An abnormal turn-off surge suppression concept for PT-IGBTs at high voltage operation

In this paper, we investigate the turn-off surge behavior of PT-IGBTs, and in particular, abnormal increases in surge voltage appearing at high voltage conditions, which are required for a hybrid vehicle with a more powerful motor output. Simulation and experimental results showed that the abnormal surge voltage can be suppressed by increase of an extra-carrier at the interface between the n-drift and n+buffer layers, because the abnormal phenomenon resulted from depletion of the accumulated carrier during the turn-off period. This countermeasure is achieved by designing the PT-IGBT as the increase of the extra-carrier at the interface during the turn-off period. This allows reduction of the surge voltage, and thereby makes it possible to use the device for higher voltage operation over 600 V, such as in hybrid vehicle application, and consequently, to increase the motor power of the hybrid vehicle without sacrificing reliability and cost.