Hey, Win! CCFL Inverter "self-learning" resonant frequency?

That they've been listening to too much Rush Limbaugh?

Getting involved in patent cases again? I see a patent application "High-efficiency adaptive dc/ac converter," is that the one? "... the circuit is self-learning and is adapted to determine the optimum operating frequency for the circuit with a given load"

Well, we can read two nearly-identical already-issued self-learning CCFL patents, US6259615 and US6396722,

I know about US6259615 and US6396722, what's the third? Same guy, Yung-Lin Lin? All dating to Nov 9, 1999?

There are three patents, actually ;-)

Already scheduled to court.

Just poking around to see what's in the prior art.

...Jim Thompson

Who he ?:-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

And US6804129 B2, taking note of "Other Publications" on the first page ;-)

...Jim Thompson

Have a look at Baxandall's Class-D oscillator

Baxandall, P.J, Proc I.E.E 106, B, page 748 (1959)

The oscillator self-oscillates at the transformer resonant frequency.

Jim William's used it in his classic application notes on CCFL drivers

though he calls it a Royer inverter, which is pretty strange for a variety of reasons (Fred Bloggs begged to differ in our little spat on the 29th July 2002).

Baxandall didn't develop the circuit explicitly to drive CCFLs - he needed to generate high voltages for other purposes - but it was fairly clearly intended to deal with the relatively high winding capacitances of transformers with a high step-up ratio.

Pity that Jim has got me kill-filed - he'll never read this ...

----------- Bill Sloman, Nijmegen

I'd dither, synchronously demodulate and integrate.

Best regards, Spehro Pefhany

Thanks, Joerg! That's the kind of lead I'm looking for... really old prior art.

I'm seeing an awful lot of issued patents these days that would indicate that the examiners aren't doing proper prior art searches... issuing patents on stuff us old farts knew about when we were kids ;-)

...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

As far as I can tell, while the patent office may well not be doing as much of a prior search as they should, these days every Tom, Dick, and Harry who comes up with a circuit that wasn't on one of their college homework assignments figures it ought to be patentable and the business people running many companies will do nothing but encourage them to do so -- prior art be damned.

The immediate issue isn't to find a workaround, it's to find a way to invalidate a patent whose owners assert infringement by products using their patented scheme. Sadly, despite even good evidence of obviousness, it's very hard to get a jury to overturn a patent that enjoys a good presumption of validity, having passed careful review by patent examiners --- Who are amateur jurors to overturn a patent professional? To succeed one has to find something serous, like real evidence of fraud (applicant intentionally didn't mention significant prior art), or gross incompetence (the examiner failed to find or respect significant prior art), that forces the jury to feel compelled to over-rule the examiner.

In other words, one must find EXACT instances of prior art.

Either that, or the expert witness and defense lawyer (and his entire team) need to have *extraordinary* skill with the jury, so the jury feels the patent owner is a s**nk, and are looking for good excuses to do the right thing as citizens, and overturn his patent. That doesn't happen very often.

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

One of the reasons I'm so depressed about patents lately is that whenever I go looking at patents to figure out whether I'm going to be sued for some obvious idea I've used, I see all kinds of other obvious things being patented. And I'm anything but a clever engineer, as Fred Bloggs has correctly observed on occasion, so if something's obvious to me it's just absurd that it's patented.

Here's an example, patent 6,372,976, filed in 1998 and granted in 2002. "A pickup for an electric guitar includes a housing made to fill an existing cavity in an electric guitar body originally used for a dual-coil humbucking pickup. The pickup also has a single pickup coil mounted in the housing."

In other words: they've patented the idea of putting something small into an enclosure, so that it fits a bigger existing hole.

Is it conceivable that solving this problem took an engineer more than 30 or

I suppose now if I patent the idea of stuffing Kleenex into the end of hand-me-down shoes to make them fit, I'll have to cite this patent as prior art.

Hello Jim,

I am not Win and also not the expert on this but AFAIK the frequency is swept during start-up and upon strike is being locked into current maximum.

However, I am only familiar with series resonant conversion and that's how it is often done there, in cases where max power transfer is desired instead of regulation. When regulating it is customary to slide up and down the lower frequency slope (with SRCs).

If you are thinking about doing this in a chip, the method might be patent protected for CCFL. Not sure but a quick Google found this one:

Regards, Joerg

"Jim Thompson" a écrit dans le message de news: snipped-for-privacy@4ax.com...

Yes, how do they have the capacity to induce such a frequency?

Hello Jim,

Doesn't the common oscillator count? After all it 'self-learns' the resonance of the LC circuit connected to it :-D

That would put prior art back into the days of Heinrich Rudolph Hertz who passed away in 1894. As for switch mode controllers a frequency adaptive scheme was easily done with chips such as Unitrode's UC3860. Those are really old as well.

Regards, Joerg

In court (or more likely, before an arbitration panel) the test is: Would this be obvious to an engineer "trained in the art"?

If so, it's not patentable. That's how most are beaten.

I knocked off one last summer simply by hauling out a 50 year old textbook ;-)

...Jim Thompson

Excellent!

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

Yep ;-)

...Jim Thompson