In article , Gary H wrote:
On Mon, 24 Nov 2008 08:17:33 -0500, George
wrote:

[snip]

But the Chi Coms need to meet our requirements if it is sold here. I
can't remember the last time I saw a new walwart that wasn't a much more
efficient switcher design instead of an inefficient transformer.

The new wall-warts are smaller, but it's NOT by eliminating the
transformer. These new ones begin with an AC-to-AC converter, that
operates on line voltage and raises the frequency. A higher frequency
requires a smaller transformer.

"Switcher" refers to a more efficient voltage regulator, that controls
the DC output by turning it on and off rather than by wasting power
like a linear regulator (as in older wall warts) does. This also makes
it smaller by reducing the need for a heat sink.

The "Switcher" can refer to not only a DC voltage regulator, but also to
circuitry operating a greatly smaller transformer that may require voltage
regulation means.

"Switcher"/"Switchmode" even applies to high frequency usage of a
miniaturized high frequency gransformer than can weigh close to or even
under 1/4 ounce, along with voltage regulation *that in more-crude form*
can be merely an analogue of a thermostat, as in there is an "output
filter capacitor" AKA "smoothing capacitor", and the switchmode circuitry
in question is "on" when the output voltage is "insufficient/low" and
"off" when the outputv voltage "exceeds target by whatever margin".

- Don Klipstein )