Omnicoupled Inductors (OCI) Applied in a Resonant Cross-Commutated Buck Converter

All input and output inductors of a resonant cross-commutated buck (rccBuck) converter are coupled to shrink the core size while maintaining efficiency. The steady-state current ripples of the omnicoupled Inductors (OCI) are modeled by separating common-mode and differential-mode voltages. The coupling coefficients are derived to minimize inductance and energy. In this article, the twisted E-E cores with one-turn printed circuit board (PCB) windings are proposed to realize the recommended coupling coefficients. The magnetic flux paths and reluctances are analyzed. A prototype was fabricated to demonstrate the OCI in a 2-MHz rccBuck converter with 12-V input and 3.3-V output. Magnetic volume was 57% smaller and efficiency was 0.5% higher (over the entire load range) than those of the reference rccBuck converter with discrete inductors.