月份：2012年12月

LED diode is in hot water

Now, even we do this upstream fluorescent powder materials which are owed money. ” Talking about the LED industry of trigonometry debt, Li Yi (a pseudonym ): ” cherish a deep-seated hatred for business when you speak goods to the payment, but once the goods to customers, have a heap of reason prevaricate. ”

LED diode is in hot water

 

Li Yi is one of the main LED Down Light fluorescent powder materials company general manager, before a few years the rapid development of industry to the company to bring rich and generous profit, in recent years the company is planning a listing. But recently, the industry of triangular debts continue to spread.”
Equipment factory and factory lamps used a longer account period, but our material factory previously used in a short period of time to pay, we buy rare earth material is to use cash to. we can not be timely recovery of cash, cash is difficult to continue. ” Li Yi told the Securities Times reporter, phosphor material manufacturers is bigger, and the majority of the cash transaction, if the downstream firms credit seriously, be equal to enterprise interest-free support customer operating funds, but also take the price risk of rare earth. The funds for the weak strength of small and medium-sized enterprises, especially prone to cracking of the capital chain.

In fact, this chain of debt risk has partial exposure. By the end of 2011, with Shenzhen Jun Tatsutaro as the representative of the group of Southern China region led diode display because the enterprise fund chain break and close down in succession. November of this year, photoelectric closed after about 20 million of the payment in arrears discovered, supplier surfaced, Southern China, East China and many listing Corporation are temporarily which will be unable to recover.

At present, the company involved in the LED industry innumerable, industry chain debts have spread. Only from a public information listing Corporation, as of the three quarter of this year, with the led diode industry in the 21 listing Corporation accounts receivable balance total up to $5519000000, payable balance reaches 34 million RMB, the company total accounts receivable already accounted for the first three quarters of the total revenue 89.13%.
At present, some listing Corporation put part of accounts receivable to commercial bills, so from the results we can seen on the amount.
The company knows the credit funds smooth Road, on the supplier psychology. ” A lot of downstream manufacturers are no cash payments to suppliers. Supplier has no way, do not continue to supply means that the inventory backlog and carrying a loss. ” A domestic chip companies responsible person said reluctantly.

Design principles of LED display divers

Large screen area is always a part and parcel of LED industry, an important part of large entertainment, sporting events, square theme display. Full color screen technology maintained a rapid development since the birth of blue-ray LEDs. LED plays a positive role in the outdoor decorative display market, with obvious expending trend. China is the largest producer of LED screens, from LED chips, to LED display divers, LED display controllers, screens, China’s products take the dominate position in the global market in almost every respect.

 

Large screen area is always a part and parcel of LED industry, an important part of large entertainment, sporting events, square theme display.

 

16-bit shift constant current IC is most commonly used module in LED display divers. Black-and-white screens are text-display-based. Microcontroller scanning was more convenient. With the increase of the number of LED chips, in order to save O/I ports, engineers started to adopt 74HC595 shift scanners. Based on this, engineers then integrated constant current setting function, which can improve the current driver capability. Finally, 16-bit shift constant current IC was created and adopted by full-color screens, which is more in line with demand.

 

Essentially, the driver capacity of LED display divers was continuously reducing. Earlier TLC5940 has a output driving current as high as 120mA (single line). Followed by TB62726, ST2221, MBI5026, the driving current of which was declined to 80-90mA. The current driver for LED screens has a driving current of 45mA, like MBI5024 and CYT62726, mainly because of the increase of LED High Bay output luminance (brightness).

 

At present, about 80% LED screens in the international market was produced in China. 16-chiannel constant current designs are commonly used, and will not be replaced in short term. All supporting technologies are mature, plus the serialization of products, expect for large innovations in control systems and driver designs, 16-bit shift constant current IC will hardly be replaced. In recent years, many companies continuously introduced new architectures, which were not recognized and accepted by the market. Lacking of innovations in control system is the largest problem. For example, changing color consistency of LEDs without any major breakthroughs on the new technology will have very little attraction in the market. It is expected that the mainland chip design companies will occupy the LED display market, just like SILAN AZURE, which has become the largest suppliers of mainstream LED display chips. Their products have good qualities and satisfied assurance.

