Non-dimmable LED lightbulbs are damaged by Triac dimmers?

[kubeek]

I think that the main advantage of havin a PFC in a power supply is the ability to have wide input voltage range.

 

[NorthGuy]

Since you altering both the switch and the bulb, it would be much easier to put all the circuicity at the switch and run DC to the bulb, with only LEDs in the bulb. Simpler, cheaper, more reliable.

 

[Nigel Goodwin]

I think that the main advantage of havin a PFC in a power supply is the ability to have wide input voltage range.

The regulated PSU's already provided that - the PFC's have been added before it.

 

[Flyback]

yes, just about all pwm controllers for ledlight bulbs are power factor corrected, even if only for 8Watts or so.

http://www.powerint.com/linkswitch-ph
http://www.ti.com/product/lm3447
...take your pick, theyre all a couple of watts , and all PFC'd.

...unless the PFC is because they cant put big electrolytics after the mains diode bridge due to the way triac dimmers interact with filter inductors and big electrolytics?

 

[tcmtech]

And yet all TV's, for a fair number of years now, have to be fitted with PFC circuits - so I suspect you're incorrect in your theory.

What PFC correction circuitry are you referring too?

All I am familiar with is the simple multistage RF and line noise dampening filters on most every solid state power supply I have ever taken apart.

I can't see how a few .1 uf capacitors and MOV's connecting the lines to common and ground and one or two small RF chokes could do much to change the overall power factor on one of these power supplies?

Am I missing something here in their design or are they designed to different specs where you are?

 

[ronsimpson]

I think that the main advantage of havin a PFC in a power supply is the ability to have wide input voltage range.

Power factor correction has to do with making a "computer power supply" look like a resistive load. Most things like a TV only take power at the very peak of the sign wave. The current waveform is "pulsed" not sign wave. The current is very high for 20% of the sign wave.

A resistive load has a current waveform that matches the voltage waveform (sign wave). The power company wants a resistive load.

 

[NorthGuy]

Here's the background draw in my house - lights and electronics. Doesn't seem like much of it is power factor corrected.

 

[Nigel Goodwin]

What PFC correction circuitry are you referring too?

All I am familiar with is the simple multistage RF and line noise dampening filters on most every solid state power supply I have ever taken apart.

I can't see how a few .1 uf capacitors and MOV's connecting the lines to common and ground and one or two small RF chokes could do much to change the overall power factor on one of these power supplies?

They didn't and don't.

Am I missing something here in their design or are they designed to different specs where you are?

Haven't you seen any recent TV's?, LCD/Plasma ones for the last few years (4 or 5 years?) have a separate PFC supply before the main PSU.

Here's one of the many datasheets about such things.

https://www.ti.com/lit/an/sluu341b/sluu341b.pdf

 

[ronsimpson]

What PFC correction circuitry are you referring too?
All I am familiar with is the simple multistage RF and line noise dampening filters on most every solid state power supply I have ever taken apart.

In light bulbs the PFC is very simple. There is not two stage switcher in most I looked at. The design posted above, the IC watches the line voltage. When the voltage is at the peak of the sign wave the PWM runs at full current. When the line voltage is less than peak, then the current in the MOSFET is also less by that amount. They added a multiplier to the output of the error amplifier. error out * line voltage = duty cycle

There is not a second inductor, second (IC + FET + diode). The major change is in silicon.

 

[tcmtech]

Haven't you seen any recent TV's?, LCD/Plasma ones for the last few years (4 or 5 years?) have a separate PFC supply before the main PSU.

I just picked up a 2012 Vizio HD LCD TV for cheap because it supposedly had a blown power supply. (Bad micro fuse on the 24 volt power for the backlighting driver board)

I didn't see anything out of the ordinary in its primary power supply design. Standard layout from what I know SMPS input circuitry as.

 

[Nigel Goodwin]

I just picked up a 2012 Vizio HD LCD TV for cheap because it supposedly had a blown power supply. (Bad micro fuse on the 24 volt power for the backlighting driver board)

I didn't see anything out of the ordinary in its primary power supply design. Standard layout from what I know SMPS input circuitry as.

