Many efforts have been devoted to describe the multi-timescale thermal dynamics of power modules and frequency-domain modeling is a relatively new approach. Unfortunately, only the frequency-domain response of thermal impedance has been studied in recent works, so the existing models can only describe the temperature behaviors of semiconductors. In the reality, it is not only the temperature of semiconductors which is important but also of other parts of the package. In this article, a novel perspective to study the thermal dynamics by analyzing heat flow behaviors is proposed. Frequency spectrum analysis in finite-element method simulation has been first used in this article, and it reveals that heat flow of the power semiconductor device behaves as a multi-layer low-pass filter (LPF). As a result, a novel modelling method of heat flow with a 7order-3frequencies LPF has been developed in this article and it can provide a comprehensive description of heat flow behaviors for power modules at full bandwidth. Meanwhile, the effects on heat flow behaviors brought by boundary conditions are also considered to ensure that the proposed model can be easily adapted to different boundary conditions. The effectiveness and accuracy of the proposed model has been verified by both simulations and experiments.

Published in: IEEE Transactions on Power Electronics ( Volume: 38, Issue: 2, February 2023)