Our products use "multi-layer structure" to manufacture voltage-current dependent resistors, which have a non-linear V/I curve, and its resistance will decrease with the increase of voltage. The product is connected in parallel to the circuit of the electronic device for protection.
Major applicable series: SHA、SHV、SHN、SHC、SEA、SEV、SHR、MLC、MLA、MLE、SEH
Zinc oxide grains surround the high-impedance bismuth-rich phase and produce a special non-ohmic contact. At low voltage (Normal condition), this structure maintains a high impedance. At this time, the current is very low to achieve the effect of power saving. When there is a surge voltage, when the voltage exceeds the critical point, the current will be breakdown (over voltage occur), and the product impedance will quickly drop to 0.5~3Ω, and the current will be guided to the ground to achieve the function of surge protection.
The I-V curve is shown in the figure above. The current range drawn by this curve is 10-8~40A , and the voltage change is observed within this current range. Three areas can be roughly marked on this figure, the working voltage region, breakdown region and high current region. In the working voltage area, the leakage current is very low at this time, only about 10-8~2x10-7A level, and the power consumption is quite low.
When the surge voltage exceeds a critical point, the product collapses, and the surge current can be quickly turned on and grounded, and the voltage can be suppressed to a lower level. This voltage value is called the clamping voltage. As can be seen from the figure below, when the current conducted to the ground is 1A, this voltage can be clamping below about 320V.
If the varistor always works in the working region and Breakdown region, the device can maintain the original characteristics for a long time, that is, it has a long life, but if it often works in the high current region, excessive electrical stress and thermal stress will cause affects the structure of the internal grain or grain boundary layer of the device, it will cause the electrical performance deterioration, it will become low voltage resistance, and increased leakage.
