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.
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.
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 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.
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've several years experience in drivers for LED lamps, and did investigate visible and non-visible flicker. Next link provides my input for Energystar guidelines on LEDlamps and light modulation.
I bought a LED desk lamp recently which runs off a switching "wall wart" type 20W supply. The separate PSU is probably good for 50000 hours. The way forward with LED lamps is probably to decouple the bulb from the power supply - the low voltage DC supply should be part of the lamp socket, not the lamp itself.
Good idea - there are CFL fittings that work like this, the 2-pin lamp has the tube and the starter and the ballast is separate. There are also 4-pin types for electronic ballasts. So same idea should be good with LEDs - and reduce the ongoing cost a bit maybe.
An interesting question as to why need electrolytic capacitors. A portion of the problem is indeed avoiding flicker, although I am not convinced that a small PP capacitor right behind the line rectifier would not be adequate. Of course one other challenge is the emphasis on absolute minimum BOM cost, notwithstanding the quality problems that result. One dollar more to assure the 50K hour lifetime would be quite reasonable to me.
What I think to be very interesting would be a cost breakdown on the various devices, since I doubt that any of them has over $5 in electronic parts, and I am talking Digikey prices. Knowing just where the cost lies would be a very good start.
I have also wondered about why nobody markets an LED device that uses the rectified line voltage and a current limiting resistor, and perhaps 80 or a hundred "fairly bright" surface mount, or even through hole, LEDs. No filtering, just leds on the full wave rectified line, with 120HZ flicker, which I don't think we could see. Does anyone see a fundamental problem with that?
I guess Incandescents have a good bit of thermal inertia and don't dim much if at all in between half cycles.
TV's would also have a bit of persistence on the phosphor...and CFLs also usually have an electrolytic in them. Whereas LEDs would definitely be on-off devices.
Memo to self...when studying engineering textbooks, do not move head.... ;-)
Those would be directly emmitting diodes then. These diodes shine onto phosphors to make white light. The phosphors continue to glow for brief period after the diode stops emmiting and might be able to mask the flicker. We ran into a problem with white LEDs on a system that was trying to blink at a 50% duty cycle only to have the phosphor glow distort it.
Hi I am from India and developed LED lamp that works out from the regular incandecent bulb sockets.All led bulbs require Electronics to step down the voltage as they work on 3.3 to 4 volts only.As the current requirements are more heat will be developed and cannot be avoided.The led may last more but the electronics is bound to fail soon than claimed.
Electrolytics are available which survive 12,000 hours at 105C. Unless you are cooking your LED's then you can get extremely long lifetimes and my own patented 900 lumen, 90+lumens/w 60W equivalent dimmable design exceeds 98% efficiency so almost no heat from the driver. And all that with 0.993 PF excellent coliur rendering and NO EMI!
I just picked up your query about my design. Yes it is still an application but has no objection raised as yet. It applies to UK, Europe and USA. If you can tell me a little more about what you'd like to know I'd be happy to help. email@example.com
I have two remarks:
1. 105*C capacitors are commonly used in PC power supplies and PC mainboards. They still die in much lower temperature than 105*C.
2. 105*C capacitors are more expensive than typical one (like 85*C). I don't think if typical LED bulb goes higher than 80*C, so why someone should use 105*C capacitors?
I guess problem is not in high temperature but capacitor quality.
I've liked this article as it has answered the same question I had: Why the LED lamps are so costly and I understand, more than electronics, the manufacturers need to do something on the heat management and the casing part to bring down the cost.
Like many of my fellow readers, I am also surprised to see the claim of high lifetime with the electrolytic capacitors in it.
A concern that I don't see addressed is vibration. I have had a CFL blowout in a ceiling fan installation. I haven't seen vibration ratings for CFLs. I These board designs with the air-chassis electrolytics don't look to have reliability in a vibration environment such as a ceiling fan fixture.
If you develop a PFC LED driver, you can use the deramic cap instead of the E-Cap. The E-cap life time shrinks one half for every ten degree ambient temperature. We have been designed the ACDC offline LED drivers for the LED lighting and to reduce the BOM cost. If you are interested in the products, please check out the web site.
We design our products in the 700V process, so the 500V HV NMOS and the 700V Power MOSFET can be integrated.
Please send email to Phil.Lei@sqme.com.tw to find out more.
The manufacturers are probably not counting on the bulbs meeting the specified life but rather replacing them in the future with cheaper to manufacture products. Or just counting on consumers to not follow up with early failure replacements, as we were trained to accept with CFL bulbs which failed to live up to the marketing claims.
Blog Doing Math in FPGAs Tom Burke 6 comments For a recent project, I explored doing "real" (that is, non-integer) math on a Spartan 3 FPGA. FPGAs, by their nature, do integer math. That is, there's no floating-point ...