Leds in parallel?

[Flyback]

Companies such as Forge Europa are producing LED Lights comprising LEDs in parallel without any series limiting resistors being used.
Is this ok?
Do you believe the contents of the attached report evaluates the situation correctly?

 

[Nigel Goodwin]

Presumably you wrote the DOC file?, what is it with you and parallel LED's?, you seem to have some bizarre vendetta against perfectly viable commercial applications.

Anyway, I'm moving this to a more suitable forum, as it's not really anything to do with Electronics - just a further continuation of your rantings.

 

[jpanhalt]

It is a fairly lengthy report with no author or corporate attribution. Why is the author not listed? Did you write it? It seems to reiterate most of what has been said on ETO in various links and in the LED literature.

Do you believe the contents of the attached report evaluates the situation correctly?

Are there any parts of it that you specifically doubt? What is your purpose in posting that document here for comment?

As for Forge Europa's product, according to the document, each of the parallel strings has 11 LED's in series. Maybe their production data support the assumption that that arrangement sufficiently balances out differences between individual LED's.



John

 

[Flyback]

I am evaluating paralleled leds without limiting resistors......if this is viable, it will revolutionise the led lighting industry...only one led driver would be needed for potentially hundreds of leds......I am a businessperson evaluating a situation which could benefit us all. I am sure that others than myself will benefit if it is possible

 

[tvtech]

Companies such as Forge Europa are producing LED Lights comprising LEDs in parallel without any series limiting resistors being used.
Is this ok?
Do you believe the contents of the attached report evaluates the situation correctly?

Flyback...we all know what you are on about with IS*****.
You keep coming back and keep getting told the same thing.. You need to do the Marketing research yourself to see where this system can/or would work....

 

[Flyback]

yes I did write the report. There is no other report about this on the www, and led foundrys wont write about it in the detail required.

 

[jpanhalt]

yes I did write the report. There is no other report about this on the www, and led foundrys wont write about it in the detail required.

I just don't believe that LED manufacturers don't provide the same detail your report provides. Please give some examples of detail that you provide that is not provided elsewhere.

For example, here is a report (one of many) that discusses the needs for powering LEDs: **broken link removed**
Specifically, go to page 5 or search on "parallel," and you will find several pages that discuss using parallel-series LEDs.

John

 

[tvtech]

I am evaluating paralleled leds without limiting resistors......if this is viable, it will revolutionise the led lighting industry...only one led driver would be needed for potentially hundreds of leds......I am a businessperson evaluating a situation which could benefit us all. I am sure that others than myself will benefit if it is possible

Flyback

I believe you have already been advised that LED's in parallel only work properly when they mostly come from the same batch and their Forward voltages are matched.....

NOT A GOOD WAY OF DOING THINGS.

Cheap yes but NO. Unless you are Chinese and have millions of crappy LEDs and lots of people that are hungry and will work for a plate of food a day.

ETO promotes accurate advise. I want no part of or any talk of Paralleling LEDS without limiting resistors. It is not good practice and that is that.

The last thing that I need is people watching this thread getting confused. Nah.

tvtech

 

[tvtech]

OK Flyback. I know you are Online because you liked my post in spite of me being cross with you..

Once and for all, tell me everything and I mean EVERYTHING. I have a heart. I will help you wherever I can.

Tell me the whole story. All the facts why you are you are in the situation you are now....

PM me if you want. I will be there for you. Posting all the time on the Forums does not help.

Almost all members here have sussed you out as an IS***** marketing tool.

Regards,
tvtech

 

[Flyback]

I wouldn't need to market for a government initiative, the taxpayer will pay for it whether they like it or not.
Nobody had to market the new digital energy meters that everyone in uk had to install in their homes/business's.
Nobody had to market the new CFL bulbs over 100w incandessants because the gov't just outlawed 100w incandessants.
Nobody had to market the pay-for-your-bag initiative in uk supermarkets, the gov't is just saying the supermarkets aren't allowed to give them away.
Nobody had to market unleaded petrol, it just came in by order.
Nobody had to market unleaded solder, leaded solder just got banned (and we suffer whisker growth due to this now)
Nobody had to market blue recycle dustbins....the governement just said we had to use them for certain waste.

 

[tcmtech]

I don't see what the big fuss about running LED's in parallel about.

If the manufacturer designs the LED's with an extra PTC resistance in series with the LED die they will automatically compensate themselves for equal power draw when ran in parallel operation even with large numbers being used of of a common constant voltage power rail.

