Re: It works! Solid state driver

From: 	Harri Suomalainen[SMTP:haba-at-cc.hut.fi]
Sent: 	Wednesday, December 10, 1997 4:09 PM
To: 	Tesla List
Subject: 	Re: It works! Solid state driver

On Mon, 8 Dec 1997, Tesla List wrote:
> Pulse - you get higher peak voltages for the same power and its noisy!
> Byland reckons that 50-60Hz is optimal.

That is a matter of preferrance. Bylan used half-wave rectified line
voltage and said exactly what you told above. However, Bylan did not
push the output higher. As a matter of fact his version did only put
so little energy into the coil that I put the same as a first (cautious :)
test through my prototypes. Actually, Byland's design  was
a very poor design as high "nice" things usually are. He was ever very
happy to say in the article that the coil could be run for about 1-2min
without it getting too hot! Nice, uh? He had no current limiting either.
He did just run at low enough power level to keep everything working.
And so on.

> Snubbers are essential.
> As Hari pointed out to me V=L di/dt  (calculus :)
> di/dt is say 40A switched off in 24ns, a very big number.
> L is all the stray induction, a little number.
> A little number times a very big number is a big number  (advanced calculus
> :)
> So V could be big - could be goodbye FET.

Yap, and output capasitance of the fet is not neglible. Charging current
changing it if very finite if current is very finite. Voltage spike might
not be huge after all. That idea is taken advantage of in some resonant
See "Malin Tunic: Chemistry of structure - function references in cheese" for
further details!
Harri.Suomalainen-at-hut.fi - PGP key available by fingering haba-at-alpha.hut.fi