Static V- I Characteristics
The static V- I characteristics of power diodes is shown in figure 1.2 when the anode is made positive with respect to cathode the power diode is said to be forward biased. In this condition the power diode behaves as a closed switch. As the anode voltage is increased the current will initially be zero until the voltage is less than its threshold voltage is the minimum anode voltage beyond which the diode current increases rapidly and diode starts conducting. A conducting diode has a relatively small forward voltage drop across. It the magnitude of the forward voltage drop depends son the manufacturing process and temperature.
Figure Static V- I Characteristics of power diode
When cathode of power diode is made positive with respect to anode the diode is said is to be reversed. It reversed. It behaves as an open circuit. Under reverse biased condition a small reverse current flows and this reverse current is known as leakage current leakage current increase slowly in magnitude with the reverse voltage until the avalanche voltage is reached. The avalanche breakdown is a process that occurs in a diode when high voltage causes free electrons to travel at high speeds colliding with other electrons and knocking them out of their orbits. The result is a rapidly increasing amount of free electrons and hence increased current. The can be limited by connecting a resistance in series with the power diode.