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A dynamic thermal controller for power semiconductor devices

Failures of power switches are linked directly to the reliability of power converters. Two most dominated failure mechanisms of insulated gate bipolar transistor (IGBTs) are solder fatigue and bond wire lift-off. These failure mechanisms are mainly triggered by the coefficient of thermal expansion (CTE) mismatch in the material interfaces. Generally, the CTE mismatch weakens the IGBT layer interfaces over time due to repetitive thermal cycling caused by load variations and environmental conditions. This paper proposes a dynamic thermal controller for power semiconductor devices to protect them from over temperature and thermal-cycling stress failures, and therefore, enhancing their reliability. The proposed control method consists of two temperature-related control parameters, namely, the gate voltage and fundamental frequency. These parameters are controlled individually or together to smoothen the junction temperature variation of a power semiconductor device. A 1.5-kW three-phase inverter prototype is developed and tested to validate the proposed thermal control technique.