Relay fault detection circuit

Abstract

The utility model relates to a relay fault detection circuit, which comprises a relay driving circuit, a driving current sampling circuit, an amplifying circuit and a signal shaping circuit, and is characterized in that the output end of the relay driving circuit is connected with a coil of a relay, and the other end of the coil of the relay is connected with the driving current sampling circuit; the output end of the driving current sampling circuit is connected with the amplifying circuit, and the output end of the amplifying circuit is connected with the input end of the signal shaping circuit; the output end of the signal shaping circuit is connected with a controller. According to the utility model, the relay fault detection circuit is used for collecting relay driving current signals and relay pull-in current signals and outputting square wave signals to carry out fault judgment on the relay, the relay does not need to be loaded, the safety is high, the integration is convenient, and the universality is high.

Description

Technical Field

[0001] This utility model relates to the field of electrical control technology, specifically to a relay fault detection circuit. Background Technology

[0002] In the field of automatic control, electromagnetic relays are a very common switching control device used for controlling high-voltage circuits with low-voltage signals and controlling high-power circuits with low-power signals. Their basic structure generally includes an electromagnet (composed of a coil), a return spring, an armature, and contacts. The basic principle is that when the electromagnet is energized, it generates magnetic force, which overcomes the tension of the return spring and attracts the armature, causing the moving contact to connect the stationary contact, thus closing the load terminal of the relay. When the electromagnet is de-energized, the magnetic force disappears, and the armature, pulled by the return spring, causes the moving contact to move away from the stationary contact, disconnecting the load terminal of the relay.

[0003] Common faults in electromagnetic relays generally include coil drive circuit failure, coil burnout, and contact sticking. The first two prevent the electromagnet from generating electromagnetic force, thus failing to attract the armature and complete the relay's load-connecting action. The latter occurs because the moving and stationary contacts of an electromagnetic relay are typically made of metal, and there is contact resistance between them. Therefore, if the load power connected to the relay is too high, the current flowing through the contact surfaces after the relay engages will be excessive, causing a large amount of heat to be generated at the contact surfaces. This eventually melts the stationary and moving contacts, causing them to stick together, resulting in a contact sticking fault that prevents the relay from disconnecting.

[0004] A common method for detecting relay faults is to add a detection circuit to the load side of the relay to check if the signal input to the load appears at the output, thus determining whether the relay is engaged. This detection method has two main drawbacks. First, the detection circuit must be adapted to the type of relay load. For example, the detection circuit for a 220V AC load is incompatible with that for a 24V DC load, making it impossible for the same hardware to control two or more types of loads and detect relay engagement. Second, the detection circuit requires a signal to be present at the relay output; it cannot be left floating. For instance, in a relay circuit controlling a 220V AC load, if there is no 220V power input to the load, the relay's load output will not produce any signal, and the relay engagement detection circuit at the load side cannot detect whether the relay is engaged. Summary of the Invention

[0005] To address the issue that existing relay fault detection requires operation on the load side, this invention proposes a relay fault detection circuit. This circuit collects relay drive current signals and relay pull-in current signals, outputs a square wave signal to determine relay faults, and eliminates the need for the relay to operate under load, ensuring high safety and ease of integration with strong versatility.

[0006] To achieve the above objectives, this utility model proposes a relay fault detection circuit, including a relay driving circuit, a driving current sampling circuit, an amplification circuit, and a signal shaping circuit. The output terminal of the relay driving circuit is connected to the coil of the relay, and the other end of the coil of the relay is connected to the driving current sampling circuit.

[0007] The output of the drive current sampling circuit is connected to the amplifier circuit, and the output of the amplifier circuit is connected to the input of the signal shaping circuit.

[0008] The output of the signal shaping circuit is connected to a controller.

[0009] Furthermore, the relay driving circuit includes a first resistor, a second resistor, and a transistor. The first resistor is connected to the second resistor and the base of the transistor. The emitter of the transistor and the other end of the second resistor are connected to ground. The collector of the transistor is connected to the coil of the relay.

[0010] Set up a relay drive circuit to turn the relay coil on and off.

[0011] Furthermore, the drive current sampling circuit includes a sampling resistor and a DC blocking capacitor. One side of the sampling resistor is connected to a power supply, and the other side is connected to the coil of the relay and the DC blocking capacitor, respectively. The other end of the DC blocking capacitor is connected to an amplifier circuit.

[0012] Furthermore, the amplification circuit includes an amplifier, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor;

[0013] The DC blocking capacitor is connected to the non-inverting input of the amplifier via a third resistor. The non-inverting input of the amplifier is grounded via a fourth resistor. The inverting input of the amplifier is grounded via a fifth resistor. A sixth resistor is provided between the inverting input and the output of the amplifier. The output of the amplifier is connected to a signal shaping circuit.

[0014] The amplifier circuit amplifies the input current signal.

