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September 22, 2008...Sometimes it can seem as though the "ready for prime time any minute now" mantra can be repeated enough that it loses meaning. So how ready are high brightness LEDs for the various "prime time" opportunities that many of us would contend that they are destined for? Might be a good idea to take a step back from the day to day to see how far the industry has come, and postulate on whether it really points to an acceleration or just a steady march towards the various applications LEDs can find themselves in. (If you're highly lighting-oriented, it might prove interesting for you to catch some thought-snippets from outside the lighting mainstream to assist with the "belief thing").

So what has happened with the various adoption curves so far? The 'grandaddy' application for high brightness LEDs would likely be traffic signals. Red and yellow LEDs had a substantial lead on the blue ones, and as a result, found an early niche in our stop/mash-the-gas-its-yellow friends that keep things flowing along the streets of the world. The 'go' light lagged behind since traffic signal green isn't green but "cyan" and falls in the "blue" technology spectrum that had to wait for the 2003 "blue revolution". They've turned out to work well and live up to the vast majority of the promises for lifetime, energy and maintenance cost-savings. "But," you say, "I've seen traffic signals with a streak of dead LEDs in them." To take a semantic twist on it, what you've most likely seen is a streak of unlit LEDs. One of the largest suppliers of LEDs to the signal industry, Philips Lumileds, reported last February that they had received reports from one of their customers who has deployed a sizable percentage of the traffic signals over the years, that they have had zero failures attributed to the LEDs themselves. If we assume for a minute that it hasn't been quite that perfect, but just nearly so, it's a handy data point. If LEDs were indeed a noticeable culprit, as opposed to the drivers or other circuits and interconnects, the signal manufacturer would have said so. Few companies like to keep the blame if they can find a friend to share it with. At a minimum, it would appear that any individual LED failure has been of such little consequence, it hasn't been worth reporting. Reliability doesn't get much better than that. Keep in mind as well that since 2001 or so, the state-of-the art in LED signals has not been the "light full of LEDs" where you can see a string of them dead, but rather a handful back there essentially where the old bulb would have lived, with a diffuser and lensing in-between. If you see the individual LED, the odds are that you're looking at a pretty old signal.

A March 2002 report from the California Energy Commission reported that, "...through its program offering loans and grants to local agencies, over 236,780 old incandescent red, green and amber traffic signals, along with pedestrian walk and don't-walk signals, have been replaced with new lamps that use light emitting diodes (LEDs). The new LED lights reduce the State's need for electricity by nearly 10 megawatts, enough electricity to power nearly 10,000 typical California homes. That reduced electricity demand should save the 80 public agencies participating in the program $7.9M annually." That was 2002. LEDs won the battle and today it's pretty much simply a question of when a city can allocate the capital investment to make the retrofits and realize the payback.

In another recognizable application area, cellular handsets jumped in to the LED adoption curve with the "hip" blue key lighting, shortly followed by widespread adoption of white LEDs for those and the displays. Low profile, low power, long life and undemanding color requirements drove quick acceptance starting in 2003, leading to virtually 100% market share a short time later. During 2004-2005 period, we watched those LEDs drop in price by a factor of 10 or more. Other handheld devices, including PDAs and music/video players made the move to LEDs right on their heels, and it hard to find a non-LED based small display at this point in history. What a difference 3-4 years has made.

In the larger display markets if you have the space, the cold-cathode fluorescent (CCFL) incumbents are cost-effective and long-lived. It's when color rendering demands raise their heads that LEDs start to shine. RGB solutions are pretty much the only choice at that point, which tends to drive the costs pretty high due to the component count. Continued efficiency increases and a few technical innovations, including Luminus Devices Phlatlight "blades" are suggesting there could be a rapid change in the large display dynamic, especially as LED-driven solutions appear in showrooms and put to shame the incumbent's color capabilities. We're passed the point in 2006 when a "big-box" consumer product store salesperson confided to me that they couldn't show the $10,000 LED-based flat panel TV because the color was so much better, they feared consumers would simply stop buying big screen TVs for two years waiting for the price to fall.

