Single-stage high power factor step-up/step-down isolated AC/DC converter

This study presents a single-stage (S²) isolated current rectifier with power factor correction, based on a full-bridge flyback converter. This converter is designed to operate with adjustable output voltage so that it can operate in two distinct operation modes, step-up or step-down, depending on the input and output voltages. The proposed converter presents some features that make it attractive for many applications, such as constant switching frequency, step-down and step-up operation, high power level capability and the absence of an auxiliary pre-loading circuit to control the inrush current. This study presents the theoretical analysis of the converter for continuous conduction mode as well as experimental results based on a 3 kW prototype.