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Science Technology

Researchers Conquer "LED Droop" 113

Posted by samzenpus
from the more-shine-for-your-dime dept.
sciencehabit writes "Tiny and efficient, light-emitting diodes (LEDs) are supposed to be the bright future of illumination. But they perform best at only low power, enough for a flashlight or the screen of your cellphone. If you increase the current enough for them to light a room like an old-fashioned incandescent bulb, their vaunted efficiency nosedives. It's called LED droop, and it's a real drag on the industry. Now, researchers have found a way to build more efficient LEDs that get more kick from the same amount of current—especially in the hard-to-manufacture green and blue parts of the spectrum."
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Researchers Conquer "LED Droop"

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  • by busyqth (2566075) on Wednesday May 09, 2012 @05:07PM (#39947865)
    The solution is called "LED Viagra"?
  • by cpu6502 (1960974) on Wednesday May 09, 2012 @05:16PM (#39947961)

    I guess that's why their new LED burns-up 26 watts but only created the equivalent of a 100 watt bulb. They are losing efficiency because the LEDs are being driven to high powers. (Lower power 25W or 40W bulbs only use 3 and 6 watts.)

    • by mlts (1038732) *

      That does get me wondering... how better will bulbs made with this high current technology save electricity compared to other types of bulbs such as CFLs?

      Of course, compared to the old incandescent, they will do much better due to more light and not heat.

      Then there is usable life. With more current comes more heat, and heat is what trashes ICs.

      • by Luckyo (1726890)

        Another issue with incandescent is recycling them after they burn out.

        • by unitron (5733)

          Another issue with incandescent is recycling them after they burn out.

          Are you sure you mean incandescent? The kind (glowing filament) for which Edison was famous?

      • Re: (Score:2, Informative)

        by Osgeld (1900440)

        thats why your 1+ watt LED's usually come attached to a chunk of metal (unless you got them from china, then its metal painted plastic)

      • Anyone can buy a CFL at dollar tree for a dollar. So anyone comparing leds should compare them to those CFLs. If they save money in a reasonable amount of time I would consider buying one. By reasonable, I mean 5 years at most.
      • by cpu6502 (1960974)

        IMHO all this talk of "saving energy" with lighting is ridiculous.
        When I'm home I have 1 bulb burning. Sometimes none (I just use the light from the TV or LCD). That's 10 watts or 0.01 KWh per hour the bulb is on. Meanwhile my heat pump or air conditioner is running at 5,000 watts or 5 kWh per hour of use. We've totally messed-up our priorities by counting pennies and wasting dollars.

        • by Coren22 (1625475)

          I won't be as rude about it as the AC, but yes, AC/HP technology has come a long way. If you replace your AC unit (if it is older than 10 years) it will pay itself off in reduced energy usage. But, you can only go so far in reducing the cost of moving heat around, eventually you have to look at how your house is built, which may be more work/money than it is worth, unless you are building a new house already.

    • by Anonymous Coward on Wednesday May 09, 2012 @06:30PM (#39948691)

      That's daft. With LEDs if you want more light, you simply use more LEDs. They are not bulbs, they're bloody diodes! Overdriving LEDs results in earth deaths, this has been known for 40+ years, keeping them within tolerances will ensure they'll last forever, or as near it in human terms.

      • by ThePeices (635180) on Wednesday May 09, 2012 @07:01PM (#39948931)

        " They are not bulbs, they're bloody diodes!"

        Nobody uses bloody diodes for lighting. Not only is it un-hygenic, the loss of efficiency due to transmitting the light through blood is unacceptable, not to mention the red tinge to the light itself.

        Everybody uses clean diodes.

      • by rtb61 (674572) on Wednesday May 09, 2012 @07:53PM (#39949317) Homepage

        Now add that uplights provide the best quality illumination by reflecting light off ceilings. So rather than typical ceiling cornices, run strip leds around the perimeter of a room, with switching control to allow various switching patterns for dimming ie all on, 1 in 2 on, 1 in 3 on etc. Of course no goofy light fittings like chandeliers or fake oil lamps etc. just quality energy efficient controllable lighting example http://www.leyton-lighting.co.uk/led-tape.asp [leyton-lighting.co.uk].

