Indoor LED lighting, which is a light-emitting diode, is a semiconductor solid-emitting device. It is the use of solid semiconductor chip as a luminescent material, through the carrier in the semiconductor photon emission caused by the compound gives off excess energy between, directly emit light of red, yellow, blue, green, on this basis, the principle of three primary colors, add fluorescent powder, can be any color of the light. LED lights are used as lighting fixtures. LED lighting fixtures, reflective LED lighting fixtures can be fully qualified for any situation, large areas of indoor lighting is not mature.
LED light source, LED by Ⅲ - Ⅳ compounds, such as GaAs (gallium arsenide), GaP (gallium phosphide), GaAsP phosphorus (GaAs) made of semiconductor, such as its core is the p-n junction. Therefore, it has the i-v feature of general p-n junction, which is the positive guide, reverse cut-off and breakdown characteristics. In addition, under certain conditions, it also has the luminescence characteristic. In the forward voltage, the electron is injected into the P area by N region, and the hole is injected into N region by P zone. A small number of carriers entering the opposite area (children) are composed of a majority of carriers (multiple children).
If the luminescence occurs in the P area, then the injected electrons and the valence are directly combined with the cavitation, or they are captured by the luminescent center and then combined with the cavitation. In addition, this kind of light composite some electrons are not luminous center (the center between the conduction band, interface with near middle) capture, then with hole compound, every time the energy released is not big, could not form visible light. The higher the ratio of the luminescent compound to the non-luminous composite, the higher the quantum efficiency. Since the composite is luminescent in the children's diffusion zone, the light is generated only within mu m near the PN junction.
Theory and practice show that the peak wavelength of light is related to the band gap of semiconductor materials in the luminous region, namely, lambda is approximately 1240/Eg (mm).
The unit of Eg is electron volts (eV). If visible light can be produced (wavelength 380nm ~ 780nm red light), Eg of semiconductor materials should be between 3.26 ~ 1.63 eV. Infrared light is longer than the wavelength of red light. There are infrared, red, yellow, green and blue light emitting diodes, but the cost and price of the blu-ray diodes are high and the use is not universal.
The limit parameter
(1) allowable power consumption Pm: the maximum value of the current product that can be added to the dc voltage and the current flowing through it. Exceed this value, LED heating, damage.
(2) maximum forward dc current IFm: allowable maximum positive dc current. More than this can damage a diode.
(3) maximum reverse voltage VRm: maximum reverse voltage allowed. Over this value, leds may be punctured and damaged.
(4) working environment topm: the ambient temperature range of normal working environment of led. Below or above the temperature range, the leds will not work properly and the efficiency will be greatly reduced.
Without changing the material, in the limit range of the LED, the means to increase the brightness is to raise the current, and as the current increases, the heat of the LED will increase dramatically. Use LED light source portable projector, or micro-cast friend, must be deeply experienced, LED light source projector, very hot, and generally there will be obvious noise. These products, the fuselage of the fuselage is on the one hand, the key or its own calorific power.
With the increase of power, the LED heat dissipation problem is increasingly outstanding, a large number of actual application shows that the LED can't increase the input power, the basic reason is because the leds emit a large amount of heat in the process of work, make the pipe junction temperature rising rapidly, thermal resistance. The higher the input power, the higher the heating effect. Performance changes will lead to the rise of temperature and attenuation, the radiative recombination increases, the components of leakage current increases, the semiconductor material defect growth, metal electrode electric migration, encapsulation yellowing with epoxy resin, etc., the serious influence of LED photoelectric parameters. It even invalidated the power LED. Therefore, it is becoming increasingly important for LED devices to reduce thermal resistance and junction temperature and to study the thermal characteristics of light-emitting diodes.
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