LED Light Theory

- Jun 10, 2019-

  1. LED lamp is a semiconductor material chip of electroluminescence, solidified on the support with silver glue or white glue, and then connected with the chip and circuit board with silver wire or gold wire, sealed with epoxy resin around to protect the inner core wire, and finally installed the shell, so the anti-seismic performance of LED lamp is good.

  2. Theory:

    A Light Emitting Diode, a solid-state semiconductor device that converts electrical energy into visible Light, converts it directly into Light. The heart of an LED is a semiconductor wafer, one end of which is attached to a stand, one end is negative and the other end is connected to the positive end of the power supply, so that the entire wafer is encapsulated in epoxy resin.

    A semiconductor chip consists of two parts, one is a p-type semiconductor, in which the holes are dominant, the other is an n-type semiconductor, and the other is dominated by electrons. But when the two semiconductors are connected, they form a p-n junction. When a current is applied to the chip through a wire, the electrons are pushed into the p-zone, where they recombine with the hole and emit energy as photons, which is how leds glow. And the wavelength of light, the color of the light, is determined by the material that forms the p-n junction.

    LED can directly emit red, yellow, blue, green, green, orange, purple and white light.

    At first, LED was used as the indicating light source for instruments, and then LED of various light colors was widely used in traffic signal lights and large-area display screens, generating good economic and social benefits. Take a 12-inch red traffic light, for example. In the United States, the long-lived, low-light, 140-watt incandescent bulb produces 2,000 lumens of white light. After the red filter, 90 percent of the light is lost, leaving only 200 lumens of red light. In the new design, Lumileds USES 18 red leds, which consume 14 watts, including circuit losses, to produce the same effect. Car signal light is also an important field of LED light source application.

    For general lighting, people need a white light source. In 1998, white LED was successfully developed. The LED is GaN chip and yttrium aluminum garnet (YAG) packaged together. GaN chip emission blue (lambda p=465nm, Wd=30nm), high-temperature sintering of the Ce3+ containing YAG phosphor excited by the blue light emitting yellow light, peak 550nLED light m. The blue LED substrate is installed in a bowl-shaped reflective chamber and covered with a thin layer of resin mixed with YAG, about 200-500nm. The blue light from the LED substrate is absorbed by the phosphor, and the blue light is mixed with the yellow light from the phosphor to get white light.

    For InGaN/YAG white leds, by changing the chemical composition of the YAG phosphor and adjusting the thickness of the phosphor layer, various white lights with a color temperature of 3500-10000k can be obtained. This method of getting white light from blue leds is simple, cheap and highly mature, so it is most widely used.