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Bench CC/CV PSU Based on Daves uSupply (Not Anymore)
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iMo:
If I was designing the board, I would arrange the ref for ie 431 (with those 3 resistors and cap) and design the pcb for the noninverting amp (with those 2 resistors creating fb) - that allows to use

a) TL431 set for 5V/4.096V/2.5V and buffered or unbuffered,
b) LM329 or any other 1.25/2.5/5V precision 2 terminal Vref source buffered or unbuffered,
c) to use 78L0x buffered or unbuffered,
d) to use a zener buffered or unbuffered.

as the holes, pads and tracks will simply be there.

If you intend to offer the pcb to others I would put those 2 1w shunt resistors as well. It is also expected the pass transistor will be placed on an external heatsink, as the heatsink you plan can hardly dissipate 3W.

Kleinstein:
The CC/CV indication would with a 50% chance not work with the OPs inputs directly parallel. The usual way is to compare the outputs of the 2 regulating OPs.

For the shunt even a 1 W type can be a little on the small side.  To keep self heating low the power rating should be more like 10 times the actual power used.
One may not need the extra resistors for the fast current Limit - the shunt could be used for this purpose too.

For the reference there is no real need to plan with an 78L05 - it's normally lower stability than the cheaper TL431. The LM329 is 7 V.
iMo:
Frankly, using an 1ohm resistor as the shunt is rather rare, afaik.
Normally people use something like 0.1/0.15/0.18/0.22ohm.
With 0.22ohm and 3A the loss would be 2W, with two 0.39ohm in parallel =1Watt each.


--- Quote from: Kleinstein on March 25, 2019, 04:06:18 pm ---For the reference there is no real need to plan with an 78L05 - it's normally lower stability than the cheaper TL431. The LM329 is 7 V.

--- End quote ---
Nope, no plans for 780x. Plans are for the TL431 with 3 resistors and cap only. All the other Vrefs can be wired there as a Bonus :)
Kleinstein:
The board shown is also a rather odd combination with THT resistors and SMD electrolytic caps.  The more usual way is using SMD resistors - maybe except for the shunt and other higher power resistors and THT for the power transistor,  large caps and foil caps if needed. The filter caps tend to need a larger foot-print.

D2 and D3 can be smaller (e.g. 1N4148 class diodes). It may be a good idea to wire a diode emitter to base at the power transistor, so that the reverse voltage is limited. This also gives the supply a limited (by the OP) sink capability in addition to the current sink.

The original plan was for a low current version (e.g. 0.5 - 1 A) and the TO220 case transistor is also only good for low power, like some 30 W - so maybe 1.5 A at most. One could still use the TO220 food-print to solder wires for an external higher power transistor (e.g. TIP140).

Similar I would see the pot food-print more like a place to but wires toa pot at the front panel.
KC0PPH:
This board is just to play around with, not my final PSU. The TH is due to the fact that I have TH. The SMD Caps are because Id like to verify Footprints before I go for the final rev. Final project will be pretty much all surface mount and I will use 1206 components for everything.

I figured screwing around on a Breadboard, or order a set of boards for $7.

I think my end goal will to build a PSU with 3 of these circuits on them to provide 3 outputs in addition to  5V 3V3 2V5 1V8 1V2 fixed supplies (say 100ma max)

 
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