Abstract
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.
Highlights
The use of LED in lighting applications is overwhelming
The pulse width modulation (PWM) pulse is for the voltage control of cascade LEDs, while variable resistor manipulates the current flowing through LEDs
The control of color rendering is through the introduction of multi-chip LED light source in this analysis
Summary
The use of LED in lighting applications is overwhelming. The traditional light sources using either incandescent or fluorescent have been shifted to the solid-state’s due to their intrinsic limitations/factors, almost impossible to overcome or to be substituted. Smart lighting nowadays may be fulfilled by the employment of digitally controlled multi-chip LED systems, belonging to the category of solid state lighting (SSL). SSL offers many advantages such as control of color rendering, chromaticity control, better light quality, and energy-saving; controllability of spectral power distribution, color temperature, temporal modulation, spatial distribution, and polarization properties are feasible [1]. A trade-off must be made between color rendering and luminous efficacy of the radiation of LEDs. The most significant property of SSL is associated with the development of artificial light sources. The control of color rendering is through the introduction of multi-chip LED light source in this analysis. A prototype of LED light source with 9 different LED chips is constructed. The effects of light mixture with different color temperatures are visualized. The mimics of natural light sources with the proposed multiwavelength LED light source are demonstrated via the comparisons of the measured color temperatures and the computed ones as well as corrected color temperature (CCT)
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