最新 LED 杂志电子版

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It’stimetorenewyourFREEsubscription.LEDsMagazine,theleadingglobalpublicationcoveringtheapplicationsofhigh-brightnessLEDsandthetechnologyofLED-basedsystems..LEDsMagazineistheleadinginformationre-sourcefortheglobalLEDcommunity,servingthousandsofreadersthatspecify,designandmanufactureLED-basedproductsforawiderangeofend-useapplications.

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15 LIGHTING

Asking the right questions helps to educate

customers and suppliers alikeBrian Owen, Contributing Editor

columns/departments

NEWS + VIEWSZumtobel joins Philips’ licensing programMolex and Leviton offer LED lighting modules18 OLEDS

OLED lighting set to take off in 2011

Jennifer Colegrove, DisplaySearch

EMaGSB

______________

________________________

_____________

you, led street lights. I heard that you have an interest in Led lights. I’ve have the privi-lege of bringing into this country some of the best made, most efficient, flood and street led lights ever built. I’ve helped in the devel-opment creativity and the marketing expo-sure. I would like to introduce a web site to you, which has all the necessary information available, for evaluation of many applications of the led light fi xtures, our specialty are our led street lights. Th e lights can do the talking for themselves. With your extended interest in led lamps, you will be able to recognize park-ing lot, street, and highway and other appli-be the ‘manufacturer’.

In my presentations to lighting designers, specifi ers and energy-effi ciency organiza-tions, I highlight some of the many resources and tools that are available to vet SSL prod-ucts. Th e message is the same: educate the potential buyers in order to attempt to pre-vent purchasing pitfalls. At the same time, make the manufacturers and their channels aware of this process to put them “on notice” that the truth is out there and if they are not “bringing it” everyone will know when they are “winging it.”

ing specifi ers at this stage in applying LEDs for general lighting. “Too often the specifi er or lighting designer is put in the awkward position of not having enough information to make a fair comparison between com-peting options — whether LED or incum-bent technology,” she said. “With the wide range of performance and pricing in the LED products being off ered today, it is more crit-ical than ever that anyone reviewing LED products follow a minimum process to pro-tect his or her own reputation and to get the great performance that a well-designed LED luminaire can off er.”

we have successfully accomplished internal vetting, but a useful procedure, which saves valuable time, was long awaited and wel-comed. Besides, we can avoid some of the tire-some meetings that drain the brain, if not dis-integrate it.

solid-state lighting. It is a big step in the right direction, but there are extra steps that can be taken to ensure a good customer experience.” Examples include a require-ment for a certain ingress protection rating or salt-spray testing for outdoor luminaires. Insisting on transient voltage protection and

A measured responseappropriate safety marks (which can be val-So getting back to that email I received, we idated on the appropriate websites for UL, have taken the best that every resource or CSA, etc.) will help ensure safety. Asking the longevity and stability of the company. After all, the warranty is useless if the com-pany is not going to be around in 6 months. Giving people a list of “questions to ask” that they can copy and paste into documents, emails, etc. empowers them, making them more likely to buy a solid-state lighting prod-uct — and a good one at that.

It has now been several weeks since I sent a response to the original email. I have not

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lighting|OLEDs

OLED lighting set

to take off in 2011

As companies begin small-volume production and address various challenges, OLED lighting looks to be well-suited for a range of applications, writes JENNIFER COLEGROVE.

undreds of millions of dollars have been invested in OLED lighting, especially in Europe, the US and

Japan. Currently, more than 130 companies and universities, and over a dozen organiza-tions are working on OLED lighting.

Compared with the other major lighting technologies in the market — incandes-cent, fluorescent, high intensity discharge (HID) lamps, LEDs and electrolumines-cent (EL) — OLED lighting has several advantages:

• OLED lighting devices emit from the sur-face, can be made fl exible/rollable, and even transparent like a window or refl ec-tive like a mirror.

