RE: MOSFET arrays

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

Original poster: "Justin Hays by way of Terry Fritz <teslalist-at-qwest-dot-net>" <pyrotrons2000-at-yahoo-dot-com>

For very precise switching of series MOSFET's, why couldn't a single
gate transformer be used with as many secondaries as there are
MOSFET's?

For instance, if you had an H-bridge using 3 series 900V MOSFET's to
make a 2700V device, the transformer would have one primary and (3 X
4) 12 secondaries.

I believe this is the technique used in fission bombs, where a
capacitor is dumped into the primary of a transformer with multiple
tens of secondaries. Each secondary is distributed to it's own
detonator, which is buried in a block of HE. If all blocks of HE
don't detonate within nanoseconds of each other, the bomb won't go
nuclear.

So my point is, if it can work in a nuclear device with this kind of
precision, I bet it could work in an SSTC. If relative care is taken
with layout, my theory is that it would work just fine.

And......my speculation is, using a feedback coil topology (like on
my website) would help tremendously when using series MOSFET's, as
all switching is guaranteed to be done right around zero crossing
(where there isn't much voltage...ZVS). So, even if a MOSFET in the
leg was slow to turn on, it's BVdss wouldn't be exceeded b/c there
wouldn't be much voltage available in the first place...

While we're on the subject, I must add that high voltage inputs (and
a series-MOSFET topology) is *not* necessary for massive arcs. High
*power* input, is. I got 14" arcs at only 120V input, with a half
bridge (!!) using 60 amp MOSFET's and a 3 turn primary. Voltage
doesn't matter. Current doesn't matter. Power does ; )

3 foot arcs would not be a problem at all with an H-bridge running at
120V. Lower than 120V though, impedance matching to the resonator
becomes difficult (a one-turn primary is as low as you can go).

Justin Hays
KC5PNP
Email: justin-at-hvguy-dot-com
Website: www.hvguy-dot-com