The Drive Circuit Design for Paralleling Operation of Enhancement GaN HEMT in an Isolated DC-DC converter

For current limitation of a single low voltage enhancement mode GaN HEMT, paralleling of GaN HEMT are essential in high current and low voltage applications. Through parallel GaN HEMT, the converter will increase the power handling capability and realize high efficiency. Driving paralleled operation GaN HEMT needs special care on parameters design of both driving circuit and power device layout, because the low gate-to-source maximum voltage (V
_gs
) rating and low gate threshold voltage (V
_th
) raise some strict constrains and challenges. This paper presents the driving challenges in paralleling of GaN devices in an isolated dc-dc converter. The design rules for gate driver and PCB layout are concluded based on the analysis of parasitic. The hardware prototype of a 300W flyback forward isolated converter with paralleling of GaN devices is implemented and presented in this paper.