Re: Self-resonant 555 astable conversion?

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

Original poster: "Jolyon Vater Cox by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>

I have re-posted  the circuit diagram as "555 sr astable.jpg" on the
hot-streamer-dot-com/temp to reduce the file size.

With regard to the phasing issue, I am wondering if a capacitor, connected
across the secondary of the current transformer, would compensate for the 90
degree phase lag between primary and secondary currents  in the same that
the capacitor does in K.C's feedback scheme.

Jolyon

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Tuesday, May 20, 2003 7:11 PM
Subject: Re: Self-resonant 555 astable conversion?


 > Original poster: "Stephen Conner by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <steve-at-scopeboy-dot-com>
 >
 > At 07:53 20/05/03 -0600, you wrote:
 > >Original poster: "Jolyon Vater Cox by way of Terry Fritz
 > ><teslalist-at-qwest-dot-net>" <jolyon-at-vatercox.freeserve.co.uk>
 > >
 > >I have posted the  diagram of my proposed  setup is at
 > >http://hot-streamer-dot-com/temp/555%20sr%20astable.bmp.
 >
 > I didn't download this as it was an incredibly large file (2MB)
 >
 >
 > >Looking at the diagram again I am concerned about phasing - should the
 > >current transformer should be in one the primary leads from the H-bridge
to
 > >the step-up transformer, rather than the secondary- this after all, is
the
 > >position of the current transformer in half-wave converters used in
compact
 > >flourescent  lamps and electronic halogen transformers -but what is
 > >implication of primary current  feedback on the TC frequency
distribution/
 > >bandpass characteristic?
 >
 > There has been a fair amount of discussion about this recently. K.C.
 > Herrick, Richie Burnett and me reckon that the current transformer in the
 > primary lead won't work very well. It works in simulations but once the
 > corona loading is applied to the resonator, the impedance reflected to the
 > primary doesn't show enough resonance. Of course a parallel-tuned primary
 > (like Vladimir Mazzilli used) might fix this one.
 >
 >
 >
 > >With the current transformer in the secondary lead- isn't there a phase
 > >discrepancy between the output of the current transformer and the primary
 > >voltage that would need to be corrected in some way e.g by connecting a
 > >capacitor in parallel with the secondary of the current transformer,
 > >perhaps?
 >
 > Yes, that's why K.C.'s feedback TC scheme used a capacitor as the sensing
 > element _instead_ of a current transformer. The voltage across a capacitor
 > leads the current by 90deg. I'm not sure why this is needed, but I think
 > it's because the mutual inductance between pri and sec causes the
secondary
 > current to lag the primary current by 90deg. Antenna feedback schemes like
 > Justin & Aron use get the 90deg phase lead from the capacitance between
 > topload and antenna.
 >
 > Of course it would be nice to have an adjustable phase shift to compensate
 > things like propagation delays in your switching circuit. Maybe a series
RC
 > circuit with a pot across the R?
 >
 >
 > >What appeared simple at first is now beginning to look rather more
 > >complicated...!
 >
 > That's life
 >
 > Steve C.
 >
 >
 >
 >
 >