A Conduction-Loss-Conscious 4-Level Power Converter with Tri-Path Synchronous Rectification for High Step-Down DC-DC Conversion

Multi-level power converters today are highly desirable for high step-down DC-DC conversions but face a serious challenge due to the inherent limitations of topology and operation, which severely impacts efficiency. To combat this challenge, this paper proposes a new operation strategy - tri-path synchronous rectification (TSR) to reduce conduction loss in each discharge phase significantly, which is regarded as a dominant factor to efficiency. The TSR strategy is non-intrusive and can be virtually applied to any multi-level converters without interrupting the original converter operation. To demonstrate the design ideas, a 4-level TSR converter prototype is designed and tested. It down-converts a 48V power source to an output voltage programmable from 1V to 2V with a maximum load of 25A and a peak efficiency of 90.8%.