Identifications of Thermal Equivalent Circuit for Power MOSFETs through In-Situ Channel Temperature Estimation

We propose a novel methodology for identifying thermal equivalent circuit of power MOSFETs through the measurement of thermal conduction characteristics. Drain current of the MOSFET is utilized to estimate channel temperature wherein heat is actually generated. Two measurement methods, i.e., constant voltage (CV) method and constant power (CP) method, are proposed. Those methods are different in the waveforms of input power for the target device. In experiments using a commercial SiC power MOSFET, good agreement is observed between impulse responses obtained from the two measurement methods.