On 20/05/2014 07:09, Geoffrey S. Mendelson wrote:
Switching supplies are not all the same, and some just convert the incoming
power to 400Hz (or higher) AC,run it through a transformer and reduce it
to the outgoing voltage with a regulator. If the device is plugged into
a 120 volt socket, the output voltage of the transformer is 15 volts,
if it is plugged into a 240 volt socket, it would be 30 volts.

That would be really dumb.
The power supply would run really hot on 240V and nice and cool on 120V.

In fact the converter you describe that generates the higher frequency
AC will be adjusting itself so that the transformer output is more or
less the same voltage no matter what the incoming mains voltage is.

--

Brian Gregory (in the UK).
To email me please remove all the letter vee from my email address.