This paper presents a design of the control system to control AC/DC converter. Algorithm of a control system design consists of the output voltage loop control used a fuzzy gain scheduling of PI control and the current loop control used a hysteresis control which is described in this paper. The evaluation of the proposed control system is used to control an isolated CUK AC/DC converter operation with a 250W load and a -48V output voltage. The system is achieved as the following; the tight output voltage both the steady state operation and the transient response a power factor is nearly unity and the waveform of input current is nearly sinusoidal. In addition the control system design is simple and uncomplicated