A Robust Controller for a Class of Front-end Buck-boost High Power Factor Rectifiers

This paper presents the application of variable structure control (VSC) to a high power factor correction SEPIC converter. VSC provides the advantages of simplicity of implementation and robustness leading to having an output, which is independent of input voltage, circuit parameters and/or output load. This controller is used to regulate both the output voltage and the input current waveform in order to get a near unity power factor via the selection of a proper switching function. An observer with adaptive parameter estimation is also designed to achieve current sensorless operation of the controller, and thus only two voltage measurements are needed. This leads to a smaller size and higher operational reliability of the converter. Analysis of the proposed controller and simulation results are reported. The results show a near unity power factor and a regulated 48 V output for a universal input voltage (90-260 V) and a 500 W output power