In this chapter, a boundary operation is proposed for the voltage-fed semi-dual-active-bridge (VF-SDAB) converter for applications needing only unidirectional power flow capability. The leakage inductor current works in the boundary mode under most operating conditions. The operating principle and comparison with conventional single-phase-shift modulation are presented in detail. The non-active power can be suppressed under most working conditions and the conduction loss for output MOSFETs can be reduced significantly. All the power switches can achieve ZVS while the output side rectifying diodes can obtain ZCS in most operating conditions. The parameter design including the compensated value and the dead-time selection is given. The ZVS achievement can be obtained with reduced non-active power and the closed loop implementation can be simplified. The effectiveness of the control strategy has been validated by the experimental results of 1 kW hardware prototype.