What are the functions of varistors
1. The biggest function of the varistor is that when the voltage added to it is lower than its threshold value UN, the current flowing through it is extremely small, which is equivalent to a closed valve. When the voltage exceeds UN, its resistance value becomes smaller , so that the current flowing through it increases sharply, and the influence on other circuits does not change much, thereby reducing the influence of overvoltage on subsequent sensitive circuits. Utilizing this function, it is possible to suppress the abnormal overvoltage that is common in the circuit, and protect the circuit from being damaged by the overvoltage.
(1) Better thermal characteristics are different from silicon diodes that only have one P-N junction to withstand surge currents. Zinc oxide varistors are composed of millions of P-N structures, which have better energy absorption and surge withstand capability.
(2) A varistor with a fast response speed has operating characteristics similar to other semiconductor elements. The conduction of the rheostat is very fast, and the delay is only in the range of nanoseconds, which can meet any practical needs.
(3) Stable voltage under over-temperature conditions. When the breakdown voltage is exceeded, once the ambient temperature exceeds the normal operating temperature range, the limit voltage of the Zener diode will increase with the increase of the ambient temperature, and when the limit voltage of the varistor exceeds the operating temperature range, it will remain almost unchanged . When the leakage current of the varistor increases with the temperature of the component body, the limiting voltage of the varistor does not change with the temperature.