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I have an application where I need a digitally controlled constant current power supply capable of currents up to 50A. I have made a digitally controlled constant current power supply in the past, but only up to 200mA, and I imagine I will need very different design constraints for this one.

I have skimmed the service manuals for high current power supplies such as the HP 6259 which seem to use an array of BJTs for regulating current but I am not sure of how to re-implement this design.

I am planning to use this 12V, 50A SMPS as a 12V source capable of supplying up to 50A. I have drafted up a circuit using the HP 6259 service manual, , this Stackexchange post on BJT-controlled constant current source, and this post on running BJTs in parallel:

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But I am not sure if this is correct, and even if it is, I am not sure how to calculate the relationship between DAC output and current through the load. I am also not sure how to select the specific BJT model to use or how to select the values of resistance for the balancing resistors.

If anyone could provide any advice that would be highly appreciated!

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  • \$\begingroup\$ What bandwidth and SNR is needed? Do you care about massive heatsinks, water cooling? \$\endgroup\$
    – D.A.S.
    Commented May 25, 2022 at 19:48
  • \$\begingroup\$ That's not how it was done by HP 50 yrs ago, need better load specs and ripple \$\endgroup\$
    – D.A.S.
    Commented May 25, 2022 at 19:54
  • \$\begingroup\$ Good grief that’s walking over the bridge to get to water. Get yourself a programmable CC/CV supply if it’s a one-off or build an adjustable CC/CV control loop for your existing power supply? \$\endgroup\$
    – winny
    Commented May 25, 2022 at 20:01
  • \$\begingroup\$ If you wish to build it yourself from non-expensive PSU, may be it is easier, faster and effective to add a DAC to feedback path of that SMPS (roughly)? \$\endgroup\$
    – Vladimir
    Commented May 25, 2022 at 22:20
  • \$\begingroup\$ I would like stability to about 0.01A if possible but even 0.1A should be fine. I don't mind heatsinking and cooling everything. An adjustable CV power supply capable of supplying up to 50A seems to cost about $1000 and I cannot find any CC power supply with these specs for less than $2000. \$\endgroup\$
    – king_geedorah
    Commented May 26, 2022 at 0:02

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