R12 are both 4.3MΩ with an accuracy of 1%; the resistance values of the second voltage-dividing resistors R9 and R20 are both 100KΩ with an accuracy of 1%;
[0024] The capacitive isolation branch of the AB busbar includes an isolation resistor R7 connected in parallel with the second voltage divider resistor R9 of the resistance voltage divider branch of the AB busbar, and two isolation capacitors C2 and C5. The two isolation capacitors C2 and C5 are respectively arranged at both ends of the isolation resistor R9; one end of the isolation resistor R9 is connected to the ground and C5, and the other end is connected to pin 3 of the waveform processing branch comparator U1A;
[0025] The capacitive isolation branch of the BC bus includes an isolation resistor R18 connected in parallel with the second voltage divider resistor R20 of the resistive voltage divider branch of the BC bus, and two isolation capacitors C6 and C8. The two isolation capacitors C6 and C8 are respectively arranged at both ends of the isolation resistor R18; one end of the isolation resistor R18 is connected to the ground and C8, and the other end is connected to pin 5 of the waveform processing branch comparator U1B;
[0026] The capacitance of isolation capacitors C2, C5, C6, and C8 is 1nF and the withstand voltage is 2KV;
[0027] The resistance of the isolation resistors R7 and R18 is 4.3MΩ and the accuracy is 1%;
[0028] The waveform processing branch of the AB bus includes a comparator U1A and a waveform resistor group connected to the output end (pin 1) of the comparator U1A. The non-inverting input end (pin 3) of the comparator U1A is connected to the capacitor isolation branch, and the inverting input end (pin 2) is connected to the reference voltage 1.5V; the positive power supply end (pin 5) of the comparator U1A is connected to +5V and is filtered by the first power supply capacitor C1, and the negative power supply end (pin 4) is connected to -5V and is filtered by the second power supply capacitor C4; the waveform resistor group includes a first waveform resistor R5 connected to the output end (pin 1) of the comparator U1A and a second waveform resistor R4 connected to the other end of the first waveform resistor R5, a third waveform resistor R8 and a waveform capacitor C3 for filtering, the other end of the second waveform resistor R4 is connected to +5V, and the other end of the third waveform resistor R8 is connected to -5V; the other end of the waveform capacitor C3 is grounded; the connection end (AB_RELAY_DET) of the first waveform resistor R5 and the remaining resistors is connected to the GPIO port of the MCU.
[0029] The waveform processing branch of the BC bus includes comparator U1B and a waveform resistor group connected to the output terminal (pin 7) of comparator U1B. The non-inverting input terminal (pin 8) of comparator U1B is connected to the capacitor isolation branch, and the inverting input terminal (pin 6) is connected to the reference voltage 1.5V. The positive power supply terminal of comparator U1B is connected to +5V and is filtered by the first power supply capacitor. The negative power supply terminal is connected to -5V and is filtered by the second power supply capacitor.
[0030] The waveform resistor group includes a first waveform resistor R16 connected to the output terminal (pin 7) of comparator U1B, a second waveform resistor R15 connected to the other end of the first waveform resistor R16, a third waveform resistor R19, and a waveform capacitor C7 for filtering. The other end of the second waveform resistor R15 is connected to +5V, and the other end of the third waveform resistor R19 is connected to -5V. The other end of the waveform capacitor C7 is grounded. The connection end (BC_RELAY_DET) between the first waveform resistor R16 and the remaining resistors is connected to the MCU's GPIO port. The comparators for the AB and BC buses use a dual-channel comparator chip and share the same power supply.
[0031] The comparators U1A and U1B are LM2903DR. The power supply of the comparators is ±5V.
[0032] The power supply capacitors C1 and C4 have a capacitance of 0.1uF and a withstand voltage of 50V.
[0033] The resistance of the first waveform resistors R5 and R16 is 69.9KΩ with an accuracy of 1%;
[0034] The resistance of the second waveform resistors R4 and R15 is 49.9KΩ with an accuracy of 1%;
[0035] The resistance of the third waveform resistors R8 and R19 is 200KΩ and the accuracy is 1%;
[0036] The capacitance of waveform capacitors C3 and C7 is 470PF and the withstand voltage is 50V.
