A non-invasive method to extract the junction temperature of IGBT

Insulated gate bipolar transistors (IGBT) are used broadly in DC power transmission, power converters, and drives. These applications are cost-sensitive and require high module reliability. Researchers have been found that IGBT degradation over time is directly dependent on its junction temperature. Normally the temperature is measured with a temperature sensor close to the IGBT case or module. This requires the predesigning of the converter or results in a cost-effective and inconvenient process. In this paper, we are proposing a non-invasive method of junction temperature extraction, which do not suffer from the difficulties mentioned above. The method is based on the analysis of electromagnetic radiation (EMR) generated by the IGBT. It has been found that the radiation is a function of switching delay of the IGBT, and this delay is directly proportional to the junction temperature. Thus the junction temperature of IGBT is extracted from the EMR. The method requires only a single loop antenna to capture the radiation. Experimentally to increase the junction temperature of IGBT, an accelerated aging method is adopted. Then the junction temperature, the delay time, and the electromagnetic radiations are measured. The junction temperature is extracted from the inverse relation of these three parameters.