An LED LAMP is a light-emitting diode (LED) product that is assembled into a lamp (or light bulb ) for use in lighting fixtures . LED lamps have a lifespan and electrical efficiency which are several times greater than incandescent lamps , and are significantly more efficient than most fluorescent lamps , with some chips able to emit more than 300 lumens per watt (as claimed by Cree and some other LED manufacturers). The LED lamp market is projected to grow by more than twelve-fold over the next decade, from $2 billion in the beginning of 2014 to $25 billion in 2023, a compound annual growth rate (CAGR) of 25%. As of 2016, LEDs use only about 10% of the energy an incandescent lamp requires.
Like incandescent lamps and unlike most fluorescent lamps (e.g. tubes and compact fluorescent lamps or CFLs), LEDs come to full brightness without need for a warm-up time; the life of fluorescent lighting is also reduced by frequent switching on and off. The initial cost of LED is usually higher. Degradation of LED dye and packaging materials reduces light output to some extent over time.
Some LED lamps are made to be a directly compatible drop-in replacement for incandescent or fluorescent lamps. An LED lamp packaging may show the lumen output, power consumption in watts, color temperature in kelvins or description (e.g. "warm white"), operating temperature range, and sometimes the equivalent wattage of an incandescent lamp of similar luminous output.
Most LEDs do not emit light in all directions, and their directional characteristics affect the design of lamps, although omnidirectional lamps which radiate light over a 360° angle are becoming more common. The light output of single LED is less than that of incandescent and compact fluorescent lamps; in most applications multiple LEDs are used to form a lamp, although high-power versions (see below) are becoming available.
LED chips require controlled direct current (DC) electrical power and an appropriate circuit as an LED driver is required to convert the alternating current from the power supply to the regulated voltage direct current used by the LEDs. LEDs are adversely affected by high temperature, so LED lamps typically include heat dissipation elements such as heat sinks and cooling fins .
LED drivers are the essential components of LED lamps or luminaries. A good LED driver can guarantee a long life for an LED system and provide additional features such as dimming and control. The LED drivers can be put inside lamp or luminaire, which is called a built-in type, or be put outside, which is called an independent type. According to different applications, different types of LED drivers need to be applied, for example an outdoor driver for street light, an indoor point driver for a down light, and an indoor linear driver for a panel light.
* 1 History
* 1.1 Examples of early adoption
* 2 Technology overview * 3 Application * 4 Effects on plants
* 5 Household LED lamps
* 5.1 Replacement for existing lighting
* 5.1.1 Lamp sizes and bases * 5.1.2 LED tube lamps
* 6 Specialty uses
* 7 Comparison to other lighting technologies
* 7.1 Comparison table
* 8 Limitations
* 8.1 Efficiency droop
* 9 See also * 10 References * 11 Further reading * 12 External links
Before electric lighting became common in the early 20th century, people used candles, gas lights, oil lamps, and fires. Humphry Davy developed the first incandescent light in 1802, followed by the first practical electric arc light in 1806. By the 1870s, Davy's arc lamp had been successfully commercialized, and was used to light many public spaces. The development of a steadily glowing filament suitable for interior lighting took longer, but by the early twentieth century inventors had successfully developed options, replacing the arc light with incandescent lights.
The first LEDs were developed in the early 1960s, however, they were low-powered and only produced light in the low, red frequencies of the spectrum. The first high-brightness blue LED was demonstrated by Shuji Nakamura of Nichia Corporation in 1994. The existence of blue LEDs and high-efficiency LEDs led to the development of the first 'white LED', which employed a phosphor coating to partially convert the emitted blue light to red and green frequencies creating a light that appears white. Isamu Akasaki , Hiroshi Amano and Nakamura were later awarded the 2014 Nobel prize in physics for the invention of the blue LED.
In the USA, the Energy Independence and Security Act (EISA) of 2007
authorized the Department of Energy (DOE) to establish the Bright
Early LED lamps varied greatly in chromaticity from the incandescent lamps they were replacing. A standard was developed, ANSI C78.377-2008, that specified the recommended color ranges for solid-state lighting products using cool to warm white LEDs with various correlated color temperatures. In June 2008, NIST announced the first two standards for solid-state lighting in the United States. These standards detail performance specifications for LED light sources and prescribe test methods for solid-state lighting products.
Also in 2008 in the United States and Canada, the
The Illuminating Engineering Society of North America (IESNA) in 2008 published a documentary STANDARD LM-79, which describes the methods for testing solid-state lighting products for their light output (lumens), efficacy (lumens per watt) and chromaticity.
