For AC-DC converter to charge a battery whose voltage range is wide, in the last chapter, an optimal peak current modulation strategy is proposed for the semi-DAB based single stage high frequency isolated AC-DC converter, but the output voltage is fixed, and there are only two modes as M > 1 within entire line frequency cycle, the turns ratio of the high frequency transformer is not optimal. The effect of the modulation strategies on THD of iac and the mechanism are not considered. The backflow power of the converter is relatively large. So in this chapter, a novel decoupled inductor current modulation strategy for a single-stage AC-DC converter based on semi-DAB is proposed, which helps to minimize the total harmonics distortion (THD) and improve the conversion efficiency. The transformer turns ratio is designed in an optimized method for higher conversion efficiency. Only two control variables are used. And the converter could achieve wider output voltage range and high power factor without mandatory current tracking loop and look-up tables. In addition, losses, THD and backflow power comparisons between the decoupled inductor current and the optimal peak current modulation are presented. The power transfer capability, mode transition mechanism, soft switching range and mode operation region and parameter design are analyzed. Switches can achieve zero-voltage-switching (ZVS) within a wide operating range and rectifier diodes can achieve zero-current-switching (ZCS) off in all operation situations. Besides, a 1 kW experimental prototype was built to verify the effectiveness of the proposed control strategy.