Electronics > Projects, Designs, and Technical Stuff
Lab Power Supply - The Lost Current
<< < (24/26) > >>
xavier60:

--- Quote from: radoczi94 on August 08, 2018, 08:37:47 pm ---I saw those chinese kits all around ebay, with a red soldermask, and a single SPT. They were too good to be true.

Alright, I just bought a few mosfets, transistors and opamps to experiment with. I think I will try 2 or 3 schematics and then decide, wich one gets into the design state. Then, the cad will be started, but for now, release, the magic smoke! Will bring some news and experiences. :popcorn:

--- End quote ---
What MOSFET did you get? The one that I'm using, psmn020-150w, was originally intended for a Buck regulator project. By chance it also has a very good SOA rating making it suitable as a series pass element.
 Keeping the loop formed by the input capacitor, MOSFET, shunt and output capacitor as tight as possible will lessen the chance of oscillations. Also the Gate resistor needs to be placed close to the MOSFET.
radoczi94:
Thanks for the tips! It's IRFP250NPBF 214W. It has the best bang for buck ratio at the local store.
xavier60:
A single op-amp could be used to buffer the CV Pot, not necessarily a 741, something that will be stable at unity gain.
I read in another thread that placing dropper resistors in series with Pots accentuates drift due to the usually high temperature coefficient of  Pot's resistive element.

I haven't done much research on voltage references, other members are likely to know more. I used a TL431 controlling a MOSFET in mine. I believe that even an LM317 can be reasonably stable when used at low power because of the resulting low thermal gradients across the die.
The attached schematic is for illustration, some parts have been omitted to reduce clutter.

On second thoughts, the CC Pot should have a divider feeding it because of its small voltage range.
radoczi94:
Hi!

Made a schematic based on the ELV22532 supply. I hope it's easily readable, tried to make the smallest mess possible.Check out the attached pdf file.

I didn't made the board or any testing yet. Right now, I just want to have a supply that just works, afraid of changing out the opamps, because the circuit is compensated to the LM324 (as far as I know, the LM358 is the dual version of LM324). There are some parts that dont have value, well, I didn't calculated them yet.(About the compensation, the more I read about it, the less I know :-[ )

One thing I don't really understand is the diodes between the BE of the TIP142's. That are they wanted to do with those? To avoid the reverse biasing of the BE diode?

Any suggestions are welcome.
xavier60:
D9 and D10 seem to be for limiting reverse B-E bias of the TIP142's.
Involving IC3B would do nothing useful. Only the loading of the 1K resistors might do something.
Navigation
Message Index
Next page
Previous page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod