Junction Temperature Measurement Based on Electroluminescence Effect in Body Diode of SiC Power MOSFET

To ensure the safe and reliable operation of the SiC power MOSFETs, an optical isolated junction temperature estimation method is proposed. The inherent electroluminescence (EL) in the body diode of SiC MOSFETs is observed and proved to be an effective thermal sensitive parameter in this paper. It is found that during the conduction of the body diode, a visible blue-green light is emitted around the SiC chip. To convert the light signal into the electrical signal, a photosensitive sampling circuit is built based on an ambient light sensor. The temperature dependence results suggest the output voltage of the sampling circuit decreases linearly with the junction temperature. Compared with the state-of-the-art junction temperature estimation methods, the proposed method is optically isolated without any physical contact, thus can be detected remotely by a digital controller. Since the EL is only related to the forward current and junction temperature, the proposed method is free from the influence of the degradation of the package, which is difficult to be decoupled in the homologous methods.