Characteristics of high-power LED package

High-power LED package has been a hot research topic in recent years, due to their complex structures and production process and directly effects on the performance and lifetime of LED chips / LED lamps. The selection of LED packaging methods, materials, structures and production process is mainly determined by chip constructions, optical / mechanical characteristics, special applications and costs. After 40 years of development, LED package technology has gone through four major stages: Lamp LED, SMD LED, Power LED Tubes and COB LED. With the continuous increasing of chip power, especially the developing demand of solid-sate lighting technology, high-power LED package need to meet more restrict requirements in the aspect of optical parameters, thermal parameters, electrical parameters and mechanical structures. In order to effectively improve the luminous efficiency, new ideas and design concepts need to be adopted.

 

High-power LED package has been a hot research topic in recent years, due to their complex structures and production process and directly effects on the performance and lifetime of LED chips / LED lamps.

 

Phosphor powder plays a role of color mixing and white-ray creating in the LED package. Their major characteristics are size, shape, luminous efficiency, conversion efficiency, stability (thermal and chemical) and so on. Luminous efficiency and conversion efficiency are key points. It has been proved that, with the raise of temperature, the quantum efficiency of phosphor powder will be reduced, as well as the output luminance. In the mean time, the wavelength will be changed, leading to variations in color temperatures. High working temperature will also speed up the deterioration of phosphor powder. Phosphor powder is coated by epoxy and silicone rubber mixtures, the thermal conductivity of which is relatively poor. When exploded under violet rays or UV rays, phosphor powder will be easily deteriorated. Besides, high temperature also exerts bad influences on thermal stability of encapsulants and phosphor powder. Generally, the refractive index of phosphor powder is larger than or equal to 1.85, while the refractive index of silica is around 1.5. Due to the unmatched refractive index, light scattering phenomenon occurs on the surface of phosphor particles. This problem can be improved by adding nano phosphor in the silica gel, increasing the refractive index to 1.8 or more for the later and increasing the luminous efficiency by 10%-20%.

 

Overall, in order to improve the luminous efficiency and reliability of LED chips, especially high-power LED package, encapsulation layers tend to be gradually replaced by phosphor practices with high refractive index. By doing so, both the uniformity and packaging efficiency can be improved dramatically.

Ten advantages of LED fluorescent tubes

The luminous efficiency of fluorescent lamps is about 55-80lm/W (the luminous efficiency of Philips T8 tubes is 72lm/W). LED fluorescent tubes can have a luminous efficiency as high as 100lm/W. Cree has announced that the luminous efficiency of their recently promoted XLampXP-G series can reach up to 130lm/W, and expected to reach 150lm/W two years later.

 

The luminous efficiency of fluorescent lamps is about 55-80lm/W (the luminous efficiency of Philips T8 tubes is 72lm/W).

 

Not all light emitted from LED chips/LED lighting boards can 100% reflected by reflectors / projectors. Fluorescent tubes can send out 360 degree light. In spite of using reflectors, some of opposite direction light will be inevitably wasted. Generally speaking, there will be about 30% light will be wasted for fluorescent tubes. The valid / lamp luminous efficiency of them is only 70% of the initial luminous efficiency. The general beam angle of LED fluorescent tubes is 120 degree. Almost all light is effective with the help of reflectors. In the view of many manufacturers and users, 120 degree is a narrow beam angle for fluorescent tubes. But this is enough in practical cases. As we mentioned before, the luminous efficiency of Philips T8 fluorescent tubes is 72lm/W, 36W fluorescent tubes can have an output luminance of 2592lm. Then the lamp efficiency of traditional fluorescent tubes is only 70%. Thus the valid luminous efficiency of the entire lamp is about 1814.4lm. Assumed that the luminous efficiency of LED fluorescent tubes is 100lm/W, a 18W LED tubes can have a output luminance of 1800lm. Sending out light with the same brightness, LED Tube Lights only consume half power than traditional fluorescent tubes do.

 

High power efficiency: All lights except for incandescent bulbs need special power supplies, including LED lighting products. Therefore, we need to take into account of power efficiency when we estimate the whole lamp efficiency. Take Philips 36W T8 fluorescent tubes for instance, the rated power of which is 36W. But as a result of accessing to magnetic ballasts, the actual measured power is 42.4W. The rest 6.4W is consumed by core inductors. Efficiency decreases to 85%. Most of domestic core inductors can consume more than 10W power due to their low quality, the power factor of them is lower than 0.512. Normally, the power efficiency of LED drivers / power supplies is as high as 90%. One 18W LED tubes only need a driver with output power of 20W. And the power factor is 0.9.

