Re: Hybrid SG/SISG idea? "IGBT-Assist Spark Gap"?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>

No comments?  In case there was any trouble
visualizing this (I doubt it, but...), here's a sketch
done using top-of-the-line schematic-drawing software:
mspaint.exe ;-)

http://silicon-arcana.com/SG-SiSG.jpg

Doubtless this sketch is **WAY** oversimplified!!  It
probably doesn't include a lot of necessary evils
required to place IGBTs in series (may need a TVS per
IGBT, divider to equalize the voltage across the whole
stack, etc.--thoughts?).

In short, the modularity of Terry's SISG is very cool,
but I'm wondering what simplifications one could make
if he/she started out assuming that they were going to
need a LOT of IGBTs, e.g., for use with a 15kV NST or
something bigger.  Ah...if only those 6500V IGBT
bricks were cheaper!! :-)

And again, the ability to adjust the firing voltage by
just varying a spark gap like in a regular SGTC would
sure be neato.

Regards,
Aaron

--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "J. Aaron Holmes"
> <jaholmes@xxxxxxxxxxxxxxxxxx>
>
> The main benefit of the SISG appears to be its very
> low loss compared to a conventional spark gap.
> However for higher voltages, it seems like the part
> count goes up pretty quick.  Would the following be
> possible (don't beat me if not, I'm a computer nerd,
> not an EE ;-)) ...
>
> Goal #1: Common drive for all the IGBTs so that a
> bunch of capacitors, resistors, and TVSs are
> eliminated.
>
> Goal #2: Get rid of *all* the SIDACs.
>
> Not sure about Goal #1, but it seems doable.  It
> just
> means you'd have to scale some of the components
> according to how many IGBTs you'd be driving, right?
>
> As for Goal #2, how about using a spark gap?
> Replace
> the SIDACs with a spark gap having a high series
> impedance such that there is insufficient current to
> cause quenching problems.  When the spark jumps, it
> would charge the IGBT drive cap just like in the
> current SISG design.  Then, when the IGBTs go into
> conduction, the voltage across the gap would be
> suddenly near-zero, further eliminating quenching
> concerns.  For added coolness, this trigger gap
> could
> be adjusted to vary the firing voltage without
> sodering, disconnecting things, etc.
>
> This "hybrid" of the SISG and conventional gap might
> substantially reduce part count while retaining most
> seemingly-critical element:  The IGBTs.
>
> Any thoughts?  Am I smokin', or could this work?
>
> Regards,
> Aaron, N7OE
>
>
>