Soft-Switching, Duty-Cycle-Extended Two-Phase Interleaved Buck with Positive Inductor Coupling for High-Density Consumer Electronics Power Supplies

Against the backdrop of rapid advances in computing, industry, and electric vehicles, DC–DC buck converters—as core point-of-load regulators—are critical for power supplies in applications with stringent voltage-stability requirements. This paper proposes a two-phase interleaved Buck converter based on positively coupled inductor with a high coupling coefficient. The innovation lies in the positively coupled inductor and two-phase interleaved architecture, where two MOSFETs and two diodes form a similar symmetrical full-bridge interleaved structures together achieve a higher conversion ratio and provide ZCS operation for all power devices, thereby effectively reducing switching losses. Relative to traditional topologies, the proposed converter delivers a higher conversion ratio without extreme duty-cycle operation while improving reliability. After detailing the operating mechanism, we derive the input–output voltage relation, outline controller synthesis guidelines, and specify the soft-switching conditions. From the viewpoint of symmetry, the proposed interleaved converter exploits the electrical and magnetic symmetry between phases to achieve current balancing, extended duty-cycle range and soft-switching. Validation is provided by both a PSIM simulation model and a 270W hardware prototype using an STM32F103ZET6, which achieves 93.3% peak efficiency at a conversion ratio of 0.45, demonstrating the practicality and effectiveness of the approach.