Multi Megahertz Buck Converters using eGaN FETs for Envelope Tracking

Abstract:
With discrete GaN devices capable of switching at slew rates up to 75V/ns, the system performance is greatly impacted by aspects outside the active power devices, such as high speed gate drivers and printed circuit board (PCB) layout. In this paper, the latest family of high frequency enhancement mode gallium nitride power transistors on silicon (eGaN(r) FETs) is presented for use in multi megahertz buck converters. These devices were designed to address high-frequency hard-switching power applications not practical with discrete Si MOSFETs, thus enabling emerging applications, such as envelope tracking (ET), that requires hard-switching at higher frequencies and voltages. Experimental 10 MHz buck converters are demonstrated at voltages up to 42V and output power up to 40W. In this paper we will also explore the limitations of switching ultra-low charge eGaN FETs using a conventional discrete silicon (Si) gate drive.