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Thermal Modeling of Power Semiconductor Devices with Heat Sink Considering Ambient Temperature Dynamics

Thermal characteristics of semiconductor devices play important roles in reliability evaluation. There is a common problem that existing thermal models ignore ambient temperature dynamics while predicting the junction temperature of semiconductor devices, especially when the heat sink is connected to a semiconductor device. In this paper, the frequency domain analysis method is used to analyze the influence of the ambient temperature dynamics on the junction temperature of the power semiconductor device with the heat sink. The results show that the slow ambient temperature dynamics are not negligible for power semiconductor devices with heat sink which has large time constants when junction temperature prediction is carried out. A universal method for obtaining first-order Cauer parameters of a heat sink is given in this paper. Furthermore, an improved frequency domain thermal model is proposed, which simultaneously considers self-heating and ambient temperature variation. It can provide authentic temperature estimates. The validity of the proposed model is verified by simulation in MATLAB/Simulink with PLECS.