This paper presents a highly efficient step-up dc-dc converter for photovoltaic system. This converter is composed of an active resonant-clamp circuit and a resonant voltage doubler. The active resonant-clamp circuit limits the voltage stress and provides soft switching of the power switches. Also small value of a clamp capacitor employed to increase efficiency can reduce the conduction loss. Moreover, the resonant voltage doubler is used in the secondary side of the transformer to remove the reverse-recovery problem and clamp voltage stress of output diodes. Thus, the power losses of the proposed converter were minimized by the reducing switching power losses and conducting power loss. A 370 W prototype has been implemented to verify its performance. Experimental results prove the superiority of the proposed highly efficient step-up dc-dc converter for photovoltaic micro-inverter. (C) 2016 Elsevier Ltd. All rights reserved.