Study Of LED Driver With Multiple Led-channels And Intelligent Lighting Technology

With the semiconductor lighting as a new generation of lighting source, it has vast potential for future development. Due to the advantage of high efficiency, long life, pollution-free and safety, lighting emitting diode becoming more attractive and has begun to replace conventional lighting source such as incandescent lamp and fluorescent lamp. With the high-brightness white LED becoming more popular, LED driving and dimming technology has been a research hot spot.In this thesis, considering the practical requirements, a 120W power and 8 channels parallel multi-output LED lamps driver is designed for residential lighting. The current of each output channel could be continuously set-up. The cascaded tow-stage configuration is selected based on the analysis of operation principles and the comparison with different projects. The first stage is an AC/DC converter using LLC half bridge resonant topology, outputting as a voltage source. The second stage is a DC/DC converter, using synchronous rectification buck topology, outputting as a current source.Firstly in this thesis, the principles of the synchronous buck converter is presented. Further more, the steady state model and small signal model is analyzed. Secondly, the principles of the LLC half-bridge resonant converter are presented and the performance of LLC resonant converter is analyzed using FHA (First Harmonic Approximation) method in detail. The closed-loop controllers of the two stages are implemented in 32bit DSP, realizing the smooth adjustment of voltage and current respectively. For dimming purpose, a sensing system and a smart dimming system are implemented, making the LED dimming automatically according to the ambient light and user's dimming custom. The ambient light intensity, human infrared signal and user's manual dimming signal are corrected by the sensing system. The optimal LED dimming command for the user is derived by the smart dimming system according to the user's dimming history data recorded in the database. Finally the LED dimming command is used as the reference input of the LED current regulator. What's more, the intelligent dimming method is also implemented in DSP. Adopting the proposed scheme, a 120W LED driver with multi constant current output is designed. The sensing system and smart dimming system is also implemented. The prototype is built and tested in order to verify the feasibility of the proposed approach.