MERGED-STAGE HIGH EFFICIENCY HIGH POWER FACTOR HB-LED DRIVER WITHOUT ELECTROLYTIC CAPACITOR

摘要

The present application relates to boost-resonant converter for driving high brightness LEDs (HB LED) that incorporates power factor correction (PFC) and does not require a bulky electrolytic capacitor. The new converter incorporates the PFC and the LED supplies into a single stage. The system allows a large voltage ripple across the intermediate energy storage capacitor reducing its value. Constant light output and dimming capability are obtained by variable frequency current control of the resonant converter. A high power factor is achieved by DCM boost front-end portion with controlled average output voltage. The converter is regulated by a digital controller that implements a variable-frequency variable duty ratio algorithm. Experimental results with a 15 W prototype verify near unity power factor operation, above 88% efficiency and constant lamp current over the entire operating range.