LED (Light emitting diode), a light-emitting diode, is a solid-state semiconductor device that converts electrical energy into visible light, which can be converted directly into lights. The LED's heart is a semiconductor chip, one end of which is attached to a bracket, one end is the cathode, the other end is connected to the cathode of the power supply, and the whole wafer is encapsulated by epoxy resin.
Semiconductor wafers are made up of two parts, some of which are P-type semiconductors, where the holes dominate and the other end is n-type semiconductors, which are mainly electrons on this side. But when the two semiconductors are connected, they form a p-n knot. When the current passes through the wire to the chip, the electrons are pushed into the P zone, the electrons in the P area are combined with the holes, and then the energy is emitted in the form of photons, which is the principle of LED luminescence. The wavelength of light, the color of light, is determined by the material that forms the p-n knot.
The first led used as the indicator light source of instrumentation, and then a variety of light color led in traffic lights and large area display screen has been widely used, resulting in a very good economic and social benefits. The 12-inch red traffic light, for example, was originally used as a light source in the United States with a long life, low light effect of 140 watts incandescent lamps, which produce a 2000 lumen white. After the red filter, the light loss of 90%, leaving only 200 lumens red. In the new design of the lamp, Lumileds company uses 18 red LED light source, including circuit loss, the total consumption of 14 watts, can produce the same light effect. Automobile signal lamp is also an important field of LED light source application.