What are LEDs?

LEDs, or light–emitting diodes, are semiconductor devices that produce visible light when an electrical current passes through them. LEDs are designated as a type of Solid State Lighting (SSL), as are organic light–emitting diodes (OLEDs) and light–emitting polymers (LEPs).

How is LED lighting different than other light sources, such as incandescent and CFL?

LED lighting differs from incandescent and compact fluorescent lighting in several ways. When designed well, LED lighting can be more efficient, durable, versatile and longer lasting. LED lighting products use light emitting diodes to produce light very efficiently. An electrical current passes through semiconductor material, which illuminates the tiny light sources we call LEDs. The heat produced is absorbed into a heat sink.

Common LED colors

include amber, red, green, and blue. There's actually no such thing as a “white” LED. To get white colored light, like we use to light our homes and offices. Different colored LEDs are mixed or covered with a phosphor material that converts the color of the light. The phosphor is the yellow material you can see on some LED products.

LED's go mainstream

LEDs are now being incorporated into bulbs and fixtures for general lighting applications. Because the LEDs are small they provide unique design opportunities. Some LED bulb solutions may look like typical light bulbs and others may not. LEDs are “directional” light sources, which means they emit light in a specific relatively narrow direction, unlike incandescent and compact fluorescent bulbs, which emit light and heat in all directions. For this reason, LED lighting is able to use light and energy more efficiently in many applications.

The Basics of LED Lighting

The useful life of LED lighting products are defined differently than that of other light sources, such as incandescent or CFL. This is because LEDs typically do not “burn out” or fail. Instead, they experience lumen depreciation (dimming), where the amount of light produced decreases and light color appearance can shift over time. Instead of basing the useful life of an LED product on the time it takes for 50% of a large group of lamps to burn out (as is the case with traditional sources), LED product “lifetime” is set based on a prediction of when the light output decreases 30 percent.

LEDs and Heat

Because LED lighting systems don’t radiate heat the way an incandescent or halogen light bulb does, the heat produced from the power going into the product must be drawn away from the LEDs. This is usually done with a heat sink, which is a passive device that absorbs the heat produced and dissipates it into the surrounding environment. This keeps LEDs from overheating and burning out. Thermal management is probably the single most important factor in the successful performance of an LED product over its lifetime because the higher the temperature at which the LEDs are operated, the more quickly the light will degrade, and the shorter the useful life will be.