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.
hi i tried to built a 24V supply from the varying input supply of 70-330V using single switch flyback configuration.initially i planned to design it with open loop condition. when i given 50V dc as input, my drain-source voltage is shooting to 400V without snubber, and mosfet(IRFP460) is getting heated. i designed one snubber by reffering some books, the shoot-up is reduced to 150V. but snubber(RCD) resistance is heating. SO I DECIDED TO GO FOR THE TWO SWITCH- FLY-BACK converter. but how to generate, hate pulse for the mosfet which is above the transformer. here condition is both mosfets has to turn-on at a time. i saw some configurations which uses pulse transformers to generate high side pulse(foating gate pulse). but dont know how to design that at 30kHz frequency. pls give me any suggestion that how to do this using any other technuiques ......
Registered Member #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
Have you considered going for a single transistor forward converter topology instead?
You didn't say what your power requirements (wattage) are but a buck derived converter is a lot easier to get working. I know it requires an additional magnetic component when compared to the flyback (the buck choke to smooth the output) but the reflected voltage and spikes at the primary side are much more tame.
A buck-derived topology like the single transistor forward converter, dual transistor forward, half-bridge or even a full bridge are all relatively easy to get working. This is particularly so if you want to run it open-loop to start with like you described...
The flyback converter generally does not like to be run open-loop: The reason is that a preset duty ratio for the primary-side switch conveys a fixed packet of energy to the secondary side during every switching cycle. If this doesn't precisely match the energy drain on the secondary side, then the output voltage will either ramp up or ramp down. This is because there is no negative feedback in place to sense the output voltage and control the sizes of the energy packets being supplied. So if you set a fixed duty ratio with little or no load the flyback pulses will just charge up the output capacitor until it fails or the reflected voltage at the primary side burns out your snubber or switch!
That's not to say you can't run a flyback converter open-loop, it's just a lot more hairy than running a buck-type converter open loop. The buck converter run open-loop acts approximately like a constant voltage source determined by the duty ratio. The flyback converter operated open-loop acts more like a constant power source.
It really depends on what the power level is, and if you need to keep the cost, size, weight down. As a guide:
<100W Single switch flyback 70-200W Single switch forward 150-400W dual switch forward 250-2kW half-bridge 1.5kW-5kW full-bridge >4kW polyphase interleaved full-bridges
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.
[moved] 2- switch flyback dc-dc converter
