This paper presents the simultaneous Maximum Power Point Tracking (MPPT) and output voltage regulation of a stand-alone Photovoltaic-battery-load power system, based on a Single-Switch DC-DC converter. In the literature, the well-known two-stage buck converter cascaded with a buck-boost one is mentioned as the most suitable non-isolated DC-DC converter for such a Photovoltaic (PV) system. Based on an unified approach to develop Single-Stage power converters, we propose to use an equivalent Single Switch Converter (SSC) for the studied PV system, thus increasing its reliability and decreasing the overall system cost, thanks to the reduced number of switches. In the same spirit, the MPPT algorithm has been chosen among the most used ones. The Perturb and Observe (P&O) algorithm appears as the best compromise, performing good tracking factor, simple implementation and satisfactory accuracy. The resulting PV system has been modeled and simulated; the results confirm the effectiveness and the robustness of the simultaneous MPPT and output voltage regulation.