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.
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!
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.
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.
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.
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.... ;-)
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 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.
Blog Make a Frequency Plan Tom Burke 17 comments When designing a printed circuit board, you should develop a frequency plan, something that can be easily overlooked. A frequency plan should be one of your first steps ...