On switchers you want the lowest ESR (Effective Series Resistance) between the
power source (the switcher) and ground, so you bypass it to ground with low-ESR
capacitors. Lots of good reasons; Sometimes the usual frequency (say 200 kHz or
so, whatever your switcher's running at, frequency wise) of your switcher is
just right for those particular capacitors, so using 3 in parallel will give
you really GOOD results. Another is that sometimes cost for those caps is
REALLY good this week, if you buy 10,000 or something. Or space in the project
(sometimes 3 smaller caps FIT better on the PC board than 1 humongous cap.)
And, also, what happens if one of the caps goes bad? If there were 3 caps and
now just 2 work, probably it'll still work, if there was just 1, it quits
working. Engineering is fun, but at times sorta a complex mess :)
Mark
From: Kerry Borgne <[email protected]>
To: neonixie-l <[email protected]>
Sent: Friday, February 19, 2016 2:51 PM
Subject: [neonixie-l] Capacitors in parallel why?
A question came up in one of my tech forums that I don't have a ready answer
to.
The questions was in regards to switching supplies (used in LCD and Plasma
Tv's) and the tech was asking why manufactures use three 1000uf35vdc caps in
parallel instead of using one 3300uf@35vdc. Other than perhaps a difference in
cost I couldn't come up with an answer. There are other examples of the use of
multiple caps in parallel instead of using one cap of equal value. I've seen
four or more.
Since I don't know a brighter, and more experienced group of guys than here on
this forum, I thought I'd ask if anyone had an idea?
Kerry
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