An LED lamp (or LED light bulb) is a solid-state lamp that uses light-emitting diodes (LEDs) as the source of light. LED lamps offer long service life and high energy efficiency, but initial costs are higher than those of fluorescent and incandescent lamps. Chemical decomposition of LED chips reduces luminous flux over life cycle as with conventional lamps.
Commercial LED lighting products use semiconductor light-emitting diodes. Research into organic LEDs (OLED), or polymer light-emitting diodes (PLED) is aimed at reducing the production cost of lighting products. Diode technology currently improves at an exponential rate.
LED lamps can be made interchangeable with other types of lamps. Assemblies of high power light-emitting diodes can be used to replace incandescent or fluorescent lamps. Some LED lamps are made with bases directly interchangeable with those of incandescent bulbs. Since the luminous efficacy (amount of visible light produced per unit of electrical power input) varies widely between LED and incandescent lamps, lamps are usefully marked with their lumen output to allow comparison with other types of lamps. LED lamps are sometimes marked to show the watt rating of an incandescent lamp with approximately the same lumen output, for consumer reference in purchasing a lamp that will provide a similar level of illumination.
Efficiency of LED devices continues to improve, with some chips able to emit more than 100 lumens per watt. LEDs do not emit light in all directions, and their directional characteristics affect the design of lamps. The efficiency of conversion from electric power to light is generally higher than for incandescent lamps. Since the light output of many types of light-emitting diodes is small compared to incandescent and compact fluorescent lamps, in most applications multiple diodes are assembled.
Light-emitting diodes use direct current (DC) electrical power. To use them on AC power they are operated with internal or external rectifier circuits that provide a regulated current output at low voltage. LEDs are degraded or damaged by operating at high temperatures, so LED lamps typically include heat dissipation elements such as heat sinks and cooling fins.
Read more about LED Lamp: Technology Overview, Application, Comparison To Other Lighting Technologies, Remaining Problems
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