The demand for decreasing cost and volume and also for increasing efficiency leads to a constantly increasing power density of converter systems. Many Electronic applications could benefit from a power converter able to achieve high efficiency across wide input and output voltage ranges. However, it is difficult for many conventional power converter designs to provide wide operation range while maintaining high efficiency and constantly increasing power density. High efficiency series-parallel resonant DC-DC converter is one which is applying on power electronics equipments (such as, telecom power supply, Mammography, computed tomography, mobile equipments charger etc.). For its high performance in telecom power supply we intended to design and implement a prototype of this converter. In this regard this paper contains the facts behind the choice of the resonant converter, prototype design and design of gate drive circuit etc. with result and complements.