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LRC develops new LED system evaluation method

Recent studies by Dr. N. Narendran, LRC director of research, and graduate students will eventually lead to the development of useful life estimates for LED systems. “With LED systems growing increasingly popular, accurate life predictions are becoming vital,” says Dr. Narendran. There is no comprehensive data available that indicates exactly how long LED lighting systems will operate before needing maintenance or replacement. “This is information consumers want to know,” he adds.

Manufacturers typically quote LED-system life to be the same as that of the individual LEDs. But according to Dr. Narendran, LED life is affected by other system components, so the system may not last as long as an individual LED would under ideal laboratory conditions.

The LRC has developed new methods for measuring LED junction temperatures. Heat at LED junctions is the primary cause of LED light output degradation. In the past, methods commonly used for testing junction temperature were not appropriate for entire systems because they required those systems to be disassembled, possibly affecting the results. The new methods developed at the LRC determine junction temperature for red LED systems and for white LED systems. “Measuring junction temperatures is not new,” says Dr. Narendran. “What is new is that the methods we have developed are quick and non-invasive, and both relate junction temperature to emission spectra.”

With these new practices in place, Dr. Narendran’s team is now working to develop data showing LED degradation rates at various junction temperatures. This data, when combined with the new, non-invasive methods, will allow lighting system manufacturers to provide accurate system life estimates and produce higher quality products. Results of these studies will be presented at the SPIE Annual Meeting, the Third International Conference on Solid-State Lighting, to be held in San Diego, Calif., in August.

About the LRC

The Lighting Research Center (LRC) is part of Rensselaer Polytechnic Institute and is the leading university-based research center devoted to lighting. Founded in 1988, the Lighting Research Center has built an international reputation as a trusted and reliable source for objective information about lighting technologies, applications, and products. Its mission is to advance the effective use of light and create a positive legacy of change for society and the environment

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