The following information is an on-line version of Cree's Application Note CLD-AP15.000. Copyright © 2007 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo, and XLamp are registered trademarks of Cree, Inc. 4600 Silicon DriveDurham, NC 27703 http://www.cree.com/xlamp
LED Luminaire Design Guide
This application note provides guidelines for the process of designing high-power LEDs into luminaires. This document uses an indoor luminaire design as an example, but the process described can be applied to the design of any LED luminaire.
Lighting-class LEDs are now available that deliver the brightness, efficacy, lifetime, color temperatures, and white-point stability required for general illumination. As a result, these LEDs are being designed into most general lighting applications, including roadway, parking area, and indoor directional lighting. LED-based luminaires reduce total-cost-of-ownership (TCO) in these applications through maintenance avoidance (since LEDs last much longer than traditional lamps) and reduced energy costs.
There are over 20 billion light fixtures using incandescent, halogen, or fluorescent lamps worldwide. Many of these fixtures are being used for directional light applications but are based on lamps that put out light in all directions. The United States Department of Energy (DOE) states that recessed downlights are the most common installed luminaire type in new residential construction1 . In addition, the DOE reports that downlights using non-reflector lamps are typically only 50% efficient, meaning half the light produced by the lamp is wasted inside the fixture.
In contrast, lighting-class LEDs offer efficient, directional light that lasts at least 50,000 hours. Indoor luminaires designed to take advantage of all the benefits of lighting-class LEDs can:
- Exceed the efficacy of any incandescent and halogen luminaire
- Match the performance of even the best CFL (compact fluorescent) recessed downlights
- Provide a lifetime five to fifty times longer than these lamps before requiring maintenance
- Reduce the environmental impact of light: no mercury, less power-plant pollution, and less landfill waste
1 U.S. Department of Energy, Energy Efficiency and Renewable Energy. LED Application Series: Recessed Downlights.