In Chap. 5 , a current-fed semi dual active bridge (CF-SDAB) DC-DC converter with symmetrical dual PWM and phase shifted control is discussed, which can extend ZVS range of switches with voltage match control strategy, but the switches turn off at very high current, so high turn-off loss is increased especially as the input voltage is low. In addition, the clamp voltage is controlled to be constant and the LVS duty cycle range is limited. This brings unstable operation issue especially under very light load conditions. To deal with the aforementioned issues, this chapter proposes a variable clamp voltage control strategy for the current-fed semi-dual active bridge dc-dc converter. For the low-voltage-side (LVS), the duty cycle of the bottom switches will be changed with the load variation. Full load operation stability and full range of ZVS can be achieved. An instantaneous turn-off current tracking loop is designed to achieve duty cycle control and ZVS. The dc inductor current ripple can be designed smaller and the turn-off loss can be reduced. For the high-voltage-side (HVS), the duty cycle will be calculated to avoid additional loss caused by body diodes. Besides, coupled inductor is adopted to reduce core loss. The ZVS resonant process is analyzed in detail. The proposed control is verified to be effective by a 1 kW experimental prototype.