The original Baxandall paper is remarkably obscure, and it was published in a British journal. Neither gets it cited by US workers. Jim Williams didn' t help.
It took me about a year before I worked out that I couldn't get a copy from any university library that I could get at, and decide that I had to pay t he money to the "U.K. Institute of Electrical Engineers, who own the copyri ght and have given me permission to make it accessible on my web-site".
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This isn't what they sold me - which had been scanned from a bound copy of the journal - but a rather better scan that I got sent a few years later by somebody who though that I was offering a rather poor quality image.
e got the circuit from England without getting the literature reference tha t should have come with it - Baxandall, P.J, Proc I.E.E 106, B, 748 (1959.
of application notes for Linear Technology, on high frequency inverters fo r driving cold cathode back-lights used in laptop computers (application no tes AN45, AN49, AN51, AN55, AN61, AN65). Jim Williams describes the inverte r as a current driven Royer inverter, referring back to the non-resonant in verter described by Bright, Pittman and George H. Royer in 1954 in a paper ?Transistors as on-off switches in saturable core circuits? in Electrical Manufacturing."
transformers which tend end up with rather low self-resonant frequencies.
s and find a shop that would wind them for you - it isn't all that difficul t.
tting something close enough off the shelf isn't easy, even if you get down right sloppy about "close enough".
the 1954 Royer converter?
r is it like for example the Cuk converter and other ?Novel? ? PhD topologies that is really only good on paper?
competitive advantage that designs using ready made components fails to ha ve. In my career I have only used ready made for a converter a couple of ti mes (not counting buck converters)
You can make quite a good sine wave relatively easily by replacing the indu ctor with a current mirror. The efficiency goes down from about 95% to abou t 50%, but the harmonics are about 80dB below the fundamental.
From my web-site
"This circuit was developed as a retrofit to excite a linear variable diff erential transformer used to measure the progressively increasing mass of a single crystal of gallium arsenide (GaAs) being grown in the Metals Resear ch GaAs Liquid-Encapsulated Czochralski (LEC) crystal puller. The circuit i t replaced had been developed a decade earlier and used components that had become obsolete in 1986. The new circuit replaced it in new machines and w as retrofitted to some older machines.
It?s quite a bit more complicated than the Class-D oscillator, and less efficient ? only about 50% of the power fed into the oscillato r ends up in the load, rather than the better than 90% transfer you can get with a classic Class-D oscillator ? but it?s quite a lot m ore efficient than any of the low distortion oscillators I know about, and it lends itself to very precise control of the output amplitude. I? ve generated quite a few Spice models of various implementations of the ide a, but I?ve yet to get around to building a current version of the real circuit ? the 1986 version worked fine, but at that time I was n?t aware how good the circuit could be and didn?t have any reason to check out its performance in detail."
That was me - the original paper you had was very difficult to read.
You should really have a link to Yarrow's paper as well (after all it was submitted and published prior to Baxandall's). The design guidelines in the two differ slightly, Baxandall was (as usual) aiming to minimise distortion.
(Sorry Klaus I emailed this reply to you by accident).
Oscillators where the switching event id determined by core saturation were common in the UK in the 30's (probably much earlier) and Baxandall, Yarrow et.all will have been familiar with them. The current fed tuned oscillator is a completely different design and is not a minimally improved Royer.
d in a British journal. Neither gets it cited by US workers. Jim Williams d idn't help.
from any university library that I could get at, and decide that I had to p ay the money to the "U.K. Institute of Electrical Engineers, who own the co pyright and have given me permission to make it accessible on my web-site".
of the journal - but a rather better scan that I got sent a few years late r by somebody who though that I was offering a rather poor quality image.
Thanks for the copy. Yarrow's paper was actually published at the same tim e as Baxandall's - both papers were presented at the same conference (with Yarrow presenting his two days after Baxandall). I read Baxandall's paper as a more general exposition about inductor-capacitor oscillators, if aimed mainly as putting his class-D oscillator into context with more traditiona l schemes.
