Electronics > Beginners
DIY power supply
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Pirateguy:
what if i use them in high current config with the power transistor?
MarkF:
I don't know what your goal is now since your AT Power Supply died.

You could try using two regulators in series to split the load as shown in the "Tracking Preregulator Circuit" example in the datasheet.
I would configure the first regulator to always be 6.5V above the output.  This would give you a 0-20V output with your 32V supply.
   Start with R1=240,  R2=1K,  R3=330,  R4=5K and see how it works.

   
   
JS:

--- Quote from: MarkF on September 01, 2018, 04:07:01 pm ---I don't know what your goal is now since your AT Power Supply died.

You could try using two regulators in series to split the load as shown in the "Tracking Preregulator Circuit" example in the datasheet.
I would configure the first regulator to always be 6.5V above the output.  This would give you a 0-20V output with your 32V supply.
   Start with R1=240,  R2=1K,  R3=330,  R4=5K and see how it works.

   
 

--- End quote ---
I think 330Ω for R3 is too high, it's supposed to meet the minimum load specs, but for both LM317 this time, if the regulation is supposed to be maintained without any load or very low loads. Also, this circuit doesn't share the thermal load evenly between the two ICs so I don't know if it's optimal for this.

JS
Pirateguy:
well i'm pretty sure i can pick up an ATX from a thrift store around here if need be.
in fact i saw one the last time i was there.

i ordered the dps3012 for my variable supply, along with a case for it.
so now i just want to make the fixed output one.

for that i intend to use the large heatsink from my disassembled AT,
continue using the AT housing (it's all i got atm) and for the time i do
stick to 3.3v, 5v and 12v outputs. leaving the negative unconnected for now.

so some ideas i had:

-using the bypass transistor for current to take some strain off the regulators.
-using multiple regulators in parallel.
-cascading regulators; 32v PSU to 24v regulator, from the 24v to 18v regulator, from there to 12 and so on.
-i have a fairly heavy wall wart that switches between different voltage levels, could i hack that?
maybe i can draw a line from the transformer directly and add a rectifier circuit for each?

assuming one of those ideas will work, i am again left with the challenge of finding an enclosure.
any suggestions for that?
it would have to be fairly big so i have room to add more stuff, incl power source(s)...
Wolfgang:
... why not just add a pass transistor and keep the LM317 cool ? Its not one of the xtra stable or noise free regulators on earth anyway ?
And if you want to be really nice you can add a current limit plus an overtemp protection plus a crowbar at the output to avoid surprises ...
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