2010-05-28

Super LED Manufactured by Diamond Islands Wafer-1

LED is revolutionizing humans lighting environments.  There have been timelines established to replace incandescent or fluorescent lamps worldwide.  However, the current white light LED is based on GaN semiconductor that is epitaxially deposited on either sapphire or SiC wafers.  Due to the non-equilibrium growth of GaN lattice on mismatched Al2O3 substrate, or defects ridden SiC, there are ample dislocations (e.g. 109/cm2) that may reduce the internal quantum efficiency of photon emission.  Worse still, the dislocations may propagate irreversibly upon heating.  This is why LED will dim with time.  In order to avoid LED chips from overheating, the heat blocking epoxy insulator on the circuit board is replaced by diamond like carbon (DLC).  The result is a dramatic decrease of the chip temperature.  
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2010-05-06

A Single Stage Flyback Power Supply Unit for LED lighting Applications

This paper presents a 75W single-stage power supply unit for LED lighting. The proposed power supply designed using flyback converter topology that is controlled by the critical conduction mode control. The secondary side of main transformer is directly connected to LED strings. By a constant current feedback circuit, this flyback converter directly regulates LED current. Although the proposed circuit doesn’t need input current-sensing and input voltage feed-forward, it can achieve high power factor for wide input range. A prototype experimental set-up has been built and tested. Through this experiment with a prototype set-up, the validity of the proposed circuit is verified.
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2009-12-29

How to choose LED Driver IC?

LED has established its unshakable position in the backlighting of portable devices. Even in the backlighting for the large-sized LCD panel, it has started to challenge the mainstream CCFL. In lighting, LED is especially popular in the market due to its highlighted features like energy-efficiency, environmental friendliness, long lifetime, and low maintenance. The driver circuit is a crucial and integral part of the LED. Whether in lighting, backlighting or the display panel, the choice of the technical architecture of the driver circuit must correspond to specific applications.
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2009-12-18

On the design and key elements of LED streetlights

In recent years, cross-strait development of various types of LED streetlights have been booming, particularly in 2008, when Taiwan and China both initiated several LED streetlight demonstration projects, spurring the growth momentum of LED industry.
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2009-07-24

Taking Advantage of SnapDriveTM to Improve the LED Display Screen Quality

Full-color LED video display screen has become popular in recent years for various applications such as indoor/outdoor commercial advertisement, stadium billboards, traffic message signs…etc. Thanks to the evolution of LED technology which enables lower cost, higher luminance, uniform wave-length and better efficacy LEDs available, the LED display screen makers are able to build high quality display screen with cheaper cost.
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2009-07-24

LED Encapsulation Process

Encapsulation is generally adopted in packaging of lamp-LEDs. The encapsulation procedure is to pour liquid epoxy into the LED moulding chamber first, and then insert the LED bracket that has undergone the press welding, then put the mould into the oven, and the LED gets shaped when the epoxy solidifies. The procedure of encapsulation sounds rather simple, while the following points should be paid attention to:
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2009-07-09

QFN Packaging Solves The Heat Dissipation Problem of LED Display

QFN Packaging Solves The Heat Dissipation Problem of LED Display Currently, almost all LED display manufacturers face the problem of heat dissipation during PCB design, with the thermal effect of drivers disturbing the normal light emitting property of LED and further influencing the color uniformity of the overall display. This article will illustrate how headaches can be prevented by changing the packaging of driving chips.
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2009-05-05

LED Digital Display

LED digital display is a semi-conductive lighting component, with light emitting diode (LED) as its elementary unit. By the number of segments the digital display is made of, there are 7-segment digital displays and 8-segment ones, with the latter with one more LED unit (also displays one more decimal point) than the former. By the number of the figure “8” displayed, there are 1-digit, 2-digit, 4-digit LED digital displays and so on. And by the way in which the LED units are connected, there are common anode digital displays and common cathode digital displays.  
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2009-03-18

On Factors Influencing Thermal Resistance of LED Components

The thermal resistance of a material is its resistance against thermal conduction. The unit of thermal resistance is degree per watt, representing the temperature difference across a structure when a unit of heat energy flows through it in a unit time. After the LED is lighted and the thermal conduction stabled, as every watt of power on the chip surface being consumed, the temperature difference between the PN junction and the linking bracket or heating panel is the thermal resistance value of the LED.
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2009-03-18

Fundamental Summary of LED SiC Substrate

Silicon carbide is also called "emery powder" or "refractory sand." The usual manufacturing process of SiC is to combine silica sand, tar (or coke), woodchip (and salt when manufacturing green SiC) and other materials in an electric resistance furnace at a high temperature. Silicon carbide is usually divided into two categories, the black SiC and the green SiC, both having a hexagonal crystal structure, a density of 3.2 -3.25g/cm³ and microhardness of 2840-3320kg/mm2.
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2008-11-12

LED —— The Fourth Generation of Automotive Light Source

The structure of modern automobile lamps is becoming more and more complicated, at the same time the function is being improved gradually. The development of automobile lamps has experienced four stages. The first generation of automotive light source is fuels (candles, coal oil or acetylene). These fuels burn to emit lights. Fuels can only satisfy the requirement of early stage automobile lamps due to its low luminous efficiency, weak light intensity, unstable performance, complex operation and etc. shortcomings.
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2008-08-20

The application of infrared LED

Common infrared LED that emits infrared rays has the same appearance with visible light LED. Its appropriate operating voltage is around 1.4v and the current is generally smaller than 20mA. Current limiting resistances are usually connected in series in the infrared LED circuits to adjust the voltages, helping the LEDs to be adapted to different operating voltages.
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2008-08-08

