[sdiy] "Zerolytics"

mskala at ansuz.sooke.bc.ca mskala at ansuz.sooke.bc.ca
Mon May 4 14:41:22 CEST 2020


On Mon, 4 May 2020, mark verbos wrote:
> questions for me. Can high value SMT ceramic caps ever perform as well as
> electrolytics in power supplies? I know that caps in parallel add together,
> but can putting 19 caps in parallel really substitute for a big one? What

I think ceramics in parallel are *potentially* better than electrolytics,
if the design is done properly.  Lower ESR and inductance, for a start.
It would be important to correctly account for the loss of capacitance
that occurs with DC bias in a lot of high-value ceramic capacitors, so
that the face value of the ceramics would likely need to add up to more
than the value of the equivalent electrolytic; but that can be done.

> about all this stuff about using different values in parallel to catch
> different frequencies?

Capacitors do have self-resonant frequencies in roughly inverse proportion
to their capacitance, so having some of different sizes to cover a wider
frequency range does make sense.  It's not rare to see a small ceramic cap
in parallel with an electrolytic to pass frequencies that the electrolytic
can't.

> They claim the whole point is to prevent the need to
> recap the supply every 5 or 10 years. Is this the solution? I looks to be

Needing to recap every 5 to 10 years is a ridiculous exaggeration and if
they're saying that, then it casts doubt on their product.

-- 
Matthew Skala
mskala at ansuz.sooke.bc.ca                 People before tribes.
https://ansuz.sooke.bc.ca/



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