Design and optimization of a wide output voltage range LED driver based on LLC resonant topology

LLC resonant converter is an excellent candidate for medium power DC/DC converter. However, it is usually used in constant voltage output application. As for the DC/DC stage in high efficiency LED driver, the output voltage may vary widely while output current remains constant. This paper proposes a new design method which is suitable for wide output range application. Design process, analysis and optimization of design parameters are also discussed in detail. A 140W experimental prototype is built to verify the design and proved a high efficiency after optimization. Experimental result shows LLC is a good topology choice for LED driver for it is highly efficient throughout wide output voltage range.