Relay protection circuit design

Optocouplers are also known as opto-isolators or optocouplers, referred to as optocouplers. It is a device that transmits electrical signals by means of light. Generally, an illuminator (infrared light emitting diode (LED)) and a light receiver (photosensitive semiconductor tube) are packaged in the same package. When the input terminal energizes the signal, the illuminator emits light, and after receiving the light, the photoreceptor generates a photocurrent, which flows out from the output end, thereby realizing "electro-optical-electrical" conversion. An optocoupler that couples the input signal to the output with light as a medium.

At the end of last year, I completed the design of the main circuit of the high-power switching power supply. The circuit uses a full-bridge topology and is rectified by high-frequency transformers. The experimental project is a three-phase incoming 15V/6KA output. Among them, the protection design and alarm design of the main circuit are indispensable. My first thought is that the control of the relay through the output of the single-chip microcomputer, and because of the anti-interference requirements, I must be isolated by optocoupler. So, the optocoupler isolation relay protection circuit design should be born.

Relay protection circuit design

The main isolation application of this relay protection is the TIL117 optocoupler chip produced by TI. The chip does not need to supply power, and the 15V output of the 15V power supply through the optocoupler diode can work normally, effectively isolating the electromagnetic influence of the output side on the main circuit.

In addition, the circuit also has a +24V power supply, most of the relay design requires 24V, the power supply design is as follows:

Relay protection circuit design

The main regulator chip of this circuit is the UA7824 chip with production design. The input voltage of the chip has wide adjustable range, good voltage regulation performance, low power consumption and low price. In the drawings of the relay circuit design, most of the regulated power supply I use this chip.

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