月份：2012年5月

white led grow lights with the LED Lighting development

LED dominate the lighting market still need some time, however, research institutions andthe government is trying to accelerate to shorten this time, also in white led grow lights.

According to the the Databeans recently published in 2011,  in the LED’s research report data, LED lighting applications is expected to 2011 compound annual growth rate of the LED market will reach 36 percent, and in 2016, it would reach $ 4.5 billion. This data over the entire LED market, it shows that market has become the first national infrastructure in Taiwan, white led grow lights are very important part of that.

Recent technological and environmental policies for businesses in this emerging market, the more business income. Light requirements including the use of LED lights transform incandescent and fluorescent lamps. Indeed, transportation is the largest LED applications in lighting applications, the total turnover high brightness LED in 2012 will reach 5 billions and 64 millions USD.

white led grow lights with the LED Lighting development

60 watt LED lamp is the most technical superiority of the product. The product is used with remote phosphor system with patented LUXEON rebel LED. According to the U.S. Department of Energy data, it is assumed that in the United States, about half of the 60 watt bulb would be replaced by LED lights. Then, the United States each year will save $ 3.9 billion energy expenses.

Because of this huge upward trend, many LED companies optimistic about LED lighting applications. One LED company’s turnover in the first half is expected to reach 41 million, of which more than half of the lighting applications. This trend is prevalent in many highly competitive companies, such as Cree and Nichia. Although Nichia plagued by patent war, it will still be able to achieveimpressive results in the LED industry, white led grow lights included.

The LED street light market growth depends not only on the backlit display and the dashboard .Obvious advantages, civil and commercial lighting will require the transformation of incandescent and fluorescent lamps. This will enable enterprises in at least 10 years, greatly increased the production of semiconductors.

Finally, there is a question worth pondering: When the LED lights to replace incandescent, will cause large fluctuations in sales? Because the LED lamp life of up to18 years. This left time to test it.

 

Analysis for LED yard lamps

LED technique has the potential to replace traditional filament lamps, fluorescent lamps and gas discharge lamps in yard lighting. However, there are still some technologic problems of LED Street Light need to be solved:

LED technique has the potential to replace traditional filament lamps, fluorescent lamps and gas discharge lamps in yard lighting.

  1. Lighting effect. Light effect is a very important parameter for LED lamps. LED lamps can save much more energy than traditional LED products, as a result of the higher lighting effect of LEDs. LED lighting effect can be improved by choosing better LED materials and improving the internal construction of LED chips. Since this part is most likely to be realized, scientist all over the world spent most of their energy and costs on it every year. With the development of LED technique, the lighting effect of LED lamps has been improved continuously, including LED yard lighting.
  2. Power efficiency. As a type of outdoor lighting products, yard lamps are usually used during the night. This requires that LED yard lamps with single LED chip have enough luminous flux. Thus, we must have sufficient power. However, the voltage (power) provided by suppliers should not exceed a certain threshold. Otherwise, LED chips will be destroyed due to high working temperatures. Obviously, besides larger area for LED surface, high power LED components also need better cooling sections.
  3. Since lights emitted by LEDs usually concentrate within a small area (solid angle), traditional projectors are no longer useful. LED manufactures need to design new reflecting covers which correspond to the optical system structure of LED lamps.
  4. Generally, LED lighting sources are comprised of several LED chips. The discrete parameter is another technological problem. On one hand, manufactures will try hard to keep the uniformity (parameters) of LED chips within one lamp. On the other hand, they need to design more reasonable lamp structures and diver circuits in case that LED yard lamps are destroyed due to energy concentration.
  5. Normally, a set of LED yard lamps will be used in yard lighting. Thus designers need to design a connection way (in series or in parallel) for these lamps before installation. Protection circuits are necessary since the whole set of yard lights will be out of work if only one or two of them are failed.
  6. LED yard lamps have strict requirements in cooling system. Continuous working in high temperature will cause a light attenuation inevitably, which is a cannot-be-ignored problem for outdoor lighting products.

