Author Topic: Filament style LED bulbs  (Read 880 times)

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Offline shakalnokturn

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Filament style LED bulbs
« on: December 07, 2018, 12:28:47 am »
Admittedly LED bulbs are the new rip off and ecological catastrophe of the decade.
They do have the excuse of higher efficiency, and longer life in theory.
In practice the long life is never there, the driving electronics never outlive the LEDs and sometimes kill them when failing.
Actually an old Edison filament bulb usually lasts longer the average LED crap.

Rant finished...

My SWMBO wants filament style LED bulbs for aesthetic reasons.
Now I haven't used enough of these to grumble about reliability yet, but they already bother me in another way and I'm the only person in my surroundings that seems to notice this: They strobe!

I've been looking for information on a typical driver circuit used for these bulbs without success yet. I'm trying to find out if there is any simple way of suppressing the strobe.
I have not measured the light waveform or tried a DC supply.

The only filament bulb I have at hand now is a V-TAC VT1962, peering down at the E27 base there is a small PCB with what could be a diode bridge, a few passive components and a SOP8 IC.
I can't read the IC reference without breaking the bulb.

How do these work? Phase angle approximation switching for current limiting, high frequency PWM?
Does anyone have pictures or schematics?


« Last Edit: December 07, 2018, 02:32:19 am by shakalnokturn »
 

Online Hero999

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Re: Fialment style LED bulbs
« Reply #1 on: December 07, 2018, 02:10:19 am »
If you get decent LED bulbs they're generally good. Cheap ones no. I replaced all of the lamps in my parent's house and have only had a problem with some of the really cheap ones bought on-line. The decent ones from reputable supermarket chains and electrical distributors have all served them fairly well and have more than paid for themselves in power savings, over five years.

Not all LED filament lamps strobe. The type with the tiny bases which look almost identical to incandescent lamps have a very simple capacitive dropping power supply, without a decent smoothing capacitor and often flicker. Get the ones with the larger bases, which will have a smoothing capacitor and they will give a nice, steady light output.
 

Offline gildasd

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Re: Filament style LED bulbs
« Reply #2 on: December 07, 2018, 03:09:15 am »
I’ve had some 1st gen led bulbs die, but they were cheap knock-offs that I treated badly.
So far, I have yet to have a single bulb from Osram & Philips die on me.
The only quality Led bulbs I have seen die are dimables that were left on 100% all the time (retail), wrong/very crap drivers or improper installation (240V wires screws not tight enough, creating a tiny spark gap at start up over time).
I'm electronically illiterate
 

Online floobydust

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Re: Filament style LED bulbs
« Reply #3 on: December 07, 2018, 03:43:56 am »
The LED filaments are high-voltage strings, I only see them in series with no SMPS.
They don't do well because heat is hard to get rid of in an enclosed air space.

 

Offline Benta

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Re: Filament style LED bulbs
« Reply #4 on: December 07, 2018, 04:18:41 am »
I stay away from cheap supermarket LED bulbs and only buy brand names and have never had problems with lifetime or strobing.
Osram, Philips, Paulmann.
 

Offline shakalnokturn

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Re: Filament style LED bulbs
« Reply #5 on: December 07, 2018, 04:51:55 am »
@ floobydust: Thanks interesting video.

Regarding "quality" bulbs that's what I figured too after trying a couple of cheapies off the fleabay, mostly dangerous and unreliable.
So I've tried well-known branded stuff since with some deceptions all the same:

Verbatim model 52119 dead after approx. 10 hours use. (Made in China)
Osram model AA68548 several randomly flickering after about 2 years of use. (Made in China)

None of the German made Osram or the Toshiba have deceived me yet.
 

Online Marco

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Re: Filament style LED bulbs
« Reply #6 on: December 07, 2018, 05:20:33 am »
Some of the older filament LED bulbs did have constant current power supplies with a transformer/inductor. Some claim the same thing today, although if you look at the pictures looking into the lamp base there doesn't seem enough room.



« Last Edit: December 07, 2018, 11:02:36 am by Marco »
 

Offline amyk

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Re: Filament style LED bulbs
« Reply #7 on: December 07, 2018, 12:13:02 pm »
It's the ones with fancy electronics that often die first, the ones with capacitive droppers are usually far more reliable unless they underspecced the capacitor's voltage rating. The filament bulbs are more likely to use this style of driver because of the space constraints.

The flickering is as others mentioned due to a lack of filter capacitance; you may be able to carefully dissect one and solder an electrolytic of appropriate voltage across the LED string.
 

Online james_s

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Re: Filament style LED bulbs
« Reply #8 on: December 07, 2018, 04:37:14 pm »
If you buy decent bulbs instead of the cheapest garbage you can find, they're not a rip-off or an ecological disaster. I retrofitted my entire house from 2011-around 2015. Throughout that time I've had only a few failures and every one of those was a cheap bulb that I was running in a fully enclosed fixture despite the fact that they were not rated for that use. The Philips and Cree bulbs I'm using have had a 0% failure rate. I retrofitted my mom's house over roughly the same time period and there they have also had a 0% failure rate, not a single LED bulb in her house has ever failed. They have paid for themselves multiple times over in energy savings. Even relative to CFLs I was using before, the energy savings are significant, the lifespan is far longer, they contain no mercury, and the light quality is much better.

