Re: SSTC DC blocking caps

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

Original poster: "Steven Ward" <srward16-at-hotmail-dot-com> 

Keep in mind that with an audio modulation you will NEED the DC blocking 
caps as the duty cycle is all over the place.  I see no point in getting 
rid of DC blocking caps, the present very low reactance, dont heat up and 
are just a cheap capacitor that will really save things under some bad 
conditions.

Steve Ward


>From: "Tesla list" <tesla-at-pupman-dot-com>
>To: tesla-at-pupman-dot-com
>Subject: Re: SSTC DC blocking caps
>Date: Sat, 25 Oct 2003 12:59:56 -0600
>
>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
> >  >
>