A High Density Three-Level Quadratic Buck Hybrid Converter for 48V-to-PoL Conversion

This paper presents a new hybrid topology for 48V to point-of-load DC-DC converters. The proposed three-level quadratic buck converter (3LQB) consists of a three-level buck converter at the front-end with an inductor-first buck converter at the back-end to achieve the high ratio conversion with 6 switches only. The three-level buck converter allows for the reduction of the inductor value, while the inductor-first buck converter allows for parallel conduction paths through two inductors to deliver more power, with phase interleaving for smaller ripples. These two factors combined contribute to significant improvement of efficiency and power density, and with the quadratic duty-cycle to voltage conversion relation, the 3LQB topology is also beneficial for high-ratio voltage conversion. The simulated peak efficiency for a 48V to 1-3.3V conversion using GaN switches is 95% and the estimated power density that will be achieved is 6.3kW/in3 for an output voltage of 3.3V and 1.9kW/in3 for an output of 1V with a max load current of 60A. Measurements are partially done; more results will be available after the student returns from his internship.