Design Of Low-voltage DC Supply Digital LED Driver

With the energy crisis and environmental problems of today’s world growing，the technology of energy saving and emission reduction has become increasinglyimportant. In the lighting field, many countries have launched the "Green LightsProject", aiming at developing efficient and environmentally friendly lighting powerand illumination. Excellent lighting driving devices provide high-quality, stablelighting environment, in addition, should also have a high energy efficiency and lowEMI interference, which meets reqeust of the "Green Lighting". In recent years,LED light gradually emerge in the lighting field. LED itself has been constantlydeveloped to be more and more mature, it has become the most promising lightingin the lighting industry field.This paper aim at low-voltage DC power, study on theLED driving device, specific research contents are shown as follows.By reusing the switches, combine the Boost converter and dual LLC converter,proposed a single-stage boost topology, which has both LLC converter’s advantagesof soft switching and Boost converter’s ability to step up. The problem ofdual-resonant converter parameter error is solved by sharing the same resonantinductor and transformer. Multi-channel LED output current sharing is achievedwith the combination of the blocking capacitor and coupled inductors. In order tosolve the problem what each output module can’t share one ground, a plurality ofisolated power supply is built by increasing the number of secondary transformercoil.Dual LLC converter has two resonance cavities, increasing the complexity ofthe analysis of the converter. This paper through simplies the dual LLC converter,deduce to a single LLC converter which equivalent to the dual. On this basis, itcompleted the calculation of converter’s key parameters. The small signal model ofthe system is approached by using Extended Describe Function method. Then drawBode diagram and pole-zero plot of the open-loop transfer function. According tothe zero-pole distribution, a compensated method is proposed, and the phase marginand gain margin improved.Accordance with the standard car lights, a LED driver prototype with fouroutputs is built. The experimental results are very consistent with theoreticalexpectations, and the overall efficiency up to95%under the rated input voltage.