7/25/2011

LED Luminaire Design Guide

Lighting-class LEDs are now available that deliver the brightness, efficacy, lifetime, color temperatures, and white-point stability required for general illumination.

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 construction . 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.

Luminaires Or Lamps


Designing LEDs into general illumination requires a choice between designing either a complete luminaire based on LEDs or an LED-based lamp meant to install into an existing fixture. Generally, a complete luminaire design will have better optical, thermal and electrical performance than the retrofit lamp, since the existing fixture does not constrain the design. It is up to the designer to decide whether the total system performance of a new luminaire or the convenience of a retrofit lamp is more important in the target application.

LED-based Luminaires For The Following Four Characteristics:


1. Luminaire light output ( lumens )
2. Luminaire efficacy ( lumens per watt )
3. Correlated color temperaure ( degrees Kelvin )
4. Color-rendering index
DOEs CPTP sets a good precedent for LED luminaire design by focusing on the usable light output of a luminaire ¡ยช not just the light output of the light source.

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