My suspicion is that Peter Baxandall - at the Royal Radar Research Establis hment (RRE) at Malvern - had been working out how to get a better inverter, and that he'd been talking to Yarrow to get him to build a few for some sp ecific application that RRE had wanted to pursue.
Publishing theory and practice at the same conference would have suited bo th of them. Making an explicit link probably wouldn't have - the British id ea that engineers had grease under their fingernails still hadn't entirely gone when I started working in the UK in 1971.
I'm still trying to get my web-site sorted out to include a reference to Ya rrow's paper - Libre Office isn't a great editor for .htm documents, and ge tting the hyperlinks to work isn't as easy now as I remember from a few yea rs ago. Presumably it has been "improved" recently.
Yarrow's paper - Libre Office isn't a great editor for .htm documents, and getting the hyperlinks to work isn't as easy now as I remember from a few y ears ago. Presumably it has been "improved" recently.
The more I dug into it, the worse it got. I ended up using Notepad to chan ge the nuts and bolts of the .htm code, and when I open the .htm file with Firefox on my own computer everything seemed to work, but when I up-loaded the same file to my web-site, and look at the page there over the web all t he hyperlinks start pointing the web-site I had when I lived in the Netherl ands, which hasn't existed for some ten years now.
I've asked for support from my current (Australian information provider) an d I fully expect to get told that I've missed something that should have be en obvious to me. The last time I talked to them the problem turned out to be that I'd swapped one space in a file name reference for the under-score that should have been there, and I won't be in the least surprised to find that this comes from the same kind of trivial error. -- Bill Sloman, Sydney
o Yarrow's paper - Libre Office isn't a great editor for .htm documents, an d getting the hyperlinks to work isn't as easy now as I remember from a few years ago. Presumably it has been "improved" recently.
nge the nuts and bolts of the .htm code, and when I open the .htm file with Firefox on my own computer everything seemed to work, but when I up-loaded the same file to my web-site, and look at the page there over the web all the hyperlinks start pointing the web-site I had when I lived in the Nether lands, which hasn't existed for some ten years now.
and I fully expect to get told that I've missed something that should have been obvious to me. The last time I talked to them the problem turned out t o be that I'd swapped one space in a file name reference for the under-scor e that should have been there, and I won't be in the least surprised to fin d that this comes from the same kind of trivial error.
Well. it didn't. They are as baffled as I am. And they don't see quite the same error, which is even odder.
When I used the "Firefox" inspect-element tool to find out what it sees on my website, it turns out not to be the same as Notepad finds in the file th at I uploaded to web-site. What I see with my copy of Firefox is perfectly consistent with the error message I get (from my old information provider in the Netherlands) but clearly that's not the error message they get.
to Yarrow's paper - Libre Office isn't a great editor for .htm documents, and getting the hyperlinks to work isn't as easy now as I remember from a f ew years ago. Presumably it has been "improved" recently.
hange the nuts and bolts of the .htm code, and when I open the .htm file wi th Firefox on my own computer everything seemed to work, but when I up-load ed the same file to my web-site, and look at the page there over the web al l the hyperlinks start pointing the web-site I had when I lived in the Neth erlands, which hasn't existed for some ten years now.
r and I fully expect to get told that I've missed something that should hav e been obvious to me. The last time I talked to them the problem turned out to be that I'd swapped one space in a file name reference for the under-sc ore that should have been there, and I won't be in the least surprised to f ind that this comes from the same kind of trivial error.
e same error, which is even odder.
n my website, it turns out not to be the same as Notepad finds in the file that I uploaded to web-site. What I see with my copy of Firefox is perfectl y consistent with the error message I get (from my old information provider in the Netherlands) but clearly that's not the error message they get.
Well, my web-site seems to be working again. I'm not quite sure what I did to fix it, but it is now displaying what I want it to display, or at least the bit that was giving me trouble looks okay now. Having a bad link to th e first image may have prompted the display software to get silly about the first hyperlink (which precedes it) but this is pure guesswork. -- Bill Sloman, Sydney
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