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.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
This was the basic idea:
And the question is simple, why doesn't it work?
I used 1,5V batteries with decoupling caps to provide isolated sources. Feedback diodes were two series 1N4148's which seemed to drop down about 2V total in this case. When I used one battery per leg, the minimal gate voltage dropped to about 1V; When I put the next one in series, the voltage went down to almost perfect zero except for some ringing. At that point I thought it's an epic success, but soon got disappointed.
When I seriesed another battery hoping for more negative voltage, the circuit didn't want to oscillate.
Same was with 9V batteries or any other source.
And I'm still banging head what's happening and what should I do. If I can get this to work it would make best possible feedback I know.
Can anyone give me a clue what's logically wrong with the arrangement?
Maybe I should use the source in series with the gate, and higher drive voltage? Or put it behind diodes?
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
I already said, I decoupled the batteries with caps, 100nF ceramics and 470uF lytics respectively. But I simply lose oscillation when I try to drive it just a fraction of volt into negative.
I bet somebody with good whack for logic can solve this easily.. ^ ^
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I think it's because both MOSFETs need to be on at once to get the circuit started. It really doesn't matter if both devices are on at once. The ZVS is a current-fed inverter, so it can't be hurt by shoot-through. Bad things only happen if both devices turn *off* at once causing the DC link choke to kick back, which is bad in the same way as shorting out the DC link with shoot-through on a voltage-fed inverter. If you want to know more, read up on the principle of duality.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi all, steve, BTW I PM'ed you again, couldn't resist, I'm sorry for being cumbersome
I completely agree with you, although off-through condition is something yet to be seen, since mosfet delays always take care of that.
I did although see some weird artifacts in voltage waveform on the inductor, but nothing over like 10% of main amplitude.
Now, I have managed to get the negative drives working! I use four small IRFU410 mosfets (2 in paralell) since they have much smaller delays, are free from CFL's and ideal for study.
The thing decided to work when I put the batteries 'before' main diodes and with reverse Schottky diode in parallel.
Batteries got quite loaded, but pulled the gate down to -5V.
The circuit did not want to start until I applied main power, and even then sometimes it would just short the supply. (Small mosfets handle the shorting nicely due to their high resistance). Definitely not something reliable yet!
From theoretical side, mosfets should turn on into metastable state same as without negative supplies, at least as I think. I don't see anything that may be causing trouble.
I really owe a hug to anyone who can resolve what is exactly happening here! lol.
If you ask why is this all about, I simply want faster and more efficient gate drive. I don't think it can be too fast in tis kind of circuit, can it?
My last circuit used a heavy slow 600V diode and large pullup resistors. Due to voltage drop of ~1.5V on the diode I was unable to drive any kind of active pullup, nor UCC's nor small mosfets with <1V treshold voltage.
With negative drive I'l be able to use a series string of 1N4148's since forward drop isn't very important anymore; very fast and cheap.
Large passive pullups were slow, hot, and caused mosfets to spend large part of half cycle in linear region, which in turn made the mosfets very hot.
Shown waveforms are slowish too despite only 400pf of capacitance, I plan to get them into perfection...
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.
Driving mosfet gates in a royer negative.
