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VZwanenberg
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re: A19 LED bulbs: What’s under the frosting?
VZwanenberg   8/15/2011 12:39:26 PM
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Hi David, 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. http://www.energystar.gov/ia/partners/manuf_res/downloads/lighting/NXP_Semiconductors_Comments.pdf With regards, Victor Zwanenberg

Hube
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re: A19 LED bulbs: What’s under the frosting?
Hube   8/1/2011 7:49:51 PM
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Read my comment, the fist one. ACRICHE is the answer you ask for. Seoul is not the only one maker of these devices. Tree years, 70 lamps always on, no defect, in a few days 2 millions cumuled hours !

Amcfarl
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re: A19 LED bulbs: What’s under the frosting?
Amcfarl   8/1/2011 3:49:58 PM
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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!

David Ashton
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re: A19 LED bulbs: What’s under the frosting?
David Ashton   7/31/2011 11:15:35 AM
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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.

MVSEENAN
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re: A19 LED bulbs: What’s under the frosting?
MVSEENAN   7/31/2011 7:57:11 AM
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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.

chris.michael
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re: A19 LED bulbs: What’s under the frosting?
chris.michael   7/28/2011 11:30:02 PM
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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.

David Ashton
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re: A19 LED bulbs: What’s under the frosting?
David Ashton   7/28/2011 4:07:29 AM
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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.... ;-)

Mongo647
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re: A19 LED bulbs: What’s under the frosting?
Mongo647   7/27/2011 8:20:50 PM
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Have you seen the flicker in the original Oriental LED christmas lights, done as you suggest? Psychedelic with any movement of your head. Festive but not so good for studying engineering textbooks.

WKetel
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re: A19 LED bulbs: What’s under the frosting?
WKetel   7/27/2011 7:11:32 PM
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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?

Battar
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re: A19 LED bulbs: What’s under the frosting?
Battar   7/27/2011 10:48:51 AM
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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.

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