LED retrofit lamps have started to show up on retail shelves. Many players in the LED industry are giddy about the anticipated growth over the next few years. Nevertheless, the road to success for LED lighting will not be completely smooth, as there are a number of pitfalls to navigate.
Bumps in the road ahead for solid-state lighting article gives a picture of the expected pitfalls. Some of the potential problems ahead are pricing, color quality, thermal management, regulatory, and consumer education. While most of these issues are not technical, the design engineer will nonetheless need to understand them.
While white LEDs are very efficient light sources, converting approximately one-third of the input power into light, the remaining two-thirds is converted into heat in the LED. Currently impossible to passively cool an LED that outputs 1,500 lm (the typical output of a 100-W light bulb) in the physical confines of the normal light bulb size form factor. So at 100 lm/W, about 10 W must be continuously and rapidly dissipated while keeping the LED well below maximum operating temperature (typically approximately 120ºC).
Thermal management will get somewhat easier in the future. As LED efficiencies improve, the thermal management improves by approximately the square of the efficiency, because the total power supplied to the LED decreases and the percentage of heat generated by that input power also decreases by the same amount.
Color quality may be the most difficult problem to solve. The industry has spent tremendous time and expense in measuring and controlling the color variability of white LEDs. But color temperature and tight chromaticity binning don’t tell the complete story, because two light sources with identical chromaticity coordinates may have very different wavelength spectra. LED spectrum is very different from the incandescent’s spectrum. If the spectra are too different, non-white surfaces will appear to be different colors under the two light sources. The Color Rendering Index or CRI is a measure of how closely the perceived color of a surface illuminated by a particular light source will be to the perceived color of the same surface under incandescent illumination. A CRI of 100 is a perfect match. A CRI above 80 for an LED is considered good.
In the short term, LED retrofit bulbs will make the initial splash, but in the long term there are great opportunities for custom LED luminaires. LEDs make possible much more complex form factors and consequently can create more interesting and useable illumination patterns than traditional bulbs and CFLs. Imagine a luminaire that not only is dimmable, but one that you can select the color temperature you desire.
When LED efficiencies reach the 150 lm/W range, it will become feasible to increase office lighting to 1,000 lux, as opposed to the 300 lux now typical in most office spaces.
86 Comments
Tomi Engdahl says:
Piccolo development kit targets LED lighting and communications
http://www.edn.com/article/520764-Piccolo_development_kit_targets_LED_lighting_and_communications.php
Texas Instruments recently announced the F2802x 32-bit TMS320C2000 Piccolo microcontroller ac LED-lighting and communications developer’s kit. The kit provides a differentiated platform for ac-mains-powered intelligent luminaires. It includes hardware and software support for remote connectivity, walking developers through implementation examples of leading lighting-communications protocols, such as DALI (digital addressable-lighting interface), DMX512, and PLC (power-line communications).
Tomi Engdahl says:
One critical parameter that needs to be improved before there is widespread acceptance of LED lighting is the CRI (Color Rendering Index). This number is typically not published, possibly because very few manufacturers are able to produce LED solutions with a decent CRI. For accectance as a replacement for incadescent lighting, the CRI must be at least 90.
Imagine the home decorator who walks into the living room and sees the “new look”. Today’s LED lights will be replaced with the former incandescents immediately!
Source: http://www.edn.com/blog/PowerSource/41609-Cree_ups_lumens_Watt_AND_lumens_dollar_with_new_LEDs.php
Plastic food container says:
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Tomi Engdahl says:
http://www.tukes.fi/fi/Ajankohtaista/Tiedotteet/Sahko-ja-hissit/Led-valaistustuotteiden-toiminnasta-loytyi-useita-puutteita/
LED lighting products, research revealed a number of weaknesses
LED lighting products, activities found in the Finnish Security Agency (tukes) and 17 other EU markets supervisory authority of the campaign plenty of flaws. Products tested, only 17 percent met all their prescribed electromagnetic compatibility (EMC) requirements.
The EU market surveillance authorities were testing a campaign within the 168-LED lighting product.
The campaign was implemented in 2011.
Test results showed that over a third of examined products sent to its environment more electromagnetic interference than allowed.
In addition, nearly one-half (47 percent) tested produced a product to the mains harmonic currents over the allowable amount of lighting products.
At the moment there is no specific defined the requirements of LED lamps for harmonic currents, but now the research in mind the tests carried out show that the requirements should take early steps to prepare.
A very significant weaknesses were found in LED lighting products required documents. CE marking and declaration of conformity were appropriate and in good condition, only about 30 per cent of the tested products.
- It seems that the manufacturers have not paid sufficient attention to the EMC requirements. Safety Technology Authority intends to continue the LED lighting products for enhanced control of the EMC this year, the first devices have been tested, Mustonen says.
Tomi Engdahl says:
LED light: Overall lousy color rendering – What can be done to fix this?
http://www2.electronicproducts.com/TechXchange_Forum.aspx?mode=thread&id=3061#3795
One thing I have noticed about “white” LEDs is although they simulate white light across the color temperature range, they are actually “peaky” from a spectrum point of view, most with a strong blue peak and another strong yellow to yellow-orange peak. That is going to have a drastic effect on color rendition.
How to improve the color “filling” of LED based lamps for reading with smooth and uniform color mixing at competitive cost?
Some recent lamps have very high color rendering capability. See for example
Bright LED modules give high color rendition
http://www2.electronicproducts.com/Bright_LED_modules_give_high_color_rendition-article-oprc05_nov2011-html.aspx
Intended for lighting applications in which rendition of color is paramount, the XSM Artist 1000 series LED module delivers up to 1,000 lm with an average CRI (Ra) greater than or equal to 95.
Intematix Phosphor Blend Accomplishes Near Perfect Light Quality for LEDs
http://www2.electronicproducts.com/Intematix_Phosphor_Blend_Accomplishes_Near_Perfect_Light_Quality_for_LEDs-article-newsrc01_13_oct2011-html.aspx
98 CRI milestone for light quality drives LED adoption in retail, hospitality, residential and museum applications
Intematix Corporation, a leading innovator of patented phosphor materials and components for high-quality LED lighting, today announced that it has demonstrated a phosphor blend that provides a near perfect color rendering index (CRI) of 98 and R9 value of 99 when applied to a reference LED package.
“Reaching 98 CRI is huge it means that by adding Intematix phosphor, an LED package can render true color,”
Tomi Engdahl says:
New Cooling Technology Uses Air “Bullets” to Shoot Down Overheated LEDs
http://www.scientificamerican.com/article.cfm?id=led-cooling-bullets
Light-emitting diodes generate much less heat than traditional lightbulbs, but the heat they do radiate makes them dimmer and cuts short their life spans
If an LED system does not have an effective way of getting rid of excess heat, rising temperatures will damage LED components, dimming the light and curtailing its lifetime, according to the U.S. Department of Energy.
