Characteristics of LED lamps
Issuing time:2018-08-22 14:06
LED (Light Emitting Diode), a light-emitting diode, is a solid-state semiconductor device that converts electrical energy into visible light. It can directly convert electricity into light. The heart of LED is a semiconductor chip.
One end of the wafer is attached to a support, one end is a negative electrode, the other end is connected to the positive electrode of the power supply, so that the whole wafer is encapsulated by epoxy resin. Semiconductor wafers consist of two parts, one of which is a P-type semiconductor, in which holes predominate, and the other end is a N-type semiconductor, mainly electrons. But when the two semiconductors connect, they form a P-N junction between them. When an electric current acts on the chip through a wire, the electrons are pushed to the P region, where the electrons recombine with holes, and then emit energy in the form of photons. That's how LEDs emit light. The wavelength of light, also known as the color of light, is determined by the material that forms the P-N junction.
At first, LED was used as the indicator light source of instruments and meters. Later, various light-colored LEDs were widely used in traffic lights and large area display screens, resulting in good economic and social benefits. In the case of a 12-inch red traffic light, a 140-watt incandescent lamp with a long life and low light efficiency was originally used as a light source in the United States, producing 2,000 lumens of white light. After the red filter, the light loss is 90%, leaving only 200 lumens of red light. In the new design, Lumileds uses 18 red LED light sources, including circuit losses, a total of 14 watts of power consumption, can produce the same light effect. Automotive signal lamp is also an important field of LED light source application.
For general lighting, people need white light source more. The white light LED was successfully developed in 1998. The LED is made of GaN chip and yttrium aluminum garnet (YAG). The GaN chip emits blue light (lambda p=465 nm, Wd=30 nm). The high temperature sintered YAG phosphor containing Ce3+ emits yellow light with a peak of 550 nm. The blue LED substrate is installed in a bowl shaped reflector, covered with a resin thin layer mixed with YAG, about 200-500nm. The blue light emitted by the LED substrate is partly absorbed by the phosphor, and the other part is mixed with the yellow light emitted by the phosphor to obtain white light. Now, for InGaN / YAG white LED, by changing the chemical composition of YAG phosphor and adjusting the thickness of phosphor layer, we can get a color temperature of 3500 - 10000K white light. This method of getting white light by blue LED has the advantages of simple structure, low cost and high technology maturity, so it is used most.
The price of LED lamp is higher than that of other lighting fixtures. In addition, the current LED industry is lack of unified standards, the quality of products produced by various enterprises is different, there are still many uncertainties in light efficiency, color rendering and life, but LED technology is also constantly improving, I believe that one day LED technology will become increasingly mature, into ordinary people's homes.