[TCML] Mosfet H bridge questions

[Scott Bogard <sdbogard@xxxxxxxxx>]

Hi All,
     I'm trying to wrap my head around just exactly how one would use 
an N channel MOSFET/IGBT on the high side of an H bridge.  What I am 
trying to accomplish is to build a more or less "universal" bridge that 
with substituting components per necessary ratings could be used for 
everything from a flyback driver, to a leg of a PWM for a VFD 
(apparently VFDs are actually feeding a PWM signal that varies duty 
cycle with time to simulate a sine wave, they don't actually put out a 
sine wave at all...) even eventually a crude DRSSTC, using the same 
PCB.  I plan on using an arduino or other similar programmable 
controller with multiple outputs to generate signals for these various 
applications.  Here is what I came up with, I want to know if it is at 
all viable, and keeping parts to a minimum is a key point for me being a 
mechanical guy.
http://bogard.110mb.com/generic%20H%20bridge.bmp
If it doesn't load take out the %20's and replace them with spaces.  The 
low side signals can be driven off a tap of the autotransformer, which I 
don't really know how to approach designing or if it will even work in 
this application (or even if it is really necessary...)  Obviously the 
number of turns will be dependent on input voltage (more like 12 or 24V 
for flybacks, 400V for PWM applications.)  I will pick the wire gauge 
based on the current capacity of the transistor, but as how to know I 
have an inductance that will keep current low enough that my transistor 
will be able to survive, I don't know how to approach this, or how to 
size my transistor for voltage considerations (would it see 120V or only 
the saturation voltage?)  This stuff is not my field so be gentle so 
very wise collection or electrical engineers.

Scott Bogard.
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