Re: Self-Resonant SSTC topologies

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

Original poster: "K. C. Herrick" <kchdlh-at-juno-dot-com> 

David-

Before I became "burned out" on SSTCs, I successfully used as feedback a
signal derived from the return end of the secondary.  Just feed that
through a low resistance (10-50 ohms perhaps) to ground.  Couple the
(sine wave) voltage across that resistance through 1K ohms or so to a
pair of back-to-back diodes, also to ground.  Take the voltage across
those diodes, amplify it, and use it to drive the MOSFETs or IGBTs.

You may need to connect a capacitor across the low resistance in order to
shift the phase appropriately.  Also, of course, you must be sure that
the amplified signal is in phase and not 180 degrees out, for driving the
transistors.

This technique causes the system always to be in tune with the
secondary's Fr.  Also, it's self-starting, with sufficient amplification
to allow noise to do that job.  I used it with an untuned primary; with a
tuned primary...I don't know.

Good luck.  Be sure to provide a big enough container for receiving your
burned-out transistors.  I'd suggest a 55 gal. oil drum.

Ken Herrick
Oakland, CA USA

On Thu, 13 May 2004 16:20:39 -0600 "Tesla list" <tesla-at-pupman-dot-com>
writes:
 > Original poster: humanb-at-chaoticuniverse-dot-com
 >
 > Hello, I have a couple questions to the folks who have
 > used the "current feedback" methode of driving their
 > SSTC's. Does this provide a "self-starting" coil? While
 > using a antenna on my self res driver, I need to touch
 > it in order to get the thing started (no oscillator
 > IC). Schematics of the self-res ISSTC show no starter
 > circuitry, so I assume this to be the case. Also, is
 > phasing just a matter of changing the direction of the
 > RF ground loop?
 >
 > I am using a half-bridge of the HGT1N30N60A4D IGBT's as
 > a test bed. While running without an interruptor
 > circuit I get 4-5 inch Hot CW plasma discharge (180
 > VDC) pulling 5 amps (panel meter) from the AC line into
 > filter. With a P-4 heatsink and fan everything runs
 > stone cold, even with 5-6 minute continuous runs. But
 > the coil does get nice and warm (4" wound with #28).
 > Seems that #28 wire may be on the thin side, at least
 > for a non-interrupted system.
 >
 > For a Picture:
 >
http://209.210.231.220/webdoc2.htg/SSTC/Pictures/Self_res_proto1/H-res_pr
oto_lash7.jpg
 >
 > Future work will include adding the Interrupter
 > circuit, and looking at adding the series res cap.
 > Also, what about a Magnifier version? With all those
 > primary to secondary flashovers, that would be a nice
 > solution, no? I allways wanted to make a VTTC Magi, but
 > never got around to it, hmm... Well, one step at a time!
 >
 > Regards,
 >
 > David Trimmell
 >
 >
 >