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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: CCFL transformer
Date: Wed, 24 Apr 2024 15:10:32 +1000
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On 24/04/2024 12:25 pm, John Larkin wrote:
> On Wed, 24 Apr 2024 01:57:36 +0200, Klaus Vestergaard Kragelund
> <klauskvik@hotmail.com> wrote:
> 
>> Hi
>>
>> I need a low distributed capacitance winding transformer, for a HV
>> step-up function (3.5kV)
>>
>> I am zeroing in on similar concept as CCFL transformers with
>> sectionalized bobbin.
>>
>> For example:
>>
>> https://www.coilcraft.com/en-us/products/transformers/power-transformers/ccfl-transformers/fl/
>>
>> Possibly using Triple Insulated Wire to create some distance between the
>> individual turns.
>>
>> Not many sells CCFLs these days.
>>
>> Guess I will keep it alive....
> 
> Can you use a C-W multiplier?
> 
> For low current, you can do resonant tricks too.

It's easier to use a voltage doubler or tripler that it is to find a 
multi-section former off-the shelf. The occasional high voltage power 
supply that I've dismantled clearly used proprietary formers, as do the 
Coilcraft parts

I suppose one could use self-bonding wire to make a series of 
self-supporting pancake windings, but I've never heard of anybody doing it.

The Baxandall configuration is definitely a resonant trick, and copes 
with the interwinding capacitance by resonating it with the winding 
inductance.

There's nothing "low current" about it, but if you are working at higher 
currents and powers you can justify even more elaborate switching 
arrangements.

http://sophia-elektronica.com/Baxandall1959JM.pdf

Jim Williams talked about it a lot - application notes AN45, AN49, AN51, 
AN55, AN61, AN65 - but described it as a "a current driven Royer 
inverter" which is simply wrong.

MOSFETs work better as switches than bipolar transistors, and don't seem 
to "squeg".

-- 
Bill Sloman, Sydney