David,
Insensitivity to input voltage is characteristic of a switching power
supply. The switcher input takes power from the AC line, rectifies it
and stores the energy in an inductor. Then the switching circuit takes
the inductor energy and dumps charge in a capacitor in its output to the
desired output voltage. Unlike a linear supply, no transformer or
linear regulators are required.
This is greatly oversimplifying the circuits and operation of a
switching supply, much additional design must go into it to control the
switching circuit, component rise and fall times and output filtering.
73,
Don W3FPR
On 7/30/2019 5:41 AM, David Wilcox via Elecraft wrote:
I also have one of these power supplies and am very happy with it. Can someone
please explain how it knows what voltage is input (120 v versus 240 v) to get
the same 12 volts output. Is there a different power cord? Am sure it needs
the correct wall plug adapter. Or is there just a 12 volt regulator in the
output? Inquiring minds (my old 74 year old one at least) want to know.
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