Hi,
The first scheme should work well.
It has protections and reasonably well chosen phase margin.
I would only double the MJ29055 to make the power supply more robust.
The second scheme is "stupid" the "designer" does not know what he is doing.
He puts two opamps in series for current limitation, that is why comparatively large capacitors are needed for C4 and C5, it is clear to me that the designer does not know what he is doing.
Can you vary the output voltage with this schematic yes!
Can you set the current with this schematic yes!
But because of the enormous inertia caused by C4 and C5, the circuit is very slow to maintain the output at varied loads.
And the circuit is also too slow to protect your load and the MJ2955 transistor.
A different waySeveral power supplies have been designed on the Dutch forum "Circuitsonline" and I give here a few links to one of them.
This power supply is designed with normal components that are readily available.
Use a translation machine if you don't know the Dutch language.
I have done many tests on this power supply and it is very good for hobby and professional use if built properly.
I have also made some improvements in a separate topic on that forum, but these are basically not necessary.
The power supply is simple in construction (Harrison Concept) and can easily be built on an experimental board.
The original board is no longer available for this project.
First page page article:
https://www.circuitsonline.net/forum/view/130041/1Schematic:
http://www.gigawatts.nl/co/projects/CO_Voeding_2016/CO%20PSU%20Guido%202015%20Schema.pdfShort discryption:
http://www.gigawatts.nl/co/projects/CO_Voeding_2016/Bijsluiter%202016%20co%20psu.pdfHave fun!
Kind regads,
Bram