High power diode laser driver

Hey, I just got a 30 watt diode laser on ebay, and as sort of an afterthought I realized that I need a sufficient power supply for it. When I actually went to look for such a thing, I realized that they are not very easy to find and bloody expensive.

http://tiwake.com/Capture.JPG according to that I'm pretty sure I need 2 volts at 10-48 amps. If it helps at all, I have 10 each of the IRFZ44 and IRLZ34N MOSFETs.

I'm kind of at a loss of what to do to just turn the thing on.

Correct. You need to build or find a driver capable of ~10-40A constant current. Not the easiest of projects, but it's certainly possible. Good luck

Cyparagon said:

Correct. You need to build or find a driver capable of ~10-40A constant current. Not the easiest of projects, but it's certainly possible. Good luck

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Any ideas on where to start? I'm interested in how to build something like this as well.

I am having some made will be 30 to 60 days around $300 small units up to 170A 250 pulse
this is what I have so far, for a QCW power LASER controller system. Essentially, there are two printed circuit boards (2.5" x 3.8") that could easily be placed side-by-side inside a portable unit. The controller board governs overall operation. The display board contains two dual seven segment displays which will sequentially display LASER power, voltage and current. Three LEDs on the controller board, viewed through the side of the enclosure, indicate whether the current display data is VOLTS, AMPS, or WATTS. Silk-screening on the enclosure can indicate "VOLTS, AMPS, or WATTS" under each LED.
Here are some of the design specifications I've come up with for this circuit:

The 747-IXFN520N075T2 n-channel MOSFET selected for this design can handle 200 amps maximum. This device needs to be mounted on the chassis of the LASER enclosure, and would benefit greatly from convection cooling (small fan).

Mouser detail page link for product:
http://www.mouser.com/ProductDetail...akFBZL2OHPWmOhQZc5h6JHmRW/S9k09qvREgHE7n4cA==
With this design concept, the frequency is fixed, but power can be adjusted by changing the pulse height of the output of the buffer amplifier U2. The voltage present at this point controls the conductivity of the channel of the power MOSFET. This type of power control is sometimes called pulse height modulation.

The rise time of the gate control signal of the MOSFET is a function of the gate charging capacitance of the MOSFET and the gate charging resistance, which is resistor R9 in the Power_Control_Stage drawing. Theoretically, the faster the rise time, the more efficient the circuit. However, going from 0 amps to 170 amps too quickly could generate a huge amount of EMI and RFI that could disrupt the control circuitry and possibly create some rapport issues with the FCC.

Per the datasheet for the IXFN520N075T2, rise time is about 26 nanoseconds with a gate charging resistance of 1ohm. In the LASER control circuitry, the external gate charging resistor, R9 is 6.2Kohm. With this value, I'd estimate the rise time of the gate signal to be about 40 to 50 microseconds. This rise time could be decreased by reducing the value of R9. However, I'd advise not to reduce the slope of the signal to a point where circuit stability is at risk.

ricktrent4 said:

I am having some made will be 30 to 60 days around $300 small units up to 170A 250 pulse

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This is by far the cheapest thing I've seen. What kind of specs is it exactly? who designed the electronics? what kind of thermal efficiency does it have? Do you have any numbers for the rise and fall time for PWM operation?

ricktrent4 said:

I am having some made will be 30 to 60 days around $300 small units up to 170A 250 pulse
this is what I have so far, for a QCW power LASER controller system. Essentially, there are two printed circuit boards (2.5" x 3.8") that could easily be placed side-by-side inside a portable unit. The controller board governs overall operation. The display board contains two dual seven segment displays which will sequentially display LASER power, voltage and current. Three LEDs on the controller board, viewed through the side of the enclosure, indicate whether the current display data is VOLTS, AMPS, or WATTS. Silk-screening on the enclosure can indicate "VOLTS, AMPS, or WATTS" under each LED.

Click to expand...

How long until you might have these ready to sell?

