Speed control of small motors through the Ćuk Converter Topology

Abstract

The Ćuk Converter offers simultaneous buck-boost operation, but requires careful design owing to its having a fourth-order transfer function and numerous practical design constraints. We exploit a serendipitous overlap between the converter circuit and the equivalent circuit of a dc motor to design a motor controller that can operate with supply voltage that is lower than the motor full-speed requirement. We examine the transfer function when such a topology is used to control the speed of a small motor. We conclude that the approach is relatively straightforward owing to the impact of the motor’s inductance. Measurements agree with theory.