A gate drive circuit with mid-level voltage for GaN transistors in a 7-MHz isolated resonant converter

Abstract

This paper analyzes the drive requirements of Gallium Nitride (GaN) power transistors as the control FETs in the resonant converters in the range of multi-megahertz. In resonant converters with multi-MHz, ZVS technique is normally used to reduce the high frequency switching loss. The commercial gate drivers for the GaN transistors focus on high reliability to the precise gate drive voltage against the parasitic components. But they do not consider the high reverse conduct voltage of the GaN transistors as the control FETs under ZVS at high frequency. To reduce the high reverse conduction loss of the GaN power transistors due to the reverse conduction mechanism before ZVS turn-on, in the meanwhile, ensure the high stability and reliability, a new driving scheme with the mid-level voltage is proposed. In addition, the proposed drive circuit is applied to an isolated resonant DC-DC converter with 7 MHz. The prototype of 18 V input and 5 V/ 2 A output was built to verify the functionality and the benefits.