IMO a capacitor that small is a no-no! The predominant factor for reducing the
output
ripple to a point where it will not cause anode modulation is the ESR of the
capacitor.
For a ripple voltage that does not exceed about 20 V p-p then you would need an
ESR circa
5 ohms. A 100nF capactitor could be made to do the job - but it would be one
of the very
expensive high voltage multi-layer types which are now available and would need
to be
rated at something like 3 times the expected ripple current. As an example a
boost
converter for 3kV out at 1A would require a ripple current rating of at least
2A to be
safe under all eventualities.
Remember that for good loop stability in a switch mode psu the minimum current
needs to
be about 30% of the maximum without having to resort to exotic mechanisms to
ensure
stability. The inductor should also be sized to maintain continuous conduction
down to
the minimum current drawn, altogether not a simple task, especially with the
kind of
voltages being used.
All in all not a project for a beginner!!
Johm ZS5JF
----------
> From: Peter Chadwick <Peter_Chadwick@mitel.com>
> To: 'Radio WC6W' <wc6w@juno.com>; 'amps' <amps@contesting.com>
> Subject: RE: [AMPS] amp
To: <amps@contesting.com>
> Date: 14 June 1999 11:40
>
>
> Marv says:
>
> >One interesting benefit of a switching plate supply is the elimination
> >of excessive "glitch" energy... and just think of the fun you could have
> >pointing out the .1uf / 10KV plate supply filter cap to visitors!
>
>
> In order to get the capacitor that low, surely you would need a loop
> bandwidth in the switcher high enough to prevent the cap discharging when
> the load is modulated at syllabic rate with a voice signal? That would mean
> out to say 5 kHz - perhaps higher, because of having a low plate supply
> impedance for the the frequencies represented in the plate current by beats
> between IM products?
>
> Anybody out there an expert on switchers? My experience is that they cause
> hash, and when something goes wrong, it's a chain reaction with every
> semiconductor in sight being taken out by the domino effect!
>
> 73
>
> Peter G3RZP
>
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