Research And Implementation Of High Color Rendering White LED Dimming System

Light Emitting Diode(LED)has be come to be widely applied in various applicantions,such as in architecture,signal lighting,backlight,display,street,and indoor lighting,with the advantages of high energy efficiency,long life,pollution-free,and so on.It has been widely paid attention to the color temperature tunable white-light LED clusters with high color rendering index in recent years.In the dissertation,it has been studied the methods of mixed white-light LED systematically with a wide range of color temperature.Firstly,according to the principle of light mixing and pulse width modulation,the two-channel and three-channel dimming relationship are derived.A warm-white/cold-white(WW/CW)cluster has been studied.The result showed that the deviation of the mixed correlated color temperature(CCT)is less than 32K in the range CCT= 3300K?7500K,but its color rendering index CRI is generally lower than 90.And then a Warm-white/G/B(WW/G/B)cluster has been studied too.The results show that the CCT is from 3200K to 7600K,the maximum error is 1.82%,while the CRI is from 86.5 to 95.3,which has further improved compared with two-channel dimming method.Secondly,based on the three-channel and two-channel pulse width modulation dimming method,a "3+2" dimming method is established to achieve white-light modulation by controlling the drive signal duty cycle of R/G/B/WW and the relationship between Tc and specific chromaticity coordinate obtained from the experiment.The experimental results show that when the mixed luminance flux is set to 3001m,the R/G/B/WW cluster can realize in the range of CCT tunable white-light(2900K-7600K),the deviations of its CCT and luminous flux are 0.56%and 2.24%respectively,whose CRIs ranges between 94 and 96 and the CRI deviation between theory and experimental values is less than 0.1.When CCT is 5000k and the luminous flux ranges between 0 and 800 lm,the error of the luminous flux is less than 2%.Finally,a intelligent dimming control system was designed according to the proposed "3+2" dimming method and design index.The system could realizes the various functions by using the APP of smartphone or IR controller,such as on-off of light,color/luminous flux/CCT adjustment,constant light and adaptive pattern,and so on.The constant-light pattern using two NRF24L01 modules to deal with light data could realize the consistent with the environmental luminous intensity and the sertting value by multiple modulations.The "3+2" dimming method proposed in this paper has the following advantage,such as the simple calculation method,the high precision of dimming light,easy use in hardware,and so on.Moreover,the light control system not only could realize the illumination environment of simulated sunlight but also help to realize the different results in the stage amd display illumination.