Paralleling GaN E-HEMTs in 10kW-100kW Systems

Industry is adopting GaN HEMT in 10kW-100kW and higher power systems due to the ultra-fast switching capabilities of GaN. Paralleling GaN HEMT transistors is an appealing idea to further increase the power capability and reduce conduction losses of systems. The characteristics of E-mode GaN HEMT, such as positive temperature coefficient of R-DS((ON)) and a temperature independent threshold voltage, are very suitable for paralleling devices. However, the main challenge for parallel operation is thought to be the diverse parasitics of the power stage and gate driver circuits, which are very sensitive to the high di/dt and dv/dt during the switching process. In this paper, an analytic model for the switching process of paralleled GaN HEMT transistors is built to analyze the effects of parasitics and device characteristics on paralleling, and the design consideration for gate driver and layout is also presented. A half bridge power stage consisting of four high-side and four low-side 60 A / 650 V GaN HEMTs in parallel is designed to undertake 240 A / 400 V hard switching on and off. Double pulse testing results are presented to confirm GaN paralleling capability.