The intention of the white paper, says Lumileds, is to go beyond simple lumen maintenance data that describes how a single LED behaves. The paper addresses lighting systems, which use multiple LEDs in a wide variety of usage conditions.

An LED luminaire's usable life is determined by a manufacturer's determination of expected lumen maintenance and by the actual usable life of the many components included in the system. Each of the components must be analyzed independently in order to provide an accurate assessment.

Philips Lumileds has collected and analyzed over 700 million hours of Luxeon LED reliability test data. Using statistical analysis and models that have long been used and proven in the automotive and electronics industries, Philips Lumileds paper describes how a luminaire manufacturer can define the "lifetime" of the LEDs in a system and understand how to scale from the behavior of one LED to many LEDs. This is an essential process for anyone that is developing product warranties and results in clear understanding of "lifetime" of the LEDs.

"Luminaire manufacturers no longer have to rely on the lumen maintenance behavior of a single LED as a proxy for the lifetime," said Rudi Hechfellner, Director of Applications. "With these new methods, companies can now balance business objectives with engineering realities to provide products and warranties that the market wants and can have confidence in." The white paper covers the following topics:

• The 'failure' modes of power LEDs, and their impacts on luminaire reliability.
• Long-term LED performance testing: the foundation of reliability data.
• How reliability models are derived.
• What the models tell lighting manufacturers about LED behavior over time.
• Predicting the "lifetime" of an LED array