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Who wants to take this project on; host for 15W IR C-Mount Diode

rhd

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What size would people need for a high-power buck? I've a few designs that work, but I just never put them into production because they were too big for handhelds.
I'm down to 13x10 in the revision I'm working with. It's proving difficult to get it much lower if you want to retain adjustability, and not have to compromise on capacitors (or for that matter, the size of the wirepads).
 



Wolfman29

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I see. My revision is bigger (but can also supply a bit more current). I think I may wait till we see more mainstream diodes that can go above 3A. Otherwise, there is no economy of scale :\
 

rhd

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I see. My revision is bigger (but can also supply a bit more current). I think I may wait till we see more mainstream diodes that can go above 3A. Otherwise, there is no economy of scale :\
I'm not planning to setup shop selling drivers, so economy of scale doesn't matter. I'm being honest when I've said in the past that Eagle is just a relaxing way to unwind at the end of the day. It's kind of like doing puzzles.

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Wolfman29

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Fair enough. My only use for a high current driver right now is for a 40W IR bar I have still be having trouble figuring out.
 

rhd

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Fair enough. My only use for a high current driver right now is for a 40W IR bar I have still be having trouble figuring out.
I like the looks of TPS53355 or IR3551. Seem like reasonably simple 30 A and 50 A buck regulators.
 

Cyparagon

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I like the looks of TPS53355 or IR3551.
The TI part looks okay (only glanced), but I can tell you right now that the IR3551 requires a lot of additional circuitry. At work, we use a small bank of them to supply the 150A of core voltage for 12-core xeons. It's just a semi-smart FET and as such it relies entirely on an external controller (like the IR3536 for example) for a gate signal.
 

rhd

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The TI part looks okay (only glanced), but I can tell you right now that the IR3551 requires a lot of additional circuitry. At work, we use a small bank of them to supply the 150A of core voltage for 12-core xeons. It's just a semi-smart FET and as such it relies entirely on an external controller (like the IR3536 for example) for a gate signal.
Here's a likely elementary question, that is nevertheless stumping me -

Why does the example circuit in the TI datasheet preface values for capacitor F and inductor H with the ohm symbol?



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shokkunlasers

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Here's a likely elementary question, that is nevertheless stumping me -

Why does the example circuit in the TI datasheet preface values for capacitor F and inductor H with the ohm symbol?



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Indeed very interesting of course there is no SI-unit like Ohm-Henry or Ohm-Farad and I don't believe they mean a sample space or some physical particles (can't remember their nam right now :) ):D

I think they just mixed Mu with Omega somehow that would explain it for me ;)

If I wouldn't be so tired right now I would send them an e-mail about their mistake :p

BTW If anybody want to actually develop a driver with this IC please send me a PM looks like an interesting project and fun to do together

P.S. I also have a luminus PT-121 from DTR laying on my desk and this could make it into a flashlight :D
 

Alaskan

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Thanks for all the advice everyone.
 
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The Lightning Stalker

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The TPS53355 looks promising for the MCU programmable based driver with modes. I might be adding
the eval board to my wish list. There are a few people out there looking for something to drive the higher
power c-mount diodes.
 

Alaskan

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Thanks, I also have some FAP bars to work with too, but no FAC lenses for them yet, still looking. (bars out of a fiber interface).

Edit: Link to the TPS53355 application note http://www.ti.com/lit/ug/sluu522/sluu522.pdf

Another edit:

I have a cheap solution to a high amperage constant current source, I've done it before to limit the current to an 800 watt array of LED's all running at 32 VDC. All you need to do is parallel as many constant current power supplies as you want to a single bus which are isolated from one another. i.e. if you need 16 amps you could use four 4 amp current limited power supplies, set each to a maximum of 4 amps out and isolate each one from another using diodes feeding a common bus, set the voltages from each to closely match one another too, of course. In my last LED project I just set my voltage regulators to 32.0 volts across a 100 watt 10 ohm resistor, that way no power supply could have more than 3200 ma or 3.2 amps demanded from it, setting the current limit to that point, after the voltage was adjusted to 32.0 VDC. I took the voltage measurement from each supply AFTER the blocking diode, that way I didn't have to worry about small differences between diodes at the full current draw I was going to have.