LED street lighting business: a new direction for street light manufactures

Recently, LED street lighting business has become a new direction for street light manufactures in China. LED street lights are quite different from traditional street lights: point light sources, high power consumption; Narrow beam output. These require more sophisticated designs for LED street lamps. It is a systematic process. In order to designer LED street lamps with higher performances, designers should make a study of street lighting standards and photo-mixing principles for traditional street lights, taking full advantage of LED street lamps: point light sources, controllable beam angle and long life cold light sources.

 

Recently, LED street lighting business has become a new direction for street light manufactures in China.

 

Choosing suitable LED light sources is the key to the entire designs, since they will directly impact LEDs’ performances, costs and working lives. Some LED street light manufacturers use single LED moudle with a power consumption of 10W. In fact, this design is unreasonable and has many defects: harder in photo-mixing; more glares; more difficult in heat radiation, etc. Some manufacturers tried to use the combination of several LED modules (with 3W-5W for each). This design also has defects: insufficient lighting effect and heat radiation problems. Above all, high power (10W) LED is more reasonable. With current high power LED technology, 10W LED street lamps have better lighting effect.

 

There are two main colors in street lighting: yellow light and white light. Basically, high pressure sodium lamps (HPSL) emit yellow rays. HPSL is the mainstream street lighting technique in China, due to its energy-saving property and strong fog- penetrability. However, yellow light has its own defects: low CRI. Under sodium lights, objects will be coated by yellow lights, which is a distortion. White light is closed to natural light, having much better CRI compare with yellow light. Metal halide lamps were used in the early stage of white-ray LED street lighting industry. Metal halide lamps have better CRI, but also very weak fog- penetrability and short service lives. They did not wide spread at that then. Then LED manufacturers concentrated on a newborn lighting technique: LED, and joint into LED street lighting business one after another. The normally used color temperature of LED street lamps is around 3500K (cool white). LED street lamps have higher CRI, better lighting effect, better fog- penetrability, and can work for a long time. It is impossible to prevent LED street lamps to be the mainstream products in street lighting business. Soon, traditional street lamps will be replaced by them completely.

How to improve CRI of LEDs? (3)

Theoretically, white rays can be obtained by combining three primary colors in a certain ratio (red : green : blue = 3:6:1). This technology can be used in LED display but not in LED lighting products, since it is based on the premise that we have seen the object. Objects can be seen by us due to the light reflected from them. During this process, lights will be absorbed by objects. Therefore, white rays generated by the combination of three primary colors have innate defects: objects absorb red rays, blue rays and green rays at different levels. Even they have been mixed exactly in ratio to create purely white rays, after reflecting, they cannot maintain the original ratio, leading to a distortion. That means, lit by LED lamps, objects will look different from looking them in the sun. CRI of LEDs reduces. However, it is not to say that this kind of technique is infeasible. The photo-mixing operation should be taken within LED lamps (before sending out) to improve the CRI of LEDs.

 

Three primary color LED photo-mixing technology is much mature currently. There are two different ways for photo-mixing: on the surface of LED chips; on the surface of lamp covers. Both of them have disadvantages. The former: distances between LED chips are too far for photo-mixing, causing inevitable distortions. The latter: this method will cause light attenuation. Although this type of LED lamps has a higher CRI, lights sent out by them are no longer white rays if captured by our eyes directly.

 

In recent years, many studies for three primary colors LED photo-mixing technology are focus on these two problems. Studies demonstrate that with the decrease of distances between LED lights, light mixing distances exponentially reduced. With the increase of color-scattered agent’s concentration, the light mixing effect will be increased. The balance point between LEDs’ distances (reduce) and color-scattered agent’s concentration (increase) will be the optimal value. With such solution, it is possible for photo-mixing LEDs to be white lighting sources one day.

 

This technology can be used in LED display but not in LED lighting, since it is based on the premise that we have seen the object.

 

Feature above depicts relation between light intensity and concentration of color-scattered agent. From it we can see that light attenuation is proportional to color-scattered agent’s concentration. Currently, transparent glue has a light attenuation of 5%, while glue with color-scattered agent has a light attenuation of 12%. With current technology, this problem will not be solve in short term.