[0015] Furthermore, the signal shaping circuit includes a comparator, a potentiometer, and a seventh resistor. The non-inverting input of the comparator is connected to the potentiometer, the inverting input of the comparator is connected to the output of the amplifier circuit, and the output of the comparator is connected to the seventh resistor and the controller, respectively.

[0016] The comparator is used to compare the relay drive current signal and the relay pull-in current signal with the threshold set by the potentiometer, thereby shaping the continuously changing analog signal into a transitional square wave signal, which is convenient for subsequent digital circuit processing.

[0017] Furthermore, the controller includes a combinational logic controller and a microprogrammed controller.

[0018] The relay fault detection circuit is easy to integrate and can be combined with various controllers to provide judgment signals for relay fault detection.

[0019] The beneficial effects of this utility model through the above technical solution are as follows:

[0020] This utility model enables relay fault detection at the relay coil side. The relay does not require a load, ensuring safe detection and offering strong versatility. When the relay coil is energized, it pulls the armature, causing the contacts to engage. After engagement, the armature enters the relay coil's magnetic circuit, causing a transient change in the coil's magnetic flux. This induces an electromotive force within the coil, resulting in a transient change in the current flowing through it. A relay drive circuit, a drive current sampling circuit, an amplification circuit, and a signal shaping circuit are incorporated to collect, amplify, and shape the relay drive current signal and the relay engagement current signal. Based on the relay's operation, a square wave signal is output to the controller. Fault detection of the relay is achieved based on the change in current.

[0021] 2. The relay fault detection circuit of this utility model has a simple circuit structure, is easy to integrate, and realizes fault detection of the relay during the relay control process. The relay does not need to be under load, which ensures high safety. Attached Figure Description

[0022] Figure 1 This is one of the circuit diagrams for a relay fault detection circuit according to this utility model;

[0023] Figure 2 This is the second circuit diagram of a relay fault detection circuit according to the present invention;

[0024] Figure 3 This is a schematic diagram of a relay fault detection circuit according to the present invention.

[0025] Figure 4 This is one of the images from the oscilloscope used during the testing of this utility model;

[0026] Figure 5 This is the second image from the oscilloscope used during the testing of this utility model.

[0027] The reference numerals in the attached diagram are as follows: 1 is the relay drive circuit, 2 is the drive current sampling circuit, 3 is the amplifier circuit, 4 is the signal shaping circuit, 5 is the relay, 201 is the sampling resistor, 202 is the DC blocking capacitor, 301 is the amplifier, 302 is the third resistor, 303 is the fourth resistor, 304 is the fifth resistor, 305 is the sixth resistor, 401 is the comparator, 402 is the potentiometer, and 403 is the seventh resistor. Detailed Implementation

[0028] The present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0029] Example 1

[0030] like Figures 1-3 As shown, a relay fault detection circuit includes a relay driving circuit 1, a driving current sampling circuit 2, an amplification circuit 3, and a signal shaping circuit 4. The output terminal of the relay driving circuit 1 is connected to the coil of a relay 5, and the other end of the coil of the relay 5 is connected to the driving current sampling circuit 2.

[0031] The output terminal of the drive current sampling circuit 2 is connected to the amplifier circuit 3, and the output terminal of the amplifier circuit 3 is connected to the input terminal of the signal shaping circuit 4.

[0032] The output of the signal shaping circuit 4 is connected to a controller.

[0033] The relay driving circuit 1 includes a first resistor 101, a second resistor 102, and a transistor 103. The first resistor 101 is connected to the base of the second resistor 102 and the transistor 103. The emitter of the transistor 103 is connected to the other end of the second resistor 102 and then grounded. The collector of the transistor 103 is connected to the coil of the relay 5.

[0034] The driving current sampling circuit 2 includes a sampling resistor 201 and a DC blocking capacitor 202. One side of the sampling resistor 201 is connected to the power supply, and the other side is connected to the coil of the relay 5 and the DC blocking capacitor 202 respectively. The other end of the DC blocking capacitor 202 is connected to the amplifier circuit 3.

[0035] The amplifier circuit 3 includes an amplifier 301, a third resistor 302, a fourth resistor 303, a fifth resistor 304, and a sixth resistor 305;

[0036] The DC blocking capacitor 202 is connected to the non-inverting input of the amplifier 301 via the third resistor 302. The non-inverting input of the amplifier 301 is grounded via the fourth resistor 303. The inverting input of the amplifier 301 is grounded via the fifth resistor 304. A sixth resistor 305 is provided between the inverting input of the amplifier 301 and the output terminal of the amplifier 301. The output terminal of the amplifier 301 is connected to the signal shaping circuit 4.

[0037] The signal shaping circuit 4 includes a comparator 401, a potentiometer 402, and a seventh resistor 403. The non-inverting input of the comparator 401 is connected to the potentiometer 402, the inverting input of the comparator 401 is connected to the output of the amplifier circuit 3, and the output of the comparator 401 is connected to the seventh resistor 403 and the controller.

