Application of Varistor in Solid State Relay Circuit Overvoltage Protection Circuit.Mini PIR Sensor Vendor

　　When the solid state relay SSR is used to drive an inductive load, a high surge voltage will be generated at the moment when the power is turned on and off. In order to protect the triac inside the SSR from damage or malfunction due to overvoltage, it can be The AC output end of the SSR is connected in parallel with a varistor MY. The choice of varistor, if it is a 220V power supply, use 470V; if it is a 380V power supply, use 830V.

　　TVS tube is short for Transient Voltage Suppressor. Its characteristics are: the response speed is very fast (ns level), and the surge resistance is worse than that of the discharge tube and the varistor. When the two poles of the TVS diode are impacted by reverse transient high energy, it can change the high impedance between its two poles into low impedance at a speed of the order of 10 to the minus 12 second, absorbing up to several kilowatts of surge power , so that the voltage between the two poles is clamped at a predetermined value, which effectively protects the precision components in the electronic circuit from damage by various surge pulses.

　　The working principle of the varistor: For example, a "nominal 300V" varistor is working at 220V, and suddenly the 220V rises to 310V! At this time, the varistor is broken down, and after the fuse is blown through a large current, The circuit behind is protected, and then the varistor returns to its original state.

　　Comparison of TVS tube and varistor: TVS tube and varistor both rely on changing their own resistance characteristics to control electrostatic discharge, transient voltage and surge voltage, and the main difference is the resistance after conduction. TVS has The high-sensitivity N/P junction is used for control, and its on-resistance is very low, while the on-resistance of MOV is much higher than that of TVS, resulting in differences in clamping voltage and clamping ratio. TVS tubes are mainly used in low-voltage circuits, while varistors are mainly used in high-voltage circuits.

Read recommendations:

High -precision thermistor selection type.Smart Microwave Sensor switch

Hand warmer thermistor selection model

PIR Lens 7709-1B

HW-US003 Offline speech recognition module

PIR Lens 8801-1