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 #8247
Joined: Thu Nov 22 2012, 03:14AM
Location:
Posts: 18
I have a high voltage DC signal I would like to convert to pulsed DC, or a sine wave for that matter. The point is to charge a cap bank which when reaching 1200V is triggered by a gas discharged tube to create a higher voltage pulse out T2 as shown. The problem is straight DC will only allow the circuit to pulse once and then short out. The way I think to solve this problem is to convert the straight DC into a fast pulse or sine wave so the gas discharge tube can see the voltage has dropped and reset to allow the recharged cap bank to pulse again.
What is the best way to invert or chop this straight DC signal? An n-channel mosfet as a low side switch (gas discharge tube between the 1200V+ and drain) does not work because the gas discharge tube still never sees the voltage drop to reset. And they don't make p-channel mosfets above 600V so I can't use one to create a repeating high side switch (with GDT & cap bank after the mosfet source).
Would an IGBT like the below link work for this? And if so how would it be wired?
Registered Member #8247
Joined: Thu Nov 22 2012, 03:14AM
Location:
Posts: 18
Maybe, controlling the nchannel mosfet with a GDT is being my expertise at this time. I was hoping for something more straight forward such as driving the IGBT/mosfet with a waveform generator.
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
Ken Williams wrote ...
Maybe, controlling the nchannel mosfet with a GDT is being my expertise at this time. I was hoping for something more straight forward such as driving the IGBT/mosfet with a waveform generator.
A GDT is extremely straight forward. Simply run your gate drive through the primary, and out it comes from the secondary- isolated.
It wouldn't be wise to drive the fet with anything other than a sharp square wave anyways. Any time that the fet goes linear, you'll be turning a massive amount of energy into heat inside that fet.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
don't know exactly what you want but a 'resonant charging' circuit may be suitable, something similar to a classic Tesla Coil, heavier output loads 'damp' oscillations I will write 'spark gap' which could also be a gas discharge tube
the 1200V dc source has a high value capacitor across it, initial charging will be slow but when it gets to 1200V it will maintain a relatively constant voltage, your 1200V source (what is the source?) may already have an output/reservoir capacitor. For this discussion, assume that the negative side of the 1200V is 0V/ground/earth, that's all this capacitor is for, smoothing the dc, not really part of the circuit.
Connect +1200V to one end of a large value high current inductor (e.g. secondary of a microwave oven transformer) connect your spark gap between the second end of the inductor and 0V. HARD PART: the spark gap flashover/breakdown voltage should be a little less than twice the supply voltage, so for a 1200V supply, maybe a 2000V spark gap or for a 1200V spark gap use about 750V dc supply etc. the nearer to 2x supply voltage for the spark gap gives better efficiency (good) but erratic operation (bad) conversely, lower spark gap voltage gives a more reliable but less efficient operation.
Now connect a suitable capacitor (e.g. MMC in SGTC) in series with the transformer primary, connect the cap+primary across the spark gap. Operation is simple, starting up is not: for an explanation just google sgtc (or one of us can give a quick description) the system is not self-starting so something clever involving high voltage/current semiconductors, or a screwdriver (consider safety) briefly jabbed across the spark gap, or a lower voltage gas discharge tube running an ignition system.
A spark gap as used in SGTCs would be good, if the voltages were higher. At 1 or 2 kV spark gaps aren't easy. The power 'wasted' in the spark gap is significant, hazardous even. you could try a HID lamp (I don't know if the over-voltage ignition voltages available are suitable .. google)
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.
How to chop straight DC?
