Led luminaire design guide

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-pointstability 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 20billion 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 reportsthat 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 halogenluminaire • 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

Table of Contents Design Approach................................................................................................... 2 Design Process ...................................................................................................... 3 1. Define Lighting Requirements ........................................................................... 4
5.000 ote: CLD-AP Application N

2. Define DesignGoals........................................................................................... 5 3. Estimate Efficiencies of the Optical, Thermal & Electrical Systems .................... 6 4. Calculate Number of LEDs Needed ..................................................................... 9 5. Consider All Design Possibilities & Choose the Best........................................... 0 6. FinalSteps......................................................................................................... 5 Where to Get Help ................................................................................................. 6



U.S. Department of Energy, Energy Efficiency and Renewable Energy. LED Application Series: Recessed Downlights.

Subject to change without notice. www.cree.com/xlamp



Design Approach
Luminaires or Lamps? Designing LEDsinto 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 thetotal system performance of a new luminaire or the convenience of a retrofit lamp is more important in the target application. Target Existing Luminaires If the target application is better served by creating a new LED luminaire, then designing the luminaire’s light output to match or exceed an existing luminaire has several advantages. First, an existing design is already optimized to target a...