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Author Topic: High power LED drivers.. 2A, 10W plus, PWM control & low(er) heat?  (Read 2181 times)
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It may be asking too much.... and probably is.

The project is essentially a lightsaber.
I've seen flashlights that put out high wattage LED current successfully so I have to think it's possible.

I was using a STCS2 from ST Microelectronics, and except for the heat it worked great.
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00185795.pdf

Anything similar that would run cooler? The problem is that the V difference between the VIN and the LED VFWD will vary a lot depending on LED choices and battery solutions used. One such issue is using several for RGB control.. VFWD is different for the R G and B dies.... so for instance red overheats when B and G are fine.

Or, is the entire approach faulty and I should be doing something else?


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You can use diodes  in series with the lowest Vf  LEDs to effectively match the Vf of the other highest ones.

Each  1N5401 for example will knock off about 0.6v, and if you want to fine tune it you can also add a schottky type that has lower Vf.
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The only way to supply a high current to a led without heat, is using a swithing constant current supply (with an inductance).
I think that something like that can not be combined with the STCS2.
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Ahha... "switching constant current supply" sounds like something worth researching..... Google, here I come. :-)

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Anything similar that would run cooler?

Those those switching mode dc/dc converters, from National or ON. Some of them have an on/off pin that you can pwm to control brightness.
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I found one that looks promising...

http://think.onsemi.com/PowerSolutions/product.do?id=NCP3066

I'll keep looking, though.
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What is the Vf of your 3 different LEDs  ( or string of LEDs ) for RGB in your test proto?
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I'm trying to design something that will work with several LEDs, although it will start with a single driver under PWM control. The eventual goal is a "shield" designed to fit on an Arduino Nano. (LED Driver, microSD, Accelerometer, Audio Amp)

The idea being is you want just a single color LED the driver will be on the board. (If you wish to drive RGB(A) then you would add on a 2x or 3X driver sub-board.) Most folks would just want to drive one LED.... somewhere between 350 ma to 1200 ma.

My personal favorite is the RGBA by Ledengin (Red, Green, Blue, Amber)

@1000 ma
R 2.4v
G 3.7v
B 3.7v
A 2.7v

Although I was running mine using the STCS2 @1200 ma. (I'm OK with a lightsaber LED that only burns for thousands of hours instead of 10's of thousands. ;-) 4xAA Nimh Pack so 4.8v source.
http://www.ledengin.com/files/products/LZ4/LZ4-00MA00.pdf
(Opps.. meant to include link to LED.)
« Last Edit: January 01, 2013, 08:15:13 pm by TroyO » Logged

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I found one that looks promising...

That's the famous 34063 in disguise, smiley

It is however, not sufficiently beefy for your application.

Depending on your power requirements, you are likely looking for a to220-5 chip. The SimpleSwitcher from National would fit the bill - and it is multi-sourced, to boot. The ON equivalent of it is also a good choice.

Another way is to get those dc/dc converters from ebay and mod them - easily done.
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VFWD is different for the R G and B dies.... so for instance red overheats when B and G are fine.


Quote
My personal favorite is the RGBA by Ledengin (Red, Green, Blue, Amber)

@1000 ma
R 2.4v
G 3.7v
B 3.7v
A 2.7v


If its only for a toy light sabre , stick a 1.2 ohm 1 watt resistor in each of the 4 wires to the LEDs, you will waste a bit of power, but its only going to last half an hour per recharge anyway.

To balance the current in each LED :-  (  or you could use different resistors )

put one 1N5401 and a 1N5822 in series with the red LED, will bring the Vf to 3.6v ( at 1 amp )

for the Amber  put two 1N5422s in series, will make it 3.5v ( at 1 amp )

Total cost under $1

« Last Edit: January 01, 2013, 09:46:59 pm by Boffin1 » Logged

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Yes, that drives the LEDs, but part of the "illusion" is carried by ramping up the light so it appears to extend down the blade, adding a pulse or shimmer effect when the blade is extended, a flash coinciding with an impact and blade retraction effects (etc.) so the PWM control is part of the whole package.

My main goal is to make an open platform lightsaber controller available... there are commercial controllers out there up to $150 or so but not much for folks who would brew thier own. It will be larger than most "pro" ones but being programmable opens a lot of possibilities (hopefully some of which I haven't though of, LOL.)

Dhenry, looking at the Simpleswitcher... it may be a winner.
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Right, I was thinking it was a one-off.

And I hate to admit it, but I havnt seen Star Wars yet :-)

If you are going to produce them, switch mode is definately the way to go.
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Hmmm, another candidate....

ST Micro LED2000

http://www.st.com/internet/analog/product/253333.jsp


Up to 3A, high effiiciency.... available in SO8

I can't really find any faults except maybe that it does need a kind of large inductor.

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Search eBay for LED drivers, there is a wide range available, some of which accept PWM input.
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