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 #5457
Joined: Mon Jun 25 2012, 06:42PM
Location:
Posts: 14
Hello,
I want to create a variable power supply which is capable of delivering a pretty high amount of current (10-20A) It needs to be compact, so I was thinking of a switched mode power supply. To make the heatsinks as small as possible, I was also thinking about zero voltage switching.
now the problem is that the mains do cross zero volts each 10ms (50Hz) but if I always want to switch there, and DO want to have a variable output voltage, that would mean I need to skip some sines, and let trough some sines to get an average voltage which is lower.
At 50Hz (in my country), this seems pretty impossible. Example: I want 10V at the output, and the input is 230V. That would mean I need to let trough approximately 4% of all incoming sines. 1 sine each 20ms and then only 4% of those sines would be like 20ms ON time and about half a second of OFF time. That half a second is just too long, I'd need an epic output filtering capacitor for that.
Another possibility would be to use 4% of each sine, but then it's no longer zvs since I'm switching the sine voltage off somewhere where it's not 0V.
Maybe I can convert the AC input to DC first, and then use a chopper, but again, that's not ZVS so I'll need large heatsinks if I want to have a 15A output.
the site transformers are centertapped to ground, so its acctualy 55v-0-55v and the amperage avalable is ususaly rather high, i persoanly have a 3.3Kva site transformer this gives you quite a lot of amps at a broard range of voltages.
--Thomas---
P.S, contary to popular belief i have no affiliation with variac companys, they just seem to be a all in 1 solution, providing you can find one cheap :D
Registered Member #5457
Joined: Mon Jun 25 2012, 06:42PM
Location:
Posts: 14
Ash Small wrote ...
Why not just use a 50 Hz transformer with a multiple tapped secondary?
That's what I have right now but I'm not really happy with it :/ it's a MOT with secondary windings rewound. For some reason it gets Really hot after running for 5 minutes, even if I'm not connecting any load. And the 50Hz buzz when I'm drawing more current is also annoying :/ It's not a constant output voltage because the capacitor drains quickly with big loads.
I'm hoping this problem to be solved if the output works at a higher frequency.
But then I still have kind of exactly the same output voltage as I've got right now. Variable 50Hz with smoothing capacitor. I need a more steady output voltage which doesn't need an epic capacitor to achieve that.
And the variac + other transformer is also quite a big setup :/ and I also variacs aren't that cheap.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Well, you still want a stepdown xformer to drive an SMPS, unless you drive it directly from rectified mains, and you'll possibly want smoothing caps as well.
Registered Member #4081
Joined: Wed Aug 31 2011, 06:40PM
Location: UK
Posts: 139
Depends really on what kind of voltage you want from it. A common one that I'm sure plenty of people use is a computer PSU, they're reliable and powerful. Only 12V max though. These are good in general for powering all sorts. Audio transformers are good, decent output voltage and centre tapped, not variable however. To solve the MOT problem you can wind a few more primary turns to take it out of near saturation and reduce heating, also add a few more filter caps. I think you need a variac though.
Registered Member #5457
Joined: Mon Jun 25 2012, 06:42PM
Location:
Posts: 14
Harry wrote ...
Depends really on what kind of voltage you want from it. A common one that I'm sure plenty of people use is a computer PSU, they're reliable and powerful. Only 12V max though.
But I needed 10-20A.
And the output voltage should be from 0v to 50v.
I don't really want to use existing supplies like using a transformer with then an already existing smps connected to it. What I'm talking about is creating one on my own. I want to create the control circuit and power circuit myself, but I'm not sure yet what type of circuit it'll be since I want it to switch at zero volts across the FET's
Registered Member #4118
Joined: Mon Oct 03 2011, 04:50PM
Location: MD
Posts: 140
Electorials wrote ...
Harry wrote ...
Depends really on what kind of voltage you want from it. A common one that I'm sure plenty of people use is a computer PSU, they're reliable and powerful. Only 12V max though.
But I needed 10-20A.
And the output voltage should be from 0v to 50v.
I don't really want to use existing supplies like using a transformer with then an already existing smps connected to it. What I'm talking about is creating one on my own. I want to create the control circuit and power circuit myself, but I'm not sure yet what type of circuit it'll be since I want it to switch at zero volts across the FET's
ZVS is not all that important at a 1kW power level. You can use a circuit similar to a computer PSU, except with variable output voltage. See
Registered Member #2919
Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652
A hard-switched half-bridge driving a ferrite transformer will do for a few hundred watts. In fact, at that point you're still within range of a flyback converter.
Registered Member #3900
Joined: Thu May 19 2011, 08:28PM
Location:
Posts: 600
I agree with bwang. A flyback is a good solution and is only limited by the core. But if you don't care about isolation, you could do a mains buck converter to eliminate the core. Keep in mind that you'll need a logic supply transformer(or another smps) to power the low voltage control circuit.
But I agree with the smps idea. I powered my zvs flyback driver off of a 12 smps and got a nice quiet hiss, but the I wanted more power. So I rewound a mot, got a 35vdc off of it, but the 15v 60hz ripple (see he exploding lytic thread :D) voltage put a humm on he arc.
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.