Re: SSTC DC blocking caps

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: humanb-at-chaoticuniverse-dot-com 

Dan, are these "blocking capacitors" the one's C5-C9 on
your PlasmaSonic II design? I notice that the parts
list only includes two of these 0.47uF caps. Thanks for
getting these boards out so fast, I look forward to
seeing these guys sing!

David Trimmell

On Fri, 24 Oct 2003 21:36:10 -0600, "Tesla list" wrote:

 >
 > Original poster: dhmccauley-at-spacecatlighting-dot-com
 >
 >
 > Actually, this is not exactly correct as well.
 > DC blocking capacitors are used in bridge circuits to
 > prevent "core-walking"
 > (and ultimately saturation) of the output
transformer.
 > This is typically
 > only used for half-bridge circuits where any
 > imbalance in the push-pull type configuration of the
 > half-bridge adds any
 > type of DC bias to the output transformer.  However,
in
 > full-bridge
 > circuits, imbalances are almost always equalled out
 > due to the topology of the full-bridge.   For what we
 > are doing, you really
 > don't need the DC blocking capacitors at all, but
seems
 > we just keep them
 > there for ease of mind.  Justin and Aaron have
 > completely eliminated them from their circuits.
 >
 > Dan
 >
 >
 >
 >  > The DC blocking caps in series with the primary are
 > not integral to normal
 >  > operation. In fact, they have no affect on normal
 > operation, so long as
 >  > they are well above the resonant capacitor match
for
 > the primary (1uF or
 > so
 >  > is a typical blocking cap value in a mains powered
 > SSTC).
 >  >
 >  > They are there in the event that the bridge stops
 > switching, and power is
 >  > applied to the primary coil for an extended period
 > of time. Without the
 >  > blocking caps, the primary would appear as a short,
 > resulting in the
 >  > potential death of your switching devices.
 >  >
 >  >
 >  > Dan Strother
 >  >
 >  >
 >  >
 >  > >Original poster: "chris swinson"
 > <exxos-at-cps-games.co.uk>
 >  > >
 >  > >Hi all SSTC ppl!
 >  > >
 >  > >am I right in thinking the DC blocking caps are
 > only there so the coil
 >  > >will only draw power at Fres ? I wonder what would
 > happen if I took them
 >  > >out and drove the coils direct. I imagine as long
 > as the frequency is
 > near
 >  > >Fres then it wont draw any more power and short
out
 > the outstage,
 > comments ?
 >  > >
 >  > >Cheers,
 >  > >Chris
 >  >