LAUSR

A novel isolated buck-boost (IBB) converter with a dual-transformer (DT) and an active-controlled three-level rectifier (AC-TLR) is proposed in this study. A new family of IBB converters is derived with different implementations of the AC-TLR. The two transformers in the converter supply power to the output alternatively through the phase-shift control of the active switch in the AC-TLR. A voltage-doubler configuration is built and three voltage levels are generated with the DT and AC-TLR structure. Therefore, the diodes and switches in the rectifier sustain only half of the high-output voltage and turns ratios of the transformers are reduced. In addition, the zero-voltage-switching operation of all the active switches on both the primary and secondary sides is achieved and the reverse-recovery problem of all the diodes is alleviated in the wide operation range. Furthermore, the output voltage of the converter is regulated in a wide range due to the buck and boost voltage conversion characteristics of the converter. The operational principles, modulation and characteristics of the converter are presented. Finally, a 400 V input and 350-750 V output prototype is built and tested to verify the effectiveness of the proposed converters.