Regulator(s) for 15 Amp power supply

Thread Starter


Joined Aug 31, 2008
Hello all,

New to the forum. I'm building a 30-32 VDC @ 15A power supply for a recently acquired toy......actually "toy" might be the wrong word for a 25 watt CO2 laser:eek:. And, yes, I have protective eyeware!

So far, I have the transformer, bridge rectifier, filter cap, chassis & misc parts & pieces. At full output, the laser uses 30-32 VDC @14 amps. Can I put LM338 regulators in parallel to reach the current needed. Would three be sufficient, or would that be cutting it too close?

I was looking for a switcher, but they are WAY too expensive.

Thank you for your help!


Joined Nov 23, 2007
You could use a high current rated transistor to take most of the current, the regulator simply controlling it with a much smaller current. See attached though component values will vary depending on your transistor and the supply voltage.



Joined Jul 17, 2007
Lasers generally require very tight tolerances on the current they're fed.

Give 'em just a tad too much, even for an instant, and you have some interesting trash can filler. It happens that quickly.

You might have something valuable, or you might just have a piece of junk. If you experiment with it without knowing what you're doing, you could wind up getting hurt along with having a piece of junk.

I do not claim to be experienced with lasers. I know how to get myself in trouble with them. However, this guy IS experienced with lasers:
Read his experiences, get to know him.

What you have there requires a lot more research than just a quick & dirty answer.

Please be careful. Do your research.

It really isn't a toy. You could easily wind up blind or dead if you make a mistake.


Joined Mar 24, 2008
We used to use 10 Watt CO2 lasers at Alcatel to solder optical components (after precision alignments they didn't want a physical soldering iron messing things up). Their max was 15 Watts, we use a 555 PWM to scale em back. These units had matching power supplies, we didn't manufacture them a bit, but added the interface to adjust power as has been mentioned.

I was the lucky guy who got to check them, and if they weren't right, pull them and send them to a specialist.