Implementation of a Non-Isolated High Step-Down Ratio DC-DC Converter with a Wide Input Voltage Range

A non-isolated high step-down ratio DC-DC converter with a wide input voltage range based on coupled inductor architecture is proposed in this paper. The proposed converter can adapt to voltage variations caused by non-ideal factors in the 48V bus voltage and provide a stable output voltage to the server load in data center applications. The pulse width modulation (PWM) method achieves a high step-down ratio through switched capacitors and coupled inductors. Zero DC magnetizing current can be achieved by connecting capacitors in coupled inductors, reducing core loss. A resonant inductor achieves zero voltage switching (ZVS) for switches to minimize switching losses. The active clamp unit achieves ZVS and suppresses the ringing issue on the synchronous rectifier switch. The output inductor ensures continuous output current, eliminating the need for a large output capacitor. A prototype with 36~60 V input voltages, 1.2 V output voltage, 30 W output power, and 500 kHz switching frequency with GaN devices was developed to verify the feasibility of the hardware circuit. Under 40 % load condition at 60 V input voltage, the proposed converter achieves a peak efficiency of 85.1%.