Principle of LED lamp
LED (light emitting diode), light emitting diode, is a kind of solid-state semiconductor device that can convert electric energy into visible light, which can directly convert electricity into light. The heart of LED is a semiconductor crystal One end of the wafer is attached to a bracket, one end is a negative electrode, and the other end is connected to the positive pole of the power supply, so that the whole chip is encapsulated by epoxy resin.
A semiconductor chip consists of two parts: one is a p-type semiconductor, in which holes dominate; the other end is an n-type semiconductor, in which electrons are the main component. But when the two semiconductors are connected, it
A p-n junction is formed between them. When the current acts on the chip through the wire, the electrons are pushed to the p region, where the electrons combine with the holes, and then emit energy in the form of photons. This is led The principle of lighting. The wavelength of light, that is, the color of light, is determined by the material that forms the p-n junction.
LED can directly emit red, yellow, blue, green, green, orange, purple, white light.
At first, led was used as the indicating light source of instruments and meters, and then led of various light colors was widely used in traffic signal lights and large area display screen, which produced good economic and social benefits. With 12 inches of red
For example, in the United States, a 140 watt incandescent lamp with long life and low luminous efficiency is used as the light source in the United States, which produces 2000 lumens of white light. After passing through the red filter, the light loss is 90%, only 200 lumens of red is left Light. Among the newly designed lamps, Lumileds uses 18 red LED light sources, including circuit losses, and consumes 14 watts of power to produce the same light effect. Automobile signal lamp is also an important application of LED light source Domain.
For general lighting, people need more white light source. In 1998, white LED was successfully developed. The LED is made of Gan chip and yttrium aluminum garnet (YAG) package together. Gan chip emits blue light（The YAG phosphor with Ce3 + was prepared by sintering at high temperature. After being excited by this blue light, the YAG phosphor with Ce3 + emits yellow light with a peak value of 550nled lamp M. The blue LED substrate is installed in the bowl shaped reflecting cavity and covered to mix YAG resin thin layer, about 200-500nm. The blue light emitted by LED substrate is partly absorbed by phosphor, and the other part is mixed with yellow light emitted by phosphor to obtain white light.
For InGaN / YAG white LED, by changing the chemical composition of YAG phosphor and adjusting the thickness of phosphor layer, white light with color temperature of 3500-10000k can be obtained. This is a way to get white light through a blue LED Because of its simple structure, low cost and high technology maturity, it is widely used.