Do you have the schematic for it? - with or without PFC the PSU board has a bewildering array of transistors and transformers.

 

[tcmtech]

No I don't. What I saw was the standard input circuity that consists of a fuse followed by an inductor a set of small AC snubber capacitors and Varasitors ending at the main rectifier and large 400 volt capacitor.

Everything after that was directly related to the SMPS control systems. All around I considered it a rather common and easy circuit to read and find out where the micro fuse was for the 24 VDC feed on the backlighting drive board while doing live voltage readings going out from the DC side of the system.

None of it jumped out at me as being extra or additional components on the AC input side.

 

[Nigel Goodwin]

None of it jumped out at me as being extra or additional components on the AC input side.

It wouldn't, why would you expect it to be in the AC side? - check the datasheet I posted the link to.

 

[tcmtech]

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The use of portable space heaters can be a green concept if they are used to heat a small area or room that is being used while a building's central heating system is kept at a much cooler temperature.

Low wattage space heaters use only a fraction of the energy of their predecessors and allow for a more consistent temperature.

I deal mostly with large power systems so to me PF control has always been an AC side control process.

Looking at the schematics of the linked circuit I see how they are doing it and the circuit is considerably different that what I found in my Vizio TV. The power supply it has went directly from the main bridge rectifier right into the main HV DC rail with a several hundred uf 400 VDC electrolytic capacitor.

I don't see how any PFC adjustment could be made in that design given the reasonably low average ripple the large capacitor would provide.

 

[Nigel Goodwin]

Here's a screen dump (sorry about the lack of detail) of part of a PSU from a2009 Sony KDL32W5800 - this is typical of all European TV's in recent years.

I know the USA tends to be rather slow in their technology, or perhaps it's just your lower standards for emissions and environmental issues?.

 

[Nigel Goodwin]

Just to show it's not just decent makes, I presume Vizio is a cheap junk make? - here's the PSU manual for a typical Vestel set, who make many of the cheap junk supermarket etc. TV's in Europe.

 

[jpanhalt]

I know the USA tends to be rather slow in their technology, or perhaps it's just your lower standards for emissions and environmental issues?.

Odd, I missed when this became a political discussion of the race to give up human rights to the government. The Brits are winning, so far.

John

 

[ronsimpson]

From a 20W bulb with a PF of 0.99.
The input current is close to a sign wave.
They did not have to add many parts to get PFC.

MOSFET current and voltage.

132 VAC, 60 Hz. Power line.
Upper: ID7, 1 A / div. Output diode current.
Lower: VD7, 20 V, 2 ms / div. Output diode voltage.

Picture on right. Expanded waveform
Upper: ID7, 1 A / div.
Lower: VD7, 20 V / div., 5 s / div.

 

[kubeek]

The input current is close to a sign wave.

Hope it doesn´t look like this, that would not be very good https://en.wikipedia.org/wiki/Sign_function

 

[tcmtech]

I know the USA tends to be rather slow in their technology, or perhaps it's just your lower standards for emissions and environmental issues?.

Around here PFC adjustment is largely done by the power company on their side of the systems. We customers don't need to worry about it on our end. It is likely why I am not familiar with seeing it on anything that has less than a few KVA rating in the devices I tend to work with.

As far as what I buy goes I could care less about who made it or how "green" it is. I have cheapo LCD TVs and computer monitors and I have high end ones too and almost all of them came to me cheap or free because they didn't work.

If you could score a 1 year old 26" HD LCD TV that retails for around $350 new for $50 because it needed a new 1 amp fuse would you really care about what its PF was?

I know the USA tends to be rather slow in their technology, or perhaps it's just your lower standards for emissions and environmental issues?.

Hey now we waste more money and fuel than any other country in the world on emissions regulations!

Does any other country burn twice as much fuel as necessary getting from point A to point B to meet politically motivated and all around poorly though up emission standards? I think not!