piclist 1998\11\27\151012a >
Thread: Electroluminescent panel power controller.
picon face BY : Russell McMahon email (remove spam text)

What you describe is eminently doable but its not the normal way to
do it. If you are doing a one off you are probably better to use an
existing design or to buy an existing module. If you are building
heaps of them then there may be a reason to do it this way. Usually a
dedicated switching regulator IC will cause you less pain.

Standard prewound transformers for this class of application are
available from major inductor makers.
Winding your own is entirely achievable but the high voltage means
care is needed. High frequency inductor design can be a black art -
if this is a one off you probably want a pre-made coil.

Linear Technology Ltd produce(d?) an utterly superb set of
application notes for their products which may well be on the web.
These are probably the best application notes wrt subject matter that
I have ever seen. They discuss analog applications in terms
understandable to all but also get into the arcane technicalities of
real life. Their App Note AN25 is named "Switching regulators for
Poets" - raw beginners and experienced engineers can learn from it.

An Application Note that exceeds your spec (0-500v variable @ 200ma)
but looks very similar to what you describe (No PIC though :-)) is
given in LT's App Note AN35 page 1-13 figures 25-30. The warnings
about danger to your health should be noted. This design is much more
powerful than your requirement but is directly applicable. They use a
(prewound?) "TRIAD TY-94" main transformer. I dunno who TRIAD are but
no doubt a search using TRIAD & INDUCTOR would turn them up. There
are many others who do this sort of thing too. eg
   Pulse Engineering Inc http://www.pulseeng.com/
           CD and printed catalog available on web!
           (LT seem keen on their products judging by their use in
app notes),
       Avnet (who are probably active in your country) sell Pulse

and many more.

Disclaimer: I don't work for have any financial interest in any of
the above companies .


               Russell McMahon

From: Gerry Cox <@spam@gcoxspamspamSTOPspamDEK.COM>

>I want to design a low cost Electroluminescent panel drive (Output
is 280
>VAC @ 450Hz and 6Watts. Input power available is at 12V). I am
considering a
>PIC12C508 with 2 of the I/O pins providing an anti-phase drive (at
>100Khz) to a pair of mosfets. The mosfets are arranged to push-pull
a center
>tapped ferrite transformer with the center tap connected to +12V.
>secondary of the transformer will be full wave rectified and
smoothed to
>provide a 280VDC supply. Another output  of the 12C508 will drive a
>transistor switch alternately to the 280V rail and then to 0V rail
at the
>required 450Hz. This 280V square wave will be fed to the panel via a
>coupling capacitor.
>My problem is that I don't know where to start with selection /
design of
>the transformer. Can I design it myself or am I likely to find an
off the
>shelf item to do the job? Anyone got any leads on ferrite

<011d01be1999$e28350e0$103061cb@mkbs> 7bit

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