作者：Blade

Compartments that determine the lifetime of LED down lamps

There are three compartments of LED down lamps that can determine their lifetime: LED beads (LED chips car led ), LED power supplies (LED drivers), cooling sections. LED beads are the core part of LED down lamps, which will directly determine their performances and service lives. Currently, most high quality LED beads are from Cree (American) and Nichia (Japan). Other LED chip manufacturers with higher cost performances are Epistar, Everlight from Taiwan and Sanan optoelectronics, Yingrui from the mainland.

 

Compartments that determine the lifetime of LED down lamps

 

Undoubtedly, Cree is the best LED chip manufacturers in the world, LED lights used these beads have higher output luminous flux, longer service life, but also higher selling prices. These products are more suitable for European and American markets. Chips from Taiwan are weaker than Cree chips in performances, but still have very long lifetime, can be afforded by customers from developing countries and regions, like the mainland, Southeast Asia and Mid-east.

 

LED power supplies are the heart of LED down lamps, having significant influences on them. LED down lights usually work under 110-220VAC. Since the development of LED lights is relatively shorter than other traditional lamps, the Chinese Government still has no uniformed standard for LED power supplies. Currently, LED power supplies that sold in domestic market have different qualities, different standards, many of which have very low power factor (PF) and cannot pass the EMC electrical tests. The lifetime of electrolytic capacitors within power supplies are directly determine the lifetime them. In order to reduce the cost as low as possible, producers tend to use low quality electrolytic capacitors, which will weak the efficiency of power supplies, making “long lifetime” LED down lamps become “short life” lights.

 

The cooling design of LED down lights also impacts their lifetime magnificently. Heat generated by LED beads will be conducted to PCBs and finally covers, then dissipated into the air though covers. Among these parts, it is the PCBs’ heat dissipation performances that determine the quality of cooling sections. PCB must have a higher thermal conductivity. The thermal conductivity of grease should be good enough. The cooling area of the enclosure should be large enough. Reasonable design of these parts can maintain the working temperature of PN junctions under 70 degrees, which can guarantee the normal working conditions of LED down lights.

General analysis of LED down lamps’ current situation

Recently, China’s National Development and Reform Commission released an announcement: “Plans for phasing out incandescent lights in China”. According to this announcement, from 1st October of 2012, incandescent lights with power consumptions higher than 100W will be banned in the mainland. And from 1st October of 2012, incandescent lights with power consumptions higher than 15W will be banned in the mainland. That means the ordinary incandescent lighting applications will leave the stage of the lighting history. As the most advanced lighting technology today, LED lights has emerged in the market and been known by customers.

 

Recently, China’s National Development and Reform Commission released an announcement

 

Since the invention of LED lights, their brightness has constantly and stably upgraded (from LED indicators to intelligent LED street lights), implying that LED lights will become the dominated lighting applications on day. Similarly, LED down lamps also transformed from the high-en lighting products to the new darling of general application market.

 

Down lights is a type of indoor lighting applications, which can be used in shopping malls, offices, factories, hospitals and also houses. LED down lamps inherits all the advantages of traditional down lights, besides they also have typical features of LED lighting technologies: less heat dissipation, save more energy, can work for a long time, small costs of maintenance and replacement. In the early stage of development, because of the over-expensive of LED chips, LED down lamps were hardly accepted by end users. However, the reduction of LED chip prices and together with the improvement of cooling section designs made it is possible for LED down lights to seize the commercial lighting market.

 

LED chips, lamp covers and drivers (power supplies) compose the main body of LED down lights. single LED chips with high power are more suitable for LED down lighting applications. Low-powered LED chips, like 5050, 5630 are more suitable for LED panels, since they cannot provide sufficient light when used individually. The normal distance from lamp bodies to the ground for indoor lighting products is around 4-5 meters. Definitely, only high-powered single LED chip can meet such requirements. The most common used high-power LED chip for LED down lights is 1W LED chip, which can be used to make 1W, 3W, 5W, 7W and 9W (25W tops) LED down lights.

