Fast Method of Computations of Ripples in the Junction Temperature of Discrete Power SiC-MOSFETs at the Steady State

Abstract

This paper presents a method of fast computations of waveforms of the junction temperature of power SiC-MOSFETs (silicon carbide metal–oxide–semiconductor field-effect transistor) operating in switched-mode circuits at the steady state. This method makes it possible to use SPICE (Simulation Program with Integrated Circuits Emphasis) models of the considered transistors given by the manufacturers. The method of the analysis is described. Using the presented methods and a compact thermal model, some computations of switch-mode circuits were performed. Typical switches and DC–DC (direct current to direct current) boost converters, including such transistors operating at different cooling conditions in a wide range of frequencies of a control signal, are analyzed. In particular, the influence of the cooling system, load resistance and switching frequency on the waveforms of the dissipated power and the junction temperature are considered. The obtained results of computations are compared with the results found using other methods of analysis given in the literature. The times required to perform computations with the considered methods are compared. On the basis of the results of the performed analyses, the operating conditions of the investigated networks, at which ripples of the junction temperature are important, are pointed out. A short discussion on the limitation of the lifetime of the power MOSFET is also given.