Peter L. Peres wrote:
>
> >You need *at least* 680v
> >insulated fets.
>
> That's the second reason why you use a buck regulator followed by a H
> switch polarity inverter.

I don't think that is a good idea either. Now you are
talking a switching semi good for 3.5kW @ 350v, a buck
inductor good for 3.5kW, and a h-bridge good for 10A
and 680v minimum. We recently had an AC engineer on the
list saying that the AC mains is typically exposed to
1.6kv spikes of considerable energy, your suggestion
is exposing the h-bridge semis directly to this.

Then you have the cost of the parts involved (not even
including the 28x 12v battery stack and maintainance).
The "typical" setup of a 3.5kv toroidal transformer and
push/pull lwo-voltage semis (probably about 36v etc)
has so many advantages. I worked in a factory and was
responsible for maintenance on a *large* series battery
stack, it's not pretty. They develop differing
characteristics, which also change over time, and need
constant attention.


> >Now look at typical HV switcher, this will use a 1500v 6A
> >MINIMUM rated switching transistor. To switch a
> >100v rail!
>
> They are somewhat reliable, and I say this on the grounds that the vast
> majority of TVs out there did NOT visit your shop(s) within their useful
> life. The high specs on the LOPT driver are due to the way you need to
> drive the H deflection yoke (it has to be half-resonant or else you do not
> get the required current to deflect the beam in a 120 degree crt).

Sure, i'll confess to being jaded. :o) But semi's
switching at high frequencies are continually exposed
to thermal and magnetic stresses. They DO wear out.
I'm real curious what voltage overhead YOU would suggest
for semis switching 340v in high frequency PWM??


> I could never understand why they used high frequency H deflection and low
> frequency V deflection. The other way around would save 25% or more
> energy, cost, etc. (the H:V ratio is 4:3 in TV).

They chose it that way to save on lines per frame.
Your way would make it 33.3% more lines per frame.
Even with the lower number of lines they still had to
interlace...
-Roman

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