        • That LED tape looks fun, pity there are no prices on their website.
          • The full colour IP 65 with IR remote (5m) I bought a while back cost me E80 on a discount website. The dutch site I bought them at. [daydealers.nl]
            The light intensity of 3 of them is "mood light". Not enough to read by but enough to have a background light while talking or watching a film.
          • That LED tape looks fun, pity there are no prices on their website.

            Go to any Chinese factory-outlet site like Alibaba or Dealextreme and you can buy these things in 10, 20, 50-metre rolls in any colour and power range you like.

          • by rtb61 (674572)

            LED lighting represents a new era in lighting technology where the light fixture becomes pretty much invisible with light being it's only output. Simple flat panel fixtures, variable output and variable colour. Illuminated door handles, using motion sensors to illuminate the part of the passageway you are in, illuminated stair treads or even very low wattage led ceilings where the whole ceiling is the light fixture. We are really only scratching the surface of LED lighting and if it wasn't for patent loade

      • by tlhIngan (30335) <.slashdot. .at. .worf.net.> on Thursday May 10, 2012 @12:05AM (#39950705)

        That's daft. With LEDs if you want more light, you simply use more LEDs. They are not bulbs, they're bloody diodes! Overdriving LEDs results in earth deaths, this has been known for 40+ years, keeping them within tolerances will ensure they'll last forever, or as near it in human terms.

        Problem is, driving more LEDs is tricky. Clusters wired in series a la Christmas lights die if one of the LEDs die (see Lights of America LED bulbs). Wiring them in parallel, you need to balance the current so one LED isn't being overdriven while the other is being starved for current.

        A proper LED bulb like philips often have a driver circuit per LED (when you're dealing with 5W LEDs, it's not a bad idea), but the downside is adding LEDs means adding a lot of cost in driver circuits.

    • It's more due to the fact that higher-power incandescent bulbs are more efficient. A 40 W bulb puts out 500 lumens, but a 100 W bulb puts out 1700 lumens. That's 3.4x the light for 2.5x the power.
  • Dumb question (Score:5, Interesting)

    by ShadowRangerRIT (1301549) on Wednesday May 09, 2012 @05:28PM (#39948109)
    Why must a single LED provide all the light? Couldn't an array of, say, four LEDs, each equivalent to a 25W incandescent and using mirrors and/or lenses to even out the light distribution, get the same efficiency and substitute for a 100W bulb? Am I missing something obvious?
    • Re:Dumb question (Score:5, Interesting)

      by cheater512 (783349) <nick@nickstallman.net> on Wednesday May 09, 2012 @05:32PM (#39948159) Homepage

      I'd prefer a led slab. Rather than individual 'bulbs' on the roof illuminating a room, whats wrong with making the roof its self a big led panel.
      Very even lighting, the individual leds would be very low current and relatively dim and it would look cool.

      Mind you making that much sillicon substrate probably wouldn't be cheap, but you could perhaps cheat a little and use a layer like a screen's backlight has so you have less actual illumination points and it spreads it evenly across the roof.

      • Re:Dumb question (Score:5, Interesting)

        by Grishnakh (216268) on Wednesday May 09, 2012 @06:39PM (#39948749)

        That's impossible. Lights have to be in a bulb shape, because that's how they've always been, and people don't like change. Look how well circular fluorescent bulbs went over: like a lead balloon. Fluorescent bulbs in general only started taking off in residential applications when they made them so they'd fit in existing fixtures, which themselves aren't significantly changed in 100 years. Even worse, lamps aren't much different from the days when they were powered by gas: anyone who's built their own lamp (the kind that sits on a table, like a reading lamp) knows this: all the "electrical" parts are actually brass rods and fittings that were originally designed for gas, and were repurposed for wires, even though running lamp cord through them (particularly the joints) is a giant PITA and really doesn't make any sense.

        Offices can do different things, like use 2x4 fluorescent fixtures, because they're more worried about efficiency (part of operational costs) and because they don't have dimwit cheap-ass home "builders" building them.

