Re: re: Bipolar question ?MOSFETS

At 08:03 PM 4/11/96 +0700, you wrote:
>>From 100624.504-at-CompuServe.COM Thu Apr 11 18:13 MDT 1996
>>Received: from arl-img-4-dot-compuserve-dot-com (arl-img-4-dot-compuserve-dot-com
[]) by uucp-1.csn-dot-net (8.6.12/8.6.12) with ESMTP id QAA08705 for
<tesla-at-grendel.objinc-dot-com>; Thu, 11 Apr 1996 16:30:54 -0600
>Date: 11 Apr 96 18:24:49 EDT
>From: Alan Sharp <100624.504-at-CompuServe.COM>
>To: "INTERNET:tesla-at-grendel.objinc-dot-com" <tesla-at-grendel.objinc-dot-com>
>Subject: Re: re: Bipolar question ?MOSFETS
>>I'm tinkering with the idea of building a coil driver
>>using a pile of MOSFETS
>>At work I work on switching power supplies that use
>>MOSFETS to switch as much as 500W at as much as 90%
>>Has any one looked at using these things to drive a coil?
>Yes, I was inspired by Mark Barton's account of a 10kW FET coil
>(400v full bridge) driving a traditional primary, secondary arrangement.
>giving 3' - 4' of electrical flame!
>I am not an electronics professional and I've been struggling to get to
>grips with PWM control, snubbing, current limiting, gate capacitance.....
>even so I've managed to get to about 100w output giving a 3" - 4" arc. 
>(Despite building with stripboard). I'm aiming at 500w, which I hope
>will give a 10" arc.

>The other way to do it is to put the FET output into a step up transformer,
>giving say 1kV, one end to earth, other end to the magnifier coil. 
>Often refered to as "bottom feeding" but that name is an enima to

I have seen pictures of bottom fed coils with good results.
>You should be able to do this very easily.
>Alan Sharp (UK)
PWM Circuits are'nt really what I had in mind.
a much simpler circuit using feedback from the primary/secondary circuit and
a schmitt trigger to drive a FET class B type circuit.

I was thinking of trying to drive the primary as a LC series circuit (not
parallel LC) The voltage on the primary would be determined only by the
losses in the primary and secondary circuits.  The drive current would be
high but it might be worth trying.  A Q of ten would turn 200V drive into
a 2000 volt primary voltage. 

of course This is all speculation. With a certian ring of truth.

Paul Harriman