[0038] The controller includes a combinational logic controller and a microprogrammed controller.

[0039] In this embodiment, the controller is a microcontroller.

[0040] like Figure 2 As shown, the relay drive circuit 1 is connected to a controller. During operation, the controller output signal SIG1 is valid, the transistor 103 (Q1) is turned on, and the current passes through the sampling resistor 201 (R5) and enters the coil of the relay 5 (K1). The current signal is grounded through the transistor 103. The current signal increased by the sampling resistor 201 generates the first signal (relay drive current signal) through the DC blocking capacitor 202 (C3), and the coil of the relay 5 is energized.

[0041] When the armature of relay 5 pulls the contact to complete the energizing action, the armature connects to the coil of relay 5, causing a change in the coil magnetic flux, thereby generating an induced electromotive force, which causes a change in the current flowing through the coil. The current generates a second signal (relay energizing current signal) through sampling resistor 201 and DC blocking capacitor 202.

[0042] The relay drive current signal and the relay pull-in current signal are respectively output through the DC blocking capacitor 202 and the sixth resistor 305 (R2), the fifth resistor 304 (R3), the third resistor 302 (R6), the fourth resistor 303 (R9), and the amplifier 301 (U1A).

[0043] After the relay drive current signal and the relay pull-in current signal are amplified, they are shaped and output to the controller via potentiometer 402 (R11), seventh resistor 403 (R7) and comparator 401 (U2A).

[0044] Example 2

[0045] To demonstrate that a relay fault detection circuit has good detection performance:

[0046] A first detection port TP1 and a second detection port TP2 are set at the output terminals of the amplifier circuit 3 and the shaping circuit 4. An oscilloscope is connected to the first detection port TP1 and the second detection port TP2.

[0047] The oscilloscope image of the relay 5 under test when it is normally engaged is as follows: Figure 3 As shown, the relay drive current signal output from the second test port can be observed. Figure 4The peak 1) and the relay pull-in current signal, ( Figure 4 The images show the peak 2 in the test and the two square wave signals output from the third test port.

[0048] The oscilloscope image of the relay under test with a 5-contact fault is as follows: Figure 4 As shown, the relay drive current signal output from the second test port can be observed. Figure 5 The signal output includes a peak (1) and a square wave signal from the third test port. There is no relay pull-in current signal output.

[0049] The coil of the relay under test 5 is faulty, and the oscilloscope shows no image.

[0050] The embodiments described above are merely preferred embodiments of this utility model and are not intended to limit the scope of implementation of this utility model. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the patent claims of this utility model should be included within the scope of the patent application of this utility model.

Claims

1. A relay fault detection circuit, characterized by comprising: Including relay drive circuit (1), drive current sampling circuit (2), amplifier circuit (3) and signal shaping circuit (4), the output end of the relay drive circuit (1) is connected with the coil of relay (5), the coil of relay (5) is connected with drive current sampling circuit (2) on the other end; The output end of the drive current sampling circuit (2) is connected with amplifier circuit (3), and the output end of the amplifier circuit (3) is connected with the input end of signal shaping circuit (4); The output end of the signal shaping circuit (4) is connected with controller.

2. A relay fault detection circuit according to claim 1, wherein The relay drive circuit (1) includes first resistance (101), second resistance (102) and triode (103), the first resistance (101) is connected with the base of second resistance (102) and triode (103) respectively, the emitter of triode (103) and the other end of second resistance (102) are connected with ground, and the collector of triode (103) is connected with the coil of relay (5).

3. The relay fault detection circuit according to claim 1, wherein The drive current sampling circuit (2) includes sampling resistance (201) and direct current blocking capacitor (202), one side of the sampling resistance (201) is connected with power supply, and the other side is connected with the coil of relay (5) and direct current blocking capacitor (202) respectively, and the other end of the direct current blocking capacitor (202) is connected with amplifier circuit (3).

4. A relay fault detection circuit according to claim 3, wherein The amplifier circuit (3) includes amplifier (301), third resistance (302), fourth resistance (303), fifth resistance (304) and sixth resistance (305); The direct current blocking capacitor (202) is connected with the noninverting terminal of amplifier (301) through third resistance (302), the noninverting terminal of amplifier (301) is grounded through fourth resistance (303), the inverting terminal of amplifier (301) is grounded through fifth resistance (304), the sixth resistance (305) is arranged between the inverting terminal of amplifier (301) and the output end of amplifier (301), and the output end of amplifier (301) is connected with signal shaping circuit (4).

5. The relay fault detection circuit of claim 1, wherein, The signal shaping circuit (4) includes comparator (401), potentiometer (402) and seventh resistance (403), the noninverting terminal of comparator (401) is connected with potentiometer (402), the inverting terminal of comparator (401) is connected with the output end of amplifier circuit (3), and the output end of comparator (401) is connected with seventh resistance (403) and controller respectively.

6. The relay fault detection circuit of claim 1, wherein, The controller includes combination logic controller and microprogram controller.

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