Question

Explain the importance of PIV rating of a diode.

Answer 1

Peak Inverse Voltage of a diode, abbreviated as PIV, is the maximum voltage the diode can withstand in a reverse-biased direction before breakdown. PIV rating plays a key role in defining the usage of the diode.

Complete step by step answer:
PIV is the maximum voltage that should be applied to the diode in reverse bias. The diode is a unidirectional device, hence if a voltage more than PIV is applied across the diode, an avalanche breakdown occurs. When this happens, the potential barrier is broken and a high impulse current flows in the circuit. This can damage the diode and the whole equipment as well. Diodes must have PIV rating that is higher than the maximum supplied voltage. Thus, PIV rating is important to know how much maximum voltage can be applied across the diode safely without damaging the diode. PIV rating is different for different diodes and It is specified in the data given by the manufacturer about the diode.

The main function of a PN junction diode is to allow the flow of current in one direction only. Hence for forwarding current, a diode should act as a conductor and for reverse current, it should act as an insulator. So if we choose a diode of the wrong PIV rating, our basic objective will not be fulfilled.

Note: Peak Inverse Voltage does not refer to the transformer voltage or the input voltage. For practical purposes, it is a good practice to always select the diode with PIV rating double of the maximum reverse voltage to ensure safety.