Bidirectional DC-DC converter utilizing magnetic and capacitive power transfer — 97.1% Efficiency at 1.2-MHz switching

A high-performance DC-DC converter is presented to improve the efficiency and modularity of the vehicular power system. The converter is capable of bidirectional power transfer between the isolated voltage sources. GaN semiconductor switches in the converter turn on and off softly by utilizing the energy stored in the leakage inductance of a transformer. A quasi-resonant operation is also explained which is suitable for low-power condition. The switches turn on at the valley of the drain-source waveform to secure soft switching. A 180-W prototype hardware was fabricated with a 63 mm × 31 mm printed circuit board (PCB) and 200-V GaN FET devices. Peak efficiency was 97.1% at 24-V/155-W output voltage/power and 1.2-MHz switching frequency. Another prototype converter demonstrated the quasi-resonant operation at 25-V/46.8-W output and 914-kHz switching frequency.