“LEDs may generate less heat,” he adds, “but it still needs to be removed.”
SynJet, a synthetic jet technology that features a diaphragm that moves up and down when voltage is applied. “We use an electromagnetic approach very much like a speaker. SynJet’s nozzles can be placed within a millimeter or two from the heat sink.”
When SynJet’s diaphragm moves, each pulse creates a “bullet” of air, Wilcox says. Because SynJet’s airflow is more thermally efficient, less air is needed to provide cooling and the system as a whole makes less noise than a fan does, he says.
Tomi Engdahl says:
Capacitor selection helps achieve long lifetimes for LED lights
http://www.leds.edn.com/blog/leds-blog/capacitor-selection-helps-achieve-long-lifetimes-led-lights?cid=EM_EDNMicro
Consumers often see LED lamp failures.
One major issue is that LED lighting environments are very stressful for the power supply. LED lamps will typically run at full load for their entire operating period and they operated in an extremely high ambient environment.
With that introduction, let’s begin by looking at what causes LED power supplies to fail. There are two basic causes: heat and time. As the temperature rises, the likelihood of LED lamp failure increases and, as we have noted, high temperatures (often in excess of 90°C) are the norm for LED lamps.
When we examine the effect of heat, we find that the optocouplers and aluminum electrolytic capacitors are the most vulnerable components in the power supply.
We are going to concentrate on what happens to an electrolytic capacitor in the circuit, how heat affects it over time, and what happens when the electrolytic capacitor gets to the end of its life. We will then look at how to fix the problem by removing electrolytic capacitors from key circuit locations.
Tomi Engdahl says:
Another advantage of LED lights: They don’t attract bugs, and here’s why
http://edn-mail.com/portal/wts/cemciv2dodsaed7wzL6Tgxif-ueyvb
Gary Trott, a product development innovator for Cree LED Lighting, noticed that the LR6 down lights installed at the entrance to Cree four years ago had no bugs in them. This is a remarkable characteristic for most lights.
Gary set out to find the reason why LED lights don’t attract bugs, and came across the answer pretty quickly: Most bugs are hard-wired with UV receptors. He asked Marianne Shockley Cruz, Ph.D., with the University of Georgia Department of Entomology, to summarize research about insects and light attraction, which she did in the paper “Insect Vision: Ultraviolet, Color, and LED Light.” In a nutshell:
“Color sensitivity in the UV spectrum plays an important role in foraging, navigation, and mate selection in both flying and terrestrial invertebrate animals. This attraction to UV light has made insects a useful model for understanding visual sensitivity to UV light.”
…which is why electronic bug zappers use UV light sources to attract insects. Specifically, one study indicated moths were most susceptible to the 405nm range where the Cree LR6 down light puts out almost no light.
Tomi Engdahl says:
LEDs provide more light pollution
Light pollution is expected to rise 6-20 percent annually worldwide populated areas. The Finnish Environment Institute senior researcher Jari Lyytimäki assess the problem had grown significantly in Finland.
New types of lamps such as LED lights offer the possibility to use the lights in places where before it might not come to mind either, such as the use of decorative lights at the cottage.
Completely natural darkness may be lost in Finland
Source: http://www.3t.fi/artikkeli/uutiset/teknologia/ledit_tuovat_lisaa_valosaastetta
Tomi Engdahl says:
Poor Lamp Socket Design Sparks Danger
http://www.designnews.com/author.asp?section_id=1367&doc_id=241948&cid=Newsletter+-+Made+by+Monkeys&dfpPParams=ht_13,bid_240,aid_241948&dfpLayout=blog
This fitting connects the shell to power-line neutral. Perhaps a loose fit or differences in thermal expansion of materials caused a slow increase in resistance between the brass and aluminum. That resistance led to a hot spot.
It’s a shame that the move to LED lights hasn’t sparked ideas for new types of lamp sockets and a new lamp-base style that overcomes design problems. Automotive lamps provide good examples of simple sockets that make bulbs easy to install and extract and ensure good connections.
Perhaps someone could design a practical and safe push-in/pull-out socket for LED bulbs. This type of socket would simplify changing bulbs, too.
Mismatched materials, cheap manufacturing techniques, and inattention to quality could lead to disasters. For lamp sockets, at least, it’s time for a new approach to design, materials, and manufacturing quality. Also, look for UL and CSA markings before you buy electrical products.
Tomi Engdahl says:
Cree claims R&D record for white LED: 254 lm/Watt
http://www.edn.com/blog/PowerSource/41719-Cree_claims_R_D_record_for_white_LED_254_lm_Watt.php?cid=EDNToday_20120412
Cree says that the R&D version of the white LED’s efficacy was measured at 254 lumens per watt, at a correlated color temperature of 4408 K at standard room temperature, 350 mA. In the past Cree has said it takes about a year for the R&D version of a device to go into generally available production quantities, so we can look for a commercial version in Q2 2013.
Cree’s previous record was 231 lm/Watt.
The device is built on a silicon carbide-based wafer technology that features advancements in LED chip architecture and phosphor
Tomi Engdahl says:
$60 Light Bulb Debuts On Earth Day
http://news.slashdot.org/story/12/04/17/1642229/60-light-bulb-debuts-on-earth-day
How much would you pay for an amazing light bulb? On Sunday — Earth Day — Philips’ $60 LED light bulb goes on sale at Home Depot and other outlets. The bulb, which lasts 20 years, won a $10 million DOE contest that stipulated the winning bulb should cost consumers $22 in its first year on the market.
ON COMMENT:
No point in buying a bulb which lasts 20 years. By 2020, there would be more efficient bulbs and this would be banned. And by 2020, both Google and Facebook would have capability to report to the Govt what bulb you turn on, the ban will also work on products which have already been purchased before the ban.
Tomi Engdahl says:
Cirrus tackles dimmer compatibility challenges with digital LED controller
http://www.edn.com/blog/PowerSource/41715-Cirrus_tackles_dimmer_compatibility_challenges_with_digital_LED_controller.php?cid=EDNToday_20120417
Cirrus Logic’s initial entry into the LED lighting market indicates that the company believes the key to success in this highly-competitive sector lies in achieving near-100% compatibility with the existing base of old-fashioned TRIAC dimming switches. The company has tested its new CS161X LED controller family, based on Cirrus’ new digital TruDim technology, with over 200 dimmer switches from around the world, and says the controller achieved 97percent compatibility.
According to Cirrus, the closest competitive LED controller performed at 71%, and the average among today’s current LED controllers was 50% compatibility.
