Initial surge current in linear LED current regulator.

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treez

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Hello,
The below linear LED current regulator regulates the LED current to 100mA using LT1086 . The LED is
rated 150mA. For the first 60us or so, the current in the LED goes up to 1 Amp.
Do you know how I can stop this initial surge current, and do you think that it could damage the LED or reduce its lifetime?

LTspice simulation attached, and also schematic.

LT1086 datasheet
http://cds.linear.com/docs/en/datasheet/1086ffs.pdf
 

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  • LINEAR LED CURRENT REGULATOR_1.txt
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  • LINEAR LED CURRENT REGULATOR_1.pdf
    12.6 KB · Views: 70

You attached a PDF file, not the LTspice ASC simulation file.
Instead of playing with a simulation, why not build the simple circuit and measure its output?
 
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thanks, but edaboard doesn't accept .asc files
The .txt file should be saved as .asc, then ltspice can run it.

I will build the cct but don't want to if it has that inrush problem.
The following circuit diverts the inrush into a fet, but I don't really want all the extra components.
(attached)
 

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  • Inrush diverter.pdf
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  • Inrush diverter.txt
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In LTspice I see the current spike at the beginning.
Does it also happen in a real circuit?
Does an LM317, LM350 or LM338 current regulator do the same thing?
 
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That's a good point. Maybe the LT1086 isn't meant to be a pure current regulator.
 

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