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Bench CC/CV PSU Based on Daves uSupply (Not Anymore)

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KC0PPH:
I am in need of a CC/CV Bench PSU and decided to build one. I could get a decent unit for a cheaper price than all the parts, but then I would not learn anything.

Anyway the goal of the project is:

1.2V - 12V 1A CC/CV PSU
20mV accuracy
20mA accuracy
5V Fixed Output
3.3V Fixed Output
All Unused IO ran to headers for future fun

I plan on powering this from a 18V Laptop Charger or something similar.

A brief description of the system:

Page 1 has the 5V and 3.3V regulators. It also has a switching regulator that should keep its output 1.2V higher than the 3080's output.

Page 2 is the microcontroller. -- Note a display and rotary encoders are the last things to go on. Display I am still torn on I2C, SPI or Parallel. I have done them parallel in the past. Rotary encoders I have not finished researching them to make an informed decision.

Page 3 is the circuit I basically copied from Daves RevC Schematic. There are a few minor changes, but 99% of it is his work.

So my question is, are there any errors that can be spotted, and what improvements should I make? In the board layout I tried to keep the analog stuff as far from the switchmode PSU as possible.

Thanks in advance.

Also if anyone would like a PCB let me know. Ill have some spares as JLC requires a min order of 5.


*Sorry did not realize I could edit once I submitted*

KC0PPH:
Sorry it did not print out correctly.

Correct Version Below.

KC0PPH:
Here is the Initial Layout.

iMo:
I would remove the IC4A buffer.. I would use it for buffering the Vref..
Otherwise the Q is how stable with different loads and fast the CC CV loop will be.

Kleinstein:
Daves circuit is a really poor starting point for a lab supply. Usually starting with a voltage regulator is a poor idea, as  is it hard to add a variable current limit. The poor starting point was a reason the ยต-supply never got finished because of problems under certain loads.

My best advice on this circuit is try to find the the errors and weak point and learn from it, but do not try to fix it, as it's starting with the wrong concept.  It's easier to start from scratch.

A much better starting point would be circuit from the start of this thread:
https://www.eevblog.com/forum/beginners/0-30v-0-3a-psu-audiogurus-version/msg2232978/#msg2232978

The task would be to get around the the negative supply. A simple way would be with 2 powerful series diodes to generate some -1.2 V. Not very power saving but with some 19 V to start with and a 12 V target the voltage is there to spare.
Something like 0-14 V at up to some 2 A should be relatively simple

However there is a downside of using a low side shunt: it is hard to add a second output. So the fixed 3.3 V and 5 V would need a different power source or fully isolated with a switched mode converter.

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