How intuitive graphical data sets help lighting designers accurately predict power LED reliability in different operating environments.
Download the PDF report "Understanding Power LED Lifetime Analysis"
When designing LED-based lighting systems, engineers need to understand LED lumen maintenance and mortality in similar terms to those used when designing with conventional light sources. However, comparable data has been nearly impossible to find. In addition, designers need extra information to predict the lifetime of LEDs under a variety of operating conditions. A number of techniques to predict LED lifetimes have been proposed, but these have not been sufficient to generate the clear and unambiguous data that lighting engineers can use easily. This white paper provides lighting designers with an understanding of a new tool introduced by Philips Lumileds Lighting Company that simplifies the process allowing full flexibility in design options. This one tool provides designers with information that they need to make decisions about product lifetimes, driver constraints, number of LEDs required, and thermal management.
1. Aging and failure modes of lighting sources
2. Established lighting industry definitions of useful life
3. Established LED industry definitions: Lumen maintenance
4. Understanding LED operation and lifetimes
5. Completing the expression for lumen maintenance
6. Designing with B/L data for optimal lighting performance
7. Predicting LED lifetimes
Conclusion
The lighting industry needs LED manufacturers to provide data that is compatible with current design practice. However, this only answers a part of the challenge. LED vendors should also be in a position to provide more detailed information about product lifetimes under various operating conditions. This data allows lighting designers to deliver the best combination of purchase price, lighting performance, and cost of ownership for the life of the product.
From a user’s perspective, this data is most usefully expressed as a combination of B- and Llifetime as junction temperature and forward current are varied. This allows the system designer to make intelligent choices about the number of LEDs required, how they are driven, and the operating temperature.
Every power LED customer should therefore expect their supplier to provide this data as a matter of course, in any combination of B, L, Tj and If values, with clear definitions of failures (e.g. lumen maintenance below specified condition, electrical failures).
Download the PDF report "Understanding Power LED Lifetime Analysis"