On Mon, 24 Nov 2008 18:48:06 -0600, "Craig M"
wrote:

Raising the frequency also is easier to rectify and filter the sine wave
out, to give DC voltage.


Yes, and there's also less iron in a high-frequency transformer,
making it lighter.

BTW, I have a new USB hub with a 5V2.1A wall wart that's MUCH lighter
than the "brick" we would have had once.

"Gary H" wrote in message
.. .
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.

--
31 days until the winter solstice celebration

Mark Lloyd
http://notstupid.laughingsquid.com

"The government of the United States is not, in
any sense, founded on the Christian religion."