Re: Solid State - progress.

To: tesla-at-pupman-dot-com
Subject: Re: Solid State - progress.
From: bigr-at-teleport-dot-com
Date: Mon, 10 Jun 1996 15:38:08 -0700
I will start to make up schematic in the next few days.

There is some discussion of the idea of disabling S-D diode in Mot 
Mosfet Databook. However, they don't go too much into detail since 
they don't want to imply that their Mosfets aren't robust.  In 
switching supplies the objective,anyway, is to remove as much leakage 
inductance as possible that causes inductive kickback to Mosfets. 

However, I did quite a bit of work designing an electronic ballast for 
fluorescent lighting for motion picture high speed cinematography 
application (100khz drive eliminates flicker).  I used a technique for 
generating the starting voltage and filament voltage that utilized a 
resonant circuit.  When driving 6 forty watt bulbs, there were 6 
resonant circuits to drive.  I found out early on that with such a 
high amount of stored energy in the circuit, the only way I could keep 
Mosfets from blowing was to disable S-D diode.  Resonant HV coil is 
similar, but even more extreme.

I would like to scrap use of the UC3825 altogether and go to one of 
Unitrodes resonant power supply IC's, which use 
"zero-voltage-switching" for the Mosfets.  However, have been unable 
to obtain these as samples or otherwise.  If anyone has Unitrode 
"connections" I would love to get my hands on these as resonant power 
supplies are the modern children of Tesla.  Part # is: UC3861. There 
are probably even more devices that I'm not aware of.

Using the "zero-voltage-switching" of mosfets, its should be possible 
to obtain drastically more power out of my setup.