GaN-based semiconductor technology is the enabler for both high power density and high efficiency power electronics systems. In these systems usually power devices are required to operate at high frequencies, therefore resonant topologies enabling soft-switching mechanism are selected. When operating GaN HEMTs at high frequency, however, in the soft-switching regime the so called dynamic Coss losses within the semiconductor die may become a critical limiting factor to the overall converter efficiency. We propose a novel method to experimentally quantify such loss mechanism by means of a novel, simple and fast calorimetric characterization approach. The method is based on selecting the measurement time instants such that the thermal time constants associated to the semiconductor packages can be neglected, which allow to accelerate and simplify both the calibration and the measurement procedure. With that method Coss losses of a commercially available 600 V GaN HEMT have been measured at various switching frequencies and several switching speeds (dVds/dt). Finally, measurement results are presented and discussed by highlighting the main dependencies of the experimental Coss losses.
