Red, green, and blue LEDs for white light illumination

Abstract

The rapid improvement of the white light efficacy achievable with light-emitting diodes (LEDs) opens up new opportunities in the general illumination market. An LED light source made of red, green, and blue LEDs (RGB-LEDs) can provide the unique feature of color variability, allowing the user to select the desired color point of the lamp. The white light color accuracy required in the general illumination market is a challenge for LEDs. The variation in lumen output and wavelength for nominally identical LEDs and the change in these parameters with temperature and time result in an unacceptably high variability in the color point of white light from RGB-LEDs. In this paper, we show that these problems can be overcome with suitable feedback control schemes that can be implemented in a practical LED lamp. We present results of experiment and theoretical modeling that shows the performance that can be achieved with a number of different control schemes.

Effects of Current Modulation Conditions on the Chromaticity of Phosphor Converted (PC) White LEDs

“…These results are compared with previous studies [16][17][18] in following several sentences. In Muthu's reports [17,18], for the case of SCM for red, green, and blue LEDs (RGB-LEDs), a change in the amplitude of the drive current caused a shift in wavelength. As the driving current increased, the spectra moved toward shorter wavelength (blue shift).…”

“…The illuminance and color coordinate of the white LED lighting were measured in different modulation conditions of forward current in both modes. In particular, the moving direction of the measured color coordinates was investigated and compared with previous studies [16][17][18]. Additionally, for the purpose of the quantitative evaluation of color deviation, color distance and CCT were also calculated by using the measured data, and then the obtained results were discussed in relation to phosphorescence of yellow phosphor and its lifetime.…”

Calculation of harmonic losses and ampacity in low-voltage power cables when used for feeding large LED lighting loads

“…Several other works have concentrated on the light distribution and visual performance of LED lamps (e.g., [9]). A few contributions focused on harmonic emissions of LED lamps [10][11].…”

On the reduction of the third-order harmonic losses in low–voltage power cables used for feeding large LED and CFL lighting loads

“…Several other works have focused on the light distribution and visual performance of LED lamps (e.g., [16]), however, a relatively small amount of works focused on the harmonic emissions of LED and CFL lamps and in strategies to reduce the harmonic distortion problem generated by them [12,17].…”