Direct Drive D-Mode GaN HEMT Switching Characteristics and Turn-Off Loss Reductions

Abstract

This article aims to evaluate the depletion-mode gallium nitride high electron mobility transistor (d-mode GaN HEMT) using direct-drive gating and double pulse test to assess switching energy. The gate driving circuit features a modified cascode structure for “normally off” operation and a charge-pump circuit to supply a negative gate voltage for turn-off operation. This article described these features theoretically and validated with experimental results. Similar to enhancement-mode power mosfets or HEMTs, adjusting the gate drive resistance can affect the switching speed and associated losses, but the d-mode GaN HEMTs present an additional feature with turn-off loss reduction through gate voltage control. Thus, the main contribution of this article is to propose and demonstrate significant turn-off loss reduction using the direct-drive approach for d-mode GaN HEMTs.