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 #4118
Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140
Destroyer of mosfets wrote ...
Please corect me if I'm wrong but for only 50khz 12 terns sounds a bit low I would try increasing to about 30
From what I've read about GDTs 12 sounds about right (or maybe a bit low) for 50kHz. You're supposed to use as few turns that work. If 12 seems to be too little, try 15.
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
yea, it does seem a little low. but it also depends on his core area, flux density and voltage. every core is different. only he can calculate his turns, unless he posted all those specs here.
15000uf turns still sounds too low considering that a 300 or so khz Sstc uses between 12 and 20 check out uzzors 15v to 40v smps he uses about 40 turns
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
ben123324 wrote ...
yea, it does seem a little low. but it also depends on his core area, flux density and voltage. every core is different. only he can calculate his turns, unless he posted all those specs here.
I have no idea what these values are (or what the first two even mean).
Edit: I was to make the gate driver part using those chips, should I uses voltage spike diodes like there is here? (top right).
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
I upped the number of turns on the GDT to 15 and it has solved the problem of the chip getting hot. Now the next problem is the MOSFET's heatsink still getting too hot to touch within minutes.
I should be getting an oscilloscope soon so I will be able to check the gate/GDT waveforms and see what is going on.
I was going to try the thing with the UCC37322 chips for faster switching but I can't find the plastic container that they are stored in I have my suspicions (looking at you mother).
I was able to get some decent sounding audio modulation using this GDT compared to the coil-craft one I was using. 8 bit pirates of the caribbean theme tune FTW!
Arcs were pretty long too for just 36v input, I experimented to see how far apart the electrodes could be and still get an arc to form. I got to just under 3 inches before the insulation of the transformer failed and it arced over, I think it could have done at-least 4 inches if the insulation was strong enough since the arc still had a white/yellow tint to it and formed with no problems just before the transformer failed.
Which isn't bad considering how small this thing is (I think it came out of a 14" TV).
This transformer is now an AC one, since I can measure the resistance of the secondary windings in both polarity's with my multimeter. It measures around 40kohm between HV out and ground.
The half-bridge was drawing around 4.5-5 amps @36v according to my meter (although most of my attention was on the arc, naturally ).
My end goal out of all of this is to make a plasma speaker that I can package into an enclosure and play at-least a few songs on it before it needs turning off for a short break. But I guess I will have to wait until I get my scope until I can finally see what is really going on, I mean I am not expecting stone cold heat-sinks after a few minutes but they shouldn't be hot enough to cause nasty skin burns on contact (I use 15v for the chip and driver section, so plenty of voltage for the gates).
Anyway I am rambling on a bit now, but does anyone happen to know why only some flyback transformers seem to work well when driven with a half-bridge driver and some don't? I have tried others that perform well on other drivers but give out very small arcs with this driver even on 36v.
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Destroyer of mosfets wrote ...
What size heat sinks are you using$ can you fan cool them Also can you post a picture of your rig
My heatsink is one out of an old ATX PSU, it also has another heatsink screwed to it via one of the spare screw holes yet it still gets very hot. I could use a fan but it shouldn't be getting too hot to touch within minutes with out one should it?
The rest of the driver is packed away right now.
Also if I made the UCC driver would I need to change the input voltage of the SG3525 chip (I have it on 15v) so it doesn't risk damaging he UCC chips? And would O need to put protection diodes anywhere?
Registered Member #3943
Joined: Sun Jun 12 2011, 05:24PM
Location: The Shire, UK
Posts: 552
Well I tried the UCC37322 buffer chips but the problem is that I get an output voltage much lower than the supply voltage (15v). The voltage from the chip output is fine at around 30khz but when I take it upto around 55khz and up the voltage from the chips and what the primary coil of the GDT sees will drop all the way down to 7vac (gets lower as I increase frequency).
What could be causing this? and the chips get very warm too after 10 seconds, everything is hooked up right too.
Why are these things never simple...Its incredibly frustrating.
Edit: Just thought of something, could my 22 ohm gate resistors be partially to blame for the original problem of heating MOSFET's (this is at 50khz).
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.
Another half-bridge gate drive transformer problem
I have my suspicions (looking at you mother).
).