Long-term performance of white LEDs and systems
نویسندگان
چکیده
In this manuscript we describe two experiments. The first one is life testing of three commercial high-power phosphor-converted (pc) white LEDs under three different operating temperatures. The second is life testing of two commercial lighting systems that use highpower pc-white LEDs. Life testing was conducted per ASSIST recommends guidelines. Results showed that LED life is very much affected by the heat at the p-n junction. To illustrate the usefulness of the ASSIST recommends test procedure for quantifying the performance of LED systems, two 26-watt commercial downlights were tested. Results showed that the life of pc-white LEDs follow an exponential decay as a function of board temperature. One of the commercial LED downlights tested showed an increasing light output degradation rate even within the first 1000 hours of testing. Both commercial products showed significant color shift over time.
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