How to improve CRI of LEDs? (2)

In the previous section, we discussed about the impact of temperature on fluorescent powder. With the increase of temperature, activities of fluorescent powder will decrease. At the same time, temperature will also affect the wavelength of light. Feature below illustrates the relation between temperature and the wavelength. We can see that with the increase of temperature, the wavelength of light emitted though fluorescent powder will red shift. In other words, CRI for LEDs of led lights will be improved (more red rays). It is contradictory to the previous statement: CRI for LEDs will decrease as temperature increases. As a matter of fact, the red shift of fluorescent powder is negligible compare with the degeneration of fluorescent powder. Overall, when temperature drops the CRI for LEDs is actually decreases.

 

In the previous section, we discussed about the impact of temperature on fluorescent powder. With the increase of temperature, activities of fluorescent powder will decrease.

 

According to above analysis, there are three solutions: reduce PN junction temperatures; improve the adaptability of fluorescent powder in high temperatures; use color compensation technology (use red led street light or amber LEDs to compensate the CRI for LEDs);

 

The most effective solution in reducing PN junction temperatures is to design new LED packaging methods with better heat radiating performances. This is one of our development directions that can have Chinese LED industry to make significant progress in intellectual property in the near future. Since LED is a type of low-voltage electronic products, there are not many strict requirements on electrical safety. Thus a lot of heat radiating materials can be used as LED bases. But Chinese LED flood lights  manufacturers have not taken enough research on this part, leading to some foreign intellectual property disputes. Improving the adaptability of fluorescent powder in high temperatures is main research area in international LED technology. Chinese current technique in this respect is relatively weak and cannot break through this bottleneck in the short term. The color compensation technique can improve CRI for LEDs though making up the deficient colors. Theoretically, this solution is feasible. But in real life, there are many restrictions in color mixing technique, with no practical value.

 

Except for the above three solutions, scientists are trying hard to find other methods which can improve the degeneration of fluorescent powder. CRI problem is the main obstacle for LED lamps to replace traditional lamps completely. It is significant to improve CRI for LEDs.

How to improve CRI of LEDs? (1)

With the development of LED products technique, LED lamps have been widely accepted all over the world. In lighting industry, color rendering index (CRI) is an important parameters. Most lighting standards have strict requests for CRI of LEDs. Currently, the immature LED CRI technique obstructs white LED lamps to be the mainstream in the lighting market.

With the development of LED technique, LED lamps have been widely accepted all over the world. In lighting industry, color rendering index (CRI) is an important parameters.

Natural light is a kind of polychromatic light (a continuous distribution in light spectrum). LED white light is closed to natural light (has a wide continuous distribution in spectrum), laying a theoretical foundation for its color rendering capacity. The currently used white LED Lights chips are blue-ray LEDs coated with fluorescent powder. This technique was invented by Nichia Corp, an imitation of the traditional design concept and fluorescent lamps. However, this technique has innate defects: lack of blue-green rays and red rays and too much blue rays and yellow rays. This gives birth to a distorted CIR for LEDs. For some color, like blue and yellow, white LED rays will “exaggerate” them, making objects with these color look brighter than normal. On the other hand, for some red-colored objects, like apple, meat, white LED Tubes rays will make them look dimmer. These are actually distortions. Designers are striving to improve this white-ray LED technique to have a more real natural light.

 

Theoretically, white rays generated though blue-ray LED Street Light chips combined with fluorescent powder are really closed to natural light. But practice is different from theory. This difference is mainly caused by heat. Heat can impact an obvious effect on fluorescent powder. As we all know, high power LEDs will continuously generate heat during the work, meanwhile cooling sections will radiation this heat constantly. And equilibrium happens when LED high bay lamps work in stable situations. The higher the final temperature, the great the influence on fluorescent powder. Feature below illustrates the relation between light intensities and temperatures. Clearly, light intensity will drop with the increase of temperature. In other words, the light emitting capacity of fluorescent powder drops as temperature increases. The best working temperature for fluorescent powder is around 40 oC. When temperature reaches up to 120 oC, fluorescent powder will lose its capacity completely, which means there will no light sent out by LED lamps.