Advantages of LED fluorescent lamps

LED fluorescent lamp is the newest product line in the fluorescent family and is considered to be the final replacement for traditional fluorescent lamp. It is made up of white LED chip modules. Provided with the advantages of long life-span, radiation-free, energy saving, environmental friendly and stroboflash-free, LED fluorescent lamp is superior to other kinds of lamps.
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2008-07-31

On causes of LED lumen attenuation

LED lumen attenuation is the weakening of the light signal during transmission. LED products made by global leading manufacturers at the present stage have lumen attenuation in different grades after used for a period of time and this phenomenon also exists in high power LEDs. Then, what causes LED attenuation? Lumen attenuation is directly related to the temperature, and is mainly determined by the chip, phosphor used and the packaging technology. At present, lumen attenuation has become the chief problem for white LED to march into civil lighting field.
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2008-07-25

Common problems in the use of LED luminous letters and corresponding solutions

LED luminous letter (or caption machine) adopts light emitting diode as lighting source. It is usually installed on the top of buildings or on wall surface in the shape of given letters or signs. LED luminous letter chooses high brightness LED chips and uses specific system to take control of the dynamic video of the letters or signs. The unique designed LED luminous letter surpasses the traditional outdoor advertisement in function. Its abundance colors make it much superior than traditional neon light and make break through in application variety.
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2008-07-16

Classification of LED products

LED which is becoming widespread owns various kinds of product. LED products can be classified into different types according to light emitting colors, outer surface trait and structure of the diodes, luminous intensity, operating current, chip material, function and etc. This passage is going to introduce four types of LED products classification. 1. According to light emitting colors of the diode: LEDs are available in red, orange, green (subdivide into yellow-green, standard green and pure green) and blue and so on.
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2008-07-09

How to improve the brightness of LED display

LED brightness can be improved through the following two methods: 1. To increase the light output of the chip itself: light output can be increased through improving the luminescence efficiency of the chip’s active layer or improving the external light extraction efficiency by optimizing chips’ shape or making larger scale chips that run high density current.
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2008-07-02

A Brief Discussion on LED Packaging Technology

LED is the acronym of Light Emitting Diode. It is a kind of semiconductor device that is commonly used in indicator light and display board. LED is capable of transforming electric energy into light energy directly in high efficiency and its life-span can reach as long as tens of thousands hours to one hundred thousand hours. Compared to traditional bulbs, LED also bears the advantages of non-friable and power-saving and so on.
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2008-06-25

On Application of High Power LED to Signal Lamps

Alone with the extensive application of LED in every trade, high power LED is widely adopted as light sources in traffic, railway and electronic equipment signal lamps. As defined by its name, high power LED is provided with higher power and heat, with larger lumen than ordinary LED, thus enable it to shine brighter. Strict requirements are posed on the selection of high power LEDs used in signal lamps. Ordinary LED can not be used as signal lamps at random for the following reasons:
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2008-06-20

Range of New and Potential New Applications of LEDs

Nowadays, LED products are being used in numeric displays and indicator lights to a range of new and potential new applications, including exit signs, accent lights, task lights, traffic lights, signage, cove lighting, wall sconces, outdoor lighting and downlighting.The following is the list of LED applications:•    Streetlights•    Large scale video displays•    Architectural lighting•    Status indicators on all sorts of equipment
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2008-06-20

Analysis of High Power LED Reading Lamps

At present, three kinds of reading lamps are commonly seen in market: the traditional incandescent reading lamp, the halogen reading lamp and fluorescent reading lamp.The incandescent reading lamp and the halogen reading lamp are cheap and emit the light with good continuity, yet they consume much energy and produce heat. If the power is high, they shine too much to make people dazzle; if the power is too low, the intensity of illumination is lower than requested.
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2008-06-18

Some Basic Information of LEDs

LED stands for "light-emitting diode," a relatively new source of light. According to Wikipedia, the principle of generating light with a solid-state device was discovered early in the 20th Century, but it wasn't until the 1960s that useful LEDs became commercially available. Only recently have LEDs developed in brightness and color technology to be considered as sources of area illumination.
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2008-06-16

How Can a Light Emitting Diode Produce Light?

A diode is the simplest sort of semiconductor device. Broadly speaking, a semiconductor is a material with a varying ability to conduct electrical current. Most semiconductors are made of a poor conductor that has had impurities (atoms of another material) added to it. The process of adding impurities is cal doping.
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2008-06-12

The Light Emitting Diode Principle and Behavior

1. Characterizing a Light Source
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2008-06-06

LED Displays Promise Thinner, Sharper Laptops

A new screen technology promising sharper and more vivid images, longer battery life and slimmer designs promises to become the standard display for laptops, pumping fresh life into the PC industry.A crop of sleek, design-led laptops, featuring light emitting diode (LED)-backlit displays was on show at the Computex trade fair in Taiwan this week, using technology once the preserve of smaller gadgets such as toys, music players and mobile phones.
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2008-06-04

A matter of light: The ABCs of LEDs

Conserving energy is now a mandate, not a choice, and part of that mandate is the need to go Green. When it comes to lighting, we can easily imagine the impact of globally improving the efficiency of lighting sources by 10 percent. But what if it could be improved by 1,000 percent?
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2008-05-28

Classification of LED Displays

A. LED displays can be classified into two types according to locations applied: indoor LED display and outdoor LED display1. Indoor LED display
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Osram Opto Semiconductors now enables remote control functionality to be incorporated in a lower profile than ever before thanks to the first flush-mountable infrared LED. The compact side-looking T-shaped Midl... READ MORE

Cree, Inc. introduces the new 8000-lumen LMH2 LED Module, a no-compromise, easy-to-use solution for high-ceiling applications. The 8000-lumen LMH2 is designed to replace 150-watt ceramic-metal-halide (CMH) lamps while using only 63 percent of ... READ MORE