Renewable Energy sources present an efficient and economically viable energy supply approach for stand-alone applications. Electricity produced with Photovoltaic (PV) panels is among the most important energy contributions in energy harvesting systems. Moreover, the produced electrical power should not be interrupted, especially in critical applications. In this paper, the service continuity of a Buck/Buck-Boost converter, used as an interface between the PV source and the load, is discussed. A new fault tolerant converter topology is proposed, which allows to guarantee service continuity in open circuit switch fault cases, when a synchronous control is applied. A single additional switch, associated with two diodes, allows to keep the same power exchanges capabilities after open switch fault diagnosis, without modifying the synchronous control applied in healthy conditions. The resulting fault tolerant system is validated by simulation and the obtained results confirm the effectiveness of service continuity under open circuit switch fault.