I like the filament type in some types of decorative fixtures but I find the color is not quite as good and they flicker more than the better lamps.
 

Online beanflying

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Re: Filament style LED bulbs
« Reply #9 on: December 07, 2018, 04:48:17 pm »
The LED filaments are high-voltage strings, I only see them in series with no SMPS.
They don't do well because heat is hard to get rid of in an enclosed air space.

Of the LED lamps I have in use they are among the lowest heat output of all of the home/globe type options. Currently running a 4W in a PLA 3D printed fully enclosed ball shade and the hottest spot I could get on the shade was 4 degrees above an ambient of 20C. Interested in how you think 'they don't do well because heat....'?

NB These are a Branded bulb not an evilbay no name. Flicker is not an issue.

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Online Hero999

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Re: Filament style LED bulbs
« Reply #10 on: December 07, 2018, 07:46:21 pm »
The LED filaments are high-voltage strings, I only see them in series with no SMPS.
They don't do well because heat is hard to get rid of in an enclosed air space.

Of the LED lamps I have in use they are among the lowest heat output of all of the home/globe type options. Currently running a 4W in a PLA 3D printed fully enclosed ball shade and the hottest spot I could get on the shade was 4 degrees above an ambient of 20C. Interested in how you think 'they don't do well because heat....'?

NB These are a Branded bulb not an evilbay no name. Flicker is not an issue.


I've had the same experience. I think decent LED filament lamps are filled with a thermally conductive gas. The cheaper ones are probably just filled with air. The thin strips of LEDs is they are cooled by convection and radiation, without the need for a bulky heat sink.

It's the ones with fancy electronics that often die first, the ones with capacitive droppers are usually far more reliable unless they underspecced the capacitor's voltage rating. The filament bulbs are more likely to use this style of driver because of the space constraints.
I found the reverse to be true. The capacitive dropper type are generally cheaper and therefore built down to a price with an under specified capacitor. The ones with the fancy electronics are more expensive and generally more reliable.
 

Offline Halcyon

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Re: Filament style LED bulbs
« Reply #11 on: December 07, 2018, 08:20:30 pm »
I've used these bulbs in one of my bathrooms for about 3-4 years now and they work just as well as the day I bought them. There is absolutely no noticeable flicker at all (and I too notice flicker, having previously worked in video/lighting). They are as close to actual candle/incandescent light as you can get in an LED light in my opinion.

I have no idea who actually makes them (I suspect they are just branded with the resellers name), but I would certainly buy them again.
 

Online Marco

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Re: Filament style LED bulbs
« Reply #12 on: December 07, 2018, 08:44:58 pm »
It's the ones with fancy electronics that often die first, the ones with capacitive droppers are usually far more reliable unless they underspecced the capacitor's voltage rating.

Probably not legal though in the EU above 5W. For a properly designed one you can also get away with an order of magnitude smaller capacitor with active switching, which allows you to use film capacitors. So it's a trade off, electrolytic durability vs. active electronics durability.

That said, running the numbers in my head I've always overestimated how much of a ripple there needs to be with electrolytic smoothing. You could indeed easily smooth that out completely with a linear regulator. Shame about the power factor.
« Last Edit: December 07, 2018, 08:51:48 pm by Marco »
 

Online james_s

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Re: Filament style LED bulbs
« Reply #13 on: December 08, 2018, 05:15:40 am »
The LED filaments are high-voltage strings, I only see them in series with no SMPS.
They don't do well because heat is hard to get rid of in an enclosed air space.

Of the LED lamps I have in use they are among the lowest heat output of all of the home/globe type options. Currently running a 4W in a PLA 3D printed fully enclosed ball shade and the hottest spot I could get on the shade was 4 degrees above an ambient of 20C. Interested in how you think 'they don't do well because heat....'?

NB These are a Branded bulb not an evilbay no name. Flicker is not an issue.

Every filament style LED bulb I've tried flickers, Philips, GE, noname stuff, the name brands are definitely better but they still have visible flicker, verified with the high speed camera mode my phone has so it's not just my imagination. A lot of people either can't see or aren't bothered by the flicker though. Just the other day I was out shopping with my mother and she couldn't understand what I was talking about when I said the LED Christmas lights on display were flickering. I took a quick phone video and played it back in slow speed at which point you could see the lights flashing on and off.
 

Offline gildasd

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Re: Filament style LED bulbs
« Reply #14 on: December 08, 2018, 11:48:17 pm »
The LED filaments are high-voltage strings, I only see them in series with no SMPS.
They don't do well because heat is hard to get rid of in an enclosed air space.

Of the LED lamps I have in use they are among the lowest heat output of all of the home/globe type options. Currently running a 4W in a PLA 3D printed fully enclosed ball shade and the hottest spot I could get on the shade was 4 degrees above an ambient of 20C. Interested in how you think 'they don't do well because heat....'?

