Extreme Step-Down Ratio Single-Stage Solution for 48V-to-1V Point-of-Load Converter

This paper proposes a single-stage point-of-load (POL) converter design to directly step 48 V down to 1 V. The converter utilizes the multi-phase series capacitor buck to serve as the extreme step-down voltage regulator module (VRM). There are 8 phases in a single VRM with a modified modulation strategy. An easy-to-design inductor model is presented with the inductor achieving optimal resistance with respect to volume and saturation limit. A converter prototype with the size of 30 x 40 x 18 mm(exp 3) is built and tested under 250kHz and 400kHz switching frequency. Peak efficiency of 87% is obtained. A 140A output current is delivered with 80% efficiency. Comparing to traditional cascaded POL solution, the proposed converter has great potential in achieving higher efficiency and higher power density. With shared current stress in multi-phases, extremely large output current (>500A) can be delivered for future data center CPU and GPU application.