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An isolated buck–boost (IBB) converter with a hybrid three-level full-bridge primary-side circuit is proposed to achieve wider voltage range regulation. The primary-side circuit is composed of a three-level leg and a two-level leg. The output voltage of the primary-side circuit is five level (i.e., $\pm V_{{\text{in}}}$ , $\pm V_{{\text{in}}}{\text{/ 2}}$ , and zero), and the secondary-side circuit is a semiactive full-bridge rectifier with two active switches and two diodes. The input voltage of the secondary-side circuit is three level (i.e., $\pm V_{{\text{o}}}$ and zero). Hence, the operation voltage range can be wider than the normal IBB converter's with three voltage levels in the primary-side circuit and secondary-side circuit. This paper focuses on the control strategy allowing the converter to operate in boundary current mode at heavy load and in discontinuous current mode at light load with smooth mode transition. The soft-switching performance and output characteristics of the proposed converter are presented in detail. Compared with the semi-dual active bridge converter, the voltage range is doubled and the peak current of the clamped inductor is decreased. An 800-W prototype with 100–400-V input voltage and 380-V output voltage is built and tested to verify the feasibility of the proposed control strategy. [ABSTRACT FROM AUTHOR]