Interestingly, the newer, so-called “digital” dimmers are the most difficult dimmers to ensure compatibility.
Tomi Engdahl says:
Why MR-16 lights are an attractive LED lighting product
http://www.edn.com/blog/PowerSource/41727-Why_MR_16_lights_are_an_attractive_LED_lighting_product.php?cid=EDNToday_20120418
Lighting Science Group (LSG), the largest producer of LED bulbs in North America, has broadened its product line to include the MR-16 light.
LSG’s MR16 Definity HO (high output) LED lamp consumes just 8W and produces up to 550lm: At 3000K if produces 66lm/W. The lamp has a 25,000-hour rated design life.
First, while MR-16s aren’t as ubiquitous in the US in the residential market as they are in Europe, they are quite popular here in commercial and display lighting
Second, display lighting such as you’ll find in general retail lighting is directional, which suits the spot light source of an LED better than the glowing unidirectional element of a halogen lamp, the traditional technology for MR16s.
And thirdly, MR16 have no constraints that they be dimmable as do the first generation of LED lights that replace incandescent bulbs
All this is not to say MR16s are an easy design-in for LEDs. Both Cree, Philips, and start-up Soraa have introduced LEDs specifically for the space-constrained design challenges of the tiny lamps, which have a a global market in the billions, with 1B in Europe alone. (Getting away from having to support temperamental TRIAC dimmers is enough to make them an attractive market.)
Tomi Engdahl says:
LED array holders bring solderless assembly to solid-state lights
http://www.edn.com/blog/PowerSource/41728-LED_array_holders_bring_solderless_assembly_to_solid_state_lights.php?cid=EDNToday_20120419
LED arrays are gaining traction in the lighting world, where their ability to cram many LED emitters into a single small package makes them attractive for high-intensity lighting. Also referred to as chip-on-board (COB) LEDs, the arrays pack in multiple LED components more closely than can be achieved with individual LED packages, making for a brighter light source as well as a larger emitting source.
Arrays can be either shared (fried-egg) phosphors or with each LED in the array having its own phosphor.
Along with higher-performance, these LED arrays can be more expensive than single-emitter packages.
And, while the arrays are smaller than the equivalent made up of individually packaged LEDs, the array package is still large and hand soldering – whether for repair or initial production – can be a challenge. For this reason the connector companies have developed high-temperature plastic LED array holders that feature no-solder compression contacts.
Tomi Engdahl says:
Simplified luminaire design with LED modules
http://www.eetimes.com/design/smart-energy-design/4371466/Simplified-luminaire-design-with-LED-modules?cid=EM_EDNMicro
LED modules in which the complete drive electronics is included simplify the design of modern luminaires.
Acrich 2 modules, made by Seoul Semiconductor, are available in different brightness levels and can be driven direct from the AC network without a ballast.
Applications of the module start from modern luminaries to complex illumination systems but also conventional replacement bulbs and tubes. Benefits of the Acrich 2 are reduced weight, high life time, high efficacy and good power factor which gives tremendous long term potential for power savings in many illumination application.
The Acrich2-IC is available for AC drive voltages of 90 – 120V (100V) / 100 – 144V (120V) / 200 – 264V (220V / 230V / 240V) and a nominal output power of 4 and 8 Watt. Based on that product range the typical AC drive voltages all over the world can be addressed. Power factor is 90%, lifetime with a minimum of 87.000h.
While designing a light fixture the designer has to consider that no hot components are unprotected and touchable by the user
Tomi Engdahl says:
Next week’s LightFair (aka LEDFair) promises newest in solid-state lighting
http://www.edn.com/blog/PowerSource/41754-Next_week_s_LightFair_aka_LEDFair_promises_newest_in_solid_state_lighting.php
Next week is the lighting industry’s pre-eminent trade show, LightFair, which to be as accurate as possible should change its name to LEDFair. The show fills up the massive Las Vegas Convention Center, and virtually every booth there is showing off LED-based lights. Which is a little strange because as it stands today, LEDs have very little penetration into the general lighting market.
Lighting isn’t like consumer electronics, susceptible to the whims of consumers who generally have very similar needs.
Building owners expect lighting systems to last for 10-20 years, so unless it’s a new construction, it’s not a slam dunk that a building owner is going to embrace a new LED-based light system. True, often (if all goes well) the payback in energy savings can make LED lights attractive, but unlike residential lighting, most commercial lighting already uses relatively efficient fluorescent lighting, so the payback may not be fast enough to pry a building owner’s wallet open.
Here’s a slide that IMS Research presented at LEDs 2012 last October:
It predicts that this year, 2012, is the year that LEDs in lighting finally start to show a pulse, gaining momentum and overtaking incandescent/halogen in five years. In revenue, they become dominant by the end of 2013, which is why no lighting company wants to be left without higher-margin LEDs in its product portfolio.
Every year, several power IC vendors announce that they’ve created the perfect LED dimming IC. Who will it be this year?
Tomi Engdahl says:
Balancing power parameters in LED apps
http://www2.electronicproducts.com/Balancing_power_parameters_in_LED_apps-article-fapo_Fairchild_may2012-html.aspx
The challenge for a low-power LED design is to keep power conditioning, conversion, and load control in balance
Low-power LED solutions typically consist of a single string of LEDs or a single input and output control point for the LED driver. These drivers must perform the basic functions of any LED power supply, such as power conditioning and conversion and load control. High-power solutions can often leverage specialist stages for these functions. Low-power solutions of less than 35 W, such as a light bulb, must perform all three functions in as few stages as possible, because cost and space are at a premium.
Tomi Engdahl says:
Drivers enable next-gen LED street lighting
http://www2.electronicproducts.com/Drivers_enable_next_gen_LED_street_lighting-article-facn_microsemi_may2012-html.aspx
What designers must consider when selecting a driver, focusing on why eliminating the step-down transformer is a good idea
In Canada and the United States, power is often distributed to outdoor lighting fixtures at 347 or 480 Vac, respectively. With the adoption of LEDs, the light fixture must then convert the power to much lower voltages on the output; in the U.S. this voltage needs to be below 60 Vdc if safety extra-low-voltage (SELV) constraints are observed.
Until now, this conversion was accomplished using bulky and inefficient step-down transformers that increased design complexity as well as power losses in the conversion stage. What is needed is a new type of integrated power supply that can provide this conversion without the need of the external step-down transformer thus simplifying the design, reducing the driver system weight and eliminating the energy losses associated with the transformer.
The driver system is the key to enabling the promise of the LEDs. LEDs are complex, sophisticated semiconductor devices whose tightly interdependent photometric (luminous flux and efficacy), electrical (current, voltage, power) and thermal (junction temperature) characteristics often behave in a highly nonlinear manner. LED drivers play a critical role in ensuring the light fixture’s efficiency, life expectancy and compliance with current regulations.
