Kill LED lamp flicker

piglet <erichpwagner@hotmail.com> wrote:

> What do you use the waste heat in R5 for, boiling water for tea?
> 
> piglet
> 

I don't think it's that bad. Futher answer in next post.

-- 
MRM

Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

> most LED lamps have a build in constant current driver so they will be
> the same brightness at any voltage high enough for the LEDs and
> regulation 
> 
> or that they have a capacitive dropper that will only work on DC and
> have a terrible power factor 

I checked. The only electronics on my LED lamps is a bridge rectifier.

A capacitive dropper will not work on DC.



-- 
MRM

fredag den 8. september 2023 kl. 21.29.18 UTC+2 skrev Mike Monett VE3BTI:
> Lasse Langwadt Christensen <lang...@fonz.dk> wrote: 
> 
> > most LED lamps have a build in constant current driver so they will be 
> > the same brightness at any voltage high enough for the LEDs and 
> > regulation 
> > 
> > or that they have a capacitive dropper that will only work on DC and 
> > have a terrible power factor
> I checked. The only electronics on my LED lamps is a bridge rectifier. 
> 
> A capacitive dropper will not work on DC. 

obviously meant "only work on AC"

Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:

> fredag den 8. september 2023 kl. 21.29.18 UTC+2 skrev Mike Monett VE3BTI:
>> Lasse Langwadt Christensen <lang...@fonz.dk> wrote: 
>> 
>> > most LED lamps have a build in constant current driver so they will be 
>> > the same brightness at any voltage high enough for the LEDs and 
>> > regulation 
>> > 
>> > or that they have a capacitive dropper that will only work on DC and 
>> > have a terrible power factor 
>> I checked. The only electronics on my LED lamps is a bridge rectifier. 
>> 
>> A capacitive dropper will not work on DC. 
> 
> obviously meant "only work on AC"

Why do you want to drop the voltage? There are the correct number of LEDs 
in series needed to work at 120VAC.

I verified there is a bridge rectifier in the LED lamps. I found a web site 
that disassembled a LED lamp and read the part number off the IC mounted on 
a small pcb. It turned out to be a bridge rectifier.

The bridge rectifier in the LED lamps is needed to convert the AC line 
voltage to rectified DC as the LEDS cannot run with reversed polarity.

There is no need for a constant current driver and none is installed. 

Obviously, the LED lamps are sensitive to line voltage since they flicker 
with slight disturbances in the line voltage.

If a constant current driver was installed, there would be no flickering 
and no need for energy storage to ride out the transients.


-- 
MRM

On Friday, September 8, 2023 at 12:29:18 PM UTC-7, Mike Monett VE3BTI wrote:
> Lasse Langwadt Christensen <lang...@fonz.dk> wrote: 
> 
> > most LED lamps have a build in constant current driver so they will be 
> > the same brightness at any voltage high enough for the LEDs and 
> > regulation 
> > 
> > or that they have a capacitive dropper that will only work on DC and 
> > have a terrible power factor
> I checked. The only electronics on my LED lamps is a bridge rectifier. 
> 
> A capacitive dropper will not work on DC. 

Usually, bridge-rectifier lamps are intended for fluorescent-type ballasts (inductive
current limiters passing AC); the ballast limits the current, the rectifiers
steer it so both half-cycles of the AC power the LEDs.   There's
maximal (100 or 120 Hz) flicker, but at those frequencies, only
video cameras catch it as flicker.

On 09/09/2023 01:24, Mike Monett VE3BTI wrote:
> Lasse Langwadt Christensen <langwadt@fonz.dk> wrote:
> 
>> fredag den 8. september 2023 kl. 21.29.18 UTC+2 skrev Mike Monett VE3BTI:
>>> Lasse Langwadt Christensen <lang...@fonz.dk> wrote:
>>>
>>>> most LED lamps have a build in constant current driver so they will be
>>>> the same brightness at any voltage high enough for the LEDs and
>>>> regulation
>>>>
>>>> or that they have a capacitive dropper that will only work on DC and
>>>> have a terrible power factor
>>> I checked. The only electronics on my LED lamps is a bridge rectifier.
>>>
>>> A capacitive dropper will not work on DC.
>>
>> obviously meant "only work on AC"
> 
> Why do you want to drop the voltage? There are the correct number of LEDs
> in series needed to work at 120VAC.
> 
> I verified there is a bridge rectifier in the LED lamps. I found a web site
> that disassembled a LED lamp and read the part number off the IC mounted on
> a small pcb. It turned out to be a bridge rectifier.
> 
> The bridge rectifier in the LED lamps is needed to convert the AC line
> voltage to rectified DC as the LEDS cannot run with reversed polarity.
> 
> There is no need for a constant current driver and none is installed.

There should at least be a small choke or resistor in series with the 
LED chain in addition otherwise they will be fried by the first line 
transient high enough to exceed their breakdown voltage.

The weakest one will die and that takes out the entire chain. Better 
designed LED lights have constant current drive and multiple chains.

> Obviously, the LED lamps are sensitive to line voltage since they flicker
> with slight disturbances in the line voltage.

You seem to have a particularly cheap and nasty LED lamp then.

