Analysis And Design Of Resonant Efficient LED Driver

In order to meet the requirement of low-carbon and Energy conservation, high efficiency and energy conservation has become the most important developing direction in lighting industry. As the most potential illuminant, LED possesses many merits such as high efficiency and long life, thus has become a hot topic and developed rapidly in recent years. High efficient high power LED driver has become a research hotpot as well. Based on this background, this project mainly research on high efficient high power LED driver, including the circuit topology and optimization design methodology. A novel LLCC resonant converter with precise current sharing for two-channel LED driver is also discussed.The research in this paper mainly includes two aspects. First is the design of high efficient single output LED driver. LLC resonant converter is chosen as the most efficient topology based on some analysis and comparison. A new design method which is suitable for wide output range application is proposed in this paper. Circuit principle analysis, working region selection, DC characteristic deduction and optimization of design parameters are also discussed in detail. Based on the analysis and discussion, a detailed optimal design procedure is proposed. Finally, a 140W experimental prototype is built to verify the design and proved a high efficiency after optimization.Based on the single output LED driver, a LLCC resonant converter with automatic precise current-sharing is proposed for two-channel LED driver. With a resonant capacitor connected in series with the transformer secondary winding, the currents of the two channels are precisely shared even for different LED strings with different voltage drops. The circuit operation principle under both CCM and DCM modes, current sharing principle, AC equivalent circuit analysis, DC gain deduction and design considerations are discussed. A prototype of 140W two-channel LED driver is built to verify the proposed current sharing circuit.