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Anonymous Poster

High Speed, High Current LED Driver

10/28/2009 6:46 AM

I'm looking for a solution to switch fast a NCSU034A (0.5A, ~3.75V) with a TTL pulse. The output current for the LED should follow the TTL signal, i.e. rising current on (within a few microseconds switching, delays are OK) and then typically a few seconds the 0.5A current, and then a fast fall (delay no problem, but switching the current should be again within a few micros).

It should be something like this: http://www.cappels.org/dproj/ledsw/Fast_LED_Driver.html

But does someone now a demoboard or something similar that is adaptable to 0.5A and fast switching + long (sec) constant high current?
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user-deleted-1105
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#1

Re: high speed high current LED driver

10/28/2009 6:50 AM

There are plenty of logic level FETs which will do the job, they will drive directly from TTL.
Are you using the led to transmit data?
Del

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Anonymous Poster
#2

Re: high speed high current LED driver

10/28/2009 6:58 AM

No, it is for some scientific experiment. The LED illuminates a sample for a few seconds and exactly the moment the LED switches on and off are the region of interest (measurements are taken).

So: TTL high: LED on, stays on for a few seconds, TTL low, LED off. So the circuit should be able to switch the 0.5A UV LED in a few microseconds, using 12, 15 or 24V as input.
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Anonymous Poster
#3

Re: high speed high current LED driver

10/28/2009 7:01 AM

specs of the LED http://www.nichia.co.jp/specification/led_09/NCSU034AT-E.pdf

I assume that the LED switching on/off time is not the limiting factor, but I'm not sure. Can you give an example of a good FET which could do the job?
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Anonymous Poster
#4

Re: high speed high current LED driver

10/28/2009 7:05 AM

Just contacted the manufacturer, the LED switching time is sub microseconds (just to be sure). (BTW, sorry, cannot find edit button here).
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user-deleted-1105
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#5
In reply to #4

Re: high speed high current LED driver

10/28/2009 7:31 AM

RFD14N05L will do it, it's cheap readilly available (google will bring up data) and can take loads of current. We use 'em here and I drive 'em from a microcontoller no problem.
I'd have though you could adjust for any delay in switch off with the logic, but the FET should be quick enough anyhow, microseconds isn't considered fast these days.

Del

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maveric_manic
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Good Answers: 1
#6

Re: High Speed, High Current LED Driver

10/28/2009 6:35 PM

My suggestion is you just spelled out the spec. for this LED driver why not design your own driver instead of spending money on something maybe made in China LOL (sorry).

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Anonymous Poster
#7

Re: High Speed, High Current LED Driver

10/29/2009 1:11 AM

Any normal NPN transistor should be able to do this providing it can handle 500mA current. Something like a BD139 should be ideal. Put a resistor of about 470 ohm from your TTL output to the transistor base. Ground the emitter and connect the LED between 3.75V source and the collector. (I assume you get the 3.75V from a current limited circuit suitable to drive such LED's) Yes a logic level MOSFET is better. Infact a normal N-ch MOSFET should work too, a resistor isn't required.
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Qqberci
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#8

Re: High Speed, High Current LED Driver

10/29/2009 1:38 AM

You should check one of these:

http://www.motien.com.tw/led.html

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garth
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Australia - Member - New Member Engineering Fields - Mechanical Engineering - New Member

Join Date: Sep 2006
Location: NSW Australia
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#9

Re: High Speed, High Current LED Driver

10/29/2009 7:56 AM

This Nat Semiconductor site might give you some ideas,

http://www.national.com/pf/LM/LM3423.html

Garth.

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Anonymous Poster (4); garth (1); maveric_manic (1); Qqberci (1); user-deleted-1105 (2)

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