A Family of High Step-up Isolated DC-DC Converters based on Fibonacci Switched-capacitor Cell

In this paper, a family of high step-up isolated DC-DC converters based on the traditional 3X Fibonacci switched-capacitor converter (SCC) is proposed by replacing one active switch with the secondary wingding of a high frequency (HF) transformer. Other replaceable active switches are substituted by diodes, while the primary circuit is built up with an active switch and the transformer primary winding. Compared with the traditional Fibonacci SCC, the proposed converters feature wider voltage-gain variation range, high step-up voltage gain, electrical isolation and fewer components, which make them potential for photovoltaic power generation system. Compared with the Flyback converter, the proposed converters obtain higher power density by incorporating switched-capacitor cell. The analysis of operating modes and voltage gain derivation is given, together with the passive components volume comparison between the proposed converters and the Flyback converter. A 40V~60V to 400V prototype was designed and tested to verify the theoretical analysis.