> Is there any efficient and not too expensive way to generate the ~5V for
> the PIC and some other devices out of the 230V AC Voltage from the net? Using
 a
> 7805 and other linear regulators is IMHO much too inefficient ...
> I need about 2 - 150mA at 5V to drive my PIC 16c84 based IR-remote receiver
> that will run 24 hours a day ...
> I thought of switching regulators e.g. TOP210 but I don`t know where to get
 the
> transformer (TDR1) mentioned in the data sheet and the TOP210 itself, because
 I
> need only a few peaces for my project ...

Bernd, using an off-line switcher for your application sounds like
crazy to me. On the other hand, the capacitor-zener-resistor
scheme is cheap but won't save power.

> Does anyone know how efficient normal transformers (230V => e.g. 6V) with
 diode
> based rectifiers are? If it is high enough so that a DC/DC switching regulator
> like the LM2574-5.0 (only about 77% efficiency :-( ) could be used? This would
> be pretty easy, because the mentioned inductors are very easy to get ...

I don't think you can gain much efficency with a switcher if your
power requirements are so low. What I would do is use an ordinary
full-bridge-center-tapped supply with a reasonably sized transformer,
and if I was that concerned about power I'd use schottkys and
perhaps a low-dropout regulator like the LT1086. But have in mind
that we're talking of about 600mW of losses for the ordinary supply
when the output is at 150mA, and with the changes you would reduce it
to not less than 400mW by spending about $3 or $4 more, besides
bothering to get less-common components. I think that would take
years to be profitable.

Regards,

Andres Djordjalian
adjordj@aleph.fi.uba.ar