Present status and future development of LED lighting technology

LED lighting technology status quo and future development
LED more popular than other types of light sources, the reason is not a mystery. According to the US Department of Energy's solid-state lighting research and development program, and high intensity discharge (HID) light bulbs, fluorescent tubes and energy saving lamps (CFL), halogen and incandescent lamps, compared, LED lamps have a higher performance and longer lifetime.
· A cool white LED's for maximum efficiency is 132 lm / W (l / W), while incandescent only a mere 15 lumens / watt, both life were 50,000 and 1,000 hours. The power consumption of buy led high bay lamps is used only 20% of incandescent lamps - which are growing importance in the global energy prices higher, but its shortcomings. Philips AmbientLED A19 replacement lamps cost about $ 40, while the incandescent lamp is not more than one US dollars. LED and energy-saving advantages of long-ordered, you can compensate for this shortcoming. Expected next year, the cost difference between the two will narrow to the current quarter.
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US Department of Energy estimates that if all people are switching to solid-state lighting, so that by 2020, the savings of electricity to meet the needs of 32 million households. LED has saved energy, equivalent to 250,000 households with electricity.
In addition, LED output level has reached 150 lm / W, and continues to rise. Several manufacturers of high-brightness LED LED, can provide a wide range of colors lighting. For example, Cree LR6 downlight production company, using a patented method of mixing colors, the light emitted by comparable incandescent, but 85% reduction in power consumption than incandescent lamps, while life expectancy is its 50-fold (Fig. 2) .

Energy-saving products as an alternative to incandescent lamps, LED bulbs proficiency continues to improve, the price decline. For example, LEDtronics PAR Series LED 90% energy than incandescent bulbs (Figure 3).

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These LED bulbs can use 120V AC power, you can also adjust the light in the 90-290V AC range, medium Edison screw lampholders and G824 pin plug-in lamps, including PAR20 (7-W), 30 (12-W) and 38 (15-W) types. Allegedly generation LEDtronics PAR bulbs 20% energy efficiency high on these products, you can directly replace power up to 100W incandescent and halogen lamps.
Today is a very important advantage.
LED bulb purchase cost in total cost of ownership only one factor, which involves not only lower energy costs, but also lower maintenance and replacement costs. Sandia National Laboratories is estimated that today's LED lighting is the incandescent bulb has twice the cost of a lifetime, is 10 times the cost of fluorescent ownership. But the lab also predicted that by 2020, the cost of ownership of LED lighting will be one of 10 points incandescent, fluorescent half.


Businesses and organizations hoping to save tens of thousands of dollars a year in energy costs above, this is the main force to promote LED lighting the way to change. Many shopping malls, shops, offices and interior and exterior buildings, all in turn LED. Bridges, tunnels, highways, streets, parking lots, airports also have adopted the stage and LED lighting.
Engaged in the design, development, manufacture and sale of high-efficiency LED solutions Lighting Science Group report, are busy installing its high performance and ultra-efficient lights, such as Definity MR16 system in these places. Simon Property Group booth at the mall, and these lights are being used to replace the original halogen lamps. The company said its fully adjustable Definity products of high efficiency light than halogen 80%, 50% higher light output than many other light sources.

One challenge facing the LED designer and the user is no standardized interface between the light source and the driving circuit. Zhaga European Union launched an industry-wide action to develop standards for LED light engine specifications. LED light engine is to have a predetermined interface LED modules, LED interface regardless of the type of technology and the internal light engine used.
Zhaga will enable products from different manufacturers are interchangeable months. By the definition of a variety of special light engine interface, you can achieve interchangeability. Zhaga standards will cover the physical dimensions, as well as optical, electrical and thermal properties of LED light engines.
Optimize your drive design
LED driver is a complex task. This is because the application of LED lighting may change. Efficiency and color accuracy and other performance parameters will be greatly affected the way the LED driver. Peter DiMaso Lighting Products Division, director of marketing strategies Texas Instruments Power explains: ". LED drive mode can affect performance, color temperature and color shift (caused by fever) and flicker effect"
Patrick Carner Texas Instruments C2000 microcontroller unit (MCU), marketing director agree with this view. He also pointed out that TI claims that its Piccolo MCU can be used for LED driver solution that allows designers to "further the hardware and software used in digital power control." The company's C2000 dc-dc LED lighting developer tool shows that the drive power of a single or a plurality of shared electrode require appropriate power supply topology (Figure 4).

