GaN vs Si Synchronous Rectifier for LLC Converter

Abstract:
Adoption of GaN switches on the primary side of soft-switching converters, i.e. LLC, to achieve higher frequencies has become widely accepted in the industry due to the benefits such as lower circulating current requirement for ZVS, lower gate drive losses, and the reduction of duty cycle loss due to faster switch-node voltage transitions. Similarly, using GaN switches in the synchronous rectifier provides clear advantages due to lower Rdson per area, lack of Qrr, and low output capacitances. This paper analyzes and investigates the benefits of these low parasitics on the system performance. It has been shown that usage of GaN switches on the secondary side, increases ZVS performance, facilitates voltage regulation at low loads, and reduces losses in both below and above-resonance situations.