Cuk converter is one type of DC-DC converter circuits which, in comparison with other conventional converters such as buck, boost, and buck-boost converters, offers many attractive features, one of which is a smooth input and output current. In this thesis, the theory and design of a Cuk converter are described. The state space averaging approach is used to model the Cuk power stage, which exhibits a fourth order characteristic. The resulted model is then used for designing a feedback control (i.e. a compensation circuit) to result in a stable converter with a satisfactory performance.