Major achievements of LED emergency lighting technology

“Studies of efficient driving technology and reliable system of emergency lighting applications” issued by Beijing University two years ago was concentrated on light source design, package technology, driver control circuit design and emergency lamp body design. After 2-year study, the research group developed new LED-related indoor emergency lighting devices with corresponding driver circuits and lamp body designs. In the mean time, the research group also participate the development of outdoor emergency lighting devices. Adding sound and light alarms, information indicators, direction guides on the basis of the original lighting features.

 

Studies of efficient driving technology and reliable system of emergency lighting applications

 

LED emergency lighting technology is mainly to solve the emergency function of semiconductor lighting control systems, with functions of day-to-day lighting, power off and audible and visual alarm for lamp failures, escape and relief emergency lighting functions. Through this project, the reliability, energy-saving capacity and technical performances of LED emergency lighting technology can be greatly improved.

 

Portable emergency lighting products are typically used to providing LED Street Lights for users in outdoor harsh conditions/environment. Semiconductor emergency lighting devices and their control systems have good portability, self-generating function, change and discharge capacity. Outdoor portable LED emergency lighting technology is necessary in wilderness and engineering rescue works.

 

“Studies of efficient driving technology and reliable system of emergency lighting applications” drove the market during the process of products industrialization and market promotion. LED emergency lighting market is an emerging market with huge potentials. Although the current situation is LED emergency lighting applications have not been fully accepted by the application market. But according to the special characteristics and adaptability of LED lighting technology, it is believed that in the future LED emergency lighting products will gradually take place of other traditional emergency lighting technologies in places of mines, shopping malls and corridors of buildings.

 

Semiconductors have very good energy-saving performances. Same brightness, LED lights consume only 10% energy of incandescent lamps, and 50% energy of energy-saving lamps. On the other hand, their service life can extend by several times. With the rapid development of LED technology and new LED applications, LED has obvious advantages in energy-saving effects. Energy-saving can extend the working time by 70%, high reliability enable them to be used in extreme environmental conditions. It is expected that within 5 years, LED emergency lighting products can widely take place to general emergency lighting applications.

Difficulties and innovations of integration technology of LED emergency lighting applications

LED technology just took the first step in the LED emergency lighting area. Advanced driver designs, emergency feature selections and sophisticated lamp body structure designs are all waiting for further development and innovation. Especially in the LED emergency lighting standards and reliability, our current technologies are still far behind international advanced technologies. Difficulties are:

 

LED packaging technology: a reasonable LED package structure is a technological key point to improve the light extraction efficiency and the photoelectric conversion efficiency of LED Tube Light  sources. Making reasonable LED structure designs to achieve a minimum light attenuation and meet cooling and design requirements of LED emergency lighting applications is a difficult point.

Difficulties and innovations of integration technology of LED emergency lighting applications

LED cooling technology: the cooling problem of LED package has become the main obstacle that restricts the development of high-powered LED lighting products. In order to effectively solve cooling problem of high-powered LED applications, engineers need to use materials with high thermal conductivity and low deterioration.

 

Secondary lighting distribution technology: the most important parameter of LED emergency lighting applications is to meet the requirement of both general indoor lighting and emergent lighting. Average luminance, luminance uniformity and working time are three major parameters. Through the secondary lighting design, combined with the LED Flood Light -emitting characteristics, engineers need to design package structures that meet the requirements of light distribution structure and emergency lighting basic functions.

 

LED intelligent control technology: Committing researches and studies of intelligent control systems and drivers in accordance with characteristics of LED light source is another difficult point of LED emergency lighting applications. Design the optimal control mode for emergency lighting applications; take study of control modes combined with all sorts of sensors to achieve multiple intelligent controls.

 

Innovations:

Light source design: using metal substrates or ceramic substrates with high thermal conductivities; using watt-level power-type LED chips or small integrated chips; making emergency lighting white-ray sources via sapphire chips + phosphors and the RGB mixing technology.

 

Optical design: LED can send out strong directional light, the optical design of LED is relatively difficult than traditional light sources. According to the light distribution characteristic, by optimization of lens and reflectors, designers can change the transmission path and direction of LED light, improving the luminous efficiency of LED emergency lighting products.

 

Cooling technology of LED lamps: cooling problems can be easily solved by using new materials and construction designs. Applying heat pipe with eutectic technology, directly connecting conductivity materials with LED chips can effectively conduct heat, and consequently extend the service life.

