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 #3823
Joined: Sun Apr 10 2011, 08:00PM
Location:
Posts: 2
I ordered samples of both the coilcraft GA3459-B, and GA3460-B flyback transformers. They are recommended to be driven in conjunction with a LT3751 charging circuit from Linear Technology of which I also have a sample of. However, the LT3751 is a very small package surface mount chip which I can't build a circuit around very easily with the tools I have access to. My question is what kind of circuit is recommended to drive this flyback to be used in charging a 12000uF 400v electrolytic capacitor? My original design was to use through hole components. It incorporated a 555 timer adjustable between 3kHz-70kHz with a 15-turn potentiometer timer driving an onsemi NTP6412ANG 100v 58A N-Channel MOSFET. The diode used is the onsemi MUR860 600v 8A ultrafast recovery diode. The power source would be 12 volts regulated from a 16 volt battery with a peak discharge of 40A. Does this design seem like it would work? I feel like I may be missing important pieces of information on how to drive the flyback.
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
How about this?
Through-hole, readily available parts, nothing critical about the design, you can probably scrounge everything you need from an old computer power supply.
Registered Member #3823
Joined: Sun Apr 10 2011, 08:00PM
Location:
Posts: 2
Thanks for the reply, I already have a boost converter I can use to charge the capacitor, but I was looking for something to do with the flyback samples I had received in the mail. The design you provided looks very useful for charging capacitors but I assume it would require a different flyback? Additionally, it raised the question, do flybacks run off AC or DC? I noticed that the design you posted used a bridge rectifier to output dc so i assume the output of the flyback to the rectifier is ac? Some flyback drivers I have seen only use a single fast switching diode so i was curious if that means that flyback can be AC or DC, or if that is just part of the design where a single diode will only output half of the AC wave? When you charge a capacitor with a flyback must it output a voltage equivalent to the capacitor or does it output higher voltages until a load is a applied?
Registered Member #3610
Joined: Thu Jan 13 2011, 03:29AM
Location: Seattle, WA
Posts: 506
This has been discussed many times under various topics but I'll try to sum it up.
The term "flyback" can mean two somewhat different things. In common terms, a "flyback transformer" is what most of Europe would call a line output transformer or LOPT. These are the transformer that produces the high voltage for the anode of a CRT display.
Flyback in generic terms is a topology of switchmode converter that uses a transformer consisting effectively of two (or more) coupled inductors and operates by closing a switch to allow current to flow and build up a magnetic flux in the core, which then rapidly collapses when the switch (transistor, mosfet, etc) opens, resulting in a high voltage pulse. This pulse is also induced in any secondary windings, stepped up or down according to the turns ratio.
In typical use, a LOPT works in a flyback topology, but the same LOPT/"flyback transformer" can be driven by other means, in which case it's not really a flyback anymore. The output of any raw transformer is AC by definition, although modern "flyback" transformers used in CRT displays almost always have a rectifier built in and thus produce half wave rectified pulsing DC.
The output voltage of any transformer will be higher with no load, and sag progressively as more load is applied. How easily it sags is dependent on a number of different factors, but some sag or compliancy is a good thing when charging capacitors because a discharged capacitor acts much like a short circuit, drawing less and less as it charges up. If the transformer is capable of more voltage than the capacitor can handle, you will need to have a trip circuit to cut off the charger at a set voltage.
If you want to build a flyback topology supply, you might check out the UC348x series, x being 2, 3 or 4 denoting various slight differences. These ICs are cheap and ubiquitous, available in an 8 pin DIP package and are relatively easy to use.
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.
Capacitor Charger from Flyback Transformer
