Reduced Order Thermal Modeling of Power Electronics Modules via Time Domain Vector Fitting

Thermal modeling of power electronics modules is often used for the prediction of internal temperatures which is essential for safe operation and life time estimations. However, the models provided by manufacturers are normally quite simplified, accounting only partially for the crosscoupling effects between chips. A more accurate analysis is possible using Finite Element Method (FEM) analysis but its combination with general time domain simulations is complicated and computationally demanding. We show a simple procedure for overcoming this difficulty by extracting a rational function-based model from time domain responses obtained by a FEM analysis. The model, which is extracted using TD-VF, is both low-order and highly accurate. We report an example from thermal simulation of an IGBT power module. The new method gives savings in computation time of the order of two magnitudes, compared to FEM simulation.