Diodes are the main component of the rectifiers.It is mostly used in electronics devices in power electronics and other.The rectifiers diodes has smaller voltage drop in froward-bias state as compared to the operating voltages. The very small leakage current flow in the reverse-bias state.The froward bias characteristics of the power diode is normally linear, which means that the voltage drop is proportional ohmic resistance and current .The rated currents of power diodes approach kilo-amperes.
At ON: the diode can be considered as an ideal switch ,because it open suddenly .In the most of the circuit the leakage current does not have significant effect on the circuit .So diodes can be considered as switch.
At OFF: only small leakage current flows through the diode.This current is independent of the reverse voltage until the breakdown voltage is reached.
The power rectifier thyristors is known as silicon controller rectifiers(SRC) which are commonly used is adjustable rectifier circuits , mostly in high power units up to 100 MVA in power electronics .If the positive voltages is supplied without gate current , the thyristors constitutes the state of forward bias blocking .A low power signal or pulse of the gate current play to switch the thyristors to the on states . The output characteristic of the thyristors in the forward bias is similar to the curve that of the normal diode with small leakage current in forward bias configuration . The thyristors show very low resistance in the forward bias connection .Once it is turn ON the thyristors remain in this state after the end of gate signal or pulse while its current is is higher than the holding level state.If the current drops below the holding level current state the component or devices turn back on the OFF state or it is known as non conducting state.