A new class of integrated drivers is now able to specifically address and eliminate the challenge of using an external step-down lighting transformer in many outdoor and high-bay LED lighting fixtures. This article will explore the choices a street light fixture designer must consider when selecting a driver and specifically focus on why eliminating the external step-down transformer might be a good idea.
Now, thanks to the availability of integrated LED drivers that provide the power conversion without needing a external bulky transformer, fixture designers can create significantly smaller, lighter, and more efficient solutions. These drivers also deliver more benefits and higher value to the end user via highly reliable designs, dimming, fault detection and management capabilities, and built in robust protections.
Tomi Engdahl says:
Philips Releases 100W-Equivalent LED Bulb, Runs On Just 23 Watts
http://news.slashdot.org/story/12/05/07/193200/philips-releases-100w-equivalent-led-bulb-runs-on-just-23-watts
Lighting giant Philips is starting things off early with the announcement of their 100W-equivalent LED bulb, the AmbientLED 23W. The model produces 1700 lumens, putting it at a very respectable 73.9 lm/W.
AmbientLED 23W (it will be called the EnduraLED in non-consumer applications) is brighter and lacking in some of the performance characteristics of the L Prize winner, including luminous efficiency and color accuracy.’
Tomi Engdahl says:
LED light bulb to last more than 20 years
http://www.bbc.com/news/technology-17992927
Light bulbs that are said to last for more than two decades while consuming very little energy may go on sale later this year.
US firm General Electric, Dutch company Philips and UK-based Sylvania all showcased their products at the Light Fair industry conference in Las Vegas.
Using light-emitting diodes (LEDs) instead of filaments, the bulbs are meant to produce as much light as a 100-watt incandescent alternative.
However, LEDs are not usually cheap.
In April, Philips introduced its LPrize LED that will cost $60 (£37) – but consumes only 9.7 watts while giving off the same amount of light as a 60-watt incandescent lamp.
The company has arranged discounts with shops that will sell the bulb for as little as $20 (£12).
The new EnduraLED from Philips looks similar, but is said to be equivalent to a 100-watt incandescent bulb while consuming nearly four times less energy.
“LEDs promise to be the way forward for the whole sector,” explained James Russill, EST’s technical development manager, in an earlier interview with the BBC.
“There are so many benefits: they can be smaller, brighter; it is one of those rare technologies where the trial has shown it performs better than the lighting systems it is replacing but, at the same time, uses less energy.”
“LEDs are the most efficient light source currently available, and are increasingly used in domestic, commercial and automotive applications,” said Mr Russill.
One of the main challenges faced by LED lighting manufacturers is dealing with waste heat produced by the bulb.
Although a lot less energy is wasted through heat than in the case of a traditional light bulb, some heat loss still occurs.
So that the intense heat does not degrade the long life promised by the companies, the lamps need some kind of a cooling mechanism.
GE, for example, uses what is called an active “synthetic jet” technology that produces an air flow inside the lamp, pulling the hot air out and creating a cooling air current.
Another obstacle used to be omnidirectional light – making the bulb give off light in all directions.
That is why in the past, LEDs were mostly used for spotlights and flashlights.
But now that this problem has been solved, they have to compete with other products used for general lighting, such as omnidirectional compact fluorescent lights and halogens.
Compact fluorescent lights are almost as energy efficient as LEDs, but cost a lot less.
Production of 100-watt bulbs has stopped in the US and Europe, while production of 60-watt bulbs has been stopped in Europe and is being phased out in the US.
From 2014, incandescent bulbs of 40 watts or above will be banned in the US.
Tomi Engdahl says:
Philips set to launch pole-free LED streetlights in Europe
http://www2.electronicproducts.com/Philips_set_to_launch_pole_free_LED_streetlights_in_Europe-article-fajb_freestreet_may2012-html.aspx
Dutch electronics company Philips was put to task last year by a group of people, the likes of which included city planners and architects, who asked the manufacturer to design an outdoor lighting system that would help de-clutter their streets of streetlight poles.
The result was FreeStreet, which went on to win the 2011 Dutch Design Award in the category of “Best professional product.”
The way the system works is simple: pods of LEDs are strung together along a network of narrow cables and hung above streets / walkways. During the day, they are virtually invisible to anyone passing by. At night, the pods — each of which contains four-bulb LED clusters — turn on to illuminate the area below.
FreeStreet runs on its own network of wires and doesn’t piggyback off any nearby power lines.
FreeStreet requires the network of wires to be electrically sourced to the street-front façade once every 328 feet. According to Philips, this is a significant improvement over other suspended systems that require energy sourcing every 66 feet.
The thing to note, however, is that these lines do not crisscross across public spaces: they run parallel to the street / walkway that they’re lighting. The result of this rather simple design is a comfortable, natural light, and a clear view of the sky above.
Tomi Engdahl says:
Progress in small LED lights: High-voltage LEDs and secondary phosphors
http://www.edn.com/blog/PowerSource/41428-Progress_in_small_LED_lights_High_voltage_LEDs_and_secondary_phosphors.php
Tomi Engdahl says:
Flame-tip bulbs show LEDs practical for the price-conscious consumer
http://www.edn.com/blog/PowerSource/41416-Flame_tip_bulbs_show_LEDs_practical_for_the_price_conscious_consumer.php
Tomi Engdahl says:
Teardown slideshow: The anatomy of the LED light bulb
http://www.eetimes.com/electronics-news/4373720/Teardown-slideshow–The-anatomy-of-the-LED-light-bulb
LED light bulbs have about the same efficacy as compact fluorescent light bulbs (CFLs), 50 to 60 lumens/watt.
However, LEDs keep getting better while CFL technology has plateaued. The 7.5W LG bulb emits 485 lumens. This corresponds to 65 lm/W. It’s a 40W equivalent. At the same 485 lumens, the old fashioned 40 W light bulb would offer only 12 lm/W, five times less.
Uniform illumination
When placed in a conventional table lamp most LED light bulbs, including this LG bulb, have a tendency to illuminate upwards. This is because of the horizontal placement of the LED emitters inside. The Philips bulbs use three vertically oriented LED panels to alleviate this concern.
The very first electric lamps were not necessarily very effective or very popular, yet their advantages prevailed and the use of oil lamps waned. Over time, and probably rather rapidly, lamps will evolve to adapt to the peculiarities of the LED sources. When LED light sources achieve lifetimes in decades, replacing them will no longer be a concern and luminaires will take on various forms and shapes. Meanwhile, forcing LEDs to assume the Edison format is akin to forcing a square peg into a round hole.
