Experimental Characterization of Dynamic COSS Losses in 600 V GaN HEMTs based on a Novel and Simple Calorimetric Method

GaN-based semiconductor technology is the enabler for both high power density and high efficiency power electronics systems. In these systems power devices are usually required to operate at high switching frequencies (i.e. several hundreds of kilohertz), therefore topologies enabling soft-switching of the employed power semiconductors are selected, e.g. resonant converters. When operating GaN-on-Si HEMTs at high frequency, however, in the soft-switching regime the so called dynamic C
OSS
losses within the semiconductor die may become a critical limiting factor to the overall converter efficiency. In this paper we propose a novel method to experimentally quantify this loss mechanism by means of a novel, simple and fast calorimetric characterization approach. That method is based on selecting the measurement time instants such that the thermal time constants associated to the semiconductor packages can be neglected, which allows to accelerate and simplify both the calibration and the measurement procedures. By means of the proposed method C
OSS
losses of commercially available 600 V GaN HEMTs featuring two different R
DS,on
have been experimentally measured at various switching frequencies and several switching speeds (dv
DS
/dt). Finally, obtained measurement results are presented, compared and discussed by highlighting the main dependencies of the experimental C
OSS
losses.