Incandescent lamps have comprehensively banned in EU, a new era for LED lighting applications

31st August 2012 is the deadline for the EU Government to comprehensively ban incandescent bulbs in any countries and regions within EU. Our researchers visited several large supermarkets and electrical stores in Brussels and found that low-wattage (less than 40W) incandescent lights have been completely replaced by energy-saving lamps with the similar power consumption.

 

Incandescent lamps have comprehensively banned in EU, a new era for LED lighting applications

 

The comprehensive ban of incandescent bulbs in EU presents the end of 100 years of “Edison Era”. As early as March 2007, the European Commission put forward proposals to replace incandescent lights with other more energy-saving lighting technologies. In March 2009, the European Commission formally adopted an order to phase out incandescent lights gradually.

 

Related tests showed that only 5% of the electrical energy can be converted to optical energy for incandescent lights, the remaining 95% energy will be converted into wasted heat. It is obvious that the elimination of incandescent lights is inevitable. Banning is mainly for the reduction of carbon dioxide emissions. It is showed that if replace incandescent lights with energy-saving lights in all EU member states, the saved electricity can supply Romania for one year.

 

The elimination of incandescent lights means the expansion of the market of new energy-saving lamps. Nowadays, among all kinds of energy-saving lamps, it is LED lighting applications and energy-saving lamps (compact fluorescent lamps) has become the two main lighting tools with higher cost-effective.

 

In assessments conducted by related institutes to all kinds of lamps available in the market, LED always obtained a high score. LED lighting applications have many advantages: high energy efficiency, environmental friendly, long service life, beautiful appearance and high luminous efficiency. They have broad market prospects. Compared with incandescent lights and city street light , the energy-saving ratio of LED lighting applications can reach up to 90%. Although, the current selling prices of LED lights are much higher, they can work 25 times longer than incandescent lights. Experts pointed out that the production costs of LED lamps will reduce with the improving of LED technology. Accordingly, the LED’s price dropping is just a problem of time. Studies published by McKinsey Analysis suggested that a current 20 euros LED lights will be sold on 3 euros in 2020. Some experts predicted that with the decline in the production cost of LED lights, these high-tech lighting products will go into mass production stage from next year.

India announced the latest trends of the LED lighting industry

Electronics For You is a flagship magazine of EFY Group. Recently, EFY has published a latest report for the LED lighting industry in India. Although LED lighting technology has a lot of advantages compared with other traditional lamps, like longer service life, more environmental friendly, more energy efficient, and less health-hazarded, LED products still cannot be mass produced in India as a result of the over-expensive initial production costs. Therefore, in India, almost every LED makers are eager to create a kind of LED lighting products that are completely competent for commercial operations, just like incandescent bulbs does. They still need innovations on the road to achieving this goal.

 

India announced the latest trends of the LED lighting industry

 

The luminous efficiency and output luminous flux of LED lights doubled every 36 months, as well as the total performance, which is consistent with Moore’s Law. In the past few years, LED lighting technology has been improved in many aspects: performance, color and quality. Based on different application solutions, the color temperature can be fixed within the range of 2700K to 6500K. And 70-95 for color rendering index (CRI). The life cycle of White-ray LED lighting applications have reached up to 100,000 hours, which dramatically reduces maintenance and replacement costs.

 

The report pointed out that the entire LED lighting industry is very optimistic, full of innovations:

 

1)       Omni-directional LED lights, just like incandescent lights does. If LED lights want to be the benchmark of general lighting industry, omni-directional lighting is necessary. Only the omni-directional LED lamp technology is able to provide solutions for multi-directional lighting modes. As a matter of fact, the LED lighting industry in India was followed this direction all the time, from the very early stage of development to now, from the simple equivalent LED lighting technologies to traditional lamps, from single-color LED lights to RGB LED applications, from lamps to intelligent lighting system.

2)       Organic LED. It is expected that this kind of LED lights can be the most environmental friendly lighting technology in the future due to their small size and high performance.

3)       Clever design. This provides an alternative for traditional incandescent lamps, similar parameters and output optical energy.

4)       Non-contact phosphor technology. This technology was mainly invented to reduce the cost.