Nevertheless, Strategies Unlimited predicts that “the global market for replacements for legacy lighting sources will grow from $2.2 billion in 2011 to $3.7 billion in 2016.” Indeed, LED light bulbs provide very pleasant illumination, much more agreeable than compact fluorescent bulbs, and they will be adopted eagerly. They outlast CFLs, contain no mercury, and are instant-on.
LED light bulbs are complex electronic devices. The LEDs themselves are semiconductor diodes, wanting a low voltage DC supply, typically around 3 volts. Common household supply is 110V or 220V AC
Tomi Engdahl says:
While commercial and industrial applications are the fastest growing segment of the LED lighting market, they are also the most demanding in terms of circuit protection required for LED luminaire assemblies.
Source: EDN’s Resource Center e-mail June 20, 2012
Tomi Engdahl says:
Highly efficient LED drivers provide intelligent lighting solutions
http://www.eetimes.com/design/smart-energy-design/4376019/Highly-efficient-LED-drivers-provide-intelligent-lighting-solutions
LED drivers play an important role in the overall design of the lighting, by regulating the “power output” and relieve the microcontroller from a huge workload with integrated functionality such as GPO, RAM and amplifier circuits. Built-in PWM control results in improved dimming performance and reduced need for external components. In order to reduce the power consumption, Rohm has implemented advanced low-power amplifiers and a proprietary oscillator technology in its LED drivers. The following article describes an intelligent lighting system featuring a TRIAC dimming-based example.
LEDs replacing traditional incandescent lamps are usually arranged as an array, which together form an evenly illuminated surface. The brightness of the LEDs driven in series depends on the operating current. The total voltage drop is between 10 and 30 V. The LED chain should be powered by a precisely controlled constant current source, and the current must be regulated accurately so that neighboring lamps have the same brightness. Therefore, the main task of an LED driver is a constant light output, means a steady power supply to the LEDs, despite possible power variations.
Other requirements to quality lighting concepts are high precision, constant output voltage and various dimming functions. A variety of dimmers including transistor or triac-based dimmers can be found in the market, all working with a phase angle detection of the alternating current.
A challenge of dimming LED lamps is the fact that a normal driver cannot identify the phase cut angle of the alternating current. In order to enable an efficient LED dimming solution, the LED driver has to determine the power supply to the LEDs by analyzing the phase angle of the dimmer.
Wrong, premature off or on switching of the TRIAC dimmer caused by a power drop has to be avoided. Since LEDs are designed to be highly efficient even with reduced operating current, this is not easy to achieve.
To avoid flickering during operation, the built-in dimmer capacitor has to be completely discharged when the triac is non-conductive. To avoid a premature shutdown of the TRIAC, a constant low current flow has to be maintained when the triac is conductive.
Various protection circuits such as the bleeder control, under voltage lockout, -and protection against over current (induction saturation), short circuit and overheating ensure reliability and fault tolerance. Customers expect a much longer lifetime from LEDs than from standard lamps which also justifies a higher purchase price. These integrated features help to achieve this goal without major development effort. A protective mechanism against the false activation of the LEDs by a leakage current is included as well.
The LED driver family BD555 is a flexible building block solution for demanding dimmable LED lamps
Tomi Engdahl says:
Combine a capacitive drop topology with constant current regulation to drive LEDs
http://www.edn.com/design/led/4376059/Capacitive-Drop-Topology-with-a-Constant-Current-Regulator-to-Drive-LEDs?cid=EDNToday
With widespread deployment now being witnessed, the need to optimally drive LED emitter strings in order to enhance longevity and reliability becomes more important. At the same time engineers are under pressure to reduce design complexity and component count as well as curbing the overall cost. The following article looks at how a constant current regulator (CCR) based LED driving scheme using a capacitive drop topology can address these requirements and meet the performance benchmarks needed to realize energy efficient, cost-effective, robust, long-lasting system designs.
If the LEDs are driven too hard by a forward current that proves to be excessive, then permanent damage to LEDs in the string can occur, reducing their operational lifetime and impinging on reliability. Also in most applications any variation in brightness of the light emitted from LEDs in a string is not acceptable. The LEDs must therefore remain biased correctly with a constant current to ensure continued stable operation of the lighting system.
A CCR is a self-biased transistor that is designed to run at a fixed current regardless of any variations in the voltage from the source or the load it is applied to. Using Kirchhoff’s current law, the CCR only supplies or sinks a regulated current on a string. Acting like a linear regulator it is capable of absorbing fluctuations in supply voltage or any changes in LED forward voltage due to production or binning variations.
To best match the CCR with the LEDs, it is important that the IReg current is about equal in magnitude to the ILED rating of the LEDs being used.
In the capacitive drop topology detailed here it is possible for the engineer to define VAK since the coupling capacitor C drops the majority of the voltage.
To ensure there is enough charge on the capacitor to let current flow to the LEDs, C should be sized so that the peak current matches the LED/CCR current at VP−.
Generally, when using the coupling capacitor for this type of application it is recommended that a high voltage, metal-film type option is specified.
The NSI45090DDT4G from ON Semiconductor is a robust CCR, based on proprietary self-biased transistor (SBT) technology, with the capacity to regulate LED current levels over a wide voltage range. Its negative temperature coefficient protects the LEDs from thermal runaway at extreme voltages and currents. The high anode-cathode voltage rating of this device also enables it to withstand the surges that can be experienced in lighting and signage applications.
The capacitive drop topology described in this article allows swings in voltage to be translated into swings in current. Using a constant current regulator to regulate the LED string current in turn allows smaller forward voltage LEDs to be driven at higher voltage levels where large swings are present.
Tomi Engdahl says:
CCFL and LED price gap closes as CCFL costs explode
http://www.edn.com/electronics-blogs/other/4392224/CCFL-and-LED-price-gap-closes-as-CCFL-costs-explode?cid=EDNToday
In spite of their implementation in high-profile applications (See LEDs score gold at Olympics), LED penetration has been slow. CCFLs in economically trying times have kept their hold on consumers as the low-cost product of choice.
The rare-earth metals used for CCFL phosphors jumped as much as 10x their 2010 price. Europium, for example, used as a phosphor in CCFLs saw price hikes of 170% in 2010. Predictably phosphor prices continued to use approximately 6x over 2010 levels.
Based on their increasing costs, demand has slowed for CCFLs, which also is pushing prices higher.
Tomi Engdahl says:
LED downlights deliver rapid payback
http://www.edn.com/electronics-products/other/4391003/LED-downlights-deliver-rapid-payback?cid=EDNToday
The CR Series of LEDs by Cree, Inc. expanded to add the CR4, a four-inch LED downlight, and the CR6, a higher lumen output six-inch downlight. The six-inch version cuts energy use by a whopping 87% when compared with incandescent lighting, delivering payback in less than a year in many commercial installations.