The importance of LED emergency lighting applications

Emergency lighting system is an important safety facility in the modern public buildings and industrial buildings, which is closely related with the personal/building safety. When fire or other disaster happened, the central control system will cut off power. Then emergency LED Panel Light system will come into work, playing an important role to evacuation, fire-fighting and rescue works. The continuous development of LED lighting technology and applications can change the status quo of lacking of standard general/emergency lighting products. Combined with the implementation of the national emission reduction plan, manufacturers start to develop new civil emergency semiconductor lighting products with energy-saving and environmental-friendly features. These lamps can provide sufficient luminance and lighting time for escape, rescue and rehabilitation of the power system in the event of an emergency. Engineers also developed special emergency lighting products with self-energy-generation function, portable, easy to operate, reusable, with self-protection function.

 

Emergency lighting system is an important safety facility in the modern public buildings and industrial buildings, which is closely related with the personal/building safety

 

In fires, earthquakes and other natural disasters, emergency lighting devices/equipments are necessary for escape and relief. It is estimated that, in the next three years, the total demand of semiconductor lighting products will reach up to more than 2 billion yuan. With the continuous growth of China’s economy, the social safety awareness and safety standards have been greatly improved, increasing the market demand and requirements for emergency lighting devices. These products not only need to satisfy basic requirements of emergency products, but also need to be more energy-efficient, user-friendly, reliable and durable. All this additional requirements give semiconductor lighting applications a large developing space.

 

Recently Beijing University released a new research topic: “Studies of efficient driving technology and reliable system of emergency lighting applications”. This topic intend to breakthrough key technologies in the industrialization of LED emergency lighting applications, improving the semiconductor lighting industry chain. This study will concentrate on the power supply development of LED emergency lighting applications, lamp body design, secondary optical light distribution design, overall thermal design, special driver, intelligent control system for LED emergency lighting applications. The major assessment indicators are: the luminous efficiency of LED light source should be larger than or equal to 100lm/W; thermal resistance should be less than 9 ℃ / W; the luminous efficiency of the whole lighting fixture should be larger than 80lm/W; color temperature: 3000-6000K; CRI: larger than 80; power factor: larger than 0.9; the current THD should be less than 20%; the power conversion efficiency should be larger than 80%.

Analysis of LED snow-covered landscape lighting applications

Snow-covered landscape art is a combination of snow/ice building and lighting art. Many lighting technologies were used as light sources of snow-covered landscape lighting applications, such like candlelight, incandescent lights and fluorescent lights. In spite of the increasingly mature of the sculpture and architectural art, those traditional light sources have seriously hindered the further development of snow-covered landscape lighting.

 

Snow-covered landscape art is a combination of snow/ice building and lighting art.

 

Under such circumstances, LED light source has many advantages, gradually becoming a developing trend in this field. Compared with traditional light sources, LED has many incomparable advantages: energy-saving, long service life, high reliability, environmental friendly, color changeable and dimmable. LED lighting is an emerging industry, especially in the field of snow/ice landscaping area. LED snow-covered landscape lighting applications face up great challenges. Special LED features must be fully understood by designers before creating beautiful snow-covered landscape buildings/sculptures with LED snow-covered landscape lighting applications. From the point of view of landscape designs, the projecting effect, brightness of LED lamps within ice sculptures and special presenting effects that lighting control system can realize become the most concerned issue. Designers need to take fully consideration of these issues, then take assessment to design plans through final lighting effects and model constructions.

 

LED snow-covered landscape lighting applications can be divided into two types: cast lighting mode and transparent lighting mode. Cast lighting mode can send light to the surface of buildings and sculptures, presenting the building facades and appearances mainly via surface reflection. Gradually, designers hope to create a type of ice sculptures can automatically emit light by themselves (invisible LED Street Light source), which is hardly achieved by traditional light sources. LED lighting technology provides possibility to ice building/sculpture amateurs. Designers take full use of the light emitting characteristics of LEDs, embedded them inside the ice buildings/sculptures. In this way, the optical normal axis of embedded LED light is perpendicular to the viewing direction. Thus LED lamps cannot be observed by viewers. They only can see the illuminated reflecting surface of ice sculptures. These embedded LED snow-covered landscape lighting applications have perfect presenting effects on the surface of ice bodies. Nowadays, LED lighting technology has already widely used in this area. These lamps need to have a large light radiated power. High-powered LED lighting devices will be more likely used in these snow-covered landscape lighting applications.

