Solid state design

To: tesla-at-pupman-dot-com
Subject: Solid state design
From: NickandSim-at-aol-dot-com (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Sun, 16 May 1999 07:08:02 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Hi All,
         as a little aside from my conventional coiling activities a friend 
has asked me to come up with a pair of little coils to run on stage with his 
rock group.  This seemed to me to be a great opportunity to build some nice 
solid state coils as they have the advantages of no exploding caps, no ozone 
producing spark gaps etc. 
After some thought I decided to avoid an output transformer because the many 
hours needed to make one didn't really seem all that exciting.  When you 
actually calculate the impeadance of a 12焙 inductor (typical helical pri) at 
400kHz it is actually quite high, about 30ohms.  So if I use a 300V H-bridge 
drive (IRF3415 FETs) I can put 10A throught it, well within the capability of 
the fets and a nice round 3kW power input. I am using the SG3524 pwm chip 
buffered by MC34151 and MC34152 drivers, inverting and non-inverting 
respectively.  A question for all you smpsu designers is how safe is it to 
just rectify 240V mains and run this off that? Should I use an iso 
transformer?  I also wondered if anyone had any ideas on my choice of pwm 
chip (does the 3524 run at 400kHz? - the data sheets are taking a long time 
to get here)? Is any of this really stupid?

Thanks in advance
Nick Field