In January 2009, it was reported that researchers at Cambridge University had developed an LED lamp that costs £2 (about $3 U.S.), is 12 times as energy efficient as a tungsten lamp, and lasts for 100,000 hours. Honeywell Electrical Devices and Systems (ED"> LEDs as Christmas illumination in Viborg, Denmark
In 2008 Sentry Equipment Corporation in
In 2009 the exceptionally large Christmas tree standing in front of
Turku Cathedral in
In 2009 a new highway (A29) was inaugurated in Aveiro ,
By 2010 mass installations of LED lighting for commercial and public uses were becoming common. LED lamps were used for a number of demonstration projects for outdoor lighting and LED street lights . The United States Department of Energy made several reports available on the results of many pilot projects for municipal outdoor lighting, and many additional streetlight and municipal outdoor lighting projects soon followed.
LED light used in photography
General-purpose lighting needs white light. LEDs emit light in a very narrow band of wavelengths, emitting light of a color characteristic of the energy bandgap of the semiconductor material used to make the LED. To emit white light from LEDs requires either mixing light from LEDs of various colors, or using a phosphor to convert some of the light to other colors.
The two simplest methods of producing white light LEDs are
The second basic method uses LEDs in conjunction with a phosphor to produce complementary colors from a single LED. The most common method is to combine a blue LED with a yellow phosphor, producing a narrow range of blue wavelengths and a broad band of "yellow" wavelengths actually covering the spectrum from green to red. The CRI value can range from less than 70 to over 90, although a wide range of commercial LEDs of this type have a color rendering index around 82.
The colors available from both the basic types of white light LED is adjustable to a certain extent, with color temperatures in the range of 2,200 K (matching incandescent lamps) up to 7,000 K are widely available. Higher CRI values can be obtained using more than three LED colors to cover a greater range of wavelengths. Tunable lighting systems employ banks of colored LEDs that can be individually controlled, either using separate banks of each color, or multi-chip LEDs with the colors combined and controlled at the chip level.
A significant difference from other light sources is that the light
is more directional, i.e., emitted as a narrower beam. LED lamps are
used for both general and special-purpose lighting. Where colored
light is needed, LEDs that inherently emit light of a single color
require no energy-absorbing filters. BAPS Shri Swaminarayan
Mandir Atlanta Illumination with color mixing LED fixtures
Computer-led LED lighting allows enhancement of unique qualities of
paintings in the National Museum in
White-light LED lamps have longer life expectancy and higher efficiency (more light for the same electricity) than most other lighting when used at the proper temperature. LED sources are compact, which gives flexibility in designing lighting fixtures and good control over the distribution of light with small reflectors or lenses. Because of the small size of LEDs, control of the spatial distribution of illumination is extremely flexible, and the light output and spatial distribution of an LED array can be controlled with no efficiency loss.
LEDs using the color-mixing principle can emit a wide range of colors by changing the proportions of light generated in each primary color. This allows full color mixing in lamps with LEDs of different colors. Unlike other lighting technologies, LED emission tends to be directional (or at least lambertian ), which can be either advantageous or disadvantageous, depending on requirements. For applications where non-directional light is required, either a diffuser is used, or multiple individual LED emitters are used to emit in different directions.
EFFECTS ON PLANTS
Experiments unraveled surprising performance and production of
vegetables and ornamental plants under LED light sources. A large
number of plant species have been assessed in greenhouse trials to
make sure that the quality of biomass and biochemical ingredients of
such plants is comparable with, or even higher than, those grown in
field conditions. Plant performance of mint, basil, lentil, lettuce,
cabbage, parsley and carrot was measured by assessing both the health
and vigor of the plants and the success of the LEDs in promoting
growth. Also noticed was profuse flowering of select ornamentals
including primula, marigold and stock.
HOUSEHOLD LED LAMPS
REPLACEMENT FOR EXISTING LIGHTING
Disassembled LED-light bulb with driver circuit board and Edison screw
Lamp Sizes And Bases
LED lamps are made of arrays of SMD modules that replace incandescent
or compact fluorescent lamps, mostly replacing incandescent lamps
rated from 5 to 60 watts. Such lamps are made with standard lamp
connections and shapes, such as an
As of 2010 some LED lamps replaced higher wattage bulbs; for example, one manufacturer claimed a 16-watt LED lamp was as bright as a 150 W halogen lamp. A standard general-purpose incandescent bulb emits light at an efficiency of about 14 to 17 lumens/W depending on its size and voltage. According to the European Union standard, an energy-efficient lamp that claims to be the equivalent of a 60 W tungsten lamp must have a minimum light output of 806 lumens. A selection of consumer LED bulbs available in 2012 as drop-in replacements for incandescent bulbs in screw-type sockets
Some models of LED lamps are compatible with dimmers as used for
incandescent lamps. LED lamps often have directional light
characteristics. These lamps are more power-efficient than compact
fluorescent lamps and offer lifespans of 30,000 or more hours,
reduced if operated at a higher temperature than specified.