Light attenuation of white LED lamps (4)

Packaging technique:

In the process of package, every step may cause an effect on the performance of LED street light chips. In which bonders and bonding wires (empty solders) are most likely to raise resistances and thermal resistances. If bonders are too tick, or with air bubble, impurities, virtual sticky in them, the resistance and heat resistance also will be increased. However, since the degeneration of fluorescent powder is too obvious. The influence from this kind of packaging defects can be ignored.

 

In the process of package, every step may cause an effect on the performance of LED chips. In which bonders and bonding wires (empty solders) are most likely to raise resistances and thermal resistances.

 

Light attenuation caused by misuses:

  1. Improper power suppliers. This situation may happen when users are not familiar with electric parameters of white LED lamps. Improper power suppliers will cause LED chips working outside the ASO, and consequently light attenuation. Surrounding temperature is measured when LED chips are working in stable conditions. For example, a piece of LED high bay lamp has been installed in the middle of a room, wait until it is in the stable condition, measure the internal temperature of the lamp (near LED chips) rather than the room temperature. If the surrounding temperature exceeds a threshold, lamp will be degenerated or even damaged.
  2. Insufficient cooling methods: the radiation of heat requires enough area for contact surfaces. Some people prefer to add copper blocks on PCBs or aluminum plates, which is meaningless. It cannot solve the heat problem but raise the cost and heavy of products. Most heat generated by PCBs or aluminum plates will be gathered in these copper blocks. When they reach the peak of their thermal capacity, no more heat will be absorbed. Using thermal capacities of materials to help radiate heat cannot solve this problem thoroughly. It can only cool the device for a short time. Designers should not choose auxiliary cooling materials according to their thermal capacities but their specific heat capacities. Water has powerful specific heat capacities, which is widely used cooling materials. The specific heat capacity is only half of aluminum. However, neither copper blocks nor aluminum blocks are unsuitable for white LED lamps. The best way is natural cooling. Natural cooling relies on the area of radiators’ surface not the volume. If these heat generated by white LED lamps can be radiated in time, the light attenuation phenomenon will be slowed down effectively.

High power LED street light will continue rapid growth

“2012, the most promising commercial lighting and road lighting”commercial lighting and road lighting with the semiconductor lighting technology has become more sophisticated and with the publishing from central to local government support policies,  LED lighting has become in 2012 a number of manufacturers to compete in the battlefield road lighting.

2012, is bound to be a year full of opportunities and challenges of China’s LED industry, how to seize the opportunity to seek progress, the pursuit of sustainable development in the longer seems particularly necessary.  Although high power led street light industry is optimistic, yet how to seperate should depends on the company’s core technology and competitive strength.

For the LED road lights, the national brand is not much, mostly regional brands. Therefore, there are still some room for development of related business. One industry expert said in an interview with reporters, “LED lighting is still in the initial penetration stage,  pre-marketing and consumer’s feedback form a significant impact on product quality and assurance, which is the core foundation fo the enterprise survival and development.

“LED industry is facing new opportunities and challenges, the opportunities are obvious, the challenge is to challenge the vast majority of the country, which is no core technology and core competitiveness in the fierce market. It is bound to be eliminated. JiangsuYangzi Electrical and Mechanical technology Co., Ltd.Technical Director said, the whole lamp 90lm / W LED lamps of the performance have been beyond other fixtures, and are continuous improving, which will inevitably become the mainstream in the near future. Of course, the current phase of the product is not perfect, such as the standard interface, the LED  heat sink material consumption and other issues to be resolved.

high power led street light standards develops lags far behind the development of industry and product. Market LED lights, visible appearance of the product, are designed various, poor interchangeability, maintenance difficulties, which have become constraints LED road lighting R & D and manufacturing. The industry also called on the relevant authorities to develop a refinement to quantify the operational norms or standards as soon as possible. 2012, LED road lighting is consistent with optimistic. High power led street light will play a more important role in the renovation and construction of urban road lighting.

