Based on the finding that the gain of heat flow inside a power semiconductor device behaves as a low-pass filter (LPF) under the frequency domain, an advanced thermal model developed in the frequency domain has been proposed in recent years. The main advantage of this model is that it can analyze the multitime scale thermal dynamics of power semiconductor devices under complex mission profiles. However, the critical frequencies in the LPF of this frequency-domain thermal model are still difficult to be accurately extracted, thus leading to inaccuracy in the predicted thermal behavior. In this article, the correlation between the first thermal path and the second thermal path in the frequency-domain thermal model has been comprehensively analyzed and modeled, and a new method to determine the critical frequencies is thereby proposed. The simulation and experimental results have been provided to verify the effectiveness of the proposed modeling and characterization method.

Published in: IEEE Journal of Emerging and Selected Topics in Power Electronics ( Volume: 9, Issue: 4, Aug. 2021)