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Need help finding/designing a constant current driver for PLT3 520D by OSRAM

solidstatefella

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Nov 11, 2020
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Hi,
I'm trying to drive PLT3 520D for surface patterning applications. The laser needs to run for 1 to 5 minutes at a time at an output power of 50 to 100 mW without pulsing.
I'm hoping to control the output power and on/off state using some serial connection (UART/SPI/I2C/etc.) by a microcontroller but I can also work with analog voltage signaling from a DAC. However, most drivers discussed on this website are pot-controlled and not applicable.
The device will not be battery powered but the supply voltage will likely be between 5 to 10V (flexible on the choice of power supply, but would prefer a buck/boost configuration for the driver)

I would appreciate any design tips and suggestions for the driving circuitry!

The datasheet for PLT3 520D is attached below.
 

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  • PLT3 520D_EN.pdf
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solidstatefella

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Have a look here at DTR's site maybe one of those will suit your need

Beyond that look on ebay perhaps something there works for you?
Thanks, it seems like their BlackBuck 8M fits my requirements except for the output current , which - if I'm interpretting correctly - has a minimum of 1A.
 

Anthony P

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Yes, BB8. You can get lower current using its PWM/ analog input pins.
 

Jimmymcjimthejim

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I personally wouldn't use an 8A laser driver for a 200mA laser diode. The reason is output current ripple. Without a specification, schematics, or testing, it's impossible to know whether the current ripple is 10mA or 100mA or worse.

If efficiency is not a concern, I would use a 12V boost converter (any number above your max input voltage should be ok) followed by a linear current regulator. The linear regulator can be an op amp current sink with a DAC, just put a big cap (e.g. 10uF) in parallel with the laser diode. (see https://www.ti.com/lit/pdf/slaa868). This circuit can easily be put together on a soldered protoboard. If you're lucky, you might be able to find a programmable current sink. Programmable LED drivers are fairly common on this front.

Hope that helps.

Best,
Grant

Edit: another option is to hack a buck-boost driver with a digi-pot (programmable potentiometer), but there's potential risks to this, such as over-voltaging the digi-pot, output current glitches, etc. I'm also not sure what driver you can hack, given the input voltage range.
 
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Hi Solidstatefella,

This sounds like a cool project, though what you need the driver to do is a bit...complicated from a "DIY driver" perspective!

I'm not sure how much experience you have with electronics, but if you have a lot of experience, I'd recommend designing a PCB and having it manufactured. It only costs a few dollars, even if you have them source and solder all the components for you. At that point it's (electrically) a pretty simple affair - whatever means you choose to regulate current, pick some way to modulate the properties of the adjust signal digitally, add your protective components, and you're good to go. If you're going this route, it's also quite easy to add a "buck/boost zone" to the PCB and do the power conversion right on the board rather than relying on an external module.

If you're not that experienced with electronics, I'd be looking out for commercial solutions that fit your needs out of the box. As Jimmymcjimthejim mentioned, it might be possible to hack a buck/boost driver - possible but not perfect. On the pure practicality side, a commercial driver might physically be rather difficult to modify/add components to. From the electronics design side, these type of drivers are simple enough that you'll probably be able to deduce the circuit layout and component identities just looking at the board, but without the full parts list, it's hard to be sure what's already on the board, potentially complicating your hack component selection.

I'm also curious about why you chose the specifications you did - are you sure that's the laser power and diode you need? Does your application require the ~520nm wavelength of that diode? Also, most laser drivers that have the kind of power modulation functionality you want are designed for higher power diodes, which, depending on your application, might also work for you. Depending on your design, you could increase the speed that the laser moves and use a higher power diode for the same or similar energy delivery.

Good luck and hope I was able to be of some help!
 
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