1 watt driver design help!
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1 watt driver design help!

by berlusconi on Sat Aug 25, 2012 8:33 am

Hi, i need a driver schematic for 1 watt ir led. Parameters are:
DC forward voltage: 1.4-1.7v
DC forward current: 350mA
Maximun pulse voltage: 1.7v
Maximum pulse current : 500mA
I don't know drop voltage (here http://tinyurl.com/cemzqfu)

I know that the best choice would be a mosfet, but under my hands only some 2n2222, 2n3904, 2n2219, tip127 .
Any suggestion, please?
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Re: 1 watt driver design help!

by PorkRhombus on Sat Oct 27, 2012 5:32 pm

Why do you think a FET would be better? It will be harder to get nice sharp ON-OFF transitions with the FET (you would need a gate drive circuit). I would start with just a 2222, wired exactly like one of the existing drivers (i.e. driven from the 2907A PNP). Actually I would add a base resistor of about 47 ohms to the 2222. The 2222 is rated for 600mA max and above that its effective resistance rises steeply, perfect for your target current. You don't need a heavyweight driver circuit because your "1W driver" is only ON about 1% of the time.
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Re: 1 watt driver design help!

by berlusconi on Sun Nov 04, 2012 6:05 am

PorkRhombus wrote:Why do you think a FET would be better? It will be harder to get nice sharp ON-OFF transitions with the FET (you would need a gate drive circuit). I would start with just a 2222, wired exactly like one of the existing drivers (i.e. driven from the 2907A PNP). Actually I would add a base resistor of about 47 ohms to the 2222. The 2222 is rated for 600mA max and above that its effective resistance rises steeply, perfect for your target current. You don't need a heavyweight driver circuit because your "1W driver" is only ON about 1% of the time.


thx mate, with a 2n2222 and a 47ohm resistor on the base it works fine! Instead i had no success driving led with a mosfet (irlz44n)
berlusconi
 
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