Electronics > Beginners
DIY power supply
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JS:
One thing you might like to know... CC dummy loads are a much simpler to build than a lab PSU, same thing for a variable power supply, but if you have both and connect the dummy load between the source and the variable supply you get pretty much a lab PSU. That's what I meant when I said using two power devices for a lab PSU. Remember to put first the CC load and then the variable PSU, otherwise it won't work. The other possible way to do it is to put it on the low side, using the high side of the CC load as the ground for the variable PSU.

CC load is basically a mosfet, a sense resistor and an opamp. The variable PSU is just an LM317 with the standard circuit around it. If you want to go this way (which I totally recommend to get something up and running for a beginner to have something to work with) let us know so we can help you choosing the right CC load to build, as it's the part that might get unstable under certain conditions, the classic simplistic design gets unstable, but just adding a resistor and a cap to make it slower makes it work fine.

JS
MarkF:
@JS:

Could you post the circuit you're tossing around so we can see your thoughts? 
I believe that @Pirateguy going to setup his ATX Supply with polyfuses so that he just needs to remove the overload condition and the fuses will reset for him.  As a start, I think he will just build the basic LM338 adj voltage in the datasheet with a polyfuse for current protection.  Then add adj current at a later date as his knowledge grows.

I actually did build Peter's Electronic Load.  The IRFP064 in a TO-247 package is a beefy MOSFET.  I have no problems with it.  However, I lowered the current capability to 1.5A for mine.  That's all I really need.
JS:
  The picture is the basic design, I've just found it on google, at least has some compensation as I said which makes it usable but the values are wrong, at least R14 which should be 1Ω or maybe lower, depending on the expected current range, properly rated for power, much higher than the actual power the resistor will dissipate to get better stability and not get too toasty. 1k there seems way off unless going for really low currents, in which case the mosfet makes no sense as a single opamp could do the job for a few mA. R1 could be 100Ω, R15 10k and C10 something like 1n should roughly work, depending on the mosfet and some other factors, like expected speed and loads. Iset will be Vref/R14

  This is the topic of my dummy load. https://www.eevblog.com/forum/projects/cccv-dummy-load/msg1589761/#msg1589761
  As you see mine is quite more involved, having CV and CC modes, and thermal shut down and a more involved compensation to keep it relatively fast and stable under many conditions. It will be in CV till the CC limit is reached. The funny connected transistor is the temp sensor which I didn't had the lib for.

JS
MarkF:
Looks nice. But, I thought we were talking about adj power supplies.
JS:

--- Quote from: MarkF on August 20, 2018, 07:42:21 am ---Looks nice. But, I thought we were talking about adj power supplies.

--- End quote ---
They have a lot to do... specially once you start talking about current limiting. As I said, with a simple variable supply and a CC dummy load you basically have a lab supply.
Also, a related but simpler project that you would need to test the power supply you build so why not build it first... is kind of the egg and the chicken as what are you testing each with, but I tested mine with a 9V battery just to check so you don't need the PS to build it.

JS
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