Electronics > Projects, Designs, and Technical Stuff

Building a bench power supply

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stev.dk:
Thanks for your reply Paul!

I'll take that into concideration. It looks soo perfectly simple, the way i like it. I like your Danish comments in there, it made me laugh :-DD

stev.dk:
Im starting my work based on my transformer, and the LM2576-ADJ chip, cause the only thing i need for this, is the LM2576-ADJ. I made a schematic for the power supply section. Pretty basic actually, but i've added some input protection stolen from a scrap part i have lying around. It's a ceramic fuse, so i believe it to be a hrc fuse? I cant see the value of the varistor, cause it has heat shrink on it, but it's from a 2.5A circuit, so it should fit my needs. I can't see the value of the cap, cause the varistor is in the way, and i've shipped out my old soldering station, waiting for my hakko FX-888 to arrive :-+ From the same circuit im able to score a 1K thermistor. The bridge rectifier is a KBL406, which should handle 600V 4A.

Im pretty happy, with what i've got this far, even though it's pretty basic. I left out a supply for volt and ammeters in the first place. When i get the chip and assemble the thing, im going to measure out reference voltages 5, 7.5, 9, 12, 15, 18 and 24 with my fluke 87 (when it arrives  :-+) and mark it with a dymo or something like that.

Please comment.

mariush:
Just read the LM2576 datasheet and pay attention to what it says.

The IC will be very unstable on a breadboard, and is quite possible to not work right on prototyping board/stripboard too... you need to have some components physically as close as possible to the IC leads and you also need as thick ground traces as possible.

That's the problem with switchers, lots of noise and issues with inductor selection (which has to handle the peak current and other specs that are mentioned in the datasheet) and placing the parts on pcb.
Either way, i think it would come out "optimized" for a particular voltage and when you adjust the voltage, the ripple will increase and the ic will be inefficient. A pi filter at the output and possibly even a ferrite bead would help smooth the output.

Paul Price:
Looks like a great start! 
I don't know what you are going to do with the 1K temperature sensitive device.
If you need to how add complete MCU control and metering and constant current to this supply I know how to do this.

stev.dk:
I am capable of making my own PCBs, so im not tied to using a vera or stripboard. I'll actually enjoy getting into designing a PCB, etching it og drill holes with my (new) drillpress (didn't have one last i did PCB's and i broke a lot of drills |O)

If you look at the schematic Paul uploaded, theres a optional filter, at the very end, looking a bit like a pi filter? I have lots of ferrite beads, so i might have one suitable for this job aswell :-)

Paul can you specify what MCU control is?

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