Who is in charge for Mainland China led lighting product standard

● the local industry standards stifle the vitality of the current LED Street Light market:

First, Reginal local standards. The standard will bring local color more or less, which can not meet national and worldwide development of the industry needs. It shackles of foreign enterprises to enter the local market competitiveness, and easily lead to local protectionism.

Second, The scientific nature of the local standards. Subject to the constraints of technology and local level of industrial development, the gold content of the proposed standard, and developers can not match the rapid development likely to cause the shackles of technology development.

Third, the led lighting product standard developed by the enterprise is unreliable.  Present in many areas of the LED High Bay industry standard is by enterprises organizations of their own making. Some companies, itself, with production standards are different to reach. Such enterprises to develop the industry standard for a bit?

The opened LED industry standard, although it is conducive to the development of the industry side, yet if it also can not reach to the national level, authoritative and scientific standard is difficult to guarantee. Because led lighting product standard itself have mandatory color, there is no objective and fair platform, easy to damage the development of the industry.

● The true sense of introduction of industry standards is imminent:

There have been frequent accident caused by the LED products. A hotel in Hong Kong recently occur the fire accidents caused by the outdoor LED display. Today it may be the LED display to cause the accident. Tomorrow may be the LED lighting to cause the accident. If there is no industry standard, who are responsible for the safety of the lives and property of consumers.

No related industries label is not benecial to healthy development of enterprises. Study is a required couse of the LED manufacturing. But if there is none of the relevant industry standards, what should be the guidance to corporate R&D. Enterprises will explore whether the results of the final outputs is adapt to the market or not, which is unknown.

Industry label can calm down price wars at some extend. With industry standards to spur business development and product quality control, the led lighting product market will not look the same product but the price different between mystery phenomenon. The strength of the small workshop enterprise is no longer possible to blind pursuit of price, profit and confuse the market.

Light attenuation of white LED lamps (3)

There are three types of bases of SMD LED Street Light chips: glass fiber, plastic, ceramic material. When in packaging, each LED chip will be fixed directly in a copper sheet, for that copper has a very high thermal conductivity. However, the volume of copper sheets is so small that heat will be radiated into external PCBs though a very short path. Experiments prove that SMD LED Street Lights chips with good cooling designs have a much longer life than plug-in LED chips. Similar low power LED chips but different packaging (low power supports/high power bases) will have different working lives. For example, 9 10 x 12 mil2 LED chips fixed in parallel on base surface, under a total working current of 350 mA. After 7600 hours’ constant work, the light attenuation is about 23%. In accordance with this trend, the estimated working life will be 18000 hours. High power packaging chips have surface current density (0.324 mA/mil) twice as much as low power packaging chips (0.167 mA/mil), but has a much longer life than them (almost 9 times), as a result of using materials with higher thermal conductivities and bases with larger area. By doing so, heat can be transmitted not only in radial but also in lateral.

 

There are three types of bases of SMD LED chips: glass fiber, plastic, ceramic material. When in packaging, each LED chip will be fixed directly in a copper sheet, for that copper has a very high thermal conductivity.

 

Other materials used in package:

Heat is the main cause of the light attenuation of white LED lamps. Thus every material related to heat radiation should be taken into account. In previous section, we discussed the LED base problem. Now let us talk about other materials used in packaging process: solid crystal glues, mix powder glues, sealants. Tests results indicate that the life of white LED lamps using silver glues is longer than using epoxy resins, but initial luminous flux is lower by 1/3. Using epoxy resins as mixed glue has a shorter working life than using silica glues, but initial luminous flux is increase by 25%. The most commonly used sealants are epoxy resins and silica glues. As a matter of fact, these two types of materials have very weak heat radiating capabilities. The thermal conductivity of iron is 230 times as much as that of epoxy resins and 150 times as much as that of silica glues. In addition to their thick, they are somehow with no capability of heat radiation.