Spectral Optimization Of White Light LED With High Color Rendering Index

Color rendering property and luminous efficacy are two of the most important factors to evaluate the quality of LED white-light source. The challenge in designing LED white-light clusters consists of achieving high CRIs over a reasonable range of color temperatures, meanwhile maximizing the LEs. We studied the spectrum optimization of the LED white-light LED with maximum luminous efficacy under different color temperatures and conditions of CRI≥80,85,90and95, which is produced by three different appproaches:mix multiple LEDs with single color to generate white light (mc-W LED); yellow phosphor excited by LED blue light to generate white light (p-W LED); use the red LED and the p-W LED with green and orange phosphors excited by blue LED die to generate LED white light (W/R LED).The results showed that the R9and R(9-12) of LED white light produced by three different approches under the different conditions are both12less than the CRI, indicating that LED white light with optimal spectrum offers poor color rendering for the samples with high saturation color. Therefor, the LED white light with optimized spectrum merely under the condition of CRI cannot get the excellent color rendering in the visual. In order to improve the color rendering in visual, we studied the optimal spectrum of mc-W LED, p-W LED, W/R LED with maximum LER under different color temperatures(2700-6500K) and different conditions:CRI≥80and R(9-12)≥75, CRI≥85and R(9-12)≤80, CRI≥90and R(9-12)≥85, CRI≥95and R(9-12)≥90, and determine the best peak wavelength of all color composition. we compared the maxium result, which can be achieved by two means:(1) under CRI and (2) under CRI together with R(9-12), the results show that the LER of white light LED under the different conditions of CRI and dirrerent conditions of CRI and R(9-12) will decline with the increasing demand for color rendering, also decline with the CCT increased; under the conditions of different CRI and R(9-12), the LER of W/R LED and mc-W LED are nearly the same, while improved greatly compared to the LER of p-W LED, especially in the low color temperature, it will increase about30%. We studied when the peak wavelength of red, yellow, green, blue light of optimal spectrum seperately changed under different conditions of CRI and R(9-12), what influence will have on the CRI, R(9-12) and LER of white light LED. Finally, we take W/R LED at2700K for example, according to the demand of Ra>90, R>90and R(9-12)>85, we simulated and checked with experiment, it shows that the test results are very close to the simulated ones. We also studied the color temperature tunable white light LED preliminarily.