• OLED lighting is thin, rugged, light-FIG. 1. EDAG, a German-based provider of engineering services, presented its

vision of an environment-friendly, future-orientated vehicle at the Geneva motor show in March 2009. The “Light Car," says EDAG, will be one of the fi rst vehicles to utilize OLED technology as an individually adaptable design and communication element. The driver can design the outlines of the car’s lights to give the car a unique appearance, or individually confi gure his cockpit and instrument panel. The transparent tailgate can be used for car-to-car communication, for example, the braking force could be communicated to the next vehicle by means of an illuminated scale on the back of the car. Light Car video: www.edag.de/pr/web_tv/webtv/en.

and is environmentally friendly. • Th e power effi ciency of OLED lighting has also improved dramatically recently. Th e unique features of OLED lighting are inspiring the imagination of designers, who are exploring various OLED lighting applica-tions: windows, curtains, automotive light, Th ere are several potential applications for OLED lighting, including:

FIG. 3. During Euroluce in Milan, Italy,

in April, Philips premiered what

it described as “the world’s fi rst OLED-based interactive

other components that are currently used in backlights. However, the OLED would need to operate at very high brightness and color temperature, while still maintaining a long lifetime. While white OLEDs can’t currently meet these requirements, over the next sev-eral years, we expect that OLED materials

will improve dramatically.

Decorative/general lighting: OLED lighting can have very attractive designs, can be rigid or fl exible, white or only high brightness but also

long lifetime is needed.

Signage/advertisement: Th is category covers signage/advertisements that can use a

direct drive backlight to light

up the pictures on a plas-tic film one area at a time. This type of signage/adver-tisement looks animated,

and can attract consumers’ FIG. 4. OLED lighting manufacturers' roadmap. Source: DisplaySearch.

ENERGY STAR

PETCHABURI, ThailandSu Zhou, ChinaGuang Dong, ChinaSAMUTSAKORN, Thailand

_____________

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standards|PROGRESS REVIEW

listed in red are currently being worked on

in committee.

Updates to existing standards

Th e virtual ink is not yet dry on the three base standards that were issued in 2008, and the Energy Star guidelines for luminaires are very new, but improvement in LED technol-ogy and the results from test laboratories will allow the community to ratchet energy savings upwards, tighten specifications and even improve the measurement meth-ods. Th e current standards will need to be improved and tightened. Typically, IES stan-dards are revisited every fi ve years, and this makes sense with mature technologies and decades-old standards. However, with LEDs continuing to evolve rapidly, this process must be more frequent.

For example, in ANSI 377.C78, the defi ned color temperature regions were a good start, but LEDs from within a given color temperature region can be perceptu-ally quite diff erent in color and tint. Th is should not be surprising since the regions

Global harmonization

A major issue for manufacturers is that of harmonization. A worldwide coordination of eff orts around LED standards will be critical. It already requires a signifi cant investment to make one product for diff erent markets. Th e various requirements of Underwriters Laboratory (North America), CE (Europe), PSE (Japan), CCC (China), the CB Scheme and others require signifi cant design and testing efforts to meet all requirements. In some cases, diff erent products must be designed for particular markets. Th is is not a new issue, but we have an opportunity with LED lighting to make new products around the world faster and easier. For national and international eff orts in reducing energy use and carbon footprints, this would be a wel-come scenario.

and then the region is expanded further by a bounding quadrilateral. Th is ensures that there are no gaps between adjacent regions, which helps to keep LED yields high. LED manufacturers, to their credit, are begin-ning to offer sub-binning within those regions and there is already work on a bin-ning standard, but it is likely that the chro-maticity regions will have to shrink or be subdivided to make sense to the end-user. Remember that a single MacAdam ellipse is the region of imperceptible change in chro-maticity. A 3-step or 4-step MacAdam is typical for most light sources in real appli-cations, and beyond those boundaries the change in color is quite noticeable.

It is also very likely that an additional metric beyond correlated color tempera-ture (CCT) will be needed; that metric is the distance above or below the blackbody curve. Th is delta uv will give an indication of tint. Too far from the curve is a color.

