Non-dimmable LED lightbulbs are damaged by Triac dimmers?

[Flyback]

MrAl: certain Triacs have a holding current of up to 40mA.....and many led bulbs, when dimmed, don't draw that kind of current anyway.
RonSimpson, i see your point, but concurring with the loss factors that MrAl points out, the primary side regulation method seems a bit inaccurate to me. I do however appreciate its cheapness, and lower component count.
When you go on powerint.com site, you can use their design software to do a smps design, and you can pick either primary side or secondary side regulation...when you pick primary side, the tolerance on vout is considerably wider. I don't really favour this, as say, if you're 10% over in output power then that's wasted energy, specially in lighting where there are so many lights

The control of peak current via the Control voltage is rather unusual in LT3799....I played with the simulation model with a linearly decreasing control voltage, and the vin_sense voltage fixed at various levels.....for each vin_sense level, the higher Control voltage values did not affect the peak current level (-say between 1 and 2v for control voltage)...then when control voltage went below 1v, say, then the peak current level changed.
I was expecting the behaviour of the "control" voltage to be a little like the "COMP" pin voltage of the uc3842, but it wasn't.

 

[ronsimpson]

the primary side regulation method seems a bit inaccurate to me. I do however appreciate its cheapness, and lower component count.

With light you eye can not see 10% change in light. (some one will disagree) Your eye see the difference between 60W and 100W bulbs as a small difference. 60/100 is just noticeable not seen as 2:1.
Primary side regulation is common in low end light sources.

Light bulbs are sold by price alone. Saving one part makes a big difference.

The control of peak current via the Control voltage is rather unusual in LT3799.

I see peak current regulation every where. "current mode regulation" vs "voltage mode"

then when control voltage went below 1v, say, then the peak current level changed.

YES

 

[Flyback]

There is some sort of interplay between 'vin_sense' level and the 'control' voltage level....the datasheet doesn't seem to explain it fully.

Below is the wall dimmer that will sweep the world, along with the led bulb that you see in post number #18.....this wall dimmer works with that bulb......you push the momentary switch, and a missed mains cycle (cut out at the zero crossings) gets to the bulb, which then either dims up or down....

Forget Triac dimmers........LEDs don't want Triac dimmers.....incandescants do.

The EMI filter of led bulbs needs tuning to ensure it doesn't resonate with triac dimmers......you need bleeders and dampers in there.....you don't know what the holding current is of the cheap triacs.....forget it....use one of these..

 

[ronsimpson]

There is some sort of interplay between 'vin_sense' level and the 'control' voltage level....the datasheet doesn't seem to explain it fully.

The vin_sense has two functions.
1) Power factor correction.
2) Triac dimming.

Forget Triac dimmers .....sweep the world

You are really wound up about this. I hope you can turn this excitement into a product.

Your parts count is tooooo high. You bulb will not be made like that because of cost. Your push button dimmer has way tooo many part.

 

[4pyros]

"going to sweep the world" Wow you are funny. Good Luck

 

[alec_t]

I see no way your proposed dimmer can identify whether the user wishes to decrease brightness or increase brightness. So it would mean cycling through a whole range of unwanted brightness levels to get to a target level?

 

[Flyback]

yes it would....though we could have a second pushbutton which gave two missed half cycles (instead of just one) ,and this could mean go up (or down).

The two missed cycles could be alternate, miss one, give one, miss one....you get the picture.......missing half cycles in a certain pattern can mean whatever you want it to mean.

 

[alec_t]

That will certainly increase the parts count .

 

[ronsimpson]

identify whether the user wishes to decrease brightness or increase brightness

I agree, I tried to show a way around that but.....The point of all these threads is to promote an idea. Maybe to get you to design it. By next year to offer it for sale.

I hope this is a learning effort. (UL, VDE, CSA), (design), (marketing), (patents), (customer acceptance) etc
We should talk about the last two.

 

[Flyback]

true, but theres no other way to do it that's simpler....we don't want separate wires going to the bulb for comms.
we don't want triac dimmers any more...and trailing edge dimmers give a morse power factor than the way described....using isolation transofmers to communicate to thebulb via the lains wires is out....to expensive.
It wont be expensive when done in bulk....and since this is the only reasonable way to cheaply dim leds...it will be a mass market seller.

 

[4pyros]

we don't want separate wires going to the bulb for comms.

Who is "we"?

and since this is the only reasonable way to cheaply dim leds

How do you know that for sure????

 

[ronsimpson]

To send twice as much information using your idea......
Remove a positive 1/2 cycle for up.
Remove a negative 1/2 cycle for down.

As above....remove 1 full cycle for down.

 

[Flyback]

RonSimpson, that the idea...but if you see the current schem, it cant tell the difference between pos and neg half cycles...as its rectified where the comparator watchs" it.

but yes, missing alternately x cycles out of 2x cycles, say, can mean whatever you want.

The competition to this idea is from trailing edge dimmers......but they don't give nice power factor so we want to see the end of them.
By "we" I mean people who want a good, efficient lighting system for the world.....all of us.

 

[tcmtech]

By "we" I mean people who want a good, efficient lighting system for the world.....all of us.

We who? I have spent the last week in Turkey with my wife and her family and to be honest when it comes to efficient lighting and its mass application they are walking all over the US on this subject.

Dimmable LED and CFL are all over the place here and from what I gather has been for a good number of years.

 

[4pyros]

but they don't give nice power factor so we want to see the end of them.

Here you go speaking for the rest of us again.

 

[tcmtech]

Power factor is irrelevant. Especially on devices that only draw a few thousand watts/VA or less.

Private power meters do not measure by volt amperes and even with poor PF levels the line losses are still too small to be worth the financial investment to improve them at every single device.

In industrial applications it's done by a central automatic PF control system of PF is a legitimate concern. Not at every single individual device.

 

[ronsimpson]

There are many PF bulbs on the marked. I have not look at it in detail. I think the PF bulbs will be just find with triac dimming. The linear IC looks like it will correct just fine.
I have designed office products and home products that are PF corrected. It is pretty common.
When I started out with PF it was costly. The linear IC design above has PF for the cost of a resistor.

 

[tcmtech]

What I am seeing over here in the Turkish stores, shops, hotels and everywhere else that is running LED and CFL lighting systems on dimmers sure look like the normal old fashioned rotary or slider type dimmers systems. Definitely nothing fancy or new hightech I can see about them.

To be honest a lot of them look rather old and well worn giving strong implications that they have been in use for a long time.

 

[4pyros]

Yes thay are so cheep I dont see them going away anytime soon.
Most consumers may not buy a Lamp if the switch needs to be replaced or a controler add.
Most will just want to replace the lamp.

 

[Nigel Goodwin]

even with poor PF levels the line losses are still too small to be worth the financial investment to improve them at every single device.

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.