Calculating On-State Voltage Drop of Bipolar Semiconductors using the αβ-Model

The commonly used bipolar semiconductor on-state model for calculating the on-state voltage drop of thyristors and diodes consists of a threshold voltage VT0 and a slope resistance rT. This simple approach is sufficient to describe the general on-state behavior of bipolar semiconductors. A more detailed approach is the ABCD-model which is mainly used for large disc devices. The main disadvantage of both models is a missing temperature dependency, which is required to implement a back coupling of the junction temperature in precise simulations. Due to the fact that paralleling of bipolar modules becomes more and more a trend in the market, a precise way to calculate the power-losses is needed. In order to predict a more detailed voltage drop description which also covers the tempe-rature dependency the TU Dresden developed the alphabeta-Model and Infineon Technologies Bipolar implemented the data in a first step for 60 mm pressure contact modules. The alphabeta-Model offers a new and easy way for accurate voltage drop calculations which are for example needed to calculate the mismatch of current sharing, including junction temperature difference, in parallel operation of bipolar semiconductors with negative temperature coefficient. Finally, a simple simulation model is derived from the model equations which are described in this paper.