Richard J Kinch wrote:

Back a ways you attempted to use a series regulator as an analogy.
This doesn't work since, in a series regulator, Iout ~= Iin and Vout
Vin.

No, Iout = Iin in a 3-terminal regulator, except for a small overhead
that runs the chip itself. Or, model it as a magic variable resistor if
you like.

What are you saying "No" to? I said Iout is approximately=equal=to Iin
and you said Iout=Iin except for ... Did you fail to understand "~="?
It's the closest approximation to the standard approximately-equal sign
available in ASCII and should be pretty obvious.

A switching regulator might be a better analogy: Vin*Iin ~=
Vout*Iout.

Hardly. A switching regulator is just a transformer, with an DC-AC
converter on the input, and AC-DC converter on the output. This would
be analogous to my imaginary "regulator" consisting of an air motor
regenerating the reservoir, not a conventional variable-restriction
regulator.

I see. Clearly you aren't to familiar with electronics terminology.
You are refering to a particular type of switching power supply in which
incomming DC is switched to provide AC which is then transformed and
rectified. Some use duty-cycle modulation to provide regulation, some
don't. The term switching regulator is usually applied to a device
where incoming DC is switched on and off into an L-C filter. The output
voltage is approximately the duty cycle times the input voltage. In
principle, neglecting switching and IR losses, the output power = input
power. In practice it can come pretty close. I've designed an built
switching regulators with over 95% efficiency.

Ted