Symmetric Four-Phase Inverse Coupled Inductors for GaN-Based Interleaving Four-Phase Point-of-load Converters

The emerging gallium nitride-based semiconductor device due to lower switching loss and smaller package size enables multi-phase point-of-load (POL) converters toward higher power density and efficiency in data centers. The discrete inductors occupy a large proportion of the size and are a bottleneck for further increasing power density. Inverse coupled inductor technology is a promising solution for core size reduction for multi-phase interleaving POL converters. In this paper, a novel magnetic core structure of fully symmetric four-phase inverse coupled inductors are presented, which overcomes the limitation of asymmetrical inductor parameters. The proposed magnetic core structure has the advantages of larger inductance value, smaller size and fully symmetric inductor parameters. A comprehensive analysis of basic magnetic circuit model, derivation of inductance value and design of magnetic core by Maxwell 3-D are discussed. A 108 W, 12-1.8 V, GaN-based prototype of four-phase interleaving POL converter utilizing the proposed magnetic core is built and tested. The experimental results demonstrate that the converter has lower output current ripples and symmetrical inductor current waveforms.