Driver Recommendation

[LaNeK779]

very interested on a schematic, parts list, advise or anything in this direction

[VDX]

... sorry can't disclose this version, as I'm integrating them in our comercially distributed machines and upgrade modules.

But I'll search for my older high current driver for IR-diodes with stepwise adjustable currents of 0,5A to 9A -- I've built it with several parallel LM317 and LM338 chips, used as constant current drivers ... and upload the shematics and layout here later.

I'ts the driver, I've posted here, under point "4. power-source:"
http://reprap.org/wiki/Laser_Cutter

Viktor

[VDX]

... OK, found the older 5xLM317-driver and attached the PDF-files of schematic and layout.

The left top socket is the voltage input - this should be something above 7 Volts and with the needed current.

The left bottom socket is for the TTL modulation - I've used this driver with up to 30kHz, but with faster opto-couplers (e.g. 6N137) this should be running with up to 1MHz.

The right socket is the ouptut for the laserdiode.

I've defined every LM317 for max. 1A in CW-mode (they can drive up to 3-4A when pulsed with low duty ratios) ... replaced them with LM338 for up to 2.5A each in CW mode (5-6A pulsed).

The current per LM-chip is set with the first resisitors - 1,2 Ohm for around 1A, so 0,6 Ohm for 2A or other values for other predefined currents.

The output current is defined by jumpers to set the amount (or type, when different current sets per LM-Chip) of LM-drivers ... made this for some drivers with switches for easier changing of the max. current ... or could be done with relays per software too.

The "effective" engraving power is defined by the pulse-ratio and moving speed.

The "coupling"/"averaging" resistors with 0,22 Ohms can be omitted (replace them with wire), they were "remnants" from another project, but aren't needed for this constant current setup ...

Viktor

[LaNeK779]

thanks a lot for sharing! much appreciated

take a look at this chip too. can take higher currents http://cds.linear.com/docs/en/datasheet/108345fh.pdf

[VDX]

... yes, I've tested with the LT1083 too, but then changed to "paired" MOSFET's with up to 20 Amps in CW mode and tested with 40Amps pulsing (max. output of my 10A-PS).

The MOSFET's are specified with up to 160 Amps CW and 650(!) Amps pulsing with low duty ratio, if not exceeding 200 Watts thermal -- so there's some "reserve", if needed more power

On the other hand - if I'll need more power, then it seems to be better, use lower Amperage per chip and wire more chips in parallel ... have some comercial drivers for pumping diodes with pretty high driving power in the kW-ranges, where too several MOSFET's were combined to serial (higher voltages with up to 160 Volts) and parallel (higher currents) groups ...

Viktor