[TCML] a conceptual SSSR

[Ken Herrick <kchdlh@xxxxxxxxx>]

Greetings, all-

I've been away from the List for quite a while (old age, lagging 
motivation, death in the family) but have still been off-&-on pursuing 
the single-resonant scheme (OK, OK!, I know... but it keeps me out of 
the bars).  Some may remember the photo I posted years ago, before I 
"improved" the design so much that it quit forever:

http://dl.dropbox.com/u/28799314/KCH_tcg1.jpg

That was a time-exposure, of 5-8 sec as i remember, plus a 2nd (double) 
exposure with flash.

(First time I've used dropbox, so I'm hoping all can view these OK--when 
I've gone beddy-by & am off-line.)

I'm now back at the task, having totally redesigned & rebuilt the 
primary apparatus.  But I have thought of a scheme that might ease the 
considerable burden on my power MOSFETs; here's the simulation schematic 
and I would invite comments on it:

http://dl.dropbox.com/u/28799314/KCH%2010%20May%2011%20ckt.jpg

The secondary apparatus is L1 + (R2 = L1's dc resistance) + (C2 = the 
ambient capacitance) + the top electrode.  I presently have that + all 
the rest in hardware, built & somewhat operating in my current redesign, 
except for TX1.  It's the use of TX1 that I'd like to get comments on.  
Very likely others have done this kind of thing years ago.

The whole thing is, obviously, a feedback loop, to sustain oscillation 
at the "secondary's" Fr.  I put that in quotes because, in this concept, 
there's no primary coil as such.  Instead, I take the 1800 V p-p that I 
already have (from E1 in the simulation) and feed it thru a 1:10 
transformer (TX1 + R3), to directly drive the "secondary" (which is to 
be my existing 12"-dia. coil whose in-place Fr is ~140 KHz).  TX2 is 
just a small toroidal common-mode filter I've had on hand; it works well 
in the hdw.

Here are simulation waveforms, each showing toroid output, 1800 V p-p 
drive from E1, and E1's output current:

http://dl.dropbox.com/u/28799314/KCH%2010%20May%2011%20graph%201.jpg

http://dl.dropbox.com/u/28799314/KCH%2010%20May%2011%20graph%202.jpg

Graph 201 shows the beginning of the ring-up and 202, the end (stopping, 
merely for convenience, at 200 us).  Notice that well before 180 us, 
switching has shifted so as to occur near current-z.c.  Also, the p-p 
E1-output current is markedly below that obtained in my more-complex 
simulation of the current setup, which is less TX1 but including a 4 uH 
primary coil of 4T on 12" diameter.  The peak current shown in these 
graphs can quite comfortably be provided by my present driver setup so 
I'm tempted to try adding in a real TX1 before I go much further.

If anyone wants to check this out in SiMetrix, contact me off-List & 
I'll email the file.

Ken Herrick
Oakland, CA
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