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 #2922
Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226
Hello. I'm developing a synchronous buck for my QCW system. The first test with GDT to drive the two IGBTs of the buck didn't work good. GDTs don't work good with duty less than 15% or more than 85%. Now I want to make a active IGBT driver, and I want to use opto-isolator to isolate the top and bottom IGBT driver and the uC controller. I want to now if the 4n25 isollator work good? And what is the better frequency for this type of buck?
Registered Member #3640
Joined: Sat Jan 22 2011, 12:16PM
Location: Germany close to Heidelberg
Posts: 39
Hallo Gregory, now it's my turn to try and help. I can't answer the question regarding the 4n25, but perhaps there's an alternative to optical drive.
Have a look at this circuit:
It could be interesting, because it should be independant of duty. It's really 2 converters - one loading the gate on a raising edge, the other unloading it.
It might be a bit heavy in part count, but it's mostly simple parts.
Registered Member #2922
Joined: Sun Jun 13 2010, 12:08AM
Location:
Posts: 226
Hi! Thanks, this is a good method to drive high gates capacitances IGBTs. But, the problem continue with this circuit too... The isolation transformers don't work good with specifics duty cycles.. like the edges ( < 15% and > 85% ), for a buck is very important a perfect square wave.. With opto-isolators driving a TC4429 in the power level of the G->S of the igbt I can get much more control and I can put even a died time in the switching square wave..
My question about 4n25 is the operation frequency.. I have already read that it run just up to 1khz.. But I have already ran this at 31Khz in my MIDI interrupter with no problem..
Registered Member #3640
Joined: Sat Jan 22 2011, 12:16PM
Location: Germany close to Heidelberg
Posts: 39
Gregory, understand, but that's actually the trick with this circuit.
Look at the entry - it has a Cf1+Rf1, which makes a pulse of 200ns (in this sizing) out of the raising edge. Only this pulse is transmitted through the GDT to switch the IBGT on. After the switch on, the capacitance of the gate will keep it on, until the switch off pulse comes. Same then for Cf2+Rf2 - it turns the falling edge into a pulse - only that this pulse switches the IGBT off.
This is the elegancy - different of other circuits, this one actually transmits the on- and off signals seperatly, and as such should work independant of duty cylce.
Certainly there will be circuits also working with optical insulators - I just thought, this could be of interest, because such GDT's are easy to make with trifilar windings.
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.
QCW synchronous buck igbt driver
