One cycle control is a large signal and new nonlinear PWM technology. This technique has the merits of eliminating error of steady and instantaneous state automatic, fast dynamic response and simple circuit structure, high control precision, control performance not affected by the variable of power parameters. This paper introduced the basic concept of one cycle control, and built a 200W circuit based on IR1150. Experiment results show that the power factor of the circuit is above 0.98, is not only simple and dependable but also less organ and high capability.