The CR4 delivers 575 lumens and more than 60 lumens per watt. It is a direct replacement for a 50-Watt 4-inch incandescent downlight.
Tomi Engdahl says:
Trying to get lots of small LEDs to a MR16 light bulb to get enough light leads to pretty odd looking light bulb and quite probably less than optimal light beam shape:
MR16 GU5.3 5W 338lm 102-SMD 5050 LED Warm White Light Bulb (12V)
http://www.dealextreme.com/p/mr16-gu5-3-5w-338lm-102-smd-5050-led-warm-white-light-bulb-12v-149080
Tomi Engdahl says:
LEDs Need Circuit Protection, Too
http://www.designnews.com/document.asp?doc_id=249288&cid=NL_Newsletters+-+DN+Daily
Designers of LED-based systems may be glossing over one of the most important components, leaving their products susceptible to catastrophic failures, a circuit protection manufacturer said recently. “When you’re designing LEDs, a lot of thought goes into driver efficiencies and power factors, and very little thought goes into the surge immunity standards you have to meet,”
Ironically, insufficient circuit protection may compromise the very reason for using light-emitting diodes (LEDs) in the first place. Many engineers specify LEDs because they offer long life and low maintenance. But both of those advantages are lost if designers fail to specify the correct protection against over-current and over-voltage situations. “LED luminaire replacements are two to three times the cost of incumbent technologies,” Patel told us. “So you want it to last a minimum of five years without having to service it.”
Patel breaks down circuit protection into two broad categories: over-current protection, which typically involves safety concerns; and surge immunity, or over-voltage protection, which often involves protection against lightning. “Over-voltage focuses on equipment reliability,” she said. “Over-current involves the risk of shock and fire.”
Both, however, can ruin an LED-based application.
“LED lighting is a very fragmented market. There are many small companies that are trying to do the entire design, but they don’t know what the standards are, or how to meet them. For many of the lighting designers, this is something new.”
A lot of designers will buy the power supply, LEDs, heat sinks and thermal parts, then try to put it all together,” Patel told us. “But the driver may only be rated at 2 kV or 4 kV, whereas an outdoor application needs to meet 10 kV.”
Engineers should start considering such issues after they’ve picked their power supply and LED driver.
Tomi Engdahl says:
Enterprise LED lighting market to pass $1 billion in 2013—Growing 40% annually through 2015.
A new report by Global Information Inc. estimates that the North American enterprise LED lighting market will tally $630 million in annual revenues. The report sites falling prices, and also an over supply as LED count in devices is falling and unit prices are tumbling even faster.
Source: http://www.edn.com/electronics-blogs/other/4395290/LED-Week-in-Review-Counterfeit-UL-mark–Disruptive-glass-cutting-method–Magnalight–Cree–and-where-are-the-light-bulb-jokes-?cid=Newsletter+-+EDN+Weekly
Tomi Engdahl says:
Infrared LEDs for camera systems
http://www.eetimes.com/design/smart-energy-design/4395631/Infrared-illumination-for-camera-systems-?Ecosystem=communications-design
Whether number plate recognition at the gate of a company’s car park, video cameras in banks, wide-range surveillance of parking lots, industrial sites or airports – Closed Circuit Television (CCTV) keeps a close watch. Many solutions add infrared light to enhance the quality of images recorded in the dark. It was the development of powerful infrared LED (IRED) which made many of these applications economical. Meanwhile, manufacturers can choose from a wide range of IRED for illumination applications. The product line ranges from devices of medium power to multi-chip modules supplying several Watt in continuous wave operation.
Tomi Engdahl says:
Extend the life of LED lighting systems with thermal management
http://www.edn.com/design/led/4396842/Extend-the-life-of-LED-lighting-systems-with-thermal-management?cid=EDNToday
With light emitting diodes (LEDs) at the forefront of new residential and commercial fixtures, engineers and designers often struggle with ways to protect LEDs from premature failure due to thermal issues. LEDs permanently lose their brightness when thermally stressed and will degrade much quicker than the manufacturer intended. The additional cost of the emitters should be balanced with the thermal design to provide not only an elegant lighting solution, but the long life promised by solid state lighting.
Today, roughly 20% to 50% of the electrical energy produced worldwide is used for lighting. With the world population growing there are only two alternatives, generate more electricity by building new power plants or work more efficiently with what is already being produced.
Today, LEDs have efficacies over 100 lumens per watt and are finding their way into a large selection of general lighting applications. One of the earliest issues converting fixture designs from incandescent bulbs to LEDs is the difference in thermal characteristics. LED manufacturers actually publish life curves for their emitters as a function of temperature… something fixture designers may have never seen before.
The secret to a successful LED fixture design is proper thermal management. There are several factors that affect the thermal performance of any fixture including the ambient air temperature, but LEDs specifically suffer from improper thermal design. Conducting away the waste heat produced by LEDs is paramount and can separate the winners from the losers quickly in this emerging industry.
Two markets exist; one is the retrofit or existing infrastructure of Edison base bulbs, “can” and low voltage halogen fixtures as well as task lighting. The other is new construction and commercial applications where reliability and overall cost of ownership take on greater importance. Both applications lack proper thermal management in the current infrastructure.
Addressing the retrofit market has additional hurdles including cost as well as dealing with the poor thermal characteristics of existing fixtures.
Tomi Engdahl says:
Automotive lighting design considerations–LEDs
http://www.edn.com/design/led/4398009/Automotive-lighting-design-considerations-LEDs-?cid=EDNToday
Automotive lighting plays a very important role to ensure a safe driving. New technologies are developing rapidly including extensive use of new light sources such as LED / LED modules, and “smart” automotive lighting systems such as automatic bending lighting, Headlamps alternately provide driving beam and passing beam and adaptive front-lighting system (AFS). These technologies deliver many advantages including better performance, reduced energy consumption, improved reliability, shorter ramp up time, anti-vibration and shock, small size and more design possibilities.
However, they also bring new problems. For LED light sources, sensitive thermal characteristics influence the stability of photometric performance and UV-radiation from LED light sources may deteriorate light transmitting components. Therefor, thermal design, stability test, usage of low-UV-type LED module and UV-resistance test of internal materials become extra important.
Newer versions of ECE Regulation No. 6, No. 7 for signal lamps require one minute and thirty minutes photometric tests for light sources other than filament lamp(s). Also, new ECE Regulation No. 112 introduces a set of tests for LED modules including color rendering measurement, UV-radiation measurement and temperature stability tests.
