A resonant LED driver with capacitive power transfer

A quasi resonant topology suitable for LED drivers, featuring power factor correction and dimming in a single stage is presented. It contains a single active switch, and operates in zero-voltage-switching, zero-current-switching. This topology includes neither electrolytic capacitors nor transformer, and provides galvanic isolation between the AC mains and the DC side. Building on this new topology, a 15 W, 30 V, LED string driver with a typical operation frequency of 200 kHz was designed and experimented. Experimental results fully support the theoretical analysis and the simulation results. Measured efficiency exceeds 90% in the entire operation range and reached a peak efficiency of 96%. The driver is dimmable through the switching frequency. Dimming in the range of 4W-19W is demonstrated experimentally.