How to choose LED flat-panel TVs

As we all know, LED components have narrow Street Light spectrum, pure colors, thus very good and eye-catching performances in the color presenting. Even in stores (bright environment), LED flat-panel TVs still can clearly unfold details. Certainly, it has closed relations to features of LED components. It is their more advanced features that determine the high color saturation, wide color range of LED flat-panel TVs. Moreover, the new side-lighting mode LED LCD TVs can be made very thin, enabling LED LCD TVs to save more energy than ordinary LCD TVs. At present, Samsung, LG, Konka, Hisense and other manufacturers all have introduced side lighting mode LED TVs.

 

As we all know, LED components have narrow light spectrum, pure colors, thus very good and eye-catching performances in the color presenting.

 

Large-sized flat-panel TV is an inevitable developing trend. But what size is reasonable? Choosing suitable size based on the size of your individual housing space is the most reasonable way. Clearly, “the size of your individual housing space” mainly refers to the viewing distance (distance between your eyes and the TV screen).

 

LCD panel display technology can be divided into hard screen and soft screen. Soft screens mainly refers to the VA class, hard screens are also known IPS panels. IPS hard screens are more advanced in all aspects of performances: fast response, outstanding dynamic pictures, stable, wide viewing angle, better cost control. The greatest feature of IPS panels is that both of their poles are on the same surface, unlike other LCD mode electrodes, which are mounted in the upper and lower sides. Since electrodes on the same panel, regardless of the state, liquid crystal molecules are always parallel with the screen, decreasing the opening ratio and the transmittance. Therefore, IPS-based LCD TVs need more assistance of backlight, and consequently consuming more power in some extent.

 

It is one-sided to say that LCD TVs can work much longer than plasma TV sets. Certainly, LED flat-panel TVs have longer service life, due to their more sophisticated technology. Although the lifetime of liquid crystal materials can be said infinitely long, but the lifetime of liquid crystal materials are not equivalent to the whole service life of LCD TVs. Dead pixels may frequently occur because of the damage to LCD driver tubes. The marked 60,000-hour service life of LCD TVs is just the lifetime of backlight tubes. With current technology, backlight tubes cannot be replaced individually.

Technical advantages of LED backlight source

LED (Light Emitting Diode) is a type of semiconductor that can convert electrical energy to optical energy. LED technology has also been applied in LCD backlight applications. As a new generation backlight technology, LED backlight source has similar features with general LED components: low power consumption, high brightness, long service life. CCLF (cold cathode fluorescent lamp) is another commonly used LCD backlight source. Using health-harmful mercury as major material, CCLF is expected to be doomed in the future. Compared with traditional CCLF backlight, LED backlight source can save more than 40% energy, having significant advantages in this aspect. In addition, LED contains no harmful materials, zero contamination.

 

LED (Light Emitting Diode) is a type of semiconductor that can convert electrical energy to optical energy.

 

LED backlight source is composed of lattice-shaped semiconductors (each of the “grid” has one LED component). In this way, LED backlight LCD TVs can easily generate evenly distributed planar light, without any complex optical designs. Another additional benefit is that LCD can be made even thinner, and also with improved reliability and stability. CCFL belongs to tubular light source. In order to obtain evenly distributed light on the final light board, complex assisted optical components are needed. And the thickness of the screen is also difficult to control. With the increase of the panel, more light sources are needed, which makes the design and the production process even more complex.

 

LED backlight can send out evenly distributed light. In addition, they have far better performance than CCFL in the color presenting. LED Panel LCD backlight screens can easily realize NTSC 118% or gamut or even more. Due to the restriction of fluorescent materials, traditional CCFL backlight technology is relatively weak in the presenting of red color. Corresponding color filters also have dissatisfactory effects. Thus CCFL LCD TVs can only realize NTSC 65%-75% color range. Even improved CCFL LCD TVs can only obtain about NTSC 90% color range, impacting the image quality.

 

The average lifetime of LED backlight source is about 100,000 hours, even if used continuously for 10 hours every day, these light source can work for more than27 years. Thus, the light attenuation condition of LED backlight LCD TV sets is much better than that of CCFL backlight. Generally, the lifetime of CCFL backlight is about 25,000 hours. The latest top-CCFL backlight still have a lifetime time less than LED backlight – 60,000 hours. At the end of their lifecycle, the brightness of LCD will obviously reduce. Users have to replace the CCFL LCD backlight module.