An Isolated Soft-switching Buck-Boost Converter Utilizing Two Transformers and Embedded Bidirectional Switches on Secondary-side For Wide Voltage Applications

A dual-phase-shift controlled isolated buck-boost converter is presented for wide input or output voltage range applications. Two transformers and a voltage-doubler rectifier with embedded bidirectional switch are employed. The primary windings of the two transformers are in series and the secondary windings are in parallel. With optimized dual-phase-shift modulation strategies, zero voltage switching (ZVS) is achieved for both the primary-and secondary-side power MOSFETs in a wide load range. The reverse recovery problem of rectifying diodes is eliminated as well. Leakage inductances of the transformers are utilized for power transferring. The voltage stresses of primary-side and secondary-side power MOSFETs are clamped to the input voltage and half of the output voltage, respectively. Besides, the converter can operate in the buck, balance and boost modes to achieve a wide voltage range. The operational principles are analyzed and experimental results of a 1-kW 100-kHz prototype are provided to verify the effectiveness of the presented converter.