RE: PWM Controller question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Trimmell" <humanb-at-chaoticuniverse-dot-com> 

Hey that is a good question, I wondered about that also. But, Phil, you
got my interest; you are going to Audio Modulate a "H-Bridge" of vacuum
tubes!? Holly cow! What mode? Triodes, Pentodes? Heck you have me
salivating on what possible design you may use?!! Of course, you can
also do it with IGBT's and drop the filament power needs and voltage
issues. I think Dan's PlasmaSonic design is good, but I could see some
improvements in using (possibly) rail modulation. Real high power plasma
audio modulation will be seriously cool! I have seen it while arcing
something "semi-grounded" to a AM radio station tower many years past
(don't ask!). My grid modulated VTTC has been the closest I have seen
yet, but quality was unreliable.

Regards,

David Trimmell

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, June 20, 2004 4:02 PM
To: tesla-at-pupman-dot-com
Subject: PWM Controller question

Original poster: "tcbfw" <tcbfw-at-charter-dot-net>

Dan, or anyone else that might know the answer.

Looking at your PlasmaSonic SSTC design,
more specifically the TL494 PWM Controller.
You have a feedback signal from the positive rail able to change the
frequency the circuit oscillates at, could you explain what the overall
goal
of that would be ?
I wanted to use the same controller IC, but drive an H bridge of tubes,
this
will make my positive rail in the thousand rather than hundred volt
range,
so the value of R27 thru R30 will be adjusted.
Just don't understand the need to have the frequency change with the
power .
. .

Thanks,
Phil