A Study on Driving Technology of LED Lighting for Saving Energy Based on Visual Test Result
Date Issued
2008
Date
2008
Author(s)
Chi, Shuan-Ju
Abstract
The main purpose of this study is to test whether we can improve the efficiency of LED by using PWM driven circuits. The human eye instead of optic instruments is the detector for judging the illumination intensity in a visual test box. Constant-current PWM driving technique is used in this study to generate square-wave and trapezoidal-wave currents. The potential of energy saving under light of different wave forms or pulse frequencies, or different background colors are evaluated. The experiment results are analyzed with chi-square test to determine the significance of energy saving. visual test box is built according to the CIE (Comission International del’Eclairage) standard. 10° visual angle is established as the appropriate size for the field of view by CIE in 1964. The results show that PWM frequencies have no effect on the observers’ judgments. However, the background colors can influence how the observers judge the illumination intensity. When the background color is the light-source color, it is easier to trick the observer into believe that the luminance of 90% duty cycle is the same as 100% duty cycle. This will save about 10% of energy. When the background color is the color of the materials, the results differ with different materials, and will save about 5-10% electric energy.
Subjects
PWM
LED
Type
thesis
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