The dimmable bulbs incorporate silicon-based Infineon or ST power transistors. We did not find silicon carbide technology in any of the lamps.
Each lamp uses a different LED driver IC. Pharox uses four ICs, 40 resistors and 16 capacitors, plus transformers and many diodes. All this to dim a 40-W-equivalent light bulb—but only, in some cases, if you purchase a new dimmer, since your old dimmer might not be compatible.
Philips uses a remote phosphor, relying on the bulb envelope material to do the wavelength conversion. Lutetium oxide is used as a fluorescent medium in more than one lamp. We have looked at many LEDs over the last few years and have never seen lutetium used before. More conventional phosphors, such as barium and cerium-doped YAG (yttrium aluminum garnet), are also seen, along with a cocktail of rare earths such as europium and strontium.
Surprisingly, everyone uses blue GaN LEDs—no RGB LEDs in this lot. There are red LEDs in the Pharox, complete with lenses, but they don’t turn on when the lamp is on. They are obviously not for color balance. Maybe the light turns red when the bulb is about to die, or to signal that the lamp is not wired properly.
Philips uses many of its own Luxeon Rebel LEDs in a modular arrangement that could possibly permit the replacement of failed modules. We expected the Sylvania to use an Osram LED, perhaps a Dragon, but that is not the case. Two of the lamps rely on Cree dice.
The LED light-emitting area varies from 4 mm2 to 12 mm2 for the 40-W equivalent bulbs—a variance of a factor of 3—yet their power consumption ranges between 6 and 9 W. Some have four LED dice; others have 48.
Click on image to enlarge.
At what point is such a lamp considered to have reached the end of its operable life, given its dozens of individual LEDs? Nowhere on the fancy packaging, with all its warnings, disclaimers and warranties, is there a definition of the point of final failure for the lamp. Will it go out with a flash? Will it still be usable for its intended purpose until the last second, or will there be a point at which the light has become so faint that the user decides to replace the bulb?
Lots of questions, and we still haven’t answered the first one: Why are A19 LED bulbs so expensive? At 50 to 60 lumens/W, the LED bulbs have the same efficacy as 40-W-equivalent compact fluorescent lights, which typically offer 560 lumens at 10 W, can be purchased for a few dollars and should last, or so the packaging claims, up to eight years. For the same savings in electricity as you’d get with a single LED bulb, you would need to purchase two or three additional CFL bulbs over the next 25 years. Luckily they are available in packs of two or four.
Light bulbs are a commodity item, no matter how long they last. For all the claims of CFL longevity, I have yet to see them reach their expected lifetime. Usually the point of CFL failure is the electronics in the neck, and the same will likely hold true for LED bulbs.
With CFLs, however, we have traded energy consumption for mercury contamination. The attraction of LED bulbs is twofold: They are instant-on, and they are mercury free. The toxicity of rare earths is low, and very little of the material is used in the bulbs anyway.
Over time, LED bulbs will drop in price and will provide a cleaner, safer alternative to CFLs—presumably with a longer life expectancy as well. We can also expect new features; the door is fully open on that front.
I don't see why the electronics needs electrolytics. If you full wave rectify the AC, it should be possible to operate the LEDs only during each half-cycle - at 100 HZ the flicker should not be visible? You could still have a switch mode inverter running to power a string of LEDs at several tens or '00s of Kc during each half-cycle? Tony41, or any other hot shot designers, could you comment?
I have been disappointed in both the cost and the working usefulness of the LED bulbs. Another thing that bothered me was (at least one brand) the lamp base was hot...seems to me if a light is generating heat it is wasting energy. I am amazed at the current cost for these bulbs and not at all happy with CFLs! The "working usefulness" issue for me is the directional-ness of these bulbs. They may work great in a reading lamp fixture or an overhead can (ignoring the heat concern) but for general lamp fixture use such as ceiling dome lights, floor/table lamps they do not shine the light in the right direction!! I am not yet going to use these and currently must suffer with CFLs to keep my electric costs down. At least with CFLs they are cheap.
Great article! I also deeply agree with Tony41.
These new LED bulbs are the same kind of trash as currently available CFL. They are intended (supposedly) to replace standard incandescent bulbs. As most bulbs are installed hanging from the ceiling, usually inside a recess, you have your fragile electrolytic cap and other components subjected to the higher possible temp! Very smart engineering!!!
And c'mom, 3 to 4 hours a day? I have a couple of lamps around my house installed for safety reasons that stays on from sunset to sunrise (~7 PM to ~6 AM). You can imagine how will be the lifespan of these electronics, staying hot for 10+ hours in a row everyday...
I have been developing LED lights for many years. I was the first to put them behind a LCD large flat screen for outdoor advertising in direct sunlight.
I would not purchase any of the LED light bulbs on the market today. The LED's may last a long time but the plastics and power supply components will not.
I designed and developed my own LED lights for my home because I could not find one I would purchase. I use long life components as well as RGB LED's to give me the color spectrum needed for proper lighting. I have also been able to get a bright light that is brighter than an equivalent 100 watt light bulb. I have experimented with quantum dots but it dimes the light too much to get a color shift.
I can dim them just by turning off a few LED’s at a time with a switch. I have an LED module that is 2” X 2” X 1/4” thick plugs directly into 120VAC as well.
I can also power them from batteries charged by a solar panel. During a power outage I have lights when all around me are black.
I can see why LED lighting is failing to gain traction in the US. I have been unemployed for over two years and cannot get a job, however just working at home I seem to be well ahead of all of you.
Well done, interesting analysis, electrolytics are the main problem with CFL, as you state these LED will be poised with this too.
ACRICHE LED with direct AC input design are more quiet solutions, I have already 3 years of full time running,70 ACRICHE lamps involved and no defect. Control after one year shows no decrease.
David Patterson, known for his pioneering research that led to RAID, clusters and more, is part of a team at UC Berkeley that recently made its RISC-V processor architecture an open source hardware offering. We talk with Patterson and one of his colleagues behind the effort about the opportunities they see, what new kinds of designs they hope to enable and what it means for today’s commercial processor giants such as Intel, ARM and Imagination Technologies.