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A simple adjustable DC power supply: hardware

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Notes & stuff

Design constraints


  • 2 adjustable outputs
  • 1 fixed output


  • adjustable outputs: 0-30V, adjustable
  • fixed output: 5V


  • adjustable outputs: 0-2A, adjustable
  • fixed output: 2A


  • voltage (for adjustable outputs only)
  • current (for adjustable outputs only)
  • current limiting active (constant voltage / constant current) (all outputs) (red LED)


  • combine to 0-60V / 2A (series)
  • combine to 0-30V / 4A (parallel)
  • link voltages (can be used for parallel mode or symmetric output)


What happens when the power supply output voltage is set to 3.3 V, and I hook that output up to a 12 V battery? Which is better:

  • The PSU pulls the voltage down to 3.3 V (or as close as possible until it hits the current limit)? or
  • The PSU supplies zero current, letting the voltage float up to 12 V?

Should have a 3.3v fixed output as well as the 5v. Easy enough to handle. 1A should be good for most purposes on the fixed supplies. Elektor ran a switching PSU module in April that I made some tweeks on and currently as waiting on boards. Galvanically isolating the adjustible supplies is a potential issue. As soon as you hook a meter panel up, the two supplies are tied together. Hack around it by using two MCUs for A/D and transmitting to a third one via optoisolators?–pstemari

Further reading

/home/ladyada/public_html/wiki/data/pages/openbench/psu.txt · Last modified: 2016/01/28 18:05 (external edit)