Journal ArticleDOI
Life of LED-based white light sources
Nadarajah Narendran,Y. Gu +1 more
TLDR
In this article, the exponential decay of light output as a function of time provided a convenient method to rapidly estimate life by data extrapolation and showed that the life of these LEDs decreases in an exponential manner with increasing temperature.Abstract:
Even though light-emitting diodes (LEDs) may have a very long life, poorly designed LED lighting systems can experience a short life. Because heat at the p-n-junction is one of the main factors that affect the life of the LED, by knowing the relationship between life and heat, LED system manufacturers can design and build long-lasting systems. In this study, several white LEDs from the same manufacturer were subjected to life tests at different ambient temperatures. The exponential decay of light output as a function of time provided a convenient method to rapidly estimate life by data extrapolation. The life of these LEDs decreases in an exponential manner with increasing temperature. In a second experiment, several high-power white LEDs from different manufacturers were life-tested under similar conditions. Results show that the different products have significantly different life values.read more
Citations
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Journal ArticleDOI
LED Based Indoor Visible Light Communications: State of the Art
TL;DR: This paper provides a comprehensive survey on VLC with an emphasis on challenges faced in indoor applications over the period 1979-2014.
Journal ArticleDOI
Light emitting diodes reliability review
Moon-Hwan Chang,Diganta Das,Prabhakar V. Varde,Prabhakar V. Varde,Michael Pecht,Michael Pecht +5 more
TL;DR: This paper provides the groundwork for an understanding of the reliability issues of LEDs across the supply chain and identifies the relationships between failure causes and their associated mechanisms, issues in thermal standardization, and critical areas of investigation and development in LED technology and reliability.
Journal ArticleDOI
LED Driver With Self-Adaptive Drive Voltage
Yuequan Hu,Milan M. Jovanovic +1 more
TL;DR: In this article, the output voltage of the preregulator is always self-adjusted so that the voltage across the linear current regulator of the LED string with the highest voltage drop is kept at the minimum value that is required to maintain the desired string current.
Journal ArticleDOI
Thermal effects in packaging high power light emitting diode arrays
Adam Christensen,Samuel Graham +1 more
TL;DR: In this paper, a thermal resistor network model was combined with a 3D finite element submodel of an LED structure to predict system and die level temperatures, and the impact of LED array density, LED power density, and active versus passive cooling methods on device operation was calculated.
Journal ArticleDOI
A Survey, Classification, and Critical Review of Light-Emitting Diode Drivers
TL;DR: Based on a survey on over 1400 commercial LED drivers and a literature review, a range of LED driver topologies are classified according to their applications, power ratings, performance and their energy storage and regulatory requirements as discussed by the authors.
References
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Journal ArticleDOI
Candela‐class high‐brightness InGaN/AlGaN double‐heterostructure blue‐light‐emitting diodes
Abstract: Candela‐class high‐brightness InGaN/AlGaN double‐heterostructure (DH) blue‐light‐emitting diodes(LEDs) with the luminous intensity over 1 cd were fabricated As an active layer, a Zn‐doped InGaN layer was used for the DH LEDs The typical output power was 1500 μW and the external quantum efficiency was as high as 27% at a forward current of 20 mA at room temperature The peak wavelength and the full width at half‐maximum of the electroluminescence were 450 and 70 nm, respectively This value of luminous intensity was the highest ever reported for blue LEDs
Journal ArticleDOI
Illumination with solid state lighting technology
Daniel A. Steigerwald,Jerome Chandra Bhat,D. Collins,R.M. Fletcher,M.O. Holcomb,M. J. Ludowise,Paul S. Martin,Serge L Rudaz +7 more
TL;DR: In this article, the authors describe the current state of high-power LED technology and the challenges that lay ahead for development of a true "solid state lamp" and demonstrate record performance and reliability for high power colored and white LEDs and show results from the worlds first 100-plus lumen white LED lamp.
Journal ArticleDOI
Solid-state lighting: failure analysis of white LEDs
TL;DR: In this paper, the degradation rate of white LEDs was investigated and it was shown that the degradation process depends on both the junction temperature and the amplitude of short-wavelength radiation.
Proceedings ArticleDOI
A noncontact method for determining junction temperature of phosphor-converted white LEDs
Yimin Gu,Nadarajah Narendran +1 more
TL;DR: In this paper, a noncontact method for determining the junction temperature of phosphor-converted white LEDs was developed. But the method only considered the 5mm epoxy encapsulated GaN+YAG Cerium phosphor white LED.
Proceedings ArticleDOI
Performance characteristics of high-power light-emitting diodes
TL;DR: In this paper, the performance characteristics of high-power LEDs under various drive conditions and ambient temperatures were investigated, including degradation and color shift properties as a function of time for five types of commercial high-flux LEDs, namely, red, green, blue, and white.