Laser Power Supply

All 4 of my PSU boards have the laser output as well as the 5 and 24 V controller supply.  It looks like a pretty standard switch-mode setup with a 220V mains input stage.  The model number is JK-KZJ3 and distributed and possibly made by Shandong Jinan Hongyuan Electric, it is mentioned on the net in a few places including a differently labelled one for sale on eBay and on a Italian language site with some reverse engineering details, I only found this site now after I had traced out the circuit myself.  It is rated at 20mA and 25kV and listed as 30W though hints of 40W are also out there though perhaps not quite up to the task.  The switcher IC is one of a range of similar ICs but the only one I could find that has possible pinouts is the SG3525A or compatibles.  It is wired up in a pretty standard way with output drive pulse-by-pulse current feedback and the trim pot and external power setting voltage are used to adjust the switching frequency.  I believe it runs the drive inductor or the output transformer to saturation, and then switches off.  The power is controllerd by how often it does this.  There seems to be no open circuit, short circuit or thermal protection of any kind.

The test button fires the laser in parallel with the controller TTL input, both are opto coupled though the test button is supplied from the onboard supply directly and hence not isolated in any real way.  These controls operates the shut-down input of the IC and so forces a soft start where needed (after some time interval) and might be cause for slow beam on in some case but I’m not sure how slow the ramp up would be.  I don’t think this would work well as a PWM input given the fact that it is controlling the shutdown circuitry and will be liable to work in a non-linear fashion.

Others have indicated that it is better to supply external laser power control to the POT input, on this design, and perhaps others, it feeds into a voltage adaptable input (though a resistor controlled current source charging pin in reality) with a minimal RC filtering that might need more added if using a slow PWM output from some micros.  I think it will work ok with the LaOS boards.

The laser enable input supplies power (24V) to the IC and should be connected through interlocks to prevent any inadvertent beam escape.

The pictures of the supplies for sale do not include the two extra connectors that also appear on the Italian site which shows an identical supply to mine.  The diagrams show the basic interface connections pretty well and I will perhaps re-draw my tracing of the IC circuitry one day and upload it if there is interest.  A Google translation is rather strange to read as it usually does a much better job but I can follow the gist of the posting, he traced the controls because the available documentation was inadequate. These extra connectors allow for connecting the interlock on the 24V line and having the test button on the JST connector while the boards without the extra connectors seem to support the interlock on the JST connector and need an externally wired test circuit and leave the laser switching IC powered all the time.


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