Tomi Engdahl says:
LED street lights: Taking a step toward smarter cities
http://www.edn.com/electronics-blogs/enlightened-insights—leds/4398073/LED-street-lights–Taking-a-step-toward-smarter-cities?cid=EDNToday
Throughout much of the lighting industry’s history, lights have been primarily a single function tool – they turn on and they turn off. Maybe a few dim and maybe a few are set to timers, but for the most part, there is no intelligence driving the majority of lighting actions.
With almost 20 percent of the world’s energy consumption* coming from lighting, imagine how much energy could be saved through a little feedback from the environment.
Municipal governments seem to be paying attention to intelligent lighting systems. As budgets have become increasingly restrictive over the years, energy consumption in cities has become a focal point for many local governments. Many have turned their attention to street lighting as an obvious way to free up budgeting resources, while maintaining or even improving safety. Not surprisingly, many cities have taken the jump to LED street lighting since seeing the positive long-term cost analysis with the potential to reduce power consumption and maintenance costs.
Tomi Engdahl says:
100’000 lm “nuclear explosion” light fixture
http://3.14.by/en/read/nuclear-light-fixture-100klm
Lamps
Modern trend is to use LED’s for lighting – but they have a number of disadvantages: their spectra is far from sun, they are very hard to cool if you are running more than 100W of them, and finally good LED’s are quite expensive. That’s why I chosen to use metal halide lamps – OSRAM Powerball HCI-TS 150W/942 NDL with round ceramic arc tube – this gives spectra close to sun (including a bit of UVA light, starting at 350nm), not very expensive (around ~25$/150W), long service life (~12’000 hours) and 99 lm/W power efficiency (which is on par with the best LED’s).
Usually it is prohibited to use metal halide lamps without enclosed fixture due to UVB/C light and small chance of lamp explosion. These specific lamps do have filter for hard UV light (so no ozone and skin cancer ) and probability of explosion is greatly reduced when using electronic ballast (opposed to ‘dumb’ magnetic one).
100’000 lm “nuclear explosion” light fixture
It is a general belief that IT geek should live in darkness with the only light source being computer monitor. Personally, I always liked bright light, but It was never bright enough. Initially my room was lit by 300W of incandescent lamps (4500 lm), then 250W of CFL (~15000 lm), then 500W halogen (~12500 lm)… But it all was way too weak. I always wanted light to be so bright, that you don’t want to make it brighter. Now I achieved this goal and happy to share the results.
Lamps
Modern trend is to use LED’s for lighting – but they have a number of disadvantages: their spectra is far from sun, they are very hard to cool if you are running more than 100W of them, and finally good LED’s are quite expensive. That’s why I chosen to use metal halide lamps – OSRAM Powerball HCI-TS 150W/942 NDL with round ceramic arc tube – this gives spectra close to sun (including a bit of UVA light, starting at 350nm), not very expensive (around ~25$/150W), long service life (~12’000 hours) and 99 lm/W power efficiency (which is on par with the best LED’s).
Usually it is prohibited to use metal halide lamps without enclosed fixture due to UVB/C light and small chance of lamp explosion. These specific lamps do have filter for hard UV light (so no ozone and skin cancer ) and probability of explosion is greatly reduced when using electronic ballast (opposed to ‘dumb’ magnetic one).
How many lamps do I need?
300W of incandescent lamps emits around 4500 lumen. 150W metal halide lamps emits around 14’200 lumen. I decided to go for a round figure – 7 lamps, which is around 1050W of power. This should yield around 14200*7 = 99400 lumen. Consumed power would be around 1050/0.9 ~1150W (including ECG efficiency) .
Tomi Engdahl says:
Use one bypass for every two LEDs
http://www.edn.com/electronics-products/other/4398679/Use-one-bypass-for-every-two-LEDs?cid=Newsletter+-+EDN+Weekly
A fault-management chip, the LBP01 provides long-lasting, smarter, safer LED lighting in such critical applications as vehicles, streetlamps and emergency lights. Used in lamps that comprise multiple channels that contain several LEDs, when one LED fails, it does not extinguish an entire channel, but continue to produce near-maximum illumination.
Tomi Engdahl says:
LED Week in Review—Ikea, Enlightenment via Texas Instruments, Plessey, Wireless bulbs shine on, LED at 50
http://www.edn.com/electronics-blogs/led-zone/4398696/LED-Week-in-Review-Ikea–Enlightenment-via-Texas-Instruments–Plessey–Wireless-bulbs-shine-on–LED-at-50?cid=EDNToday
Ikea
By 2016, Ikea intends to sell only LED lights, becoming the first U.S. furniture retailer to jump on the sustainability bandwagon in such an impressive manner. The company isn’t just following suit—it’s serious. It says it will be selling LEDs at the lowest prices available to encourage adoption. You go, Ikea! Hopefully, more retailers will follow…
Tomi says:
Graphing the efficiencies of LED light strips
http://hackaday.com/2012/10/23/graphing-the-efficiencies-of-led-light-strips/
[Bogdan] decided to see if these inexpensive LED strips were actually less expensive in the long run than regular incandescent bulbs.
[Bogdan]‘s test rig consists of a 15 cm piece of the LED strip left over from his previous installation. A Taos TSL2550 ambient light sensor is installed in a light-proof box along with the LED strip, and an AVR microcontroller writes the light level
Comparing his LED strip against traditional incandescent bulbs – including the price paid for the LED strip, the cost of powering both the bulb and the strip, the cost of the power supply, and the time involved in changing out a LED strip, [Bogdan] calculates it will take 2800 hours before cheap LEDs are a cost-effective replacement for bulbs.
[Bogdan] predicts after 2200 hours (about 3 months), the LED strip will have dropped to 70% of their original brightness.
Tomi says:
LED logger
http://www.electrobob.com/led-logger/
Why?
Lately I was thinking about adding more LED strips and was checking the options. One important aspect that comes to mind is about the lifetime of these products, are they better than bulbs, overall? Obviously there’s no specification you can trust anywhere. So, how do I know if cheap strips are good enough or it is worth spending the money on more expensive ones? Measure some data for the cheap ones and see if they are good enough.
LED strip vs incandescent: Preliminary conclusion
Based on the price I paid for the LED strip (~4.5 EUR/m), local electricity price of about 0. 09 EUR/KWh and bulb price, but excluding the LED PSU and workmanship for installing everything it takes 2800 hours for the LEDs to become cheaper than the incandescent.
Since my strip is not considered useful after 2200 hours as it becomes too dim, it means that it is not a cost effective solution for illumination, compared to incandescent bulbs. LEDs are supposed to save energy and money. It appease that low cost strips are not a good way for that.