        • Re: (Score:2, Interesting)

          by Anonymous Coward

          Dunno. That idea sounds pretty cool to me. Instead of having a flourescent lighting fixture in something like a dropped ceiling you could have LED panel that fits in the same place as one of those plaster tiles. Not quite one huge panel, but a more reasonable adaptation. If it's done right it shouldn't weigh any more than a typical ceiling tile either. Also, because it's not a fixture, if you don't like where the light is, it would be easy to swap it out with an adjacent ceiling tile. (Well, provided the ca

          • The fluorescent fixtures frequently used in offices are already made to replace one or two ceiling tiles. Not only could a new LED fixture do the same, but there are already LED replacement lamps that may increasingly replace the lamps in existing fluorescent fixtures. They're expensive right now, but expect prices to drop.
          • by Grishnakh (216268)

            Yes, an LED panel would make perfect sense and probably be a drop-in replacement for a 2x2 or 2x4 fluorescent office fixture. It'd also work great in a garage/workshop. But I don't ever expect to see LED panels in a residential home, unless it's custom-built by someone who's forward-thinking. Everyone else absolutely requires point-source lights, because that's how it's always been done, that's how residential fixtures all are, and we simply can't change.

            • by Coren22 (1625475)

              My house built in 1974 has fluorescent lights in the kitchen. It isn't all that uncommon in certain places in the house.

        • by legont (2570191)
          We need iLight (c)
          • by Grishnakh (216268)

            You have a good point there. If Apple came along and started selling LED lights in different form factors (like panels) for residential applications, people would probably buy them like hotcakes, even if they cost an absolute fortune.

            • by Coren22 (1625475)

              Unfortunately, they would be designed so you would have to replace your computer for them to get software updates.

        • by dadioflex (854298) on Thursday May 10, 2012 @01:18AM (#39951029)

          That's impossible. Lights have to be in a bulb shape, because that's how they've always been, and people don't like change.

          I suspect in a lot of households, one half doesn't care what their "light bulbs" look like so long as they save them money, and one half doesn't care how much they cost to run so long as they look right in their decorative light fixtures. Typically the "it has to look right" half wins the buying decision.

          • by Grishnakh (216268)

            I think you're mostly hit the nail right on the head, but I do think another factor, at least in new houses, is that builders use whatever's cheapest and very rarely install newer technologies. That's why we have so many problems with stuff like low-flow toilets that clog all the time (there's lots of low-flow toilets that work great, but they're not the absolute dirt-cheapest toilet on the market, so builders won't use them unless they're building a custom house and the client specifically demands it).

          • Typically the "it has to look right" half wins the buying decision.

            Oh, it's worse than that. The looks are evaluated based on how it looks when the light is OFF. That is, it has too look good during the day, when it doesn't have a purpose. Doesn't matter if it produces any actual *light* at all...

        • ...Running lamp cord through them (particularly the joints) is a giant PITA and really doesn't make any sense.

          It's especially fun when you omit a spacer and shred the wire with the threads. Why does the circuit breaker trip every time I plug in this new lamp? Oh. Crap.

          • by Grishnakh (216268)

            Yes, exactly. The whole thing is completely idiotic, and if anything, some type of (wider-diameter) plastic tubes should be used, not brass. Or just nothing at all; the wire already has insulator on it, it certainly doesn't need metal tubes to protect it from the insides of the lamp.

        • TL bars were already very common way before CFL's were concieved of (at least here in the Netherlands).
          • by Grishnakh (216268)

            Not here in the USA. We've had the big fluorescent tubes for ages (probably since the 50s or 60s), but they've only been used in offices and they caught on in personal garages or workshops. But inside the house? Never. Some manufacturers have tried to push tube-type fixtures for bathrooms and other rooms, but they never caught on. You might occasionally see one in a bathroom, but only rarely, and that's the only place. I got a couple about 5 years ago for a house I lived in at the time and they worked

        • by drinkypoo (153816)

          Fluorescent lights themselves cost more than incandescents, full stop. They cost more when you put them in and the replacements cost more. Home builders put incandescent sockets everywhere because they cost fifty-nine cents instead of twenty bucks for a halfway-decent fluorescent fixture.

          Offices do different things, because efficiency is a real concern for them, because it's not practical to turn lights off during the day. Also, they are required by various workplace laws to have a certain amount of lightin

        • The "bulb" shape is frequently important because so many lampshades are designed to fit over them.
        • by Petaris (771874)

          Your right about the round fluorescent here in the US, but that doesn't apply everywhere. You see the round, and every other shape, fluorescent bulbs all over in Japan. Actually you can still find the round fluorescent bulbs in specialty lamps here too, my dad has one in his lab that has a magnifying glass in the middle, but that IS a specialty item.

