In PV grid connected power conditioners, usually both stepping-up the PV array voltage, and stepping-down the dc bus voltage for injection of a sinusoidal current to the grid is required. In this paper the design procedure of Z-source converter as a single phase PV grid connected transformer-less inverter is presented. The converter has one switch less than the conventional two stage power conditioner, which leads to reduction of cost. An optimum modulation pattern for the switches is proposed, and the low frequency ripple of the converter is modeled. The design of the converter is verified by simulation.