This paper presents a hybrid-type full-bridge dc/dc converter with high efficiency. Using a hybrid control scheme with a simple circuit structure, the proposed dc/dc converter has a hybrid operation mode. Under a normal input range, the proposed converter operates as a phase-shift full-bridge series-resonant converter that provides high efficiency by applying soft switching on all switches and rectifier diodes and reducing conduction losses. When the input is lower than the normal input range, the converter operates as an active-clamp step-up converter that enhances an operation range. Due to the hybrid operation, the proposed converter operates with larger phase-shift value than the conventional converters under the normal input range. Thus, the proposed converter is capable of being designed to give high power conversion efficiency and its operation range is extended. A 1-kW prototype is implemented to confirm the theoretical analysis and validity of the proposed converter.Index Terms-Active-clamp circuit, full-bridge circuit, phaseshift control.

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This paper proposes a single power-conversion ac-dc converter with a dc-link capacitor-less and high power factor. The proposed converter is derived by integrating a full-bridge diode rectifier and a series-resonant active-clamp dc-dc converter. To obtain a high power factor without a power factor correction circuit, this paper proposes a suitable control algorithm for the proposed converter. The proposed converter provides single power-conversion by using the proposed control algorithm for both power factor correction and output control. Also, the active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. Moreover, it provides zero-voltage turn-on switching of the switches. Also, a series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the output diodes. The proposed converter provides maximum power factor of 0.995 and maximum efficiency of 95.1% at the full-load. The operation principle of the converter is analyzed and verified. Experimental results for a 400W ac-dc converter at a constant switching frequency of 50kHz are obtained to show the performance of the proposed converter.