In general, Boost circuit is widely used as PFC circuit to achieve high power factor (PF), but the power supply needs to add a Buck circuit in the case of low-voltage output applications. Two-stage circuit requires more components and two control circuits. On the other hand, as the power levels increase, the full-bridge diode rectifier reduces the converter efficiency due to the large conduction losses. This paper presents a novel single-stage (SS) bridgeless Boost&Buck circuit. Boost circuit serves as a PFC stage and Buck as a DC/DC stage. Bridgeless structure can reduce conduction losses effectively, and improve the efficiency of the converter in low-input voltage & high-input current conditions. The proposed DCM + CCM control strategy is used to achieve high PF, high efficiency and step-down capabilities. At last, a prototype with 85~135 Vrms input and 75 Vdc/150 W output was set up to verify the theoretical analysis.