A transformerless single-stage AC/DC converter with low output voltage

This paper presents a novel tranformerless single-stage AC/DC converter suitable for universal line applications (90-270 Vrms). The topology integrates a buck power factor correction (PFC) cell with a buck-boost DC/DC cell and couples part of input power to the output directly. The proposed converter achieves efficient power conversion, sustainable power factor capability, low voltage stress on intermediate bus (less than 130V) and low output voltage. The absence of transformer reduces the component counts and cost of the converter. In addition, the main switch only handles the peak current of DC/DC cell rather than the superposition of both induction currents in two cells. Detailed analysis and design procedures of the proposed circuit are given and verified with the experiment.