Power Electronics and Motor Drive Systems

10.9. Protection Circuits (Snubbers) for Power Semiconductor Devices

Power semiconductor devices need protection circuits, which are called snubber circuits, because they have a limited SOA at turn-on and turn-off transitions. The objective of snubber is to help the semiconductor device during switching transitions to survive the voltage and current stresses that can cause its failure. These stresses are caused by the interruption of the current at turn-off and the collapse of the voltage at turn-on. A useful plot that illustrates how switching takes place from on to off and vice versa is called a switching trajectory, which is simply a plot of the semiconductor switch current i_s versus the voltage across the switch v_s. Fig. 10.78 shows the switching ...