A Novel Boost-PFM Hybrid modulated Resonant Converter with Optimal Operating Trajectory Control

This paper presents a Boost-modulated resonant converter paired with an optimal trajectory control strategy to minimize the switching frequency adjustment range for traditional resonant converters in applications requiring a wide voltage gain. The proposed topology eliminates the need for additional components by utilizing secondary-side synchronous rectifiers, enabling all devices to achieve zero-voltage switching (ZVS). A hybrid modulation strategy, incorporating secondary- side phase-shift and frequency control, is introduced, resulting in reduced current stress and enhanced efficiency compared to conventional Boost-modulated resonant converters. The feasibility of this hybrid modulation strategy is thoroughly analyzed, leading to the derivation of an optimal operational trajectory. A control method combining phase-shift open-loop control with frequency closed-loop control is proposed, simplifying the multi-variable control system. Experimental validation is performed on a prototype operating within an input voltage range of 500V to 1000V (suitable for a 750V urban rail supply system) and an output voltage range of 600V to 800V (for a three-phase inverter), with a rated power of 25kW. At the minimum input voltage, the converter achieves a full-load efficiency of 98.5%, with a maximum efficiency of 99% across the entire operating range.