🚀 go-pugleaf

Ben Bradley wrote:
> 
> In sci.electronics.design, moby@kcbbs.gen.nz (Mike Diack) wrote:
> 
> >I'm redesigning a device for blind navigation that I first designed a
> >decade or so ago, which requires a transformer to drive an
> >electrostatic transducer (sweeping 100..50KHz, around 100v P/P driven
> >from a 6v P/P source).
> >My first iteration used a (hand wound) Philips 10mm 3E25 toroid. I
> >gave one of my original samples to a local transformer outfit and
> >asked them to make me something smaller (and tidier!)
> >Everything they came back with was bigger than my original.
> >I have seen a polarisation tranny inside an AKG C460 microphone which
> >is smaller than the size of a frozen pea.
> 
>    That transformer is part of a switching power supply that runs at
> an ultrasonic frequency.  The transformers in disposable cameras (that
> others mentioned) are for the same thing, running a cheap SMPS at high
> frequencies.
>    To get any response at all down to 100 Hz you need something at
> least the size of a modem phoneline isolation transformer.
> 
> >Admittedly this tranny only
> >has to handle a single frequency wheras mine carries a sweep, but who
> 
>    It's not so much a single frequency vs. a sweep, but what the
> lowest frequency is (and the power transferred) that determines the
> minimum size of a transformer. 50/60Hz power transformers don't come
> any smaller than a wall wart, and ones for significant power are much
> larger and heavier.
>    For your application, a plate transformer that's normally used
> between the 50C5 and loudspeaker of an "All American 5 [tube]" might
> work, but the upper 50kHz requirent will likely be a problem.
>    One alternative is to make the lower limit something usable for
> very small transformers (maybe 1kHz to 5kHz) - this is probably not
> acceptable.
>     The other is to use one of the tiny switching transformers to make
> a high voltage DC supply which runs a transistor amplifier with
> high-voltage ouput.
> 
> >can make trannies like that or where can the cores be sourced
> >(preferably surface mount)
> >cheers
> >M

  What about modulating the input with a 1Mhz carrier that goes thru the
transformer, then demodulate?
  A low power 1Mhz xfmr would be fairly small....