Consequences of Temperature Imbalance for the Interpretation of Virtual Junction Temperature Provided by the VCE(T)-Method

Abstract:
The VCE(T)-method is the favored approach to determine the temperature of IGBTs by utilizing the almost linear temperature dependence of forward voltage drop at small constant collector current. The method provides a virtual temperature value reflecting an average of the lateral temperature distribution across the IGBT. The present study reveals that averaging is strongly affected, when the lateral temperature gradient is enlarged by reduced loadpulse duration and imbalanced heating of paralleled chips. This should be taken into account for interpretation of the virtual temperature value, especially when device aging by power cycling is considered.