Non destructive SOA testing of power modules

Insulated gate bipolar transistors (IGBTs), having the big advantage of joining together the bipolar conduction characteristics and the insulated gate control, have received much attention in recent years for their energy efficient and rugged performance for a wide range of power applications. These devices are frequently employed in hard-switching applications, where the device is required to turn off high currents and voltages under inductive loading conditions. Robustness of devices used in such applications is a desirable feature, and a premium is placed on those devices having larger and larger reverse-bias safe operating area (RBSOA). Although the RBSOA boundaries of the IGBT devices do not severely limit their capabilities in most applications, the possibility for them to be operated for a short time out of these limits can give a better idea about their robustness. The paper presents an experimental characterization of high power IGBT modules under clamped and un-clamped conditions and at load currents and voltage beyond the RBSOA limits. The behaviour at high junction temperatures is also analyzed. The characterization is aimed to understand the unstable phenomena and the real limits during turn-off of power IGBT modules in extreme operating conditions. The experimental characterization has been performed by means of a non-destructive experimental test set-up where IGBT modules are switched in presence of a protection circuit that is able to prevent a device failure at the occurrence of unstable behaviours.