Browsing by Author "Pan, Ching-Jen"

Now showing 1 - 2 of 2

Efficiency and Droop Improvement in Hybrid Warm White LEDs Using InGaN and AlGaInP High-Voltage LEDs
(2013-04-01)
Chen, Kuo-Ju
;
Kuo, Hsuan-Ting
;
Chiang, Yen-Chih
;
Chen, Hsin-Chu
;
Wang, Chao-Hsun
This study investigates the optical and electrical characteristics in hybrid warm white high-voltage light-emitting diodes (HV-LEDs). The luminous efficiency of the hybrid warm white LED in this study improved by 11% and 51%, compared to conventional cool and warm LEDs, respectively, solving the warm white gap in white LEDs. The efficiency droop of the hybrid warm white LED was reduced to 21.8% from 26.8% for the conventional cool white LED, and from 26.3% in the conventional warm white LED at 40 mA (35 A/cm(2)) the operated current. Furthermore, the color rendering index (CRI) and angular correlated color temperature (CCT) were analyzed, indicating a significant improvement in hybrid warm white HV-LEDs.
High thermal stability of correlated color temperature using current compensation in hybrid warm white high-voltage LEDs
(2013-03-11)
Chen, Kuo-Ju
;
Kuo, Hsuan-Ting
;
Chen, Hsin-Chu
;
Shih, Min-Hsiung
;
Wang, Chao-Hsun
This study experimentally and numerically examines the correlated color temperature (CCT) stability issue for hybrid warm white high-voltage light-emitting diodes (HV-LEDs) by using a current compensation method. This method could efficiently maintain the CCT stability factor at approximately 1.0 and yield greater color uniformity with Delta u'v' values ranging from 0.017 to 0.003 in CIE 1976 chromaticity coordinates. The simulation results show that the red chip intensity drop is the primary cause of CCT instability in the hybrid warm white system when the temperature increases. Therefore, Furthermore, results indicate that the relative lumen drop improves from 21% to 15% by using a current compensation method. (c) 2013 Optical Society of America