          Also, one of the reasons those haven't changed is because of the cost of changing perfectly good fixtures out just to fit a new bulb in them. If you haven't

          • by Grishnakh (216268)

            Changing fixtures isn't a problem. You don't see people using dot-matrix or old ink-jet printers because the cost of changing a "perfectly good" printer is too much to change to a different ink cartridge; people buy the "fixture" first and worry about the consumables later. Sure, a 40-year-old table lamp isn't going to work well with a circular fluorescent tube, but how many people are using 40-year-old lamps? People buy new lamps all the time, but the new ones are still made exactly the same as the ones

            • by Petaris (771874)

              I get your point. But I think the comparison to printer tech is a little bit too different to make a lot of impact. For example, the printers improved in other ways that were very important, size, noise, quality of print, etc. That is not the case for lamps or light fixtures for the most part, so you lack the real improvements that made the move from the dot matrix impact printers (which are still used and even sold) to inkjets and then lasers so worthwhile. That being said you have seen some improvemen

              • by Grishnakh (216268)

                Creating new standards isn't a problem, and never has been. There's standards for fluorescent tubes; there were standard compact fluorescent sockets long before the Edison-compatible ones became popular, and there's several standard long-tube type sockets (T5, T8, etc.). These standards have been used in commercial installations for ages. So there's been nothing to stop companies from making new lamps or fixtures using these standards, and homeowners from buying them. In fact, companies actually HAVE ma

        • by Eil (82413)

          Look how well circular fluorescent bulbs went over: like a lead balloon.

          Actually, circular fluorescent bulbs were very popular in the 50's and 60's, particularly in kitchens, in basements, over workbenches, and so on. Places in the home were people spent a lot of time and wanted an abundance of light. They fell out of favor later on because style and taste moved toward softer and warmer lighting, even in the more well-lit areas of the home.

      • Add a webcam and blam! instant ceiling mirror!

    • Re:Dumb question (Score:4, Informative)

      by IANAAC (692242) on Wednesday May 09, 2012 @05:40PM (#39948241)

      Why must a single LED provide all the light? Couldn't an array of, say, four LEDs, each equivalent to a 25W incandescent and using mirrors and/or lenses to even out the light distribution, get the same efficiency and substitute for a 100W bulb? Am I missing something obvious?

      That's exactly what is being done now with many of these "shed' lights. I purchased a couple of these that have 20 LEDs inside a casing that has a highly reflective back (they're attached to small solar panels) for my cabin, since our electricity is quite prone to outages from all the thunder/lightning storms we have in Northern Wisconsin. Each one is enough to illuminate a 10x12 room on their own. I can read comfortably with just this light from pretty mch anywhere in the room.

      They're not the prettiest lights, but I built a wood/translucent plastic shade, to make them at least a bit better looking. They also come with their own remote control switch so you can turn them on/off as you would any other sconce or ceiling light.

      It's only a matter of time before some decent designs start coming out for these things.

      • by ArcadeNut (85398)

        (they're attached to small solar panels)

        So you have Solar powered lights?

        • by uncqual (836337)
          Much better than that.

          He has one small solar panel on the roof which powers the LED light in one room. Then he has a solar panel in that room which captures light from that room's LED to power the LED light in a second room. Then he has a solar panel in the second room which captures light from its LED light to power the LED light in a third room. Then he has a solar panel in the third room which captures light from its LED light to power the LED light in a fourth room. Then he has...

          At night, he ju
          • Re:Dumb question (Score:5, Informative)

            by IANAAC (692242) on Wednesday May 09, 2012 @07:08PM (#39948989)
            You joke, but actually, each light array has a small 6x6 inch panel that your could mount either outside or hang in a window (the power cord from panel to battery pack is 16 ft. long). They provide enough energy to store in the enclosed small battery packs to last about 12 hours a charge. It's really not a bad solution to the problem.

            In any case, energy is energy, whether it's generated at a coal plant and then distributed or directly to a battery pack for later use.