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standards|PROGRESS REVIEW

value no longer a white light source? A small

and obscure note in CIE 13.3 mentions that CCT is defi ned only when 0.05 from the black body locus. Th is is a signifi cant distance, perhaps too large.Th is evolution is not new: even for fl uo-rescent sources such as CFLs, the defi ned regions were and are quite large, but man-ufacturers eventually reduced values so the targets became quite small, i.e. within a few MacAdam steps.

which may even call upon other standards of mentioned as a key ingredient in market performance for defi nition.creation and growth, but they are often the A friend of mine, a technical executive in essential pre-condition for large and fast-Silicon Valley, told me that those without growing markets.signifi cant market share often sought stan-dards so they could jump into the fray and Future of standards

conversely, standards are resisted by those Although the economy is in an awful state,

ect adoption and use, LEDs in leadership positions so they can main-and this will aff

tain proprietary platforms. The mistake are still viewed as a good opportunity to in this reasoning is that market growth is offer energy savings, good performance

e state of LEDs already allows often stymied without standards. In com-and more. Th

puters, chips, networks, and media this has many general illumination applications to

Standards of form and architecturebeen proven out again and again. From key-be addressed in terms of technical achieve-Th e standards discussed so far are standards board layouts to video formats the issue of ment and performance level. Th e develop-of performance, but there is a second cate-standards has been a critical market driver ment and use of standards will continue gory, perhaps just as important for a nascent once industry, trade organizations and apace, and costs will need to come down, technology such as LEDs, and that is stan-even governments have established a com-but many manufacturers are addressing this dards of architecture. Th is can encompass mon platform or architecture. In the annals now. 2009 will continue the many eff orts in standards around electrical interfaces, of technical progress, standards are rarely standardization. data protocols, and mechanical connec-tions. Consider the wall plug, lamp socket, or the various connections on your com-puter. Th ese are all standards of architecture

some of the latest LEDs require anything up to 3A.

In addition to the higher current require-ments, effi ciency improvements are becom-ing mandatory, for example through Energy Star standards. Size is often important and of course cost is always critical. To address all these requirements requires driver solu-× 1/200 seconds, or

Simplifi ed control scheme using an optimized driver.

0.5 ms. Most solutions

have an inherent soft-start feature that is in ripple can be as low as 10% of the maxi-the region of several ms, severely restrict-mum LED current through careful selec-ing the dynamic control range.tion of the inductor value and switch-Th e voltage in the current-control loop ing frequency. Th is more than meets the can be as high as 1.2V, which has a large majority of HB-LED lighting applications. impact on the power dissipation. For exam-Secondly, the control architecture deploys

EMaGSB

NEW!

PRODUCT VIDEO SHOWCASE

YOUR BRAIN

IS WIRED FOR

• More than 75% of US Internet users view online video and the online video audience is forecasted to grow to VIDEO

WEBSITE TRAFFIC STATS:*

• 404,429 MONTHLY PAGE VIEWS • 75,997 MONTHLY UNIQUES

WHY IS VIDEO SO IMPORTANT TO YOUR COMPANY?

Silicaglas Ilmenau GmbH (SGIL), has enabled the manufacture of quartz glass components result of the physical properties of quartz

glass, and ultimately this leads to very characteristics in the spectral range below 320nm, these organic materials cannot be used as optical components for UV-LEDs. Hence, manufacturers of UV-LEDs need to work with quartz glass components. Th ese feature very high transmission rates in the Wavelength in nm

FIG. 1. UV transmission of various optical materials.

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testing|THERMAL & OPTICAL

LED system design improves with optical

and thermal performance verifi cation

The ability to quickly and easily produce accurate optical and thermal measurements for LED devices has a major positive impact on the system design process, says JAMES PETROSKI.

ED systems typically are designed to deliver a specifi ed amount of light in a certain color spectrum. Th e designers of LED systems rely heavily on the perfor-mance specifi cations provided by LED man-ufacturers who typically rate their devices to deliver a certain number of lumens per watt at a certain color spectrum. Th e thermal per-formance of the package is also important, as well as the rate at which the light output drops as the temperature rises. If the per-formances diff er from the manufacturers’ specifi cations, systems builders are left with the diffi cult task of identifying the problem using trial and error methods and redesign-ing the system to compensate for the perfor-mance variations.

Traditional approaches for measuring LED performance, such as measuring opti-heat radiation, so fi xtures and sys-tems have been optimized for this mode of heat transfer. Incandescent and high-intensity discharge sources convert more than 90% of their waste energy into IR radiation, with less than 5% being lost by either convec-tion or conduction. In contrast, in an LED system, the thermal energy is removed from the LED chip by conduction, and then leaves the sys-tem primarily by natural convection with some thermal radiation. Light-ing system designers must learn to think and design for this diff erent type of thermal system.

