Design and Control of a 1 MHz DC-DC Soft-Switching LLC Converter with Wide Band Gap GaN Components

While LLC topology is well-known today, increasing operating frequency is still a challenge, especially for the starting/stopping phase of the converter. The first part of this paper describes the design of a 1 MHz LLC DC/DC converter using Gallium Nitride High Electron Mobility Transistors (GaN HEMT). Then, it presents the Phase Shift Modulation (PSM) control implemented to achieve soft start/stop of the converter, greatly reducing voltage and current stresses on the switches in comparison with other methods (PWM, FM and Burst Mode). Experimental results highlight the performance of both the converter and the PSM control method for start-up.