5A linear current regulator?

Some would say yes, but for a well-designed
driver I tend to disagree. As long as the
diode does not see spikes and surges, those
are the main things to worry about when it
comes to diode lifetime.

On an engraver, the concern is that if
startup time becomes significant, it will
end up overshooting its target. Find out
how fast the engraver moves at the desired
marking rate and how long it takes the
driver to come up to full power. That will
give you an idea of how far the
gantry/galvanometer has traveled between
the time the diode was supposed to come on
and the time it actually comes on and
weather this is acceptable to you.

Alright, Thank you for explaining.

Now I just need to find a suitable driver, which seems to be quite difficult.
Do you have any idea where I can look for good drivers?

I found single driver ICs for powering high power LED's from Linear Technologies, and Maxim, ..
But these ICs are so damn tiny I won't be able to solder them. I'll also need to assemble all additional parts like the inductor, at which I'm not really good. So for that reason I was looking here for completely ready to use drivers, but I can't find any which go up to 5A.

I can't answer your diode questions but I can steer you towards some possible drivers for the project. there is a man in Europe who makes somewhat expensive 5A drivers, but since you need 10 that won't work unless you parallel a pair of them. I had to build a 30 amp adjustable constant current power supply for a large RGB array and I just paralleled several drivers together (12 of them), isolating each ones output with a diode and put the outputs together on one common copper bar. Since they were each current limiting and each set to the same current, no one driver would pull more than a few amps, each staying within their maximum designed output rating. It worked perfectly.

I have read reports on this forum where others have done the same thing with smaller drivers, just paralleled them together but not all drivers will function properly that way, best to isolate the output of each driver with a diode between where they both join together and each drivers negative output, this will prevent the possibility of an unfriendly interaction between the two from damaging them, depending upon their design. Of course, this will require two isolating diodes, one for each driver you are joining the outputs together from, if using two. For the positive side of each driver, since that won't be the hot side for your application, they can be joined together without a diode.

To give you some other ideas, I once built a 50 amp current regulated PWM driver for a 45 watt output FAP808 laser, well, six of them in series, by using an inexpensive HHO PWM module you can get on ebay too, here's a link to one which might be something you can use: http://www.ebay.com/itm/Constant-Cu...526?pt=LH_DefaultDomain_0&hash=item233c99b08e - To get this to work for your use, you could string some power diodes in series with its output to get the voltage down to what you need for your laser diode. For my project I was using an auto battery with it and with the laser diodes themselves in series to drop the voltage down so no one laser diode received more than 2.1 VDC. This kept each of them within their individual voltage rating while using PWM to control the current.

I wired it together and played around with it for an hour but then never went any further with the project, boxed it all up and they are now sitting in storage. Whether PWM was a good way to go with these FAP bar units as far as specifications go I don't know, but I turned the frequency down to the lowest setting I could for the pulses and it worked. Long term, I don't know how PWM would have affected the devices.

Here's a link to the 5 amp driver I mentioned above: http://www.ebay.com/itm/Laser-diode...537?pt=LH_DefaultDomain_0&hash=item35db838a01 - I think two of these in parallel, each isolated by a diode from one another would be a much easier way to go, if you don't need PWM.

I'm not really fund of putting multiple regulators in parallel.
The 5A driver which you have linked to does look quite good, but it seems to be a linear regulator. I'm looking for a Buck regulator instead.

I indeed don't need the PWM. All I need is external analog current setpoint, and an enable input.

Things like these:
http://www.ebay.com/itm/DC-8A-Const...olar-Battery-Charger-LED-Driver-/171135927735
http://www.ebay.com/itm/5A-Lithium-...er-Supply-Module-LED-Driver-New-/201114996886
look promising, but they don't have an analog input for the current setpoint :/


EDIT:
Actually I don't understand how it is so hard to find a driver for this diode ?!

This is the diode:
http://www.ebay.com/sch/i.html?_odk...al&_nkw=5W+IR+laser+diode+industrial&_sacat=0
The diode being for industrial purposes, and being quite common, would suggest that there are also drivers around there for this specific diode, right?
How else is the industry going to power this diode?


EDIT 2:
The datasheet shows:
Operating temperature Tc –10 to +30 °C
Storage temperature Tstg –40 to +85 °C

What exactly does this mean? That the environment temperature, while operating, should not exceed 30°C?
Or the case temperature should not exceed 30°C? Because the heat sink does get hotter than that.. (about 45°C)

Just use the MOSFET with feedback for regulation. That's all you need. The feedback, via an op-amp measuring the voltage across a resistance, will ensure that the response is linear, regardless of temperature-induced changes in the device.

I'm not for combining drivers either, but lacking anything else which will work, I do it.

Bionic-Badger said:

Just use the MOSFET with feedback for regulation. That's all you need. The feedback, via an op-amp measuring the voltage across a resistance, will ensure that the response is linear, regardless of temperature-induced changes in the device.

Click to expand...

Oh I didn't think of that before!
Good idea this will probably be what I'll do.

If this works out, please share the results, maybe I should build something like it for my needs too, but higher than 5 amps.

FalloutBe said:

I'm not really fund of putting multiple regulators in parallel.
The 5A driver which you have linked to does look quite good, but it seems to be a linear regulator. I'm looking for a Buck regulator instead.

Click to expand...

Funny thing that you are speaking about my driver. There is one thing worth mentioning.

Yes it is linear regulator, but if you use 808nm 5W diode you need around 2,2V on the diode. Then 0,5V on the sense resitor, and around 0,1V on paths. It is total of 2,8V. When you use 3,3V power supply, it is not that much heat on the mosfet, since it is 0,5V*5A = 2,5W.

I was not using BUCK, and BOOST drivers, because I need modulation in my drivers which is not working very well when switching circuits are used.