LED Technology

How LED Lighting Works

LED - or light-emitting diode - technology has transformed the way we think about lighting in the home. At the technological level, LEDs are vastly different from the more widely understood incandescent and compact fluorescent light bulbs. Incandescent bulbs create light when a filament within the bulb is heated by electricity. Compact fluorescent lamps contain mercury vapor which, when energized, emits UV energy. The phosphor coating on the bulb absorbs the UV and fluoresces, creating visible light. With LEDs, lighting is achieved through "electroluminescence." To better understand this method of lighting, we'll first look at the make-up of an LED light.

Technically speaking, LEDs are not "bulbs." An LED "package" is a chip (called a "die") or series of chips that are made up of layers of semiconducting materials. The materials themselves determine the radiation (or color) that is emitted. The chip or chips are mounted on a heat-conducting material and enclosed within a lens. This package - used on its own or in combination with others - gets mounted on a circuit board and either built into a lighting fixture directly or incorporated into a bulb made to resemble the traditional bulb form, such as an incandescent bulb.

The semiconductor that makes up a light-emitting diode has a positive/negative junction across which electrons move when sufficient voltage is applied. Essentially it is a result of the recombination of an electron with a positive charge that electromagnetic energy is produced and emitted as a photon of light. The color (frequency) of that light depends on the material make-up of the semiconductor material, which is usually a combination of a few elements like gallium, phosphorous and arsenic.

Managing Heat

Although LEDs do not generate UV or infrared light, only about 25 percent of the power they consume gets converted into visible light. The rest gets converted into heat, specifically at the positive/negative junction. Because regulating the heat at the junction is vital to maintaining LED efficiency and performance, many LED manufacturers incorporate a "heat sink" into the design that conducts heat away from the junction.