            My point was really that, while they're currentlly not the most attractive lighting, that won't always be the case - they can be made fashionable as well as usable.

    • Re:Dumb question (Score:4, Insightful)

      by Guspaz (556486) on Wednesday May 09, 2012 @05:47PM (#39948299)

      Sure, and lots of applications do that already. There are drawbacks though: cost and space, for one thing, not to mention the different optical properties (focusing one light source versus focusing many).

      If your sole goal is to just pump out a ton of light regardless of the cost or space, that's not a problem. But if you care about cost, or need to focus the light in a specific manner, it's a problem.

      I suspect this is one of the reasons why LED-based projectors are still incredibly dim.

    • Why must a single LED provide all the light? Couldn't an array of, say, four LEDs, each equivalent to a 25W incandescent and using mirrors and/or lenses to even out the light distribution, get the same efficiency and substitute for a 100W bulb? Am I missing something obvious?

      People's houses have ceiling mounts that typically take from one to four bulbs. Lamps take one.

      If you want to deal with anything other than that, you're talking replacing the hardware as well as the bulbs. Which is too expensive for

      • Well, my point was that one socket could power multiple individual LEDs in a single "bulb." Not installing one LED per socket, but several LEDs powered off a single socket using a frame of roughly the same size as a regular bulb. Others have pointed out that they already do this to reach the power levels available now, and that it doesn't scale well in complexity and cost.
    • by Joce640k (829181)

      Why must a single LED provide all the light? Couldn't an array of, say, four LEDs, each equivalent to a 25W incandescent and using mirrors and/or lenses to even out the light distribution, get the same efficiency and substitute for a 100W bulb? Am I missing something obvious?

      If you look closely at the "high-power" LEDs that's exactly what they are.

      eg. http://www.pbase.com/kds315/image/127711917/original.jpg [pbase.com]

    • by xorsyst (1279232)

      You can buy LEDs on a roll. Just stick them to the ceiling in a line, cross, square, whatever.

      http://www.simplyled.co.uk/5m-LED-Flexible-Strip-Light-Kit-350-piece-SMD-5050-includes-LED-Driver-in-Cool-White_AZVTY.aspx?nh=0 [simplyled.co.uk]

  • But they perform best at only low power, enough for a flashlight or the screen of your cellphone. If you increase the current enough for them to light a room like an old-fashioned incandescent bulb, their vaunted efficiency nosedives.

    For a second there, I had images of LEDs hanging droopily over the edges of tables and tree branches [blogspot.com].

  • ... we should expect to see kewl blue LEDs appearing on all major appliances in the next 3 to 5 years.

    • That really sounds annoying.
      • by Qzukk (229616)

        I have a DVR with a blue power LED on front that apparently is just the right wavelength to be screwed with by my glasses. As I move my head around (or just move my glasses around) the LED appears to move around on the front of the thing. The closer to the edge of my glasses, the farther the displacement. I can even get it to overlap the other LEDs if I turn far enough, so it seems to just be that wavelength of light that's distorted, and it has to be a fairly narrow band that is affected since I've neve

        • by necro81 (917438)

          just the right wavelength to be screwed with by my glasses. As I move my head around (or just move my glasses around) the LED appears to move around on the front of the thing. The closer to the edge of my glasses, the farther the displacement.

          It's called chromatic aberration [wikipedia.org], and it is an unavoidable effect of light passing through lenses. When light passes through a lens, it gets bent, which is the whole point. But the amount of bending is wavelength-dependent, and so most lenses will act a bit like a

  • by Trogre (513942) on Wednesday May 09, 2012 @07:04PM (#39948957) Homepage

    If you increase the current enough for them to light a room like an old-fashioned incandescent bulb, their vaunted efficiency nosedives.

    Apparently this droop issue is only a problem for non-blue wavelengths. At least if my subwoofer, PC and external HDD are anything to go by...

    My eyes hurt.

    • by Khyber (864651) <techkitsune@gmail.com> on Wednesday May 09, 2012 @11:29PM (#39950529) Homepage Journal

      Actually, that's just because blue is a higher energy potential. Blue wavelengths especially have hazard warnings, as that wavelength has known issues with triggering macular degeneration or making it worse.

