The major intention of this paper is to completely design a full-bridge DC-DC converter with extremely high conversion ratio, high output power and soft-start-up capability. This paper introduces a flyback Snubber for the purpose of recycling the absorbed energy in the clamping capacitor. The flyback Snubber can effectively regulate the voltage of the clamping capacitor; as a result, it can clamp the voltage to a desired level just higher than the voltage across the low-side transformer winding. The current level of the current-fed inductor is subsequently raised up to that of the leakage inductance, which can completely reduce their current difference and, consecutively, reduces the voltage spike. A prototype with low-side voltage of 13V and high-side voltage of 63V has been implemented, from which experimental results have verified its feasibility.