According to the previous introduction for semi dual-active-bridge (SDAB) DC-DC converter topology, modulation and control strategy, the voltage-fed semi-DAB is suitable for extremely wide voltage conversion gain range. So a novel single-phase single-stage AC-DC converter based on semi-DAB DC-DC converter is proposed for unidirectional power flow applications in this chapter. Dual-phase-shift (DPS) and Single-phase-shift (SPS) modes are adopted individually according to its operation. Only two control variables which are the primary side phase shift and the phase shift between the two bridges are used. The optimal voltage and current waveforms in different operation modes are analyzed. The detailed transition process between the DPS mode and SPS mode are given, and the mode transition is seamless. The proposed converter can achieve high power factor correction without inner current tracking loop. In addition, the switches can achieve zero-voltage-switching (ZVS) within a wide operating range and the rectifier diode can obtain zero-current-switching (ZCS) off. The power transfer capability, mode transition mechanism, soft switching range, mode operation range and parameter design are analyzed. Besides, a 1 kW experimental prototype was built to verify the effectiveness of the proposed control strategy.