The research on high color rendering index white light light-emitting diode
Date Issued
2007
Date
2007
Author(s)
Lin, Su-Yi
DOI
zh-TW
Abstract
The major market of the light-emitting diode was the monochromatic light LED in the past. The application of LED was the indicative light on the products. Until the Nichia chemical company in Japan developed the high efficiency white light LED which was combined the blue LED chip with the yellow phosphor (YAG) in 1996, people started to expect the coming of the white light LED illuminative period. With the improving of the blue LED chip’s efficiency, the luminous efficiency of the high power white light LED is 90lm/W which is higher than the fluorescent lamp. The functions of the illumination are showing the shape, color and size of the object. The ability of showing the true colors is an important assize to estimate an illumination, and the color rendering index (CRI) is a stander to estimate this ability. The CRI of the general white light LED is about 50~70, and it’s not enough for the illumination.
This study aims at discuss on the simulation of the high CRI white light LED which was combined the blue chip with multi-color phosphor, and calculate the optical properties of the high CRI white light LED. The accuracy of simulation results is improved by improving the phosphor daub. This study simulates the spectra of high CRI white light LEDs and makes the high CRI white light LEDs with the CCT 3000K CRI 96 and CCT 6500K CRI 87.6 by multi-layers phosphor daub. The simulation results and experimental results are similar. It’s believed this simulation can estimate the phosphors’ abilities to make the high CRI white light LED and the multi-layer phosphor daub can decrease the absorption of the light which is emitted by the phosphors.
In the study of high CRI white light source which is formed by multi-color LED chip, I use the Gaussion distribution to simulate the LED’s spectrum. When the temperature is rising, the thermal effects on the LED chip are the decreasing of radiation power, red shift of peak wavelength and increasing of FWHM. By choosing the LEDs combination and using the feedback system the high CRI white light source can be made. The simulation results show that the CRI of four-color LED white light source is higher the three-color one and the four-color LED white light source with the smaller CRI shift when temperature rising. It’s is believed that four-color LED white light sources is a better illumination than three-color one.
Subjects
發光二極體
螢光粉
演色性
白光
照明
LED
phosphor
CRI
color rendering index
white light
illumination
Type
thesis
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