Incandescent lamps have a typical life of 1,000 hours, and compact
fluorescents about 8,000 hours. The lamps maintain output light
intensity well over their lifetimes.
Several companies offer LED lamps for general lighting purposes. The technology is improving rapidly and new energy-efficient consumer LED lamps are available.
As of 2016 , in the United States, LED lamps are close to being adopted as the mainstream light source because of the falling prices and because 40 and 60 watt incandescent lamps are being phased out. In the U.S. the Energy Independence and Security Act of 2007 effectively bans the manufacturing and importing of most current incandescent lamps. LED lamps have decreased substantially in pricing and many varieties are sold with subsidized prices from local utilities. A 17 W tube of LEDs which has the same intensity as a 45 W fluorescent tube
LED Tube Lamps
Main article: LED tube
LED tube lights are designed to physically fit in fixtures intended for fluorescent tubes . Some LED tubular lamps are intended to be a drop-in replacement into existing fixtures if appropriate ballast is used. Others require rewiring of the fixtures to remove the ballast. An LED tube lamp generally uses many individual Surface-Mounted LEDs which are directional and require proper orientation during installation as opposed to Fluorescent tube lamps which emit light in all directions around the tube. Most LED tube lights available can be used in place of T8, T10, or T12 tube designations , T8 is D26mm, T10 is D30mm, in lengths of 590 mm (23 in), 1,200 mm (47 in) and 1,500 mm (59 in).
LIGHTING DESIGNED FOR LEDS
Newer light fittings designed for LED lamps, or indeed with long-lived LEDs built-in, have been coming into use as the need for compatibility with existing fittings diminishes. Such lighting does not require each bulb to contain circuitry to operate from mains voltage .
White LED lamps have achieved market dominance in applications where high efficiency is important at low power levels. Some of these applications include flashlights , solar-powered garden or walkway lights, and bicycle lights. Monochromatic (colored) LED lamps are now commercially used for traffic signal lamps, where the ability to emit bright monochromatic light is a desired feature, and in strings of holiday lights. LED automotive lamps are widely used for their long life and small size (allowing for multiple bulbs), improving road safety. LED lamps are also becoming popular in homes, especially for bathroom and medicine cabinet lighting.
COMPARISON TO OTHER LIGHTING TECHNOLOGIES
See luminous efficacy for an efficiency chart comparing various technologies.
Incandescent lamps (light bulbs) generate light by passing
electric current through a resistive filament, thereby heating the
filament to a very high temperature so that it glows and emits visible
light over a broad range of wavelengths.
Incandescent sources yield a
"warm" yellow or white color quality depending on the filament
operating temperature .
Incandescent lamps emit 98% of the energy
input as heat. A 100 W light bulb for 120 V operation emits about
1,700 lumens, about 17 lumens/W; for 230 V bulbs the figures are 1340
lm and 13.4 lm/W.
Incandescent lamps are relatively inexpensive to
make. The typical lifespan of an AC incandescent lamp is 750 to 1,000
hours. They work well with dimmers. Most older light fixtures are
designed for the size and shape of these traditional bulbs. In the
U.S. the regular sockets are E26 and E11, and E27 and E14 in some
COST COMPARISON FOR 60 WATT INCANDESCENT EQUIVALENT LIGHT BULB (U.S. RESIDENTIAL ELECTRICITY PRICES)
Incandescent Halogen CFL LED (EcoSmart clear) LED (Philips) LED (Cree)
Purchase price $0.41 $1.17 $0.99 $5.65 $2.03 $4.99
Watts 60 43 14 6.5 8.5 9.5
lumens (mean) 860 750 775 800 800 815
lumens/watt 14.3 17.4 55.4 123.1 94.1 85.8
CRI 100 100 82 80 80 85
Lifespan (hours) 1,000 1,000 10,000 15,000 10,000 25,000
Lamp lifetime in years @ 6 hours/day 0.46 0.46 4.6 6.8 4.6 11.4
Energy cost over 20 years @ 11 cents/kWh $289 $207 $67 $31 $41 $46
Total cost over 20 years $307 $259 $70 $48 $51 $56
Total cost per 860 lumens $307 $297 $78 $52 $55 $59
COMPARISON BASED ON 6 HOURS USE PER DAY (43,800 HOURS OVER 20 YRS)
In keeping with the long life claimed for LED lamps, long warranties are offered. However, currently there are no standardized testing procedures set by the Department of Energy in the United States to prove these assertions by each manufacturer. One manufacturer warrants lamps for professional use, depending upon type, for periods of (defined) "normal use" ranging from 1 year or 2,000 hours (whichever comes first) to 5 years or 20,000 hours. A typical domestic LED lamp is stated to have an "average life" of 15,000 hours (15 years at 3 hours/day), and to support 50,000 switch cycles.