What about more expensive LED strips? I used the same thinking as above and found more expensive strips with Nichia LEDs require about 7000 hours before they become cheaper than incandescent, again excluding the PSU. This is a rather rough estimation considering the brightness and efficiency specs are right. Again, the manufacturer of the strips doesn’t give any data about the intensity decay, so the cost effectiveness of the solution is still unknown.
Tomi Engdahl says:
First Look: Hue LED Bulbs Are Your Own Personal Light Show
http://www.wired.com/gadgetlab/2012/10/hue-led-mood-lighting-lights-up-your-life/
Philips has a new and interesting way to light your home. The hue lighting system uses LED lightbulbs with adjustable brightness and color-changing features. Want to listen to Miles Davis’ Kind of Blue in a blue room? All it takes is a quick flick of the companion app.
Each bulb contains 11 LEDs in three different colors, which Philips calls royal blue, red/orange and lime. The lights combine to create up to 16 million colors. (The lime LED controls the important white light.) Philips claims that users can even dial in the bulbs to mimic traditional incandescent lights — the holy grail of alternative light sources. That Thomas Edison was really on to something.
With an array of multiple bulbs, you can even assign each a different color to create your own little light show. The app even comes with a series of templates to help you out.
Users will also be able to manipulate their lights while they’re away.
The system runs through a hub that plugs into a router via an Ethernet cable. It’s based on the open source ZigBee LightLink wireless standard, which means the bulbs will work with other devices that adhere to the standard.
It works well, and it’s simple and energy efficient (8.5 watts per bulb at full power). So whats the catch? Price. The starter system — three bulbs and a hub — will set you back $200 and will be available exclusively in the Apple Store. Additional light bulbs will cost $60 each.
Even standard LED bulbs cost about $20 each, however. The tech isn’t cheap.
Julian Boyer says:
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Tomi Engdahl says:
What testing is needed for an LED?
http://www.edn.com/design/test-and-measurement/4401983/What-testing-is-needed-for-an-LED?cid=EDNToday
The recent ban on the incandescent light bulb, government incentives, and the ingenuity of industry experts have all played a role in LEDs becoming the predominant new product in the North American lighting market today. As this technology continues to rapidly evolve, lighting manufacturers and others involved in the industry are finding it increasingly challenging to validate product claims and keep up with industry standards and testing requirements.
In an attempt to offset the price, lighting manufacturers highlight the performance of their products, some claiming 10-year lifespans compared to the typical one-to-two-year lifespan of traditional lighting products. Since these marketing claims are difficult to prove, new criteria has recently been developed for LEDs to help manufacturers avoid customer backlash and negative publicity and provide verification for their products.
Standards and Specifications
In order for lighting products to be sold in the market, they must meet certain national and international industry standards. The standards identify recommended test methods, which are typically the same among third party testing laboratories. Some of the key lighting performance standards for North America include:
• IESNA LM-79-08 – Electrical and Photometric Measurements of Solid-State Lighting Products
• IESNA LM-80-08 – Measuring Lumen Maintenance of LED Light Sources
• IESNA LM-82-12 – Characterization of LED Light Engines and LED Lamps for Electrical and
Photometric Properties as a Function of Temperature
• IESNA TM-21-11 – Projecting Long Term Lumen Maintenance of LED Light Sources
In turn, there are several North American and international energy efficiency programs, each with its own specifications.
Third-party testing plays a key role in product certification. Nationally Recognized Testing Laboratories (NRTLs), organizations approved by OSHA, provide unbiased assurance that products meet the requirements of industry standards and energy efficiency programs and confirm consistency through proficiency tests and factory inspections.
Typical areas of testing and measurement include total luminous flux, luminous efficacy, correlated color temperature and electrical power consumption, among others. While most tests are done directly within the lab, they can also take place at a company’s manufacturing facility if necessary.
When testing LEDs, an integrating sphere and a Type C goniophotometer are the two main types of equipment used. The integrating sphere provides certain key values such as color temperature, and the goniophotometer identifies how the light will project. For example, if a product is placed in a 360° plot, the goniophotometer will tell what area will light up at a given distance, allowing architects to project light paths and determine where they should place lights.
Equipment functions oftentimes overlap. For example, total luminous flux is measured in the integrating sphere for LED lamps or small luminaires and in the goniophotometer for larger luminaires. To perform this and other tests, both the integrating sphere and goniophotometer require certain accessory equipment including an AC/DC voltage source, voltage regulator and temperature probes to energize the lights and take measurements.
Tomi Engdahl says:
Gadget Freak Case #230: The Inexpensive Dimmable LED Desk Lamp
http://www.designnews.com/author.asp?section_id=1362&doc_id=254910&cid=NL_Newsletters+-+DN+Daily
With the cost of high-brightness LEDs coming down, Andrew Morris decided he wanted a dimmable LED desk lamp. Yet he found the ones on the market were very expensive, and few of them were dimmable. So he decided to use his engineering skills to build his own.
He installed his circuit into a fluorescent desk lamp he had picked up years ago at a flea market. He also discovered the LED driver circuit was dirt cheap and simple to assemble.
Johnathan Eversmeyer says:
Very informational. Thanks.
Karey Bulgin says:
Great article. I’ll give it a try when I start raveling again.
Tomi Engdahl says:
Here’s one LED light that didn’t make it to 50,000-hrs
http://www.edn.com/electronics-blogs/powersource/4311896/Here-rsquo-s-one-LED-light-that-didn-rsquo-t-make-it-to-50-000-hrs?cid=EDNToday
Almost two years ago I did my first LED teardown on a 7W LED bulb from Taiwanese manufacturer TESS.
As a dedicated proponent of solid-state lighting, I was a bit nervous – was it the LEDs themselves that pooped out after only a few years of relatively light use? [cue ominous music] Or would it be the power management circuitry, including the control IC, the switching transistors, or the much-maligned electrolytic capacitor?
Nope. Prosaically, the failure was a poor solder joint on the power wire from the power supply to the LEDs.
Tomi Engdahl says:
Focus LED Design on Driver Topology, Circuit Protection
http://www.designnews.com/author.asp?section_id=1365&doc_id=256288&cid=NL_Newsletters+-+DN+Daily
The driving force behind the switch from incandescent lighting to LED technology is to gain power efficiency and longer life. However, the cost of LED assemblies is much higher than incandescent and CFL lamps for equivalent lumen outputs. In theory, higher LED costs can be offset by lower power consumption and longer service life. LEDs can last for 50,000 hours or more, but that may not be the case for a complete lighting assembly.
As a designer, you’re well aware that environmental factors have a strong influence on end-product reliability. Therefore, careful attention must be paid to the type of LED driver topology used and the selection of protective devices for various locations in the circuitry.