Design of A Second Harmonic Current Based High Step-down 48V-to-1V Resonant DC-DC Converter

This paper presents an isolated DC-DC converter topology with a single ground-switch resonant inverter and a current driven rectifier. The inverter circuit oscillates the input voltage at a fundamental switching frequency and a series resonant tank is used to obtain the second harmonic current for power delivery. The circuit operates features constant current (CC) output, which means that the voltage gain never depends on the switching duty cycle. After the circuit’s main waveforms are analyzed and the key parameters are optimized, a 5MHz prototype featuring 48V-to-1V transfer and up to 10A output current is verified by simulation with discrete ferrite transformer and GaN power switches.