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 #76
Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458
as i think, that this would be very interesting for those who wants to build an H bridge out of bricks, i´ll post my results with the dc restore gatedrive.
the current needed to drive a siemens bsm75 brick with a gdt at 100khz is high, and so i searched the net for ideas. im not very familar with high side drivers and for gate capacitances up to 20nF they are not neccesary, if the drive frequency is below 100khz.
The drive signal induced in the gdt secondary charges up the gate capacitance and discharges the gate within the negative signal state. this is resulting in a constant current draw for a certain frequency/gate capacitance..
The idea was to use a pnp transistor to discharge the gate within the negative signal state to relieve the gdt and the connected driver. With this little Circuit on the Gate emitter on the brick the drive current for a given frequency/gate cap is halfed. Cause the gdt is only used to charge up the gate to V+ but not to discharge the gate. The pnp transistor i used is a low power bd744c The siemens bsm75 bricks i used have a gate cap of 16nf and with this circuit they are eysy to drive with a 1:2:2 gdt from a single pair of ucc driver ics. At 100khz the current draw of the driver in CW! Mode is around 250-300mA at 15V in.
heres a pic of my test H bridge with driver.
And heres the gate signal at 100khz measured on each halfbridge at 20v in
Sure, the idea is not new, but i dont know, why nobody uses this technique
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Active pulldown is indeed nothing new. Those IGBTs don't look like something too big and hard to drive, they should be as easy as TO247 30N60's (and their current rating isn't much better). GDT with two pairs of UCC's should do it well alone.
The BD744 itself is actually very slow, delaying the entire thing probably more than if it wasn't there. I would personally use a small mosfet in this place if I wanted to.
Registered Member #76
Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458
hehe, okay, maybe its time to start comparison with or without this circuit and take a few scopeshots. then you will see, things are much better with..
a 30n60 igbt has a gate cap of around 7nf. yeah with a little fiddling this sweetys are easy to drive from a single pair ucc driver ics. but whats about 16nf gate cap on the bsm thingys? no to 247 sized igbt has a gate cap that big... the most conventional bricks i know and i own have a gate cap of around 15 up to 80nf..
with this circuit i can drive the bsm bricks up to 180khz without any big problems..
and do you really think the bd744c is much slower than the brick actually is? Look at the waveforms.
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.
success with dc restore gatedrive
