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Help with how this PSU works. (With revised design)

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aheid:
Yeah, the idea with the extra opamp is to limit the terminal voltage to something slightly above the setpoint, in case the sense probes aren't connected to the right part of the DUT or similar.

Of course not strictly needed, just some extra dumbass protection for absent-minded folks like me :)

Evangelopoulos Panagiotis:
While I was designing the circuit I thought to my self: "Hey! I can add a switch to the Vsense wire so I can have a remote sense for voltage drop on the leads!"
But then it hit me. What if the sense wires are not connected or connected in the wrong place? It will probably cause the output to rocket to 30V and destroy everything.
So I quickly dropped that idea. But it is something that I might add if there is a need for a v2.0 in the future ;) I might also add the auto tap switching in v2.0 if I see a need for it.

I'll post here again when that time comes. 

jaycee:
Sense wires not being connected would be catered for by the resistors that are between the outputs and the sense. You would get some error, but it would stop the voltage rocketing too far away from the setpoint.

Even if you do not need remote sensing, it is worth incorporating it into the board, even if you then just have sense wires connected directly at the output terminals. It improves regulator accuracy considerably.

Evangelopoulos Panagiotis:
Greetings again,

I have good news! The PCBs and components finally came! I've put everything together and powered the PSU up!
No magic smoke escaped!

I only found two "bugs" in the design. First, the two LEDs seem to be the other way around for some reason. :P When CC lights up that means that the voltage is stable and when CV lights up that means that the current is being limited. Just keep that in mind if anyone decides to build this design.

The second "bug" is that I could only get a maximum output voltage of 18V even though my input supply was 45V. I tried changing the 47k (R20) pot but with no luck. After poking around I found that the reason was the 4.7k (R18) resistor. I put a trimmer in parallel and found that with an extra 3.2k resistor in parallel with R18 gives me an output voltage of 43V and after tweaking R20 I got it down to the 42V I wanted.

Anyway, I did some quick tests and it seems to working ok for my taste. So I'm overall very pleased!

Thank you all  for your help!
Have a nice day,
E.P.

P.S. have some pictures :P Note the bodge resistor.

aheid:
Awesome, cool to see it built, so thanks for sharing!

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