LRC Releases Free, Open Access Circadian Stimulus Calculator
The Lighting Research Center (LRC) at Rensselaer Polytechnic Institute has recently released a free, open-access circadian stimulus (CS) calculator to help lighting professionals select light sources and light levels that will increase the potential for circadian-effective light exposure in architectural spaces, utilizing the CS metric. Developed by LRC researchers, the CS metric is a new way to quantify light’s impact on acute melatonin suppression, a marker of circadian system activation.
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LED Lighting: All Eyes on Flicker by Tridonic
Flicker was a familiar problem with early fluorescent lamps. However, increasingly powerful electronic control gear has largely offset these interferences over time, banishing them from current perception. Since LEDs (light-emitting diodes) have become established in all areas of lighting, including general lighting, flicker has reemerged. LED Drivers play a key role in producing light that is as flicker-free as possible.
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Background Information on the Luxeon C LED Family from Lumileds
In an exclusive interview, Rahul Bammi, Vice President of Marketing & Product Management at Lumileds, and David Cosenza, Product Manager for the Luxeon Color LED Family, disclosed some background information on why this new product family was designed and why the very specific, new, and unique properties were implemented.
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Researchers Propose New Technology without Rare Earth Metals for LED Lighting
At the 250th meeting of the American Chemical Society a novel approach to generate white light without using rare earth metals was presented. The reaserachers claim that this approach will lead to cheaper warm white LEDs than the currently used technologies. A press conference on this topic was held on Wednesday, Aug. 19, at 9 a.m. Eastern time in the Boston Convention & Exhibition Center.
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Researchers from Oregon State University Develop Quantum Dot Technology that may Help Light the Future
Advances at Oregon State University in manufacturing technology for quantum dots may soon lead to a new generation of LED lighting that produces a more user-friendly white light, while using less toxic materials and low-cost manufacturing processes that take advantage of simple microwave heating.
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Litecool Demonstrates that Narrow Beam LED Packages Are a Real Possibility
Litecool has been working on various LED package designs to give luminaire manufacturers an LED package that doesn’t need any further lensing or reflectors to give the desired beam patterns for lighting applications.
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BluGlass Demonstrates Improved Performance Results for Green RPCVD Manufactured p-GaN LEDs
BluGlass has succeeded in its initial experimentation of applying low temperature RPCVD p-GaN to Green LED applications with highly promising results. These results show that the green LEDs produced using RPCVD p-GaN are demonstrating greater efficiency than the BluGlass grown MOCVD benchmark LEDs using the exact same MOCVD grown multi-quantum wells (MQWs), the critical light emitting region of an LED device.
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Configuration Via the Mains: Simple, Reliable and Professional
As the heart of any LED luminaire, the LED driver not only has to meet strict requirements in terms of quality and reliability but also be flexible enough to adapt to different conditions. ready2mains – a new technology from Tridonic – helps enormously. The article explains what is needed and how it works.
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TRIAC Dimmable, Isolated LED Driver with High Power Factor Needs No Opto-Isolators
As environmental concerns over traditional lighting in-crease and the price of LEDs decreases, high power LEDs are fast becoming a popular lighting solution for offline applications. In order to meet the requirements of offline lighting - such as high power factor, high efficiency, isolation and TRIAC dimmer compatibility - prior LED drivers used many external discrete components, resulting in cumbersome solutions. By Wei Gu Applications Engineering Section Leader at Linear Technology demonstrates how new solutions reduce complexity while improving performance.
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The Future of More Efficient LEDs and Lasers Probably Starts in 2D
The future of electronics could lie in a material from its past, as researchers from The Ohio State University work to turn germanium - the material of 1940s transistors - into a potential replacement for silicon.
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Osram Improves Efficiency of Blue LED Chips by Reducing Forward Voltage
Osram Opto Semiconductors has achieved one of the best values in the world in terms of forward voltage for blue high-current chips. This has led to an increase in efficiency of up to eight percent. Optimized InGaN chips (Indium-Gallium-Nitride) featuring UX:3 chip technology are the basis for blue or white LEDs – and are already used in production. Osram experts also see considerable potential for reducing the value by a further 20 to 30 millivolts (mV) by the summer of 2015 – offering a further boost in efficiency.
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Universities Develop Novel LEDs by Band-Structure Engineering in van der Waals Heterostructures
Semi-transparent, flexible electronics are no longer just science-fiction thanks to graphene’s unique properties, University of Manchester researchers have found. Published in the scientific journal Nature Materials, University of Manchester and University of Sheffield researchers show that new 2D ‘designer materials’ can be produced to create flexible, see-through and more efficient electronic devices including semi-transparent LEDs.
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Ending the Invisible Threat - Confronting the LED Flickering Issue
One of the topics in 2014 International LIGHTFAIR DOE training was “SSL Flicker Fundamentals and Why We Care“ (Michael Poplawski and Naomi Miller 2014),this reignited the industry’s discussion on light modulation. This topic was already raised by ASSIST earlier, where research on human’s level of tolerance to high-frequency flickers have been done and published in several lighting magazines by Rebekah Mullaney, hoping to encourage LED manufacturers and distributors to put more emphasis on finding a permanent solution that is more suitable for people’s well-being. - Andy Fei and Nina Chen from ALT-LED summarize these flicker research results and explain how to avoid flicker issues.
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LpS 2014 Scientific Award Winner Article: New Binning Strategy for White LEDs
After having recognized the deficiencies of the ANSI binning strategy, which is based on the visually false magnification of MacAdam’s ellipses, Dr. Peter Bodrogi and Prof. Tran Quoc Khanh from the Technical University Darmstadt propose a new binning strategy based on a so-called semantic interpretation to describe and easily communicate the magnitude of acceptable chromaticity differences.
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Compute Simulation Sheds Light On Why Blue LEDs Are So Tricky To Make
![New research from academics from the University of Bath Department of Chemistry has uncovered the mystery of why blue light-emitting diodes (LEDs) are so difficult to make: (1) Calculated spin density resulting from (a) a Mg0Ga-associated hole localized on a neighboring N in the basal plane, (b) a Mg0Ga-associated hole localized on a neighboring axial N, and (c) a N vacancy. Light gray (green) [darker gray (blue)] spheres represent Ga (N) atoms. The darkest gray sphere represents a Mg atom in (a) and (b) (purple) and a vacancy in (c) (orange). Spin densities are indicated by (red) isosurfaces of density (au) 0.05, 0.025, and 0.01 for (a) and (b) and 0.01, 0.005, 0.0025 for (c). (2) Formation energy of VN (black line) and MgGa [light gray (red) line] as a function of Fermi energy above the VBM. Anion-rich conditions are assumed. The position of the conduction band minimum (CBM) is indicated by the broken line. For each value of Fermi energy, only the most stable defect charge state is shown, with a change in slope indicating a change in charge state](https://www.led-professional.com/technology/light-generation/compute-simulation-sheds-light-on-why-blue-leds-are-so-tricky-to-make/University%20of%20Bath%20Department%20of%20Chemistry%20has%20uncovered%20the%20mystery%20of%20why%20blue%20light-emitting%20diodes%20-LEDs-%20are%20so%20difficult%20to%20make.jpg/@@images/dd63b2df-d470-4f03-8bb0-9457a16f63d6.jpeg "New research from academics from the University of Bath Department of Chemistry has uncovered the mystery of why blue light-emitting diodes (LEDs) are so difficult to make: (1) Calculated spin density resulting from (a) a Mg0Ga-associated hole localized on a neighboring N in the basal plane, (b) a Mg0Ga-associated hole localized on a neighboring axial N, and (c) a N vacancy. Light gray (green) [darker gray (blue)] spheres represent Ga (N) atoms. The darkest gray sphere represents a Mg atom in (a) and (b) (purple) and a vacancy in (c) (orange). Spin densities are indicated by (red) isosurfaces of density (au) 0.05, 0.025, and 0.01 for (a) and (b) and 0.01, 0.005, 0.0025 for (c). (2) Formation energy of VN (black line) and MgGa [light gray (red) line] as a function of Fermi energy above the VBM. Anion-rich conditions are assumed. The position of the conduction band minimum (CBM) is indicated by the broken line. For each value of Fermi energy, only the most stable defect charge state is shown, with a change in slope indicating a change in charge state")
Researchers in our Department of Chemistry have collaborated with groups at University College London (UCL) and Daresbury to uncover the mystery of why blue light-emitting diodes (LEDs) are so difficult to make, by revealing the complex properties of their main component – gallium nitride – using sophisticated computer simulations.
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