This paper analyses a ZVS isolated active clamp Sepic converter for high power LED applications. Due to the recent advancement in the light emitting diode technology, high brightness, high efficient LEDs becomes achievable in residential, industry and commercial applications to replace the incandescent bulbs, halogen bulbs, and even compact fluorescent light bulbs. Generally in these devices, the lumen is proportional to the current, so the converter has to control the LED string current, and for high power applications (greater than 100W), is preferable to have a galvanic isolation between the bus and the output; among different isolated topologies and taking into account the large input voltage variation in the application this paper is targeting, a ZVS active clamp Sepic converter has been adopted. Due to its circuit configuration, it can step up or down the input voltage, allowing a universal use, with lamps with different voltages and powers. A 300W, 5A, 48V input voltage prototype has been developed, and a peak efficiency of 91% has been reached without synchronous rectification.
