Comparative study of determining junction temperature of SiC MOSFETs during power cycling tests by a Tj sensor and the VSD(T)-method

During power cycling tests the junction temperature Tj needs to be measured as fast and accurately as possible. State of the art is to measure Tj of silicon carbide (SiC) MOSFETs indirectly using the dependency of the forward voltage of the body diode VSD(T) on temperature at low measurement current. This method however has some drawbacks as measurement delays and applicability to SiC MOSFETs with module integrated anti-parallel Schottky diode. To overcome them, a measurement method for Tj in a power cycling test bench by using a chip integrated sensor is investigated. For validation, FEM simulations as well as measurement results gained by the VSD(T)-method will be compared with sensor measurements. Devices under test are SiC MOSFETs equipped with chip integrated temperature sensors. The purpose of this study is to correlate Tj measured directly with the results gained by the VSD(T)-method, to fulfill the stipulation of the automotive qualification guideline AQG 324.