If you need assistance, please send an email to forum at 4hv dot org. To ensure your email is not marked as spam, please include the phrase "4hv help" in the subject line. You can also find assistance via IRC, at irc.shadowworld.net, room #hvcomm.
Support 4hv.org!
Donate:
4hv.org is hosted on a dedicated server. Unfortunately, this server costs and we rely on the help of site members to keep 4hv.org running. Please consider donating. We will place your name on the thanks list and you'll be helping to keep 4hv.org alive and free for everyone. Members whose names appear in red bold have donated recently. Green bold denotes those who have recently donated to keep the server carbon neutral.
Special Thanks To:
Aaron Holmes
Aaron Wheeler
Adam Horden
Alan Scrimgeour
Andre
Andrew Haynes
Anonymous000
asabase
Austin Weil
barney
Barry
Bert Hickman
Bill Kukowski
Blitzorn
Brandon Paradelas
Bruce Bowling
BubeeMike
Byong Park
Cesiumsponge
Chris F.
Chris Hooper
Corey Worthington
Derek Woodroffe
Dalus
Dan Strother
Daniel Davis
Daniel Uhrenholt
datasheetarchive
Dave Billington
Dave Marshall
David F.
Dennis Rogers
drelectrix
Dr. John Gudenas
Dr. Spark
E.TexasTesla
eastvoltresearch
Eirik Taylor
Erik Dyakov
Erlend^SE
Finn Hammer
Firebug24k
GalliumMan
Gary Peterson
George Slade
GhostNull
Gordon Mcknight
Graham Armitage
Grant
GreySoul
Henry H
IamSmooth
In memory of Leo Powning
Jacob Cash
James Howells
James Pawson
Jeff Greenfield
Jeff Thomas
Jesse Frost
Jim Mitchell
jlr134
Joe Mastroianni
John Forcina
John Oberg
John Willcutt
Jon Newcomb
klugesmith
Leslie Wright
Lutz Hoffman
Mads Barnkob
Martin King
Mats Karlsson
Matt Gibson
Matthew Guidry
mbd
Michael D'Angelo
Mikkel
mileswaldron
mister_rf
Neil Foster
Nick de Smith
Nick Soroka
nicklenorp
Nik
Norman Stanley
Patrick Coleman
Paul Brodie
Paul Jordan
Paul Montgomery
Ped
Peter Krogen
Peter Terren
PhilGood
Richard Feldman
Robert Bush
Royce Bailey
Scott Fusare
Scott Newman
smiffy
Stella
Steven Busic
Steve Conner
Steve Jones
Steve Ward
Sulaiman
Thomas Coyle
Thomas A. Wallace
Thomas W
Timo
Torch
Ulf Jonsson
vasil
Vaxian
vladi mazzilli
wastehl
Weston
William Kim
William N.
William Stehl
Wesley Venis
The aforementioned have contributed financially to the continuing triumph of 4hv.org. They are deserving of my most heartfelt thanks.
I'm currently working on a plasma speaker utilzing a PWM TL494, UCC3722 9A mosfet driver and a GDT. Gate waveforms are, from what I can tell, looking good. I have two MOSFETs in phase running in a half controlled fullbridge similar to this:http://www.eetimes.com/design/power-
management-design/4012212/Two-switch-topology-
boosts-forward-flyback-designs/ I was hoping that this output stage would solve my problems of designing a snubber or having a horribly oscilatting transformer waveform, but no such luck. My drain to source waveforms oscillate much worse than I had anticipated and I don't know how to remedy the problem. Does anyone have any advice?
New from the lab: I took a scope to the gate and found that when the high voltage PSU is turned on my gate starts to oscillate quite badly. I've increased the gate damping and before I quit for the day I had increased it to more than 70 ohms. I feel like this is already quite high, but I will try some higher values tomorrow. I will also try to add an RC circuit in series with the flyback and see if that helps at all.
Registered Member #816
Joined: Sun Jun 03 2007, 07:29PM
Location:
Posts: 156
You’ve not given a lot of information, as lot’s of things can cause oscillation poor ground layout, stray capacitance +inductance due to the type of construction, and lack of decoupling, if the output is causing noise spikes on the ground or supply rail’s this can get back to the drivers causing them to oscillate.
What are you using for the high side drive? It is difficult to scope the drive there due to the floating nature of everything.
Some ringing will always be apparent when driving any inductive load, especially a transformer with its self capacitance, so I don’t know if this what you mean by horrible waveform, you could always try applying a drive frequency that’s related to the transformers natural resonant frequency.
I’m not sure what the advantages are, for using a two switch topology in flyback mode, apart from returning the energy back to the supply instead if dissipating it in a snubber or clamp. The down side is you can’t get as high voltage out with the same supply voltage and turns ratio, as you do with conventional flyback operation.
This site is powered by e107, which is released under the GNU GPL License. All work on this site, except where otherwise noted, is licensed under a Creative Commons Attribution-ShareAlike 2.5 License. By submitting any information to this site, you agree that anything submitted will be so licensed. Please read our Disclaimer and Policies page for information on your rights and responsibilities regarding this site.
Half controlled fullbridge oscillating problem