The use of high current and low stack voltage drive LED, and the need to meet Energy Star and Lighting Facts Label requirements and European standards, has become a challenge. Lighting Facts Label by the US Department of Energy and the Environmental Protection Agency (EPA) developed jointly. One countermeasure is to use fewer LED elements with higher current to drive, in order to obtain a higher level of light output.
Use less of the LED, means that you can reduce product costs, but not necessarily conducive to improving the efficiency levels required by EPA. In fact, the efficiency levels tend to decline, it was noted that the situation in the early A19 and E27 bulb retrofit applications. Power efficiency is too low level.
With the improvement of the level of the output light, LED drive becomes more complicated. According Haitz law, for a given wavelength of light (color), the unit cost of packaged LED lumen decreased 10 times every 10 years, the amount of light generated by each LED package is increased by 20 times. With the continuous improvement of the light output, efficacy LED package in some applications (for about 1 kilometer of residential lighting and commercial lighting about 10 km) will become more limited.
Although today's LED technology can easily meet these needs, but in the next few years, LED will be limited to specific applications, and limited commercial significance, unless LED drive technology innovation and thermal management have been greatly developed. In this regard, the solid-state lighting industry is progressing steadily impressive, but the next few years, this trend can be maintained remains to be seen.
When a higher current drive time, LED performance in flux. Higher current not only lead to higher lumen output, and will significantly improve the temperature so that the environment is much higher than the LED temperature. It is estimated that 70% of the LED efficacy as heat distributed, you must remove the heat by conduction or convection. This is the traditional incandescent LED want to replace incandescent light bulbs in stark contrast.
According to Jeff Perry, senior development director for National Semiconductor, 100W incandescent bulb efficiency of only 2.2%, while the best quality LED efficiency is only about 30% of the market. However, most of the heat of incandescent lamps emit infrared radiation by the way. LED is not the case, it needs to take advantage of the heat sink and fan control. The higher the temperature, the shorter the mean life and reliability decrease (Fig. 5).

Vintage LED driver topologies early solid-state lighting products used primarily to modify the original voltage regulation scheme has been difficult to see in today's LED. Further, LED's are used for solid state lighting dedicated. For example, LED A19 / PAR bulb uses a different type of modification than LED street lighting and MR16 applications. Recognizing this point, LED manufacturers now offer a dedicated LED elements.
The new LED driver is more complex advanced. They can sense the drive current level can be adjusted when the current exceeds recommended levels. They are also able to compensate for changes caused by heat and aging, to ensure the stability of the light output. And their degree of thermal protection circuitry allows the LED to minimize the damage caused by overheating, better protection against LED failure due to overheating.
LM3464 and LM3424 National Semiconductor drive employs a thermal management by reducing the output current to regulate the LED remains within the maximum operating temperature range. National Semiconductor has introduced the LM3445 LED driver to meet European EN61000-3-2 standard, total harmonic power exceeding 25 W lighting products distortion imposes strict limits (Figure 6). In order to achieve power factor correction (PFC) requirements, use of the drive so that the input current PFC to remain in phase with the input voltage.

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STMicroelectronics HVLED offline led high bay light for sale having a primary sensing feedback (Figure 7). This high-voltage pulse-width modulation (PWM) current-mode controller to a low-voltage PWM controller with a 800-V power MOSFET combined in a microwave SO16N package (8.75- by 3.99-mm) into. It uses AC power, accuracy ± 5% or less, and provide quasi-resonant zero-voltage switching function. It is adapted for E27 and GU10 lamps.
IC drives can also be used in more and more applications that backlight, including TVs, notebook computers, mobile phones and other consumer electronics products. Advanced Analogic Technologies AAT14xx series of 31-mA single-channel boost LED driver that can drive a string of up to 10 LED. AAT14XX has a 1.15 x 1.55 mm wafer-level package (WLCSP) size. According to the company, AAT14XX series provides 10-pin WLCSP package, the size of 80 percent more than the 1.3- by 2.9-mm SOT23 package smaller than 55% of 2- by 2-mm QFN package is small.
Microsemi Corp. recently announced a reference design that enables lower-cost LCD panel produces higher quality images. The design takes advantage of Sony's CXD473063 timing and lighting controller, and Microsemi Company for 3D LCD TVs DAZL! LED driver technology. Microsemi's two-chip solution includes DAZL! 2000 Series 32-port LX24232 logic chips, and 8-port LX23108L LED driver power chip.
Driven clusters LED, such as lighting applications up to 20 or more for each string of LED, there may be problems. An LED failure will lead to a whole string goes out. For this problem, Bourns LSP series shunt can protect a single LED string LED.
For manufacturing, the yield is the key
LED solid-state lighting to get more and more widely adopted in large-scale manufacturing LED wafer above and achieve a higher yield, is the key to reducing its costs. Most LED current is produced in 2 inches and 4 inches above the sapphire wafer GaN-based, there are inconsistencies yield problems, so the need for color brightness, forward voltage and other variables to detect and produce the results bins.
Plus assembly and packaging steps, LED costs will rise even higher. The current yield is generally 30% or less. In fact, experts predict 2020 will reach 40% or higher.
LED manufacturers plan the next few years of transition to 6-inch wafers, followed by 8-inch wafer, a higher yield MOCVD epitaxial process. By strictly controlling the temperature, flow and material composition, can make a big wafers. LG Electronics last year, six-inch wafer production above the LED. Philips Lumileds and Lextar close to do that. Some companies will be next year 8-inch wafer production samples.
"If the LED industry continues to grow in the future, the power must come from the general lighting field," European Photovoltaic Industry Alliance (EPIC) Secretary-General Tom Pearsall said, "and it continued to make significant progress depends on all aspects, ranging from basic research and materials until product design and manufacturing efficiency. "EPIC is a non-profit organization dedicated to the promotion and development of LED industry in Europe.