1. Luminescence mechanism of LED light source

Luminescence mechanism of white LED: The commonly used scheme is to apply a full-color or yellow phosphor on a monochromatic blue or near-ultraviolet semiconductor solid-emitting chip to obtain a white LED. Therefore, the quality of the phosphor and the thickness of the coating A slight impact will seriously affect the LED color rendering index, color temperature, light efficiency and light decay. It can be seen that the illuminating mechanism is somewhat similar to that of fluorescent lamps. However, fluorescent lamps are converted into ultraviolet and visible light by gas arc discharge with an input power of 70% or more. The ultraviolet light is converted into visible light by phosphor, and 30% of the total power is left. Used in lamps to maintain the optimum operating temperature and highest luminous efficiency of the lamp.

Heat dissipation problem: LED is a free electron in an n-type semiconductor that crosses the barrier layer into a p-type semiconductor. When combined with holes in it, all potential energy is converted into light energy, and at the same time a photon is generated, which is a cold body illumination due to The total sub-efficiency of such luminescence is <50%. All the energy other than the radiant light energy, including the resistance heat when the current passes through the n-type and p-type semiconductors and the barrier layer, and the kinetic energy of the electron itself are dissipated in the semiconductor and concentratedly blocked. Heating near the layer causes a temperature rise of the pn junction, and this temperature rise causes the barrier resistance to decrease, the barrier to decrease, and the internal and external quantum efficiency and luminous efficiency of the carrier recombination are lowered. The high temperature of the pn pole also affects the luminous efficiency of the phosphor and even causes permanent damage to form a light decay, and the life of the LED which should be long should be greatly reduced. It can be seen that heat dissipation is the deadly and lingering "magic" of LED "long life" and "high light efficiency"!

2. Can Chinese LED street lights in “old bottled new wine” be profitable?

Modeling doubt: A large number of LED street lamps developed by enterprises use the original road lamps and replace the light source with LEDs. It is an "old bottled new wine". This kind of lamp can be re-opened by the reflector, and the development cost can be It is the lowest, according to professional LED people, it seems to be "unremitting care", they believe: the heat dissipation area of ​​this LED lamp is obviously not enough, LED light efficiency and life expectancy can not meet the design requirements, is a "primary school "The LED street light of the grade!" The LED light source manufacturer, which has a new courage to enter the lighting industry, has not developed the shape of the traditional street lamp. All the parts of the LED street lamp have to be re-opened, and the development cost is very high. If you can't sell a good price, you are absolutely sorry for the returnees of the returnees! The design flaws of its hedgehog shape (someone nicknamed "toothbrush" LED street light) have detailed analysis in the previous article in our blog, which is an LED street light belonging to the "middle school students" grade. These two kinds of LED street lamps are very difficult to sell in the eyes of government leaders in many places in China. In this way, it is difficult for LED light source enterprises entering the lighting industry to have stable sales channels for street lamps. The long-life, high-efficiency and high-efficiency LED lighting lamps are not widely used. The investment return period of LED street lamps will be very long!

Light distribution design question: Recently, the LED street lamp developed by a certain brand lighting enterprise in Zhejiang has dug a number of small holes on the original street lamp reflector, and then installed a lot of small LED particles, and also passed the provincial technical appraisal to promote ! ? It seems that the designers of this lighting factory did not study the light distribution design course of the street lamp. In fact, it is not difficult to find that the original street light reflector is only suitable for the linear light source HID. The mathematical model of the lamp and the distribution photometer is also based on the linear light source model when performing the light intensity calculation in each angular direction. Now, is this method of designing light distribution? The reason why the light distribution curve of the brand street lamps in the world adopts the batwing shape is that the reflector design of the street lamp is most beneficial for obtaining the uniformity of illumination (brightness) and glare control of the luminaire on the road surface, and the safety of driving is also the most Favorable, we don’t want to learn about the special papers on the design of streetlights for Professor Liu Haijun in the 2005 Shanghai Institute of Lighting Annual Conference.

3. What is the feasibility of LED light source?

Unless the LED has a single power of 10W and the luminous efficiency is above 150lm/W, a special solution has been found to solve the heat dissipation problem of the LED! It is only possible to integrate multiple LED units into a street light source. We have reason to believe that the owner of the LED light source manufacturer will not only be the "greatest" academician of the Chinese Academy of Engineering, but also the Nobel of this century. Winner of the Physics Award! Let's cheer!

In fact, the biggest advantage of LED light source is the purity and small volume of monochrome color, rather than the long life and high light efficiency that many people mistakenly believe, because the so-called LED long life and high light efficiency are determined by the design of the heat dissipation system. The life is more "one-vote negation" by the reliability of its driving power supply. Great power means that large current and high current bring great heat... This is the common sense of physics! LED small particles above 3W must have a huge heat sink block, which brings great problems for the design of large-power LED light source and lamp miniaturization. Why do you go black on this road? Why can't you take advantage of the LED itself and instead die on its shortcomings?

N years ago, the light source of indoor lighting fixtures: the small light cup made of LED replaced the tungsten halogen lamp, and the progress of the downlight for small-scale orbital lighting in commercial lighting was great. Later, some people invented the energy saving of the ring type. The lamp cups compare the advantages of LEDs because the energy-saving industry in China is too big and too cheap! The mainstream lamps used in the field of commercial lighting - the light source used in the track spotlights are still all 15-70W ceramic metal halide lamps! (And the simultaneous use of magnetic ballasts and electronics, each has its own merits, and the large-power electronic ballasts above 70W have not been used in commercial lighting, because it is not only too expensive, but also not very reliable.) The three giants make a lot of money in China! Although the light effect of a small metal halide lamp is similar to that of an LED, it is much smaller than the LED integrated light source! The miniaturization of commercial lighting design has become fashionable.

Outdoor lighting fixtures: LED wall washers and small tree lights have triggered the “revolution” of landscape lighting and architectural floodlighting design, which is refreshing! However, the original expensive white LEDs used in the high-end interiors used in the high-end interiors have been replaced by the cheap T5/T4 fluorescent lamps “relentlessly”!

4, the status of European LED light source for road lighting

In June 2008, an international lighting launched the second experimental landscape-type luminaire in Europe three years after the release of the first LED walkway lamp (pictured above), which is interchangeable with the 35W-150W/HID light source. The design method of the luminaire structure, LED power and initial luminous flux are: 40W/3500lm, 60W/5000lm, 82W/6300lm, the power of the driving power is less than 15% of the power of the light source, the life is 60000h, the cooling system is air-cooled, and the LED particles are used. Unique integrated batwing light reflector and lens package, the pole height is required to be within 5 meters. references:
1. "Progress and Application of White LED in Solid State Lighting" Yang Zhengming;
2, "Application analysis of LED in the field of lighting" Lin Yandan.

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FAQ

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