Performance evaluation of a 650V E-HEMT GaN power switch

GaN power switches have better characteristics compared to the state-of-the-art Si power transistors. These devices offer high operating temperature and current densities, fast switching and low on-resistance. However, currently only a few producers offer technology of high voltage GaN transistors. Immaturity of this technology is the reason why experimental evaluation of GaN parameters must be performed to properly exploit their advantages. In this paper a prototype of synchronous buck converter with two 650 V GaN HEMT power switches from GaN Systems Inc. is presented. Alternative approach to cooling surface mounted transistors through the PCB is proposed. Paper presents a solution with copper stud attached directly to thermal pad of the device and shows results of thermal measurements. Also electrical power losses are measured depending on switching frequency and output current. Finally, guidelines for proper PCB layout design, including methods for suppressing overvoltages, are given.