Lighting system design

Lighting systems are typically

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testing|THERMAL & OPTICAL

are the diff erent thermal interfaces

along the junction-to-ambient heat-flow path. The LED chip is typi-cally attached with a bond layer to a metal interconnect layer which is then attached to a ceramic substrate and an electrically isolated thermal pad; other designs have made use of a metal “thermal slug” under the die to conduct the heat. Th e entire pack-age is designed to move heat away from the back of the LED chip in

order to maximize optical output. FIG. 2. Automated LED testing station combining Novel, improved materials, such thermal and optical test systems. as the graphite-based heat spread-ers developed by GrafTech, can be used in I know that they are doing the best job they applications to distribute heat evenly where can to deliver consistent performance. weight, thickness, or volume of the thermal On the other hand, I have been involved

in many projects where many additional design must be minimized.

weeks and months were required to track

Optical performancedown and later correct performance prob-As someone who has designed LED systems lems that were traced to variances between for many years, I trust the specifi cations device manufacturers’ specifi cations and provided by device manufacturers because actual performance. So it should come as

no surprise that I recommend asking at the early stages of the project: do the LEDs that we are planning to use actu-ally put out the right amount of light, at the right colors, and does the pack-age live up to our expectations in mov-ing heat from junction to board?In the past, measuring package ther-mal performance required setting up a series of thermocouples and looking for signifi cant changes as one moved from junction to ambient. Th is type of test-ing is a bit of an art and the accuracy of the results depends on your ability to “guesstimate” junction temperature. Measuring optical performance with an inte-grating optical sphere is also a tricky manual task that can take a considerable amount of time and again requires the ability to guess-timate and maintain junction temperature. Fortunately, a new generation of measure-ment systems (see photos) has substantially reduced the time and eff ort required to mea-sure optical output and thermal performance

EMaGSB

KEEPINGIS HOT STUFF.

EMaGSB

last word

Changing times ahead for large-area

LED display manufacturers

Small manufacturers of large-area LED displays should form a consortium and develop a Common Module Approach, says PETER PIHOS, partner of EDG RESEARCH & CONSULTING.

en years ago there were over 350 companies worldwide that manu-factured large-area displays. Th ese companies produced a variety of diff erent technologies for specifi c applications. Th e industry demographics showed most were small, with 85% having sales less than $15 million annually. Many existed by fi nding a niche for their technology, such as split-flap technology for use in railway sta-tions, or electromechanical fl ip-disc for the road transportation market. Th ey also benefi ted from a certain degree of national protectionism.

Now that LED technology has replaced other technologies, with 95% of the man-ufacturers selling LED technology, it is Already we are hearing some negative sto-ries about some of the product coming from these small OEMs. Most simply do not have the resources to properly support their prod-uct. With the recent downturn in the econ-omy I suspect these problems will only con-tinue to increase.

Over the years my clients have shared with me their concerns about product development costs and component buying power. Th ey simply do not have the economies of scale aff orded to them like those that may be enjoyed by industry leader Dak-tronics with sales approaching $600 million.

So what is the small manu-to considerably more companies, rather than being the exclusive domain of current market leaders. It would level the playing field, so to speak.

It would also be beneficial for indus-try suppliers, especially the ones making LEDs, to have the opportunity to develop new products that are more specifi c to our industry, and to be able to easily reach the

“long tail,” which is consider-able in our industry. A con-sortium is just the vehicle needed to exploit the oppor-tunities that may exist.

In our most recent indus-try report (see link below), we discuss in more detail this

Contents|

Zoomin|ZoomoutFor navigation instructions please click here SearchIssue|NextPage

Renewingisfastandeasy.Followthelinkontherighttocompleteanupdatedqualificationformtocontinueyoursubscriptionwithoutanyinteruption.Youwon’twanttomissanissue!

RD09

CLICK

tocont

inueyo

urfreesub

scriptio

ntoLEDsM

agazine

withou

tinteru

ption.

