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Color tunable light‐emitting diodes with modified pulse‐width modulation
Author(s) -
Cho Jaehee,
Shan Qifeng,
Kim Jong Kyu,
Schubert E. Fred
Publication year - 2009
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.200903267
Subject(s) - chromaticity , light emitting diode , phosphor , materials science , optoelectronics , blue light , modulation (music) , diode , optics , pulse width modulation , color temperature , full width at half maximum , physics , voltage , quantum mechanics , acoustics
In this study, a color tunable light source, operated by a modified pulse width modulation method, is investigated. By utilizing this method along with anti‐parallel connected discrete light‐emitting diodes (LEDs) and two electrical terminals, a wide range of the chromaticity coordinates is attained and varied by electrical control. Using the combination of a blue LED and a phosphor‐converted yellow LED (blue LED plus yellow phosphor), the chromaticity range is varied by electrical control from pure blue to pure yellow. In addition, using the modified pulse‐width modulation method and a combination of white and red LEDs, white light with correlated color temperatures ranging from 5000 K to 2000 K is demonstrated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)