A new compact and high efficiency resonant converter

This paper explores a new resonant converter which features compact size, high efficiency, and compatibility with self-driven synchronous rectifiers. The proposed resonant converter and the LLC series resonant converter (LLC-SRC) are in the same three-element resonant converter category and these two converters both consist of 2 inductors and one capacitor in their resonant tanks. While the LLC-SRC converter has all of its resonant elements on the input side, the proposed resonant converter has one of its resonant inductors on the output side. Utilizing the output resonant inductor allows the proposed resonant converter to implement self-driven synchronous rectifiers. When comparing the series resonant inductor in the LLC-SRC, the output inductor in the proposed resonant converter generally has lower cost and smaller size in voltage-step down applications. Operational analysis of the proposed resonant converter is made through sinusoidal approximation. A 250W prototype of the proposed resonant converter is built to verify the analysis made in this paper and evaluate its performance. With the same soft-switching characteristics as the LLC-SRC has, the proposed resonant converter can achieve 95.7% efficiency in a 430V to 27.5V/9A conversion even with diode rectifiers.