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


Jim Thompson wrote:
> Win,
>
> What do you know about CCFL inverters that claim "self-learning" of
> the transformer resonant frequency?

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

http://www.linear-tech.com/pdf/an55fa.pdf


http://www.linear-tech.com/pdf/an65f.pdf

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 ...

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Bill Sloman, Nijmegen

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