A number of automotive applications have made use of LEDs, but like commercial lighting applications, the business case has been selective. Center high-mounted safety lamps (CHMSLs or "third brake lights") made the move most quickly, since they were a short wide display where space constraints were of paramount concern. Add to the equation that they were red, which has always been the brightness and cost-effectiveness leader of the LED colors, and virtually every CHMSL today is LED-based. The remaining taillights are an interesting example of somewhere that LEDs do work better from a maintenance and form-factor perspective, but are so interrelated to other engineered systems that they are having to follow a methodical take-over process from higher end vehicles on down. More than one automotive lighting integrator has had the question asked of them regarding the ability to add resistance or increase drive currents in the LED circuit so that the automobile systems designers didn't have to re-engineer their full lighting system, with its various methods of detecting a failed bulb and interconnections to remote entry and security systems. (You're correct if you suspect that higher resistance and more current are characteristics that the incumbent incandescents are famous for... no improvement there.)

Other markets, including indoor and outdoor signage show similar mixed bags regarding the current cost-effectivity of an LED-based solution, but it's important to note that all of the available applications are being served to some extent by LEDs, and not for their novelty or "just to be trendy". They work and are winning with reality-based business cases. And we've seen LED solutions reach a tipping point in a number of applications where they become the solution and progress from there to take over the market.... it isn't hard to reach towards a conclusion that LEDs take over every niche they are qualified for, and that it really seems to be about "when" and not "if" LEDs can meet a specific lighting application need.

Which brings us to the big kahuna application, general lighting. LED lighting is proving itself viable right now in any 24x7 application being served by a compact fluorescent or halogen downlight (and many spotlights) where contract-maintenance is required (if an employee just pulls out a ladder and does it themselves, the energy savings versus CFL is on the verge, but not fully there yet... if they fall off the ladder, it becomes a different story). In addition, the efficiency has moved quickly enough that the "when" for many industrial and outdoor applications, which don't shy away from the cooler color temperatures, is "starting now". According to Dr. Robert Steele of Strategies Unlimited, "The efficacy of commercial cool white LEDs has nearly doubled since 2005, now approaching 100 lumens-per-watt. Warm white is lagging the cooler white in terms of efficacy, and probably always will, but with the best warm white now being close to 80 lumens-per-watt, progress has been equally good." How soon until the breakthrough? Bob goes on to say that, "Most general lighting markets need warm white, and I think that we will need 100 lumens-per-watt in warm white to really crack those broad lighting markets."

Given the unslowing trend to improve the efficiency, the key threshold that has been a principle "gating element" is about to be met (100 lm/watt). From there, the business cases begin to expand, adoption criteria are satisfied, adoption begins, volumes rise and prices drop. History is no longer just telling us that suitability is soon and large scale adoption can follow, but that suitability is on us and we're about to find ourselves on the adoption curve that we've all been watching for. The conquering history of LEDs in the first wave of applications is bearing witness to 2009 being positioned to mark "the year it really began" for the second wave of LED adoption.

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Osram and Philips Finalize LED Cross-license Agreement for LED Technologies in LuminairesLIGHTimes Staff

Seoul Semiconductor Contends it is not Infringing Nichia's PatentLIGHTimes Staff

Sony Introduces LED-backlit Bravia ZX1 TVLIGHTimes Staff

Evident Technologies Announces Issuance of Patent for III-V Quantum DotsCompoundSemi News Staff

Lightfair International Calls For SpeakersLIGHTimes Staff

Nichia Initiates U.K. Patent Infringement Lawsuit against Seoul Semiconductor for Important Thermal Annealing PatentLIGHTimes Staff

Bay County to Have Special Financing Arrangement for Traffic Signal ConversionLIGHTimes Staff

Cree Widens Distribution of its LEDsLIGHTimes Staff

Freescale Introduces LED Driver for LCD ScreensLIGHTimes Staff

How Is That LED Thing Doing?Tom Griffiths - Publisher