Junction-Temperature Sensing of Paralleled SiC MOSFETs Utilizing Temperature Sensitive Optical Parameters

Online condition monitoring of power electronics relies on high-accuracy and high-bandwidth junction temperature information. One promising sensing approach is the extraction of temperature-sensitive electrical parameters (TSEPs) due to their direct junction-temperature dependency. However, the attractiveness of TSEP extraction diminishes when applied to power modules that use paralleled semiconductors since no individual but only superimposed temperature information of the parallel devices can be extracted. Superimposed temperature information leads to inaccuracies in monitoring due to non-uniform temperature and current distribution between the paralleled semiconductors caused by device variations. To overcome these limitations, this work presents a sensing approach utilizing the electroluminescence (EL) of silicon-carbide (SiC) MOSFETs as a temperature-sensitive optical parameter (TSOP) that can determine the junction temperature of each paralleled semiconductor independently of the individual device current with low computational effort. This approach allows not only a more accurate state of health estimation but also enables active load balancing and thus operational and lifetime optimization of parallel semiconductors. While previous publications have shown that temperature information can be extracted from EL, these methods relied either on additional current information or on complex post-processing techniques, resulting in higher implementation complexity and cost. The proposed sensing approach is characterized and validated by measurement results of two SiC MOSFETs within an industry-standard power module.