Design Methodology of a One-Turn Inductor With Significant DC and AC Fluxes—Demonstration in a Resonant Cross-Commutated Buck Converter

Abstract

One-turn inductors must cope with high dc flux in conventional hard-switched point-of-load converters. These inductors need to handle both high dc and ac fluxes in soft-switched converters with high current ripple, for example, resonant cross-commutated buck (rccBuck) converters. In order to understand the losses associated with those fluxes, the winding loss in megahertz range is modeled in this paper through calculating the fringing field in the window area. The dc-biased core loss for resonant waveforms is modeled by the equivalent elliptical loop (EEL) method. According to the loss models, winding and core dimensions are designed systemically to minimize the total loss within a volume smaller than that of a commercial product. Four 1-turn inductors were fabricated for a 12 to 1.2 V rccBuck converter switched at 2 and 2.5 MHz. The designed one-turn inductors demonstrated 2.1% higher efficiency at 20 A output and 50% lower total magnetic volume than commercial inductors with similar inductances, on the same rccBuck converter.