Very-High-Frequency Resonant Flyback Converter with Integrated Magnetics

This paper proposes a gallium nitride (GaN)-based very-high-frequency (VHF) resonant flyback converter with integrated magnetics, which utilizes the parasitic inductance and capacitance to reduce the passive components count and volume of the converter. Both the primary leakage inductance and the secondary leakage inductance of the transformer are utilized as the resonance inductor, while the parasitic capacitance of the power devices is utilized as the resonance capacitor. An analytical circuit model is proposed to determine the electrical parameters of the transformer so as to achieve zero voltage switching (ZVS) and zero current switching (ZCS). Furthermore, an air-core transformer was designed using the improved Wheeler's formula, and finite element analyses were carried out to fine-tune the structure to achieve the accurate design of the electrical parameters. Finally, a 30 MHz, 15 W VHF resonant flyback converter prototype is built with an efficiency of 83.1% for the rated power.