 

[Flyback]

If the manufacturer designs the LED's with an extra PTC resistance in series with the LED die they will automatically compensate themselves

LED manufacturers dont do this, as its too expensive, and just increases led heating

 

[tvtech]

Flyback....please listen to me.

You are not helping by posting.....you need to discuss away from Forums. You need someone to guide you. Someone that can think clearly...that can tell you that is a bad idea or a good one...the good one needs to be pursued and the bad one needs to be lost.

I am no expert at all. Just someone that kinda knows people. And I believe at this stage you are not a IS**** marketing tool.

Once I have figured you out, you will fly. The truth is needed though so be brutally honest with me.

No ******** and no lies and no pretense.

PM me when you are ready and have read all above.

Regards,
tvtech

 

[tcmtech]

I am seeing lots of low voltage lighting devices running large numbers of LED's in parallel off of common rail power sources on the market now so obviously the people designing them know something you don't being they are obviously making work and work well enough and reliably enough to be mass producing the design.

You seem to be continually fixated on the theoretical issues while completely ignoring the reality that obviously somehow manufactures have found a way of making it work and work well.

 

[Flyback]

the lights you speak of have series resistances to limit the current, and its acknowledged that that is a viable solution..i am speaking of leds in parallel but with no series resistors used.

 

[tvtech]

Hi tcm

Please remember we teach "basics" here.

And I stand by my statements above. I really don't care if clever people try and well "be clever".

And now, it's time for me bail out from ETO.

My little X2 light has surprised the testers beyond belief....Uses have been found that I never dreamed of....

And yes, LED's with dropper resistors. And strings and all that...

And little SMD Duris doing the job....

Proper Analogue design.... kicks ass.

Regards,
tvtech

 

[tcmtech]

Perhaps but electronics design in reality goes way past the basics and people do need to know that there are many things that use additions to the basics that not everyone is aware of or understands.

Just because their basic theory did not include something does not mean it isn't a common addition to a real life manufacturing process.

That and one persons applied basics are not the same as anothers. Which basics do you prefer?

Lower grade school or college level or manufacturing level or advanced R&D basics?

I am assuming that being you are good at your job your level of electrical and electronics basics are past those of simple grade school understandings right?

The problem I see is flyback wants the world or LED lighting explained and accounted for using only the bare theoretical basics of electronic device operating principles which unfortunately do not allow for the addition of more complex design attributes that when viewed from the real life application make something work that basic theoretical concepts would suggest otherwise too.

 

[Flyback]

OK Tcmtech,

Though which camp are you in?..(considering a series parallel array of leds fed by a single current source)....

1a...Series parallel arrays with no limiting resistors and LEDs not Vf matched
1b...Series parallel arrays with no limiting resistors and LEDs are Vf matched
1c...Series parallel arrays with no limiting resistors and LEDs are Vf matched and all from the same production batch
2a...Series parallel arrays allowed , with no limiting resistors, but only if each led string has a minimum of eight in series
2b...Series parallel arrays allowed , with no limiting resistors, but only if each led string has a minimum of eleven in series
2c...Series parallel arrays allowed , with no limiting resistors, but only if each led string has a minimum of (>eleven) in series
3a...Series parallel arrays allowed , with no limiting resistors, but only if LEDs are all operating just above the kness of the I vs V curve
3b...Series parallel arrays allowed , with no limiting resistors, and the LEDs allowed to operate up to their maximum rated current level.

4a...Series parallel arrays allowed , with no limiting resistors, but with what degree of thermal coupling (eg all mounted on MCPCB etc)

5...Series parallel arrays with no limiting resistors not allowed.


If you are in a combination of the above "camps", then please explain.

 

[tcmtech]

I am in the camp that knows from personal visual confirmation that obviously they have a way to make it work reliably and predictably enough to be able to mass produce and sell them to the public.

How I don't care so much about.

 

[Flyback]

The following is a series parallel array with no limiting resistors....its FR4 and no heatsink underneath.

What would you say is the maximum physical spacing allowable for each led to keep them adequately thermally coupled given that its 1oz copper thickness?

The forge product has eleven in series....what is the minimum length of series led strings that can be paralleled?....or do you say that even single leds can be paralleled without series limiting resistors.?

well, I wrote to Philips and asked if they had leds that could be paralleled without limiting resistors.
For some reason, I was answered by someone from futureelectronics.com, and he said that he really did not recommend the paralleling-without series -resistance of hi power leds of philips and LGIT. He also said that mid power leds (50-150mA) of Philips and LGIT did get paralleled by some people, but he recommended against doing this.