[0037] The detection principle process of this utility model:
[0038] The principle of relay adhesion detection on AB and BC lines is the same. Taking AB line as an example, under normal working conditions, Figure 2 The relays K1, K2 and K3, K4 are closed. Figure 3 At both ends of R9 is an AC signal with an amplitude of 5V and a frequency of 50HZ. After isolation by capacitors C2 and C5, at both ends of R7 is an AC signal with an amplitude of 5V and a frequency of 50HZ with GND as the reference. This signal is connected to pin 3 of U1A and compared with the reference voltage of 1.5V at pin 2. When it is higher than 1.5V, pin 1 of U1A output terminal is an open collector output. The signal AB_RELAY_DET divided by R4 and R8 is about 3.003V at this time. When the signal at pin 3 is lower than 1.5V, pin 1 of U1A output terminal is a low level value of -5V. R5, R4 and R8 divide the voltage, and AB_RELAY_DET is about 0.093V at this time. As the AC signal at both ends of R7 changes periodically, the AB_RELAY_DET signal is a square wave signal with a high level of 3.003V and a low level of 0.093V, which is captured by the GPIO port of the MCU.
[0039] When the system is abnormal or the main circuit needs to be disconnected for other reasons, a remote control signal is sent through the system to disconnect relays K1, K2, K3, and K4. Under normal circumstances, the voltage across R9 is 0V, the voltage across R7 is 0V, the input of pin 3 is 0V, which is lower than 1.5V, and the output of pin 1 is a low level value of -5V. After voltage division by R5, R4, and R8, the AB_RELAY_DET signal is low, indicating that the relay is working normally and no adhesion occurs. If the AB_RELAY_DET detected by the MCU's GPIO is a square wave signal, it means that there is relay adhesion in K1, K2, K3, and K4, and the MCU performs a series of protection actions.
[0040] The applicant declares that the above is only a specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Technicians in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technicians in the relevant technical field within the technical scope disclosed in the present invention fall within the protection scope and disclosure scope of the present invention.
Claims
1. A relay adhesion detection circuit in an AC circuit, characterized by: It includes a resistor voltage-dividing branch, a capacitor isolation branch and a waveform processing branch connected in sequence; the resistor voltage-dividing branch includes two voltage-dividing resistors connected in series, and the free ends of the two voltage-dividing resistors are respectively connected to the connection points on adjacent busbars; the capacitor isolation branch includes an isolation resistor connected in parallel with the second voltage-dividing resistor and two isolation capacitors, and the two isolation capacitors are respectively arranged in a parallel circuit between the isolation resistor and the voltage-dividing resistor; one end of the isolation resistor is grounded, and the other end is connected to the waveform processing branch; the waveform processing branch includes a comparator and a waveform resistor group connected to the output end of the comparator, the non-phase input end of the comparator is connected to the capacitor isolation branch, and the inverting input end is connected to the reference voltage; the waveform resistor group includes a first waveform resistor connected to the output end of the comparator, and a second waveform resistor, a third waveform resistor and a waveform capacitor connected to the other end of the first waveform resistor, and the connection end of the first waveform resistor and the remaining resistors is connected to the GPIO port of the MCU.
2. The relay adhesion detection circuit in an AC circuit according to claim 1, wherein: The connection point is arranged between two adjacent relays on the busbar.
3. The relay adhesion detection circuit in an AC circuit according to claim 1, wherein: The positive and negative power supply terminals of the comparator are connected to the positive and negative electrodes of the power supply and are grounded through capacitors.
4. The relay adhesion detection circuit in an AC circuit according to claim 1, wherein: The other ends of the second waveform resistor and the third waveform resistor are connected to the positive and negative electrodes of the comparator power supply respectively, and the other end of the waveform capacitor is grounded.