HERE

LEDs make a great showP.2

features

15 LIGHTING

Asking the right questions helps to educate

customers and suppliers alikeBrian Owen, Contributing Editor

columns/departments

NEWS + VIEWSZumtobel joins Philips’ licensing programMolex and Leviton offer LED lighting modules18 OLEDS

OLED lighting set to take off in 2011

Jennifer Colegrove, DisplaySearch

EMaGSB

______________

________________________

_____________

It has now been several weeks since I sent a response to the original email. I have not

EMaGSB

lighting|OLEDs

OLED lighting set

to take off in 2011

As companies begin small-volume production and address various challenges, OLED lighting looks to be well-suited for a range of applications, writes JENNIFER COLEGROVE.

undreds of millions of dollars have been invested in OLED lighting, especially in Europe, the US and

Japan. Currently, more than 130 companies and universities, and over a dozen organiza-tions are working on OLED lighting.

• OLED lighting devices emit from the sur-face, can be made fl exible/rollable, and even transparent like a window or refl ec-tive like a mirror.

• OLED lighting is thin, rugged, light-FIG. 1. EDAG, a German-based provider of engineering services, presented its

FIG. 3. During Euroluce in Milan, Italy,

in April, Philips premiered what

it described as “the world’s fi rst OLED-based interactive

will improve dramatically.

Decorative/general lighting: OLED lighting can have very attractive designs, can be rigid or fl exible, white or only high brightness but also

long lifetime is needed.

Signage/advertisement: Th is category covers signage/advertisements that can use a

direct drive backlight to light

up the pictures on a plas-tic film one area at a time. This type of signage/adver-tisement looks animated,

and can attract consumers’ FIG. 4. OLED lighting manufacturers' roadmap. Source: DisplaySearch.

ENERGY STAR

PETCHABURI, ThailandSu Zhou, ChinaGuang Dong, ChinaSAMUTSAKORN, Thailand

_____________

EMaGSB

standards|PROGRESS REVIEW

listed in red are currently being worked on

in committee.

Updates to existing standards

Global harmonization

EMaGSB

standards|PROGRESS REVIEW

value no longer a white light source? A small

conversely, standards are resisted by those Although the economy is in an awful state,

ect adoption and use, LEDs in leadership positions so they can main-and this will aff

tain proprietary platforms. The mistake are still viewed as a good opportunity to in this reasoning is that market growth is offer energy savings, good performance

e state of LEDs already allows often stymied without standards. In com-and more. Th

puters, chips, networks, and media this has many general illumination applications to

some of the latest LEDs require anything up to 3A.

Simplifi ed control scheme using an optimized driver.

0.5 ms. Most solutions

EMaGSB

NEW!

PRODUCT VIDEO SHOWCASE

YOUR BRAIN

IS WIRED FOR

• More than 75% of US Internet users view online video and the online video audience is forecasted to grow to VIDEO

WEBSITE TRAFFIC STATS:*

• 404,429 MONTHLY PAGE VIEWS • 75,997 MONTHLY UNIQUES

WHY IS VIDEO SO IMPORTANT TO YOUR COMPANY?

Silicaglas Ilmenau GmbH (SGIL), has enabled the manufacture of quartz glass components result of the physical properties of quartz

FIG. 1. UV transmission of various optical materials.

EMaGSB

testing|THERMAL & OPTICAL

LED system design improves with optical

and thermal performance verifi cation

The ability to quickly and easily produce accurate optical and thermal measurements for LED devices has a major positive impact on the system design process, says JAMES PETROSKI.

Lighting system design

Lighting systems are typically

EMaGSB

testing|THERMAL & OPTICAL

are the diff erent thermal interfaces

in many projects where many additional design must be minimized.

weeks and months were required to track

EMaGSB

KEEPINGIS HOT STUFF.

EMaGSB

last word

Changing times ahead for large-area

LED display manufacturers

Small manufacturers of large-area LED displays should form a consortium and develop a Common Module Approach, says PETER PIHOS, partner of EDG RESEARCH & CONSULTING.

So what is the small manu-to considerably more companies, rather than being the exclusive domain of current market leaders. It would level the playing field, so to speak.

“long tail,” which is consider-able in our industry. A con-sortium is just the vehicle needed to exploit the oppor-tunities that may exist.

In our most recent indus-try report (see link below), we discuss in more detail this

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