Hybrid Fixed/Variable Frequency TCM Average Current Control Method Enabling ZVS MHz Operation of GaN HEMTs in PFC Stages

The emergence of GaN semiconductors with superior figure-of-merit has opened up new possibilities of using advanced control schemes for further increasing the performance of next-generation PFC rectifiers. With the goal of achieving a high efficiency over a wide mains input voltage range for universal operation world-wide, in this paper, a novel modulation method of hybrid fixed/variable frequency TCM operation is presented. This method features a dynamic increase of switching frequency while still maintaining a full-ZVS operation over the entire line cycle, which leads to up to a 20 % reduction of system losses at light-load and/or high-line operation without the need for any additional circuitry.