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 #952
Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388
I'm building a small SSTC along the lines of Steve Ward's Mini SSTC. The electronics are finished and I've been testing them with about 70 VDC on the bridge. The secondary resonant frequency is estimated at 500–600 kHz by JavaTC.
With antenna feedback everything works as expected – with a 1-turn primary (just for testing) I get nice ~1.5" streamers off the breakout point. Their intensity increases as I increase the interrupter on time. So I believe the essential functionality is correct.
However, I'd rather use a secondary base CT as a feedback method. I've wound about 70 turns of magnet wire around an Epcos N30 toroidal ferrite core with 1" outer diameter. When I ran the secondary base wire just once through the toroid, I got some barely visible breakout at the same 70 VDC input. I then wrapped another turn of the secondary base wire around the toroid, I got a little bit longer streamers but they're still weak. It seems the CT feedback isn't enough to sustain oscillation, as increasing the interrupter duty cycle doesn't increase the streamer intensity. Respectively, if I pull the gate driver enables high for CW operation, the coil gives just one snap of streamers and then nothing. Further increasing the number of turns around the CT didn't give any noticeable change.
What could cause these symptoms? I wouldn't like to give up on the CT feedback just yet. Of course, I've tried all possible primary / CT phasing combinations. FWIW, the secondary is grounded to the mains ground. I also tried shielding the base wire with some grounded strip of aluminium foil.
The feedback section is identical to Loneoceans' SSTC2 schematic except with the 0.1nF filter capacitor removed (I had it in first but removed it in an attempt to improve the feedback).
I'm building a small SSTC along the lines of Steve Ward's Mini SSTC. The electronics are finished and I've been testing them with about 70 VDC on the bridge. The secondary resonant frequency is estimated at 500–600 kHz by JavaTC.
With antenna feedback everything works as expected – with a 1-turn primary (just for testing) I get nice ~1.5" streamers off the breakout point. Their intensity increases as I increase the interrupter on time. So I believe the essential functionality is correct.
However, I'd rather use a secondary base CT as a feedback method. I've wound about 70 turns of magnet wire around an Epcos N30 toroidal ferrite core with 1" outer diameter. When I ran the secondary base wire just once through the toroid, I got some barely visible breakout at the same 70 VDC input. I then wrapped another turn of the secondary base wire around the toroid, I got a little bit longer streamers but they're still weak. It seems the CT feedback isn't enough to sustain oscillation, as increasing the interrupter duty cycle doesn't increase the streamer intensity. Respectively, if I pull the gate driver enables high for CW operation, the coil gives just one snap of streamers and then nothing. Further increasing the number of turns around the CT didn't give any noticeable change.
What could cause these symptoms? I wouldn't like to give up on the CT feedback just yet. Of course, I've tried all possible primary / CT phasing combinations. FWIW, the secondary is grounded to the mains ground. I also tried shielding the base wire with some grounded strip of aluminium foil.
The feedback section is identical to Loneoceans' SSTC2 schematic except with the 0.1nF filter capacitor removed (I had it in first but removed it in an attempt to improve the feedback).
I found that secondary base feedback could be problematic without proper shielding. I encountered similar problems until I encased all the drive electronics and the feedback CT inside a grounded metal case - I think I described this a bit on my page. Or is your circuit already in a shielded box?
Registered Member #952
Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388
Hello Gao,
Thank you for the reply.
I do have the driver in a shielded casing. Actually I just managed to solve the feedback problem. I noticed the feedback network is a bit different from that in Steve Ward's original circuit. I redid the network to correspond to that schematic and the CT feedback started working beautifully. So the changes made were: the 1k resistor removed, diodes and 100n capacitor swapped the other way round.
BTW, thank you for your awesome SSTC tutorial! It's been very helpful for building my first SSTC, and the UVLO section is also something unique to your design.
Sounds great and glad that my page was somewhat useful. I can't quite recall why I added the 1k resistor there but looks like I can improve this by swapping it out. Appreciate the feedback as well. :)
Registered Member #952
Joined: Mon Aug 13 2007, 11:07AM
Location: Finland
Posts: 388
I'll report how it works out when I get to use full 325V on the bridge.
I don't know which mattered more, removing the resistor or swapping the order of the capacitor and diodes in the feedback chain.
Anyway, at 70VDC the feedback seems very steady and works with a topload as well (which the antenna didn't do). I didn't have to wind any extra turns of the base wire around the CT – just put it through the toroid once.
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.
Secondary CT feedback – oscillation not sustained
