Programmable-output PFC rectifier with dynamic efficiency and transient response optimization

This paper introduces a digitally-controlled 2-stage single-phase rectifier with power factor correction (PFC) that is well suited for emerging low-power applications requiring programmable supply voltage. The rectifier is a modification of a flyback-buck cascaded configuration where the intermediate energy storage capacitor is replaced by a non-symmetric capacitive divider with independent control of tap voltages. The voltages are dynamically controlled through a single secondary winding, such that the optimized efficiency and reduced size of the downstream stage are achieved without sacrificing dynamic response. Results obtained with a 30W universal-input experimental prototype confirm fast transient response during efficiency optimization, operation with a near unity power factor, and about a 50% reduction in the flyback capacitor value, as compared to single-stage solutions.