MAGAZINE: LED system design improves with optical and thermal performance verification

June 2, 2009
The ability to quickly and easily produce accurate optical and thermal measurements for LED devices has a major positive impact on the system design process, says James Petroski.
ThermalLED systems typically are designed to deliver a specified amount of light in a certain color spectrum. The designers of LED systems rely heavily on the performance specifications provided by LED manufacturers who typically rate their devices to deliver a certain number of lumens per watt at a certain color spectrum. The thermal performance of the package is also important, as well as the rate at which the light output drops as the temperature rises. If the performances differ from the manufacturers’ specifications, systems builders are left with the difficult task of identifying the problem using trial and error methods and redesigning the system to compensate for the performance variations.

Traditional approaches for measuring LED performance, such as measuring optical performance with an integrating optical sphere, take considerable amounts of time and require interpretation of results that can lead to inaccuracies. A new generation of integrating test systems can reduce the time required to measure LED optical and thermal performance. This approach combines traditional thermal testing with photo detectors to automatically provide a complete optical and thermal characterization of power LEDs. Thermal metrics, as well as optical parameters such as luminous flux and efficancy, can all be measured as a function of temperature and operating current.


This article was published in the May/June 2009 issue of LEDs Magazine.

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