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 #1232
Joined: Wed Jan 16 2008, 10:53PM
Location: Doon tha Toon!
Posts: 881
Whatever method you choose, it's always going to include a large dollop of trial and error, because the losses in the corona are hard to predict.
You first take a guess (or educated guess based on previous experience) at some of the Class E component values, coupling coefficient, primary turns etc. Then you tentatively power up the circuit at low voltage and try to get a look at the drain waveform. You then make some changes to the component values, and maybe the tuning or coupling to get closer to the ideal Class-E waveform and power up again. These changes might be very effective and get you close to the ideal waveform. Hooray! Only the problem is that it's still only at low supply voltage and low power. Small sparks suck Soooo...
You turn up the supply voltage, and this is where things start to get funky. The corona volume gets larger as more RF power is fed in, but this means the corona losses increase and the resistive base impedance of the resonator changes. As the discharge gets bigger this also tends to add capacitance to the top of the coil lowering the resonant frequency. Both of these effects disturb the drain voltage waveform away from the ideal waveform with a soft-landing at turn-on for efficient Class-E amplifier operation. The MOSFET's own intrinsic drain-source capacitance also falls as the drain-source voltage increases, further muddying the waters.
So, in general the design process and particularly the "gradual increasing of power" part is very much an iterative process with frequent tweaks to the tuning, coupling and drain-source shunt capacitor being required. The ultimate goal being Class-E operation with 99% efficiency (hence cool MOSFETs) whilst simultaneously exhibiting a roaring high-power plasma discharge at the top of the resonator. To achieve this you have to sacrifice the nice looking idealised Class-E drain waveform at low-power, and remember that efficiency at low-power isn't as important as at full power because voltages and currents are lower. You'll also run it at full power anyway because that's what looks most impressive!
RF engineers designing high-power Class-E broadcast transmitters have got it easy with their nicely specified purely resistive 50 ohm loads. And for these cases the conventional Class-E design equations, or Excel spreadsheets work very well. Although the variation of MOSFET device capacitances with voltage can cause some minor headaches as the power is modulated.
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.
How do you determine component values for Class-E operation?
Soooo...