The ac side structure of a bridgeless single-stage isolated ac–dc converter reduces the number of components by sharing power switches between the bridgeless rectifier and the dual-active-bridge (DAB) dc–dc converter. However, it also makes it more difficult to achieve zero-voltage switching (ZVS) for the ac side switches. Therefore, a modulation scheme is proposed to achieve ZVS for all switches over the full ranges of the grid voltage and load. A quasi-fixed switching frequency control method is also applied, in which the switching frequency is constant during a half-cycle of the grid voltage. By adjusting the switching frequency, the grid side inductor can operate in critical conduction mode without a zero-current-detection circuit, which facilitates the ZVS realization of the ac side switches. In addition, a natural power factor correction can be realized without the grid-side current sensors. Finally, a 500 W prototype was built to validate the theoretical analysis and the effectiveness of the proposed modulation scheme.

The isolated dual active bridge DC/DC converter is widely used in power electronic conversion systems due to its security, scalability, and easily realized soft switching. Meanwhile, interleaved technology is also widely used in high current conversion applications due to its low current ripple. Current sharing characteristics are analyzed in detail in this paper based on the topology characteristics of an interleaved low current ripple isolated DC/DC converter. At the same time, under dynamic conditions, the altering trend of the current deviation ratio and the relationship between the current deviation rate and the phase-shifted angle are revealed by small signal modeling. In addition, a single-zero double-pole compensation control method in the current loop is proposed. Finally, an experimental 670 W prototype is built to verify the correctness of the theoretical analysis and the effectiveness of the proposed method.