Zinc oxide varistors are based on zinc oxide (ZnO), mixed with various metal oxides such as Bi2O3, Co2O3, MnCO3, and are made through multiple processes such as high-temperature sintering, welding, and encapsulation. Oxide semiconductor resistors are sensitive to voltage. At a certain temperature, the resistance value increases sharply with the increase of voltage. Zinc oxide varistors have a high resistance value under normal voltage.

The origin of zinc oxide varistors As early as 1967, someone added Bi2O3 metal oxide to zinc oxide (ZnO), and found that this move made zinc oxide (ZnO) varistors have nonlinear volt-ampere characteristics. Later, after research, people have added Co2O3, MnCO3, Sb2O3, Cr2O3 and other metal oxides to the zinc oxide (ZnO) pressure sensitive material, and found that the nonlinear coefficient of pressure sensitivity can be greatly improved.

Zinc oxide varistors are characterized by large flow capacity, low limiting voltage, fast response, non-polarity, and low temperature coefficient.

The microstructure of zinc oxide varistors includes zinc oxide grains and grain boundary layers around the grains. The crystal molecules inside the zinc oxide grains are neatly arranged, so the resistivity is very low, while the molecular arrangement inside the grain boundary layer is very disordered, so the resistivity is very high, and the two crystal grains are in contact with each other to form a varistor unit.

The breakdown voltage of each varistor unit is about 3.5V, and many varistor units are connected in series and parallel to form the matrix of the varistor. The more varistor units are connected in series, the higher the breakdown voltage is, and the more varistor units are connected in parallel, the greater the flow capacity.

When the zinc oxide varistor is working, each varistor unit is under the surge power, unlike the Zener diode, which only has the junction area to bear the electric power. Cause of surge energy.

A zinc oxide varistor acts as a small capacitor under normal voltage conditions. When an overvoltage occurs in the circuit, the resistance value of the zinc oxide varistor drops sharply and turns on quickly, and its working current increases by several orders of magnitude, thus effectively protecting other components in the circuit from being damaged due to overvoltage.