Short circuit behaviour of IGBTs correlated to the intrinsic device structure and on the application circuit

It is shown that the analysis of parameters influencing short-circuit operation of insulated gate bipolar transistors (IGBTs) allows the design of a suitable protection circuit to be realized even when the devices have modest short-circuit performance. To safeguard the power system from false alarm, it is necessary to introduce a delay time (t_delay<5 μs) in the short-circuit detection circuit. During this delay, the IGBT must support all the short-circuit stress. Using IGBTs with poor short-circuit capability, the saturation voltage is low, (V_CEsat=2.5 V), but a circuit reducing gate voltage during a short circuit is necessary. The optimization of the IGBT structure allowed the fabrication of an IGBT having sufficient short-circuit capability (t_W MAX=10 μs) and a value of V_CEsat=3.5 V. This device requires a simplified short-circuit protection network without compromising the efficiency and the short-circuit ruggedness of the system