Development Trend of LED lighting technology in 2013

LED is small and light, low driving voltage, full color, long service life, high efficiency, vibration resistance, easy light control and other characteristics. it provides superior conditions for designing lighting systems for different places and purposes. People are used to looking at things in sunlight. For general lighting, what people need is mainly a light source close to the quality of sunlight, so white LED is an important indicator of semiconductor lighting technology. Due to the small power and low brightness of a single LED, it is not suitable to use it alone. Therefore, multiple LEDs must be assembled together to design a practical LED lighting system. However, there is still a certain distance between white LED and general lighting requirements, and there are still many technical and cost problems that need to be solved urgently. 1 The heat management of lamp system is generally called LED as cold light source, because the principle of LED luminescence is that electrons emit photons directly through recombination without heat. However, due to the existence of Joule heat, LED is accompanied by heat while emitting light, and for occasions with high power and multiple LED applications, heat is too much to be underestimated. LED is different from traditional lighting sources such as incandescent lamp and fluorescent lamp. Excessive temperature will shorten or even terminate its service life. Moreover, LED is a temperature sensitive device. When the temperature rises, its efficiency drops sharply. Therefore, system structure design and heat dissipation technology development are also topics that LED applications need to face. Since forced air cooling is usually not desirable in light sources, with the increase of input electric power, heat sinks and other methods to enhance natural convection cooling are playing an increasingly important role in the design of LED lamps and light sources. 2 improve the color rendering. At present, White LED generally uses Blue LED to superimpose yellow yttrium aluminum garnet excited by blue light (YAG)Fluorescent powder, synthesized as white light. Because its luminescence spectrum only contains blue and yellow spectra, it has the problems of high color temperature and low color rendering index, which does not meet the requirements of ordinary lighting. The sensitivity of human eyes to chromatic aberration is much higher than that to light intensity. For illumination, the color rendering of light source is often more important than luminous efficiency. Therefore, adding a proper amount of red fluorescent powder and maintaining a high luminous efficiency is an important topic in LED white light lighting. 3 The secondary optical design of the lamp system, the traditional lamp has long used incandescent lamp and fluorescent light source as reference to determine the standard of the light and shape of the lamp. therefore, the LED lamp system should consider abandoning the Assembly mode of traditional lamps and LED light-emitting modules, fully considering its optical characteristics, and specially designing different lamps for LED light sources. The design contents of the optical system mainly include the following aspects: ① determine the shape of the optical system, the number of LEDs and the power according to the requirements of lighting objects and luminous flux; (2) the combination of several LED luminous tubes is designed as a secondary light source of point light source, ring light source or surface light source, and the illumination optical system is calculated according to the combined secondary light source; (3) it is very important to control the light distribution of each LED tube on the secondary light source that constitutes the design of the illumination optical system. Because the light beam emitted by LED is concentrated, it is easier to control and does not need reflector to concentrate light, which is beneficial to reduce the depth of lamps. For example, using a plane mirror optical system, only 1 ~ 2 LEDs can illuminate a large surface, and the depth of the lamp is very thin; By using the light guide technology, the LED is directly installed next to the light pipe, which can greatly reduce the volume occupied by the light source and other components, and make ultra-thin lamps.