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Optimum design consideration and implementation of a novel synchronous rectified soft-switched phase-shift full-bridge dc/dc converter with a primary-side energy storage inductor for server adapter application is presented in this paper. By employing a primary-side energy storage inductor, the main switches can achieve a soft-switching condition, and there is little reverse recovery loss in the body diodes of a secondary-side rectifier due to relatively slow downslope of the triangular current. Since the output capacitive filter reduces the voltage stress across the rectifiers, the synchronous rectifier with a lower breakdown voltage rate can be utilized to improve the conversion efficiency dramatically. Thus, this converter can obtain relatively high conversion efficiency for some medium-power applications with low output voltage and high output current, such as the server adapter. Several key optimum design considerations of this converter are also presented in detail in this paper. Finally, a 100-kHz, 300-W (12 V/25 A) laboratory-made prototype for a given server adapter application is built up based on the proposed optimum design procedure of this converter to verify all the theoretical analysis and evaluations.
Date of Publication: Feb. 2009