AbstractGenerating sources of renewable systems, like photovoltaic module or fuel cell, have a low‐output voltage that has to be boosted for most of applications, such as grid‐tie inverters. To accomplish this, an isolated DC–DC high step‐up single‐ended primary‐inductor converter (SEPIC) with a Greinacher voltage doubler cell is presented. It has the advantage of continuous input current, high efficiency, and high‐voltage gain and isolation and demands a single switch, being suitable for low‐power grid‐tie photovoltaic systems. The operating principles and steady‐state analysis are presented, including the detailed analysis of resonant stage, and the effects of transformer winding capacitances on converter operation are investigated. Moreover, the effects of resonance frequency variations on converter efficiency are experimentally investigated. Experimental results on a 50 kHz and 200 W prototype are presented to validate the proposed concept.