A novel dual-mode control scheme is developed here to enable synchronous buck converters (SBC) to operate in a continuous-conduction mode under heavy-load conditions and in a discontinuous-conduction mode under light-load conditions. When an SBC operates in a discontinuous-conduction mode, a quasiresonant valley switching technique can be employed to turn on a synchronous switch, perform zero-voltage switching at main switches, and improve the light-load efficiency. The proposed scheme does not require the addition of an auxiliary circuit in the SBC, providing it with the advantages of low cost and easily built-in integrated circuits. To verify its feasibility, an SBC equipped with the proposed control scheme is developed, with output voltage and output power of 5 V and 25 W, respectively.