Simulation and experimental investigation of parallel connected IGBTs

The increasing demand for large power ratings and the physically limited maximum current density of semiconductor devices in power electronics make the connection of semiconductor in parallel or series an interesting alternative for high power applications. The major problem of the IGBT parallel connection is the current unbalance of parallel devices, which requires the selection of the devices, a manual parameterization of gate units and a substantial device derating in state of the art high power IGBT Voltage Source Converters. This paper presents a new scheme for the non-destructive parameter extraction of IGBTs and a simulative study of the influence of different parameters on the current distribution of parallel connected IGBTs. The investigations show that the delay time of parallel switched IGBTs can be used to achieve a balanced current distribution despite potentially varying parameters like gate-emitter threshold voltages and internal gate resistances. The results are experimentally verified by measurements in a 500 V, 800 A test set-up applying 1700 V, 450 A IGBTs and inverse diodes.