High Power Density and High Efficiency ac-dc 250W Adapter based on GaN HEMTs

With the advent of Gallium Nitride High Electron-Mobility Transistors (GaN HEMT), new scenarios have opened in power conversion regarding topologies, switching frequencies and operating modes. Compared to Silicon MOSFETs, GaN devices show low capacitances, higher switching speed and zero reverse recovery charge, resulting in reduced switching losses and smaller dimensions due to higher achievable frequency. This paper presents a two-stages ac-dc adapter composed by a resonant Totem Pole PFC in ZVS and a resonant LLC converter. A STM32G474 microcontroller drives both stages, meeting the no-load consumption requirement (Pin < 150mW). Design criteria and experimental results are provided on a 250 W prototype, with 1W/cm3 power density.