<angus.oliver@[EMAIL PROTECTED]
>
>
> The subject describes pretty much my question. I have been spending
> several days trying to debug a circuit, only to find that it wasn't my
> fault:
>
> I have a normal (pretty cheap) switch-mode plug-pack power supply
> (240V, 50Hz in; 12V, 200mA out), and nominal voltage appears to be
> somewhere around 12V (so far so good). With an electrolytic cap across
> the output (correctly polarised), the voltage rises to somewhere
> around 17V - 18V. I had no idea this would occur, and was thus trying
> to find the problem in my circuit.
>
> Does anyone know why this happens? Presumerably a poor regulating
> circuit in the plug pack, but does anyone have some more thorough
> answers?
>
** A small SMPS plug pack I have here (12 volt, 780mA ) produces a strong
100 Hz ripple ( ie hum) at the output if you add even 100uF of external
capacitance - but it was built to power a particular ( telecoms ) device
rather than general purpose use.
I suppose something in the output voltage control loop goes out of wack
when
you add extra C.
But you one you have sounds like a menace to equipment.
...... Phil
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