On Wed, 20 Mar 2002, Graham North wrote:

> >
> > >This is a hand held device, and thus space is tight so a custom
> > >transformer is out of the question i'm afraid.
> >
> > Hmmm.  OK, but a custom transformer need not be any bigger than
> > whatever off-the-shelf inductor or transformer you would have to
> > use anyway.  I've had custom transformers done that measured
> > barely 1 cm. on a side.
> >
    Wayting to someone answer my question, I saw this.
  I'm agree with custom transformer solution. Driver must run with small
  voltage. But getting less than 10mV noise on such supply is a real
  challange. The biggest problem with switching supply is not only the
  amplitude of the noise but also the noise frecvency  spectrum. Such
  high frequency noise is difficult to suppress. Even using three
  terminals or other analogic linear regulators after switching supply
  will not improve too much the result.
  Anti parallel inductance filters ( on the same core ) with capacitors on
  both ends may reduce the noise 10 times.

best, Vasile

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