LAB PSU (Analog circuit for µC driving)

[JS]

  Thinking about something like this, started playing around in spice and this starts to look like it does what's supposed to do. I'm thinking on LM338 (LM350 or LM317 for lower current options) two LM358 for now, a µC on a PCB (blue pill STM32C108 ready to test) and LCD display. I've already wrote a firmware to test it, waiting for a protobard to eat the components or something...

  First step at least. µC sends a PWM signal for voltage, another one for current. Two signals go back to the ADCs. Also added a current range select pin that should be open drain (as the STM32 has or switched between output low and analog input if open drain not available) I'm not aiming for the precision of the µSupply but a rather simple approach with off the bin components.

  If I want to keep this almost as simple as it looks now and avoid an extra output switch (relay or something) I might need to fix the output to get to zero (right now gets to about 0.8V in simulations) but that might be an easy fix swapping D1 and D2 with BJTs (and reversing the two left opamps)

  Other thing I'm considering to add as an option is a input voltage selector, to select between two different DC PSU, to swap ranges and not burn all that much heat. I do have a suitable transformer so I might be thinking about it. In any case that would be some transistor working as a switch when the output voltage reaches certain limit and a diode, I think I can get that to work. Other options could be added once I get the concept going, 16bit ADC with the ADS1115, DAC for faster response, some options with the regulators (maybe LT308X could work with some circuit and compensation mods)

  Listening for thoughts, opinions, whatever you want to add.

JS