5)       AC LED lamps. These lamps can maintain the same output optical output with DC LED lamps. There will be no need to conduct the AC to DC conversion.

The surge of China’s LED chip production triggered global overcapacity crisis

LED chips produced by China’s manufacturers and led enterprises can generally be divided into two types: 1. cheap but low performance. Mainly used as backlight of keyboards, children’s toys, shoes, and power indicators; 2. good quality LED chips used in high-end products. Normally, manufactures produce this type of LED chips would co-operate with large foreign companies. Currently, the soared increasing of China’s LED chip production led to the global market overcapacity. Dropping prices of LED chips is inevitable.

 

The surge of China’s LED chip production triggered global overcapacity crisis

 

In recent years, governments all around the world made great efforts to support the LED industry, subsidized related infrastructure, improved the efficiency of LED chips, drove the penetration in emerging markets, established special funds to develop industry standards, etc. The goal is attracting more LED manufacturers to invest and build factories.

 

The Chinese Government is undoubtedly the most hard-working government in the world that in the promoting of LED lighting technology. On one hand, every domestic manufacturer that invested the new epitaxial reactors could get a 1.5 million USD from the government, which has occupied nearly 75% of the total cost. On the other hand, the government expected a rapid development of every LED manufacturer and provided low-interest loans, tax breaks and ultra-low prices of land rent (or even free) for new-born LED manufactures. It can be said that the substantial support of the Chinese Government that indirectly the surge of China’s LED chip production and accordingly the overcapacity crisis in the global lighting market.

 

Ross Young, senior vice president of IMS Research indicated that “All of these LED chip makers can benefit from the growth of LED equipment investment. A large amount of Chinese LED companies have declared to enter the sapphire market (a typical LED chip material). They must have seen the opportunities and huge potentials behind the market.” Among these enterprises, a large part is successful poly-silicon manufacturers with potential advantages in the development of sapphire substrates. As for the organic metal, gas sources and MOCVD equipments, China’s LED chip manufacturers still relied on overseas imports. Mr. Young also indicated that applied materials companies have handed over the first set of MOCVD to the Chinese Government. Korea epitaxy reactor vendor Jusung started to target the Chinese market due to the falling of domestic sales. Meanwhile, Taiyo Nippon Sanso from Japan also turned to the Chinese market.

The America Government decided to installed LED road lighting applications to reduce urban crime rate

The American Austin City Police Department and Austin Energy Board cooperated recently to provide more protections to their residents. Since 2011, the crime rate of Austin was significant increased. In order to control this phenomenon, these two institutions planned to installed LED road lighting applications at three most dangerous places in Austin.

 

The America Government decided to installed LED road lighting applications to reduce urban crime rate

 

Austin Energy spokesman Carlos Cordova announced that “criminals do not like to commit offenses in broad daylight and also in well-lit places. They do not want to be seen when they do bad things.”

 

According to the requirements of local Police Department, Austin Energy erected 25 pieces LED street lights in three “most dangerous places”. “LED lights are more energy efficient. That is the reason why at the same power consuming level, LED lights send out more light than other traditional lamps.” It has also been proved that, places that installed LED road lighting applications are much brighter than before. Cordova also said that “in good lighting environment, people can enjoy their recreational activities, need not to worry about security issues.”

 

The test results of the 8th and the 9th Avenue were really satisfactory. It seems that urban lighting projects also became one of a series of policies against urban crime. From 2011 to the early of 2012, the violent crime rate of Austin grew by 15%. But by July, 5 months after LED street lights have been installed, the violent crime rate only grew by 7.8%. The local government indicated that they were planning an even larger LED-technology involved city lighting project, in which around 70,000 pieces LED lamps will be updated. This project will still be conducted by Austin Energy and supported by the local government.

 

This new LED lighting products can reduce the crime rate effectively. Japan is the first country that applied this technology to reduce the exaggerated urban crime rate. At first, these lamps have been named as LED guard lights, gradually replaced traditional fluorescent lamps and were installed in narrow streets. Besides, it has been proved that blue-rays can make people calm down. Some LED guard lights would be made in blue light.