    • by adolf (21054)

      FWIW, I find that placing red vinyl electrical tape over an eye-burning blue LED tones it down appropriately enough that it can still be seen, but is never too bright.

      My application of it is sloppy, but at least I can look at the damned things once the tape is covering them. (I could trim the tape with a good knife if I cared, but I really don't.)

      Amusingly, capacitive buttons (such as those on the external Lite-On DVD-R drive on my desk) still work fine even with the tape over top of them.

      • by nadaou (535365)

        I do the same thing with the tape, as I've never actually bothered to open the thing up and add a resistor in series. The farthest I've got is to take out the LED and grind the plastic housing so that it is flatter and rougher, to make it a bit more diffuse.

  • by Anonymous Coward

    My experiment with LED each of the first 3 bulbs I bought lasted between 500 and 2000 hours est. I bought a different brand, one died the first week. I now use CCFL simply because while they use slightly more energy, they are 10% of the price and also burn out way too soon, but not any sooner than LED and the light is better too..

    Rod

    • and yet I just bought a 30 pack of 40 watt Incadescent bulbs for better lighting and environmental efficiency - No Mercury. Do they burn out any faster? Not as far as I've seen based on the quality of the damn CFL bulbs we've been able to get cheaply. Those don't last anylonger then an incadescent bulb and have mercury in them plus they look horid where I really need them.

      What I'm doing now is moving towards the halogen based 12v bulbs in low voltage track light systems. quite a bit of light and can be run

      • by wrook (134116) on Wednesday May 09, 2012 @08:05PM (#39949399) Homepage

        CFLs burn out quickly if you cycle them. Once you turn them on, they shouldn't be turned off for 20 minutes. This makes them less than ideal for some locations (like the bathroom, hallway, etc). I currently have CFLs as the main lighting in areas like the living room, but LEDs in other areas. LEDs are expensive, but it's not like I'll starve if I spend a couple of hundred dollars on lights. Prices are dropping fast (at least here in Japan). It wouldn't surprise me if the cost per lumen approaches CFLs soon.

        I've never been one to dislike CFLs. Personally, I like the color of "daylight" bulbls *much* better than incandescent. But I must say that I like my LEDs better than the CFLs. The biggest issue is that the lumens don't drop off as quickly through use. They also come to full brightness more quickly (basically instantly). I will probably switch over completely in the next couple of years.

      • by sunspot42 (455706) on Thursday May 10, 2012 @12:37AM (#39950861)

        >I just bought a 30 pack of 40 watt Incadescent bulbs for better lighting and environmental efficiency - No Mercury.

        Unless coal is used to generate some - or worse most - of the electricity where you live, in which case powering those incandescent bulbs will release far more mercury into the environment than an equivalent number of CFLs would.

        Worse, the mercury that comes from burning coal isn't elemental mercury, as you'd find in a CFL. Which means it's far more easily absorbed by living things like us.

    • by Khyber (864651)

      So why not build your own? It is ridiculously simple, with the exception of a little math.

  • There are other droops in life I'd rather see solved...

  • by rossdee (243626) on Wednesday May 09, 2012 @10:05PM (#39950103)

    Since the have laws banning incandescent bulbs because they are inneficient, when are they going to do something about the large incandescent light source 92 million miles away? Not only is it inefficient, it is the major cause of global warming.

    (PK so there might be some issues of jurisdiction, but the owner of said light source (Oracle) is in this country...

  • Pushing the diode at 200mA only resulted in an actual drop of roughly 8 points from that 52 percent. That's better than current blues used in my panels, which are top-line and only roughly 35% efficient.

    But that isn't solving droop. Droop is the speed at which an LED driven at higher currents loses light output, which is a secondary byproduct of this. This mitigates the hell out of it, but doesn't solve the overall issue of light output loss over operative time.

    But the higher efficiency is very welcomed. Ap

    • by JRIsidore (524392)
      What they did is they compared the light of LEDs and HID to that of sodium lamps, mostly found in outdoor lighting (for those who don't RTFA). The blue light, which is missing in the sodium spectrum, supresses the melatonin production. The same process happens every morning when you get up and turn on the light or go outside. As sodium lamps are mostly used in streetlighting etc. I think this is actually a benefit instead of being dangerous. Supressing the melatonin fights the fatigue which might prevent so

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