Ultra-low inductance phase leg design for GaN-based three-phase motor drive systems

This paper presents an improved phase leg power loop design for enhance mode lateral structure Gallium Nitride (GaN) transistors. Static characterization results of a 650V/30A GaN transistor are presented. The gate driver circuit is designed based on the characterization results. In order to reduce current commutation loop inductance within the GaN phase leg, an improved power loop design with vertical structure is proposed for lateral structure GaN transistors. The control of Common Mode (CM) noise current propagation is also considered during the gate driver design by optimizing the power distribution and grounding structure of the gate driver and digital control circuits. By differentiating the propagation path impedance of digital control circuits and their power supply circuits, conductive CM noise can propagate through power supply path to protect the digital control circuits. The design is verified through experiments on a phase leg prototype which prove the effectiveness of the proposed phase leg on the overvoltage reduction during current transition along with less cross-coupling between power loop and gate loop compared with conventional lateral power loop design. Finally, a three phase motor drive system is designed and tested based on the proposed phase leg.