The conventional grid-connected photovoltaic (PV) inverter that steps up low DC voltage to high DC voltage and cascades with the high frequency inverter is complicated in control and of low efficiency due to two stages. This paper presents a novel PV inverter system formed by a hybrid DC-DC converter and a full-bridge DC-AC converter. The hybrid DC-DC converter combines the boost and flyback topologies to produce a semi-sinusoidal output current and to achieve the high step-up objective. A full-bridge DC-AC converter controlled with low-frequency switching techniques is then used to convert the current into sinusoidal form and to feed power to the grid with unity power factor. The overall efficiency of the designed system is high due to the losses of both stages are reduced. In this paper, the circuit operating theory of the proposed PV inverter is firstly addressed then an 80W prototype system is designed and built. The feasibility and effectiveness of the proposed circuit are confirmed with some simulation and experimental results.