 

In the mean time, City of Pontiac, Michigan, USA also replaced some of their traditional road lamps with LED street lights. Totally 112 pieces LED street lamps (approximated $68,3800) were used.

Analysis of LED resin luminous words

Resin luminous words have several requirements for lighting sources:

1)       The complex constructions and various specifications of LED resin luminous words requested that the lighting source should have versatility.

2)       Since the maintenance of fully installed LED resin luminous words is extremely inconvenient, in order to reduce the maintenance cost, lighting sources should have longer service life than other lighting sources.

3)       LED resin luminous words should have sufficient brightness to be readable.

 

Resin luminous words have several requirements for lighting sources

 

Resin luminous words are mostly used in super-tine light-emitting advertising boards. Similar to other applications used for commercial purposes, resin luminous words usually need to maintain normal working conditions for a long time. In order to reduce the electrical cost, merchants were looking for lighting sources with longer service life and higher energy efficiency. LED resin luminous words emerged at this moment.

 

There are several things need to be noticed for using LED technology making resin luminous words in addition to the stability: setting beam angle according to the specific requirements; brightness and wavelength should within the allowed range. Only choosing right LED products in different specifications can guarantee the final effect and minimize the production cost at the same time.

 

Outdoor landscape LED lighting systems is a hot topic in the current society, which may impact the sustainable development of human. For the power-relied lighting industry, energy-saving green lighting technologies were always the followed direction. The birth of semiconductor green lighting sources has been considered as a great revolution in the lighting history. Gradually, semiconductor light emitting diodes (LED and order led ) transmitted from the special lighting market to the general lighting market, known by more and more people. They have good future. Among them white-ray LED lighting products have demonstrated huge performance advantages, strong momentum of development and rapid growth in market demand. LED lamps may probable become the mainstream in the lighting market in the next five years.

 

As one of the latest LED lighting sources, compared with other traditional lighting sources, white-ray LEDs can save more than 20% energy than the former and have much longer lifetime (100,000 hours, nearly 10 times longer than incandescent lights). In addition, they are more reliable, saving more costs in maintenance. Working under low DC voltage (no more than 5V) makes them portable. Therefore most emergency lights choose to use white-ray LEDs as lighting source.

Three development steps of LED ceiling panels

With the continuous innovation in LED lighting technology, LED gradually took place of some traditional lighting products both in the commercial area and in the industrial area. In many developed countries, LED has been treated as main lighting applications. LED ceiling panels, LED track lights, photonic crystal led ,LED bulbs, LED tubes and other LED indoor lighting applications have been widely used in some commercial places in where the over-expensive electrical bills were always a big trouble for managers. In this article, we will discuss about the three development steps of LED ceiling panels.

 

With the continuous innovation in LED lighting technology, LED gradually took place of some traditional lighting products both in the commercial area and in the industrial area.

 

First step: in the very early stage of development, LED was praised for features of high lighting efficiency (low power consuming) and long service life. But the over-expensive selling prices (high production costs) drove them apart from the residential market. Most of people still could not afford them. But during this period, LED ceiling panels began to attract the attention of commercial users. Compared with traditional lighting sources, LED lamps are more energy effective and more durable. Thus they are more popular among commercial applications.

 

In the second stage, LED lighting applications has been recognized and accepted by the lighting market, especially for LED ceiling panels. More features of LED lamps have been gradually prominent, like environmental protection, small size, high reliability, etc. LED manufacturers developed a series of products that completely different from traditional lighting sources, extending the developing space for the lighting industry. It was in this period that LED started to be recognized as the 4th generation lighting source. It made people realize that lighting sources did not only play the role of lighting tools any more, they were also a part of decorations of your house.

 

With the development of new technology (internet of things), as a semiconductor industry, LED will also catch a tour of such high-speed train and present the characteristic of high controllability. Form household decoration to office construction, from streets to tunnels, from assisted lighting tools to major lighting tools, LED ceiling lamps with intelligent control systems will bring more sophisticated services to us. Other LED lamps will complete the transformation from making products to design products, providing more comprehensive and more advanced solutions for us.

