CS  Vol.3 No.1 , January 2012
A High Color Rendering Index on Multichip LED Light Source
Light source carrying a high color rendering index (CRI) finds potential applications in people’s everyday life as well as lighting industry. Combination of multi-wavelength LED light sources with designated direct emission sources can achieve warm-white and cool-white light. A generic design of high CRI multi-wavelength light-emitting-diode (LED) light source, using flyback converter, pulse width modulation (PWM) voltage control, variable resistor, and timer, is proposed. The PWM pulse is for the voltage control of cascade LEDs, while variable resistor manipulates the current flowing through LEDs. A design of dimming drive with cascade-connected electronic switch is also proposed. By adjusting the width of the dimming signal, the average value of forward current pulse can be changed, and therefore the objective, the tuning of the amount of light output, can be fulfilled. The advantage of the proposed design is its short response time.

Cite this paper
J. Shieh, L. Wang and M. Chiu, "A High Color Rendering Index on Multichip LED Light Source," Circuits and Systems, Vol. 3 No. 1, 2012, pp. 107-110. doi: 10.4236/cs.2012.31014.
[1]   E. F. Schubert and J. K. Kim, “Solid-State Light Sources Getting Smart,” Science, Vol. 38, 2005, pp. 1274-1278. doi:10.1126/science.1108712

[2]   C. Biber, “LED Light Emissions as a Function of Thermal Conditions,” 24th IEEE SEMI-THERM Symposium, 2008, pp. 180-184. doi:10.1109/STHERM.2008.4509387

[3]   http://www.handprint.com/HP/WCL/color12.html.

[4]   C. S. McCamy, “Correlated Color Temperature as an Explicit Function of Chromaticity Coordinates,” Color Research & Application, Vol. 17, No. 2, 1992, pp. 142-144. doi:10.1002/col.5080170211

[5]   http://en.wikipedia.org/wiki/Color_temperature.

[6]   http://en.wikipedia.org/wiki/Color_rendering_index.

[7]   Improvement to Industrial Color Difference Evaluation, CIE 141-2001, Technical Report, ISBN: 9783901906084.