LED System Design:
You Get What You Pay For
http://www.ebnonline.com/author.asp?section_id=1221&doc_id=205971&itc=ebnonline_sitedefault
LED lighting can clearly have advantages over traditional lighting technologies.
LEDs can have a long lifespan (>50k hours), use less energy, and provide more flexibility in a lighting design.
However, a poorly designed system, or making too many compromises on cost, can cause LEDs to underperform relative to expectations.
When designing, the process all starts with the LED selection.
While there is a wide selection of manufacturers and LED types to choose from, most LEDs are designed for specific applications. These applications include, but are not limited to:
- Portable (flashlights, medical headlamps, etc.)
- Signage (full video, variable message, traffic lights, etc.)
- Backlighting (TVs, handhelds, etc.)
- Transportation (planes, trains, automobiles, etc.)
- General lighting (luminaries and LED bulbs)
Furthermore, there are LEDs specifically designed for sub-segments of these applications. When selecting the LED for an application design, it is important to choose one that can perform within the appropriate lifespan, efficacy, color shift, uniformity, thermal, electrical, and optics expectations. The manufacturer should be able to support the customer’s expectations by providing the necessary data to prove an application’s quality. While it can be tempting to select the most cost-effective LED, designers need to be careful of the potential compromises that choice may entail.
Thermal design is an important next step in the process. Designers should be sure they have the necessary space within the envelope to design a heat sink to effectively keep the LEDs in the system cool. For example, a 100W-equivalent A-19 replacement LED bulb does not exist — yet. Designing a system without adequate thermal management will also cause the LEDs to potentially underperform customer expectations.
Optical design is an important consideration as well. Directing the light effectively onto the required target will minimize the number of LEDs and power required to drive the system. This could, in fact, lower the overall cost of the system.
Designers also need to consider electrical design. LEDs are current-driven devices. There are several ways to design a constant current driver. Drivers that are simpler and more cost effective tend to be less efficient as well. Depending on the application, it is important to select the appropriate driver to meet the desired results.
Solid-state lighting solutions are only as strong as their weakest component.
Depending on the application, designers should be aware of the allowable compromises they can make in order for LEDs to become the leading technology light source.
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