I really wanted to build an indestructible, foolproof power supply, that is why I used that massive transformer and heatsink. With the case I built, it's weight is around 20 kgs, and not even used the full 5 amps of the transformer.
No such thing exists. All have limits and is up to user to keep connected load in limits.
Example a 30v power supply and idiot connects a 48v battery to output.
For power supply to protect against this is very hard to do, best to think of limiting the damage.
Example 1000F cap bank connected to output. The power supply would be at current limit for days. How long can power supply survive with output at 0V & Max current.
Sure you can add to this list.
So the best you can do is the limit damage and user has to supply remaining protection.
One thing I would not pass on is using what you have to learn. A lot could be learned.
Back in the 80's HP was doing a lot of internal research. A lot of things HP sold were first designed,built & used to cure a research problem. Often a power supply consisted of many modules or boards. This makes upgrades or new designs easer.
So before you look for something better, would be good to know what to look for.
The separate parts have to work together to make the whole thing good.
You can have very good blocks in schematic, but they have to be connected together in a way that makes total good.
You also have to keep in mind that nothing is perfect.
You have a cap across output terminals.
For CC mode you want no cap or small cap. The reason is that cap charge gets dumped into a short on output.
For CC mode any cap on output slows rate of current change to hold desired current.
For VC mode to hold constant output you want that cap huge.
For VC mode to detect a load change on output, smaller lets circuit see same change sooner.
The right cap or caps can stop supply from oscillations.
There are more things
So output cap is war of sizes with an option of making CC or VC better.
Then it could be that expected loads will survive the dump of output cap on short such that a little larger cap is ok.
Or load is not effected badly with a voltage change.
For a lab power supply you need to think of all the nasty loads that could be connected.
Step one for lab power supply is to protect connected load.
If connected load is real bad then step two is for lab power supply to try to protect it's self.
Then you have option of big load power supply & small load power supply where you pick best for load
So at cost of some of your time you could learn a lot from what you have.
Keep in mind the many ways to do things.
One change from last schematic to first is power and reference.
Last schematic used op amp's power supply rejection to lower noise.
First schematic I see creating problems by coupling noise into control power.
Again bad schematic hides details.
Take last schematic and redraw it.
Power section
on left is D1-D4, R1 & C1
on Right is
current sensor R7
Output control Q2,Q4 & R16
? C3
Some protection by D10, D11
Output filter C7
What is left is Control circuit.
Now if you do not have ability to easily do this, use your versions.
Now the Control circuit needs inputs to function.
Voltage and Current inputs should be differential.
Voltage sense is connection to Circle 3 and Circle 4
Current sense is connection to each side of R7
For control circuit to control output you could need connections to circle 7, circle 3, circle 4, left side of R7
Note that control and sense should be separate wires or paths, A
Kelvin connection.
Time to learn
Does current PC board do this separation?
Does your first do this?
It's not shown on any schematic posted, yet is simple and cheap to do.
If you look for new design, something to look for.
Note also this separates the high heat parts, parts that fail on heat.
With the schematic redone, You should be able to see some problem areas and have some ideas on how to improve circuit
So a great schematic is very important.
Makes it easy to understand the circuit quickly. Can show problem areas & and many more things.
Now for control section separate out it's parts.
Reference section
U1, D8, R4,R5,f6
it;s outputs are connection to R18 & circle 6
Should note a few things here
Power is via U1 V+ & V-
Part of differential sense is by R4 & R6 being connected to circle 4.
Should note that V+ and current set pot is main source current changes.
Should note that last schematic makes great use of op amp's power supply rejection to lower noise. A change to less is not an improvement.
The V+ connection of U1,U2 & U3 is connection to circle 7 for output control.
Adding a second line across to circle 7 could show this.
So I see a good first step is to learn from what you have now & fix schematic to show details and make understanding easer.
Take a huge number of measurements with your meter with different settings & loads. Save this to look back to to see a change is good or bad.
Each change a new spreadsheet of measurements.
Unknown is how well the last schematic functioned before changes.
Could be original has problems or you created problem for CC mode. Only measuring will tell.
One common thing is to have separate power for control & load supply.
So you have a massive transformer, would be a shame not to use it if you see a need for the power supply it can be a part of.
The way I see a single PCB is a way to mass produce something.
If you want something good that can upgrade then many PCB's or circuits is better. A good circuit design also makes this easy.
If you look at old HP supplies you often see it is made of many modules. A module is often used in many different supplies.
Think of future some, today you build best power supply you can. Next year you could think of it as junk. Easy to change junk could become new supply better then first.
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