Simulation prototyping of high power modules

Abstract

This paper studies the voltage sharing mechanism for series operation of high power modules. It is shown that the device mis-match is the main cause for the voltage unbalance and junction temperature unbalance during the conduction state. A 2D mixed device and circuit simulator was used to extract the resistances of the bonding pads and of bonding wires inside the module. Moreover, the device internal resistance profile was extracted and the mechanism of voltage sharing is explained. It is found that the junction of P-base and N-drift region gives rises to the major contribution to the negative temperature coefficient of IGBTs at elevated ambient temperatures. Because of the characteristics of negative temperature coefficient at low current density, voltage unbalance was aggravated at high junction temperature. The understanding of this mechanism provides a good insight to circuit and device designers and help to minimize the series unbalance in high power IGBT modules.