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 #1526
Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216
Hello, I`m trying to build a general purpose inverter for playing with but I just can`t get it to the point where I dare apply power. These traces are my best after much tweaking of damping resistors. Even with no resistors at all the rise and fall times are no better! The GDT is 1:1:1, driven from the output of SG3525 and the fets are IRF540s. I was hoping that an old hand could just look at the traces and give me some hints - could it be the suppression toroid I`m using for GDT?
Registered Member #1526
Joined: Mon Jun 09 2008, 12:56AM
Location: UK
Posts: 216
Oops! The the bottom trace is 1us/div and 10V/div. I have to go to uni. now but in a bit I`ll put a pic of the GDT and general layout. It is wound trifilar as you advise however. Thanks for the responses.
Registered Member #2481
Joined: Mon Nov 23 2009, 03:07PM
Location: ITALY
Posts: 134
Fraggle wrote ...
Oops! The the bottom trace is 1us/div and 10V/div. I have to go to uni. now but in a bit I`ll put a pic of the GDT and general layout. It is wound trifilar as you advise however. Thanks for the responses.
Well, a rise/fall time of 1us on a frequency of about 170kHz I think is too much... I think is leakage inductance and/or poor current capability of the GDT driver...
Registered Member #95
Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308
They're not great, but not terrible either. I've run several bridges on gate waveforms like that myself without incident. If you look closely the mosfets aren't in the linear region for that long. If you feel compelled to improve the waveforms, get a gate driver because you won't get good waveforms from a SG3525 no matter how hard you try.
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
IRF540s are chunky old large die MOSFETs and the SG3525 will struggle to drive four of them. You don't say what the switching frequency is, but I wouldn't be surprised if it is getting a little hot with this much capacitive load.
As other's have said there is no overshoot or ringing, so the gate-drive waveforms are "serviceable". They just don't have the quickest of rise or fall times, so don't expect the best possible efficiency out of the inverter.
I'm guessing you're not switching that much power with IRF540s so a few percent of switching losses due to the slow gate waveforms probably won't cause too much heating. Just remember to check the gate-drive waveforms when the inverter is actually switching power. Pristine drive waveforms usually stay good under power, whereas poor ones often get worse or display HF oscillation in the Miller plateau region!
If you want to improve things then buffer the outputs from the SG3525 via some proper gate drive IC's like TC4421, TC4422 or those UCC devices that are popular with people on here. They can provide much more peak current. Then you will find that your choice of damping resistor is more critical but you can get much faster rise and fall times!
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.
Worst gate waveforms ever?
