> I'm looking for some inverter designs to drive EL wire (ie
> http://www.coolneon.com, www.coolight.com, etc)  Something more elegant
> and controllable than driving the input of a commercial inverter, I
> guess.  Note that the EL wire likes something like 120VRMS at 2kHz,
> which is a
> lot different than the 160V P-P at 400Hz that flat el panels seem to
> like, which is where all the chip manufacturers (sipex, micrel, etcZ)
> aim their special purpose EL drivers.
>
> Looking at the special purpose drivers, they ALMOST look like something
> where you could substitute a PIC and some high-voltage transistors.
> They have a more-or-less conventional step-up switching converter that
> generates about 80v, and then a HV H-bridge that drives the el-panel in
> push-pull fashion to get the 160Vp-p.  I MIGHT be able to do that with
> a PIC.  What are the normal limits on how high a voltage you can get
> out of a step-up converter, anyway?

More details anon if nobody else weighs in - but they probably will.

You can get eg 80v with no great effort with a single inductor and a choke
from supply to collector of a small high voltage transistor (eg MPSA42) .
Operate from 5v or as high as is available. Turn transistor on for
appropriate period (~~ tmax = IL/V where I = peak inductor current allowed,
L = inductance, V = supply voltage) then turn off for longer than tmax x
Vin/Vout. Collector will "ring" to a large voltage. Actual max value will be
limited by LI^2 = 0.5 CV^2 so high stray capacitance can set a local limit.
80v odd should be easy enough. For eg 50 mA, 100 uH, 5v  say you get tmax =
0.050 x 100E-6 /5 ~= 1 uS on. 500 MA max = 10 uS etc.

I went to mention a single driver solution at 160v then realised the EL wire
will want AC so the full bridge makes sense. That can take as little as 6
transistors with eg 5v drive.

Let us know what you come up with.


        Russell McMahon

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