I have seen similar in the classic bulb configuration with a simple 
rectifier, resistor and enough ~60 LEDs to take UK mains 240v. MTBF is 
piss poor because the first LED to fail takes the entire thing down.

Better quality mains powered LED bulbs do have some capacitance and a 
crude constant current supply. The ones I have are so good that even 
with one phase down everything is at full brightness, but the problem 
becomes obvious if I turn on the kettle which takes forever to boil.

> If a constant current driver was installed, there would be no flickering
> and no need for energy storage to ride out the transients.

You would still need a capacitor somewhere to store energy for it to use.
Capacitors are often the weak link in LED bulbs as they get cooked.

-- 
Martin Brown

On Fri, 8 Sep 2023 08:10:41 -0000 (UTC), Mike Monett VE3BTI
<spamme@not.com> wrote:

>
>Note the 1N4007 diodes are replaced by a regular bridge rectifier with 
>suitable ratings. It is easier to model using 1N4007s than trying to find a 
>bridge rectifier in LTspice.

The 1N4007 works more like a PIN diode, the other 1N400x diodes are
normal diodes.

On Friday, September 8, 2023 at 11:25:43 AM UTC-4, John Larkin wrote:
> On Fri, 8 Sep 2023 08:10:41 -0000 (UTC), Mike Monett VE3BTI 
> <spa...@not.com> wrote: 
> 
> >I recently changed the overhead fluorescent lamps for LED replacements. 
> > 
> >Very soon, I noticed they were flickering a lot more the the old 
> >fluorescents. 
> > 
> >They flicker on the slightest line disturbance, from someone turning on a 
> >microwave to who knows what outside the building. It turns out the 
> >bandwidth of LEDs is much higher than gas lamps. Good to know if you're in 
> >the spying business, but not good in the shop.
> I doubt that the fluorescents are much slower, at visual speeds, than 
> LEDs. You can verify that with a photodetector and an ocilloscope. 
> 
> Maybe you have cheap flourescent-replacement tubes.

Uh-huh. LEDs don't flicker. They're all powered by regulated switching ***current*** sources operating in the 20kHz-30kHz range. LEDs are not directly powered by voltage, and the current sources are immune to voltage fluctuation.

Maybe he bought a "previously owned" bulb for a discount, as in previous owner ran them for 10 years..

lørdag den 9. september 2023 kl. 14.46.48 UTC+2 skrev Fred Bloggs:
> On Friday, September 8, 2023 at 11:25:43 AM UTC-4, John Larkin wrote: 
> > On Fri, 8 Sep 2023 08:10:41 -0000 (UTC), Mike Monett VE3BTI 
> > <spa...@not.com> wrote: 
> > 
> > >I recently changed the overhead fluorescent lamps for LED replacements. 
> > > 
> > >Very soon, I noticed they were flickering a lot more the the old 
> > >fluorescents. 
> > > 
> > >They flicker on the slightest line disturbance, from someone turning on a 
> > >microwave to who knows what outside the building. It turns out the 
> > >bandwidth of LEDs is much higher than gas lamps. Good to know if you're in 
> > >the spying business, but not good in the shop. 
> > I doubt that the fluorescents are much slower, at visual speeds, than 
> > LEDs. You can verify that with a photodetector and an ocilloscope. 
> > 
> > Maybe you have cheap flourescent-replacement tubes.
> Uh-huh. LEDs don't flicker. They're all powered by regulated switching ***current*** sources operating in the 20kHz-30kHz range. LEDs are not directly powered by voltage, and the current sources are immune to voltage fluctuation. 
> 

some are linear, enough LEDs in series to add up to most of the rectified line voltage 

On Saturday, September 9, 2023 at 9:01:28 AM UTC-4, Lasse Langwadt Christensen wrote:
> lørdag den 9. september 2023 kl. 14.46.48 UTC+2 skrev Fred Bloggs: 
> > On Friday, September 8, 2023 at 11:25:43 AM UTC-4, John Larkin wrote: 
> > > On Fri, 8 Sep 2023 08:10:41 -0000 (UTC), Mike Monett VE3BTI 
> > > <spa...@not.com> wrote: 
> > > 
> > > >I recently changed the overhead fluorescent lamps for LED replacements. 
> > > > 
> > > >Very soon, I noticed they were flickering a lot more the the old 
> > > >fluorescents. 
> > > > 
> > > >They flicker on the slightest line disturbance, from someone turning on a 
> > > >microwave to who knows what outside the building. It turns out the 
> > > >bandwidth of LEDs is much higher than gas lamps. Good to know if you're in 
> > > >the spying business, but not good in the shop. 
> > > I doubt that the fluorescents are much slower, at visual speeds, than 
> > > LEDs. You can verify that with a photodetector and an ocilloscope. 
> > > 
> > > Maybe you have cheap flourescent-replacement tubes. 
> > Uh-huh. LEDs don't flicker. They're all powered by regulated switching ***current*** sources operating in the 20kHz-30kHz range. LEDs are not directly powered by voltage, and the current sources are immune to voltage fluctuation. 
> >
> some are linear, enough LEDs in series to add up to most of the rectified line voltage

I'm pretty sure they've never used that method for the commodity lighting bulb market. Maybe for signs and indicator bulb types of applications where it has to be dirt cheap.