Re: Comparison with resonant switching topology (was Re: My FET T.C.)

Hi Marco,

> Original Poster: "Marco Denicolai" <Marco.Denicolai-at-tellabs.fi> 
> Tesla List <tesla-at-pupman-dot-com> on 17.11.99 05:53:10
> To:   tesla-at-pupman-dot-com
> cc:    (bcc: Marco Denicolai/MARTIS)
> Subject:  My FET T.C.
> >Original Poster: Alan Sharp <AlanSharp-at-compuserve-dot-com>
> >>3.  Driver-- 24, 85A, 500V power MOSFETs electrically in push-pull
> >>parallel, together driving the equivalent of 1 primary turn (in a
> >>patent-applied-for circuit).  Soon to be increased to 48, then--if
> >>my endurance holds out--to 72.  That will double, then treble the
> >>spark length (and the input current for a given spark rate).  The
> >>primary is untuned.
> >Do you mean 85A or 8.5A mosfets - why so many? they will handle
> >a peak current many times greater than the continuous current rating.
> >I thought that 8 was a lot.
> Just a little comparison with the switching topology I am using
> (resonant load, full-bridge). I use 4 1200V 35A IGBT (oversized in
> terms of current). I switch 560 VDC into a 15 (fifteen!) turns primary
> transformer, using a primary peak current of only 12A. At the
> secondary I get 5kV at 1A. All the switcher fits on a 100x160 mm
> (eurosized) board. The 4 IGBT use together the same 4 'C/W heatsink
> and stay pretty cool all the time.

I suspect that the design being talked about is not a cap charger but 
a CW driver. If so, it would be an interesting exercise to see 
whether resonant type switching might be used successfully to 
overcome the switch stresses. The problem CW toplogy is up 
against is a frequency change with secondary loading.