Electronics > Projects, Designs, and Technical Stuff

Found a very good lab supply design.

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FenderBender:
I ran across this maybe 2 years ago, shrugged it off because it didn't have any LM317s and therefore was impossible.

Now that I look at it, it's really not that bad of a circuit to build at all and it has a a lot of the features that you'd want in a good bench supply.

http://electronics-diy.presstoday.net/2011/07/bench-power-supply-circuit.html



Tell me what you think!

Seems like a winner to me.

george graves:
subscribed

HLA-27b:
no criticism but some questions

first of all I wonder what software was used for the schematic. Magazines used to be full with these and sure they look nice.
second..As far as I get it the R17 is the current sense resistor, but what does the R15 do then?
and lastly..the voltage reference for the entire circuit is the LM7815 but it also carries all the current. Is this a good topology?
 

FenderBender:

--- Quote from: Electronics DIY  on April 23, 2012, 09:01:30 pm ---R15 ensures that capacitive loads with low effective resistance do not make the control loop unstable.

--- End quote ---

Whatever that means...

And.


--- Quote from: Electronics DIY  on April 23, 2012, 09:01:30 pm ---Frequently in simple designs the amplifier is not powered from a regulated supply, which can lead to an unstable current regulation loop. This circuit avoids the difficulty by using a low-cost fixed voltage regulator to supply the feedback circuit with a stable voltage. This arrangement greatly simplifies current measurement and regulation.

--- End quote ---

So I guess there is some purpose though it would probably work okay without it. This designer does seem to understand electronics so I won't doubt him too much.

free_electron:

--- Quote from: HAL-42b on April 23, 2012, 08:47:48 pm ---no criticism but some questions

first of all I wonder what software was used for the schematic.
--- End quote ---

looks like an elektor symbol sceme. they used McCad for a long time + ultiboard to do PCb. they switched to Altium in 2004 and recreated that style library in Altium as well. i know there's eople that have done this for eagle as well.

as for the design ... what a hairball..
the reason this thing has a tendency to oscillate is that he is using an n-mos as a top side driver.
Give more output voltage -> Vgs diminishes until the opamp can catch up thus the mos conducts less, opamp overshoots
in other words : the opamp and the mosfet are fighting each other constantly in the regulation loop.

how does he fight it ? by adding AC feedback to dampen the opamp.

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