Brightness controlling design for LED street lighting products

At present, in the area of high-brightness LED street lighting drivers, there are two major solutions that widely used in the world: “special power chip” and “switching power supply with discrete electrical components”. In order to meet the needs of intelligentization, single chip microcomputers (SCM) are usually embedded into devices as the CPU. Thus both of these two solutions can be classified as “system supervisory + power controlled traditional multi-chip technology program”. However, this sort of sophisticated solution has a lot of disadvantages: multiple chips and complex constructions. When using on LED street lighting products that need to drive multiple LED strings with high brightness, this shortcoming is particularly prominent.

 

Brightness controlling design for LED street lighting products

 

The new Piccolo TMS320F2802x/3x MCU adapted the latest architecture technology and enhanced peripherals. The minimum package size is 38 pins, providing 32-bit real-time control functions for low cost LED street lighting products. The real-time control are usually embedded with intelligent devices, like solar micro-inverters, LED lighting applications light solution , large household appliances, hybrid board battery industry, automotive applications, etc. to realize the implementation of advanced algorithms, higher system efficiency and accuracy.

 

The Buck-type switching power supply is one of the most widely used power solutions. This type of power supply can make the entire system work in the continuous inductor current mode by choosing correct output inductor and switching frequency. LED lighting Demo based on TMS320F28027 fully adapted working principles of Buck-type switching power supplies, combined with multi-PWM channels (8 channels tops) and ADC modules (16 channels tops) to realize the closed-loop control of current.

 

This single-chip solution for high-brightness LED street lighting products combined system management and power supply control, dramatically reducing the complexity of hardware constructions and meanwhile improving the flexibility of driver circuit designs. LED street lighting products applied this solution can automatically control multiple parameters, like current amplitude, on-off period, on-off mode, ambient brightness and system temperature by changing the memory of CPUs. They have basic properties as below:

 

1)       Low cost – single-chip realize multiple constant current control, eliminating the need for a dedicated constant current chip, which effectively reduces the production cost.

2)       High efficiency – non-insolated power supplies, without any magnetic flux leakage loss causing by transformers. The overall efficiency can reach up to 95% at fully loaded.

3)       Strong driving ability – 8-channel non-isolated current driver output can drive 8 strings (not less than 14 chips per string). The total output power is not less than 100W.

Power consumption and costs control of multi-LED applications

In this article we will introduce to you an effective method to control the brightness and consequently the power consumption and costs of multi-LED applications. Providing each LED a PWM controller and converting input voltage to LED current via this controller is a traditional brightness control method for multi-LED applications. This application applied voltage-controlled PWM controllers. Usually, led pn junction  will be cascade with a current-sensing resistor, which will send feedback voltage signals to controllers. Basically, this type of controllers operated in the voltage mode and maintained the feedback voltage signal at a fixed value, stabilizing the internal current.

 

Power consumption and costs control of multi-LED applications

 

Using multiple RGB LEDs to generate white rays is a common application. In addition to red rays, green rays and blue rays, there will be 1-2 more LED chips that used to swift LED white rays into a certain tone. In order to simulate the proportion of red rays, green rays and blue rays in the white ray spectrum, working current for these three different types of LED chips will be fixed at a certain ratio by three controllers. Normally, the output green rays occupy 50-64% of total, 25-40% for red rays, and blue rays only account for 5-15%. In this way, at least three PWM controllers are needed, which increases the production costs virtually. Each controller provides power for each colored LED. In addition, the control system also needs to change the brightness of LED lamps by adjusting the load cycle of PWM controllers.

 

Another approach is applying single-current driver onto theses cascaded LED chips. The brightness of each LED chip is controlled by FET switches, which is connected with these chips in parallel. When FET is turned on, current will pass through it, stopping the parallel connected LED chip. On the contrary, switching off FETs will drive the current to pass through LED chips. Another system is responsible for the control of on-time ratio of LEDs in each clock cycle, including the three cascaded single-current controlled LEDs. The brightness of each LED will be adjusted by each FET. Compared with the three individual PWM controllers mentioned above, multi-LEDs with one PWM controller but multiple FETs will costs much less and save more power consumption. Removing each PWM controller will reduce the load dramatically and reduce the power consuming accordingly.