I have an OSRAM 85W 450nnm laser array.

It's essentially a large 'chip' with 24 integrated laser diodes (break it down they're approx 3.5W diodes each.) The Chinese source I purchased it from also sold me a "laser driver" which I've quickly determined is just a boost converter of some kind with no current control whatsoever. I've already designed and produced a circuit (with current and case temperature feedback data) which has the array in a series configuration, meaning you could imagine the diode as one big diode with a compliance voltage of 105 to 110V and 2.5A maximum. The cooling part of the equation has been solved, powering the diode in the manner described definitely works - quite well infact.

I happen to have 3 N-channel 200V 30A MOSFETs (NTB30N200T4G) from an old project, so if they're usable in the design even better.

I've two trains of thought for this:

  1. DC-DC approach, start with a 12V or 24V SLA battery or similar high current DC source and create a boost circuit to attain 110V. Then I build a laser driver fed by the power source.

  2. AC 240V through a custom made transformer, nice and simple 1:2 ratio for a 120V output, bridge rectifier and DC cleanup then voila I have my 110V with plenty of current to spare. Then regulate voltage and current (MOSFETs might come in handy here?) to construct my laser driver circuit.

Does anyone with more experience with power supply design or more specifically laser power supply design have any input, ideas?

Partially answered my own question for those reading who may be interested in the solution i've found. Datasheet for diode below for further context:

Datasheet for Osram PLPM4L

Sourced a 300VAC Toroidal 240 primary -> 55V - 55V secondary transformer. With the taps joined provides an ideal 110VAC RMS output. This will be used to form a basic power supply with filtering to clean up DC, buck converter to reduce voltage to desired range. See datasheet for min (20.7V) to max (28.8V) forward voltage per channel, with all 4 channels in series this yields a requirement of lower bound 82.8VDC up to 115.2VDC (Perhaps this explains my earlier desire for a 110VDC supply..).

Datasheet for toroidal transformer: https://au.rs-online.com/web/p/toroidal-transformers/2238241/

My question remaining is: what is an ideal circuit topology for voltage and current regulation (110VAC RMS, 2.73A)?

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    \$\begingroup\$ Links to off-site documents or websites don't constitute an answer. Take the tour. Nobody can understand what it is that you need without product data sheets to the lasers and detailed technical knowledge of the driving requirements and what you are using the lasers them for. \$\endgroup\$
    – Andy aka
    Commented Nov 26, 2020 at 11:14
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    \$\begingroup\$ Arguing the semantics of what constitutes an answer seems rather tangental from the apparent purpose of this website: share knowledge, answer questions, build a constructive community. But thanks for the warm welcome. \$\endgroup\$
    – psivosbi
    Commented Nov 26, 2020 at 11:32
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    \$\begingroup\$ There is a framework for this site and you should work within that framework. The framework ensures that good questions are asked. A bad question does not lead to good answers. Welcome to the site. Information on questions. \$\endgroup\$
    – Andy aka
    Commented Nov 26, 2020 at 11:36
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    \$\begingroup\$ @pjc50 all things aside, I think what Andy tried to do here is to motivate psivosbi to refine their question so that really has a great answer that helps the asker and was worth the time the answerer spent on it. I think that's a good thing. \$\endgroup\$ Commented Nov 26, 2020 at 12:06
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    \$\begingroup\$ @psivosbi exactly what Andy asked you to clarify: what's your precise question that you need help with? "does anyone have input" is a start of a discussion thread, not a question with a correct answer – and we really don't mean to be rude, but we really try hard to not be a discussion forum, but a Question&Answer site! \$\endgroup\$ Commented Nov 26, 2020 at 22:03

1 Answer 1


Firstly, I'm going to assume you've got enough laser safety qualifications and protective equipment to work with 85W safely, where even transient reflections can blind bystanders instantly. That's a class 4, so you need a key switch and a safety interlock to keep humans out of the area in which the beam could be.

I don't see any advantages for the battery approach unless you somehow need this to be terrifyingly portable, so I would take the mains approach.

Power transfer can only be achieved in those parts of the cycle where the input voltage exceeds the output voltage; since the output is rather high, I don't see the advantage of the 2:1 transformer other than isolation, since the voltage on the output (both AC and DC) is also lethal. From there it's "just" a very high voltage buck converter with a fairly large capacitor on the output.

Safety interlocks go on the output side.

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    \$\begingroup\$ Laser radiation safety has been considered thoroughly, there will be a key required to "arm" the system and a secondary momentary switch to "fire" implementing a deadman switch of sorts. I have high quality PPE from a reputable optics lab supply source providing an optical density over 7 at 450nm and will only be operating the device in a room with appropriate signage. Very safety conscious (12 yrs+ working in HV dist / transmission). Hope the above addresses any concerns of myself handling an extremely dangerous source of laser radiation. \$\endgroup\$
    – psivosbi
    Commented Nov 26, 2020 at 11:14
  • \$\begingroup\$ More on topic: I'm inclined to go the AC route because it's much easier to attain my desired voltage of 110v (correction 1:2 ratio) in an ideal world halving 240v on primary and supplying 110v with more current available than I could need. I've been researching current source laser drivers over the last week and found most do so by exploiting a linear voltage regulator and a 'sense' resistor, but these circuits are well beneath the power requirements of my application. Unfortunately voltage regulators that will regulate 110v will supply 500mA maximum from my searching of components... \$\endgroup\$
    – psivosbi
    Commented Nov 26, 2020 at 11:21

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