This worked for me before without problems and no one power supply can have too much current drawn from it as they all have their current limiting set the same. There will be minor differences between power supplies which can cause some unbalance so I just ordered several extra ones and was able to find some which were close enough to balance out fine between one another at the operating load without any strange looping going on. This wasn't really necessary because most of the 12 power supplies I used were close enough except for one odd one out power supply that was acting wierd when paralleled like that but I found that the current drawn from each is more stable if you match them, they can "act up" and you can get some strange current loops if they aren't close enough to one another. Additionally, some small super capacitors across the bus can help if running close to the rated current outputs, if they are big enough and you don't need a 100% duty cycle over the time the capacitors can make the difference.. Also, a 5 to 10 percent constant load across the bus is good to have too, depending upon some factors but if using batteries, I wouldn't waste the power.

I am sure some power supply designs are more stable than others for this arrangement, some won't give any problem at all, others might. These were all 600W rated switching step-up DC-DC power supplies operating off of 12 VDC to produce 32 volts DC which are more finicky in this mode of operation than just a straight DC current limiting circuit board and batteries (my step-up units would only produce 3 amps out each at 32 VDC, extras were used to give lots of overhead). You wouldn't need a step up switching power supply with voltage and current adjustable outputs for a laser diode, as low of a voltage as they use. Just using a battery with a small linear voltage regulator board with current limit adjustments would be much easier to deal with and you probably won't have to concern yourself with much except for setting the voltage and current limitings identical as well as the outputs from each board being diode isolated from one another. Oh, I didn't do so with my project but it would be a good idea to have the isolation diodes matched for voltage drop too, or as close as you can reasonably get them, mine must have been close enough as they were, since it didn't cause a problem I didn't look into it but for a laser project, I'd deffinately check that. Also, you must take into account the voltage drop through the blocking diode(s) to determine the voltage you need from your battery or power supply prior to going through it to have enough for your laser diode on the paralled output bus side and use large enough wire to the laser diode so there is a minimum voltage drop there too. You obviously won't be using a sense wire on the laser device side of the reverse blocking diode, so no issues there.

I am not claiming this arrangement will work with all configurations, but you can configure your circuits so it will work. Someone ought to put some of these boards together in the size of a battery with mini screw driver current setting pot adjustments all along the side to make sure the current drawn from each board all match up, some kind of output test points for each individual circuit board to be able to match them up, if they go out of calibration. You could also have a main voltage regulator built into them too, adjusting the voltage input to all of the current regulators (really just individual looped voltage regulators with paralled outputs through blocking diodes) to make the thing work for a large range of lasers, allowing a lot of variability for the batteries used with them at the needed output voltage and current. It would also be nice to have slip on sleeves so they can work with larger diameter battery tubes too, perhaps with metal springs wrapped around them to help transfer heat to the tube. All of that said, better to just use a single regulator capable of high enough current to cover a range of laser diodes and build it the size of common batteries used in laser pointers. For my project I need close to 15 amps, so paralled boards might be easier, using existing designs with a couple of tweaks to them. I like the idea of a battery sized adjustable constant current regulator to simplify home brew pointer designs. Of course, for professionally done pointers, you could save some length building it into the head of the pointer with better cooling too, compared to having it burried in a battery tube.

Here's an example of the kind of constant current regulator I am thinking might be good to parallel together in a tube: Shanhai 3 7 4 2VDC 1W 1 4W 2W Blue 445nm 450nm Laser Diode LD Driver Power Supply 2 5A: Amazon.com: Industrial & Scientific - Just as an example, I don't know anything about this particular unit. Key to making this work is to be sure not to run any individual current limiter too close to it's max power because due to some variables, some will likely draw a bit less than others (never more than rated current, if properly current limited). I'd have a conservative margin of 25 percent less than maximum allowed current draw from any unit, in other words, all the boards together should be rated for 25% more current draw than you will actually be using as a total current draw, even better pull only 50% of the maximum allowed current load if you can (Some engineers already build this margin into the design anyway, it just depends on what they have done). You can try running them closer to maximum, but this gives some wiggle room due to variables which otherwise might end up being a pain in the backside to balance. With some experimentation I am sure you can find out what you can really do or not, or how close to maximum current rating you can really go without concern of a board taking more than its fair share of the load, but in the end, it won't matter that much because they are current limited not to exceed their individual rated outputs, I just like everything to run on the conservative side, this means a lower failure rate if ambient temperatures are higher than normal etc..
 
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