Re: CCFL transformer

On 24-04-2024 16:23, John Larkin wrote:

On Wed, 24 Apr 2024 09:37:24 -0400, legg <legg@nospam.magma.ca> 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
stepup 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....
>
Regards
>
Klaus

>
When there are a lot of turns, 3xFEP is not the way to
go. Too bulky. The three layers is basically a trick to
avoid creepage requirements for pri-sec safety. That's
not what you need here.
>
Anything off the shelf will be a great time saver.
>
RL

 I sometimes use an autoflyback stage with a DRQ-series dual inductor,
followed by a c-w multiplier using sot-23 dual HV diodes. That's cheap
and easy, given a reasonable supply voltage, like 24.
 

I cannot use capacitive doubler thingies, there's no output DC voltage.

You can also just buy a potted HV supply and move on to design
something else.
 

I need it cheap, so cannot buy COTS

There are also potted c-w bricks, but they are a lot more expensive
than buying the diodes and caps.
 Custom magnetics only makes sense at high volume, or for real exotica
like transmission-line transformers.

I have almost never used standard magnetics. Most projects has requirements that dictate custom, or in higher volumes price is the key.

 I'm about to embark on a custom tapped inductor and I'm not looking
forward to it. Drawings, quotes, revised drawings, more quotes,
samples, tests, released drawings, MOQs, all that.
 

Yeah, boring work.