HELP WITH LASER DIODE DRIVER

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#1
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Hi there,

 

I already built a constant current source (using a NPN BJT, a N-MOSFET and some resistors, 30mA) that drives a red laser diode (I bought it from ebay for 1$). I also placed a N-Mosfet switch that disconnects the whole circuit from the GND. So I can on and off the Laser output in high frequency (I m gonna measure it and post it).

 

My problem is that after some minutes the Laser output brightness decreases.

 

Does anybody have the experiense on laser diodes driving to help me understand and solve the problem?

Also is there any Laser Diode driver ic ?

 

Thank you in advance.

Michael.

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is this bread boarded.  Is there enough inductance in your leads to have ringing or oscillations  that exceeds the diodes rating?

 

I assume you have checked you CC driver does not overshoot on turn on.

 

There are lots of laser driver ICs but they are all for a lot more complex tasks than a simple red diode doing square waves.

 

Also - if you want to on/off at high frequency (you have not defined what high is BTW) then you often want to modulate the current between two levels.  "Off" being a low current that is around the lase threshold and "on" being the higher current that is - well on obviosuyl.

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icarus1 wrote:
My problem is that after some minutes the Laser output brightness decreases.

So how hot is your diode?   Does it have a heat sink? 

Do you have a part number for your diode?   and a datasheet?

 

Jim

 

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d

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Last Edited: Mon. Jun 24, 2019 - 08:51 AM
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icarus1 wrote:
Also is there any Laser Diode driver ic ?
modules

Laser Drivers/Laser Controllers/Laser Diode Drivers| Analogtechnologies.com

 

"Dare to be naïve." - Buckminster Fuller

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Where is your schematic??!!!

 

Make sure you keep the laser diode cool!!

 

It will have very low tolerance for overdriving...once you do, can blow apart the internal mirror facets from too high of  an energy density and/or will run dim...forever

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