Incandescent and Halogen lamps naturally have a power factor of 1, but Compact fluorescent and LED lamps use input rectifiers and this causes lower power factors. Low power factors can result in surcharges for commercial energy users; CFL and LED lamps are available with driver circuits to provide any desired power factor, or site-wide power factor correction can be performed. EU standards requires a power factor better than 0.5 for lamp powers up to 25 Watt and above 0.9 for higher power lamps.
ENERGY STAR QUALIFICATION
* Reduces energy costs — uses at least 75% less energy than incandescent lighting, saving on operating expenses. * Reduces maintenance costs — lasts 35 to 50 times longer than incandescent lighting and about 2 to 5 times longer than fluorescent lighting. No lamp-replacements, no ladders, no ongoing disposal program. * Reduces cooling costs — LEDs produce very little heat. * Is guaranteed — comes with a minimum three-year warranty — far beyond the industry standard. * Offers convenient features — available with dimming on some indoor models and automatic daylight shut-off and motion sensors on some outdoor models. * Is durable — won’t break like a bulb.
To qualify for
* Brightness is equal to or greater than existing lighting
technologies (incandescent or fluorescent) and light is well
distributed over the area lit by the fixture.
Many will not work with existing dimmer switches designed for incandescent lamps.
Color rendering is not identical to incandescent lamps which emit close to perfect Black-body radiation as that from the sun and for what eyes have evolved. A measurement unit called CRI is used to express how the light source's ability to render the eight color sample chips compare to a reference on a scale from 0 to 100. LEDs with CRI below 75 are not recommended for use in indoor lighting.
LED lamps may flicker. The effect can be seen on a slow motion video of such a lamp. The extent of flicker is based on the quality of the DC power supply built into the lamp structure, usually located in the lamp base. Longer exposures to flickering light contribute to headaches and eye strain.
LED efficiency and life span drop at higher temperatures, which limits the power that can be used in lamps that physically replace existing filament and compact fluorescent types. Thermal management of high-power LEDs is a significant factor in design of solid state lighting equipment.
LED lamps are sensitive to excessive heat, like most solid state electronic components. LED lamps should be checked for compatibility for use in totally or partially enclosed fixtures before installation as heat build-up could cause lamp failure and/or fire.
The long life of LEDs, expected to be about 50 times that of the most common incandescent lamps and significantly longer than fluorescent types, is advantageous for users but will affect manufacturers as it reduces the market for replacements in the distant future.
The human circadian rhythm can be affected by light sources. The effective color temperature of daylight is ~5,700K (bluish white) while tungsten lamps are ~2,700K (yellow). People who have circadian rhythm sleep disorders are sometimes treated with light therapy (exposure to intense blueish white light during the day) and dark therapy (wearing amber-tinted goggles at night to reduce blueish light).
Some organizations recommend that people should not use bluish white lamps at night. The American Medical Association argues against using bluish white LEDs for municipal street lighting.
Research suggests that since the shift to LED street lighting attracts 48% more flying insects than HPS lamps, which could cause direct ecological impacts as well as indirect impacts such as attracting more gypsy moths to port areas that have ships that could give the pests a transoceanic pathway. These moths cause forest defoliation that impacts birds and causes economic losses.
The term "efficiency droop" refers to the decrease in luminous efficacy of LEDs as the electric current increases above tens of milliamps (mA) . Instead of increasing current levels, luminance is usually increased by combining multiple LEDs in one lamp. Solving the problem of efficiency droop would mean that household LED lamps would require fewer LEDs, which would significantly reduce costs.
In addition to being less efficient, operating LEDs at higher electric currents creates higher heat levels which compromise the lifetime of the LED. Because of this increased heating at higher currents, high-brightness LEDs have an industry standard of operating at only 350 mA. 350 mA is a good compromise between light output, efficiency, and longevity. Thermal management of high-power LEDs often involves using heat sinks to keep the junction temperature at lower levels.
Early suspicions were that the LED droop was caused by elevated temperatures. Scientists proved the opposite to be true — that, although the life of the LED would be shortened, elevated temperatures actually improved the efficiency of the LED. The mechanism causing efficiency droop was identified in 2007 as Auger recombination , which was taken with mixed reaction. In 2013, a study conclusively identified Auger recombination as the cause of efficiency droop.
* ^ "How Energy-Efficient