SodaAnt said:

How long until you might have these ready to sell?

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30 to 60 days

You can start by googling constant current, and beefing up the circuits you come across, or you could just buy a complete turn-key unit like this one. Used supplies are cheaper on ebay if you're patient - potentially <$100.

Cyparagon said:

You can start by googling constant current, and beefing up the circuits you come across, or you could just buy a complete turn-key unit like this one. Used supplies are cheaper on ebay if you're patient - potentially <$100.

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do you have link for one for a $100 that one was $289

I think you missed the part where I said "patient." Browse ebay for used DC power supplies and have a look for yourself.

this sounds like the power supply conundrum in ham radio and CB. Most people are amazed at the cost of a half decent PS once the amperage gets above a certain level. I'm actually amazed units can be had for dozens of amps for lasers that are that hungry, at a reasonable price level.

most hobbyists across several disciplines end up "accidentally" getting their feet wet with DIY power supply costruction. Actually, this is my first encounter with needing constant CURRENT power supplies, so, I am treading slowly. LIke i said, i am amazed the price of evrything has come down enough its as affordable as it is.

I always "avoided" power supply construction by salvaging stuff. But like i said, that ws alwys constaant voltage, not constant current, it makes me like a little kid all over again. I know i am showing newb ignorance, but, is it possible to let a small driver current control a LARGEer driver or parallel bank of drivers? SHort of that approach, my next tack would be seeing about "scaling up" existing components in an existing power supply. or a hybrid approach of the two.

myself, i would end up simply waiting for a unit to go on sale, though. (as an academic exercise though, i am sure schematics of existing project builds exist) The power supplies we wanted/needed in HAM raadio and home CB opertion, the main sticking point was always the danged transformers. They got big, bulky, and expensive off the shelf.

73, KB3OYZ

sedstar said:

this sounds like the power supply conundrum in ham radio and CB. Most people are amazed at the cost of a half decent PS once the amperage gets above a certain level. I'm actually amazed units can be had for dozens of amps for lasers that are that hungry, at a reasonable price level.

most hobbyists across several disciplines end up "accidentally" getting their feet wet with DIY power supply costruction. Actually, this is my first encounter with needing constant CURRENT power supplies, so, I am treading slowly. LIke i said, i am amazed the price of evrything has come down enough its as affordable as it is.

I always "avoided" power supply construction by salvaging stuff. But like i said, that ws alwys constaant voltage, not constant current, it makes me like a little kid all over again. I know i am showing newb ignorance, but, is it possible to let a small driver current control a LARGEer driver or parallel bank of drivers? SHort of that approach, my next tack would be seeing about "scaling up" existing components in an existing power supply. or a hybrid approach of the two.

myself, i would end up simply waiting for a unit to go on sale, though. (as an academic exercise though, i am sure schematics of existing project builds exist) The power supplies we wanted/needed in HAM raadio and home CB opertion, the main sticking point was always the danged transformers. They got big, bulky, and expensive off the shelf.

73, KB3OYZ

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Interesting perspective. (though I wouldn't count CB as there's a 4W emissions limit there, unless you want to break those rules)

73,

KJ6MXY

The topology of choice will always be a compromise between simplicity and power inefficiency vs complexity, routing challenges and EMI issues.
i have made my own 13.8v/25A linear power supply (uA723) with massive heatsinks for ham purposes with a custom made 500w toroid xformer, but later i bought a neat compact SMPS that costed about as much as the combined BOM cost of the linear beast.

ricktrent4 said:

30 to 60 days

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The only thing I ask is that there is an easy way to PWM this... So yeah.. I'll probably buy one given that.


When I got my tax return back I was like "yay, time to buy a laser so I can make that CNC engraving machine I've always wanted. I'll just get the power supply later once I get the laser and know exactly whats needed."

Turns out diode lasers are current driven... I didnt even know what that meant until after I got the laser. It also turns out that high powered diode lasers are a lot less common than I thought.

heh