Building your own power supply: An actual example

[Khron]

Re: Building your own power supply: An actual example

The ferrite mixes might also be slightly different, for a given core size, so just to be on the safe side, you might wanna measure the Al (measured in nH per turn of wire) of the core (big A, small L); it's a parameter given in the datasheets.

[rogfanther]

Re: Building your own power supply: An actual example

Thanks, but I mean, if I have a no-name core, thus no official datasheet from the factory, can I use some "typical" values for that core size ?

[Khron]

Re: Building your own power supply: An actual example

Oh, yeah, core sizes are quite standard. Ferroxcube have a pretty comprehensive and nicely-classified set of datasheets on their site.

[rogfanther]

Re: Building your own power supply: An actual example

sorry if I cannot explain it clearly, but just to be sure I don´t misunderstand you, what I mean is if I could take a Al value say for a EI-33 core from Ferroxcube, and use it for some salvaged EL-33 core from undetermined origin...

[Khron]

Re: Building your own power supply: An actual example

I wouldn't Don't you have any possibility of measuring inductances?

[rogfanther]

Re: Building your own power supply: An actual example

Yes, i can measure them. Do you mean using some turns of wire in the unknown core, measuring the inductance of this coil, then calculating the other parameters from it ?

[Khron]

Re: Building your own power supply: An actual example

Eeeeeeeexactly Actually, measuring the inductance of a few turns of wire, and dividing that by the number of turns will get you exactly that Al you're looking for

And then you can compare that with whatever datasheets you can find, and see which "mix" is the closest match to the result you got.

[rogfanther]

Re: Building your own power supply: An actual example

Ok, understood. Thank you very much. Now back to reading about UC3842 psu design ...

[Khron]

Re: Building your own power supply: An actual example

You're welcome, and good luck

[Th3_uN1Qu3]

Re: Building your own power supply: An actual example

You're welcome, and good luck

Uh, i forgot you're, you know, alive on this forum. Coz i sure know you're alive on YM... Or actually, it could just be too much for tonight. I'm sure Chris knows how much i had... Not enough to be drunk, but certainly enough to not be fully operational.

@ all others: In either case, we'll be around, and always willing to help you with whatever we can. Switching power supplies aren't THAT hard to understand, i suggest anyone willing to learn to start with an unregulated PSU and then try to close the loop.

Before closing the loop, it's not that different from a regular mains transformer, just working at a higher frequency, hence enabling a smaller size. After closing the loop, it's not that different from a linear regulator, just with an extra inductance in the mix... sometimes. When working with current-mode controllers, the inductance goes out of the frame and things are quite a bit easier.