Application of Varistor
Varistors are generally used in circuit surge and transient protection circuits. Varistor is a component with transient voltage suppression function, which can be used to replace the combination of transient suppression diode, Zener diode and capacitor. When using, only need to connect the varistor to the protected IC or equipment circuit. When the voltage is higher than a certain value in an instant, the resistance of the varistor drops rapidly and conducts a large current, thereby protecting the IC or electrical appliances. Equipment: When the voltage is lower than the working voltage value of the varistor, the resistance of the varistor is extremely high, almost open circuit, so it will not affect the normal operation of the device or electrical equipment.
Varistors can protect the circuits of ICs and other equipment to prevent them from being damaged by electrostatic discharge, surges and other transient currents (such as lightning strikes, etc.). . For the application of varistor, it can be roughly divided into four types:
The first type is the connection between power lines or between the power line and the ground. As a varistor, the most representative application is when the power line and long-distance transmission signal line are struck by lightning and cause the wire to have waves. It protects electronic products under conditions such as surge pulses. Generally, connecting a varistor between the lines can be effective for the induction pulse between the lines, while connecting a varistor between the line and the ground is effective for the induction pulse between the transmission line and the earth. If the two forms of line-to-line connection and line-to-ground connection are further combined, the surge pulse can be better absorbed.
The second type is the connection in the load, which is mainly used to absorb the inductive pulse caused by the sudden opening and closing of the inductive load to prevent the component from being damaged. Generally speaking, as long as it is connected in parallel to the inductive load, but according to the current type and energy size, it can be considered to be combined with the R-C series absorption circuit.
The third type is the connection between the contacts. This connection is mainly to prevent the contact of the inductive charge switch from being burned by the arc. Generally, it is sufficient to connect the varistor in parallel with the contact.
The fourth type is mainly used for the protection connection of semiconductor devices. This connection method is mainly used for semiconductor devices such as thyristors and high-power transistors. Generally, it is connected in parallel with the protection device to limit the voltage below the resistance of the protected device. Voltage rating, which is an effective protection for semiconductor devices.
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