A software frequency response analysis method to monitor degradation of power MOSFETs in basic single-switch converters

The efforts on more reliable power conversion systems are gaining momentum in the recent years. Majority of the studies concerning reliability of power switches focus on the package related failures, mainly caused by the thermal stress. The basic failure precursor for this type of stress has been identified as increased on-state resistance for power MOSFETs in recent literature. However, calculation of on-state resistance requires a voltage sensing circuit which can block the high voltage across the switch during off-state not to damage the measurement or control unit. This also limits the implementation as it requires additional hardware. This paper proposes a software frequency response analyzing algorithm to determine the health status of the power MOSFETs through evaluating the variation in the plant model using the same DSP that is used for control purposes. The proposed concept has been analyzed for basic single-switch converters, and experimentally verified on a dc/dc boost converter.