An Adaptive Thermal Equivalent Circuit Model for Estimating the Junction Temperature of IGBTs

Implementation of real-time health assessment and thermal management of insulated gate bipolar transistors (IGBTs) require thermal equivalent circuit models that can be used to predict the junction temperature of the modules. Solder aging in IGBTs has a substantial impact on the accuracy of junction temperatures estimated by the models. This paper proposes an adaptive thermal equivalent circuit model that can estimate the junction temperature of IGBTs with precision under solder aging conditions. First, the solder aging process is monitored in real time by the temperature gradient of the baseplate of the IGBT module, which is easily implemented by placing two thermal sensors at the interface between the baseplate and the cold plate. Then, when the solder aging is detected, the actual junction temperature obtained by an ON-state collector-emitter voltage of the IGBT is utilized to update model parameters based on the thermal behavior of the device. By combining the two stages, the effect of solder aging on the accuracy of the junction temperature estimate is removed in time. Simulation and experimental results are provided to verify the effectiveness of the proposed method.