The LED diode is a semiconductor light-emitting electronic components. This electronic component first appeared in 1962, early emit only low luminosity red, after developing other monochromatic version, to make today's light has spread all over the visible light, infrared and ultraviolet spectrophotometry, also improved to a considerable luminosity. And use from the beginning as the indicator, the display plate; with the continuous advancement of technology, the light-emitting diodes have been widely used in display, TV lighting decoration and lighting.
LED can only go in one direction conduction (electricity), called the forward bias (forward bias), when the current is flowing, electron and hole in the composite and emit monochromatic light, this is called electroluminescence effect, and the wavelength of light, the color with the semiconductor materials and the incorporation of impurities the the relevant. Has the advantages of high efficiency, long service life, not easy to be damaged, switching speed, high reliability and high light than traditional. The luminous efficiency of white LED, in recent years has been significantly improved, at the same time, in every thousand lumens of purchase price, but also because of influence of investment firms competing, decreased. Although more and more people are using LED lighting, office furniture, decoration, or even street signs use, but technically, LED in the photoelectric conversion efficiency (the ratio of effective illumination on electricity consumption) was lower than the fluorescent lamp model, it is a semiconductor diode development civilian to country, can electricity can be transformed into light. Light emitting diodes and diode is composed by a PN junction, also has a one-way conductivity. When the light emitting diode plus forward voltage, from P injected into the N region of holes and electrons are injected into the N region P region in the PN junction, near a few microns in e-commerce and P District N District of the hole recombination, produce spontaneous emission of fluorescence. Electrons and holes of different semiconductor materials in which the energy state of different. When the electron hole recombination at the release of energy, more energy is released, the shorter the wavelength of light. Commonly used is red, green or yellow light diode.
Light emitting diode reverse breakdown voltage of approximately 5 volts. Positive volt ampere characteristics of it is very steep, the use must be series limiting resistor to control the current through a tube. The current limiting resistor R can be calculated using the following equation: R= (E UF) /IF where E is the power supply voltage, UF LED forward voltage drop, IF is a general LED working current