NB These are a Branded bulb not an evilbay no name. Flicker is not an issue.

Every filament style LED bulb I've tried flickers, Philips, GE, noname stuff, the name brands are definitely better but they still have visible flicker, verified with the high speed camera mode my phone has so it's not just my imagination. A lot of people either can't see or aren't bothered by the flicker though. Just the other day I was out shopping with my mother and she couldn't understand what I was talking about when I said the LED Christmas lights on display were flickering. I took a quick phone video and played it back in slow speed at which point you could see the lights flashing on and off.
I have 4 Segula bulbs over the table I am typing this.
No visible flicker using Mk1 meatball optical devises.
Might be worth checking if your supply is up to snuff.
I'm electronically illiterate
 

Online james_s

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Re: Filament style LED bulbs
« Reply #15 on: December 09, 2018, 05:49:16 am »
There's absolutely nothing wrong with the supply, nice clean 60Hz sine wave as is typical anywhere in the US. There is no room in the lamps for any sort of bulk capacitance, it's impressive they get the flicker as low as they do but it's there.
 

Online beanflying

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Re: Filament style LED bulbs
« Reply #16 on: December 09, 2018, 09:22:35 am »
Shooting with a high speed frame rate camera showed flicker. Have a serious think about what shooting with a frame rate higher (not specified) than the supply frequency was showing. Yes at times the voltage swings low so the LEDS will quite rightly appear to be off to its electronic interpretation.

Regardless of high frame rate or not our eyes are not camera sensors and our brains work differently (not a fixed frame rate) interpreting what is seen by them. Those of us that see no discernible flicker see no flicker.
« Last Edit: December 09, 2018, 09:24:46 am by beanflying »
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Online james_s

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Re: Filament style LED bulbs
« Reply #17 on: December 09, 2018, 11:43:38 am »
I never claimed otherwise, a lot of people such as my mother cannot see flicker, I on the other hand can. I'm not claiming to be superior, if anything it's a fault that causes me discomfort but that isn't something I can change. For those who are not sensitive to flicker there's no reason to avoid flickering lamps, that doesn't mean that everybody is not bothered by them.
 

Online beanflying

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Re: Filament style LED bulbs
« Reply #18 on: December 09, 2018, 12:23:48 pm »
So a quick fossick through a junk box and I still had the board from a filament bulb I took apart earlier in the year. 3.3uF Cap and the chip http://www.szjuquan.com/upload_files/qb_sell_/pdf/SM2082ED.pdf or translated https://translate.google.com.au/translate?hl=en&sl=zh-CN&u=http://www.szjuquan.com/upload_files/qb_sell_/pdf/SM2082ED.pdf&prev=search


So not a simple Cap dropper in the case of this branded globe.
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Online Marco

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Re: Filament style LED bulbs
« Reply #19 on: December 09, 2018, 02:51:29 pm »
There's absolutely nothing wrong with the supply, nice clean 60Hz sine wave as is typical anywhere in the US. There is no room in the lamps for any sort of bulk capacitance, it's impressive they get the flicker as low as they do but it's there.

Lets do simplified math for a 120V LED bulb, lets say 10 msec between peaks, lets say 50 mA current, lets say you want to keep the ripple to 20V to be burned off with a regulator. So 50e-3*10e-3/20 =~ 22 uF. So you can be completely flicker free for a little over 10% loss in efficiency with a capacitor which easily fits in E27.

PS. of course PWM'ing it to keep it even in between peaks would be better, but when you start down that road you might as well do a proper PFC driver.
« Last Edit: December 09, 2018, 02:54:28 pm by Marco »
 

Offline amyk

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Re: Filament style LED bulbs
« Reply #20 on: December 10, 2018, 01:54:20 pm »
So a quick fossick through a junk box and I still had the board from a filament bulb I took apart earlier in the year. 3.3uF Cap and the chip http://www.szjuquan.com/upload_files/qb_sell_/pdf/SM2082ED.pdf or translated https://translate.google.com.au/translate?hl=en&sl=zh-CN&u=http://www.szjuquan.com/upload_files/qb_sell_/pdf/SM2082ED.pdf&prev=search


So not a simple Cap dropper in the case of this branded globe.
That's a linear current regulator. Great power factor and quite cheap, but they run hot! bigclivedotcom on YouTube has some teardowns of bulbs using them.
 

Online beanflying

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Re: Filament style LED bulbs
« Reply #21 on: December 10, 2018, 02:12:50 pm »
It was his fault and the fact that they were $3 AUD each that I brought a bunch in the first place ;) So far after maybe 10 months of use all are still working fine.

I have forgotten the voltage per string but seem to think it was around 70V so at a nominal 1W each about 14mA. So in the order of 0.8W peak being dropped across the IC? I have seen them available in small quantities for about 10 cents.
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Online beanflying

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Re: Filament style LED bulbs
« Reply #22 on: December 12, 2018, 08:13:01 am »
Youtube thinks I needed to know more about filament globes so this turned up in my feed.

Quality Driver Circuitry  :-+


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