A photovoltaic (PV) power conditioning system (PCS) must have high conversion efficiency and low cost. Generally, a PV PCS uses either a single string converter or a multilevel module integrated converter (MIC). Each of these approaches has both advantages and disadvantages. For a high conversion efficiency and low cost PV module, a series connection of a module integrated DC-DC converter output with a photovoltaic panel was proposed. The output voltage of the PV panel is connected to the output capacitor of the fly-back converter. Thus, the converter output voltage is added to the output voltage of the PV panel. The isolated DC-DC converter generates only the difference voltage between the PV panel voltage and the required total output voltage. This method reduces the power level of the DC-DC converter and enhances energy conversion efficiency compared with a conventional DC-DC converter. (C) 2009 Elsevier Ltd. All rights reserved