"Tom Bruhns" Wrote:
(Avery Fineman) wrote in message
...
... Suffice to say
that a square wave cannot be used with a passive
diode doubler; all the energy is contained in
the short transition times and that is rarely
enough to be worth it.
?? Lots of energy in the fundamental; filter to
extract the fundamental and feed it to your
full-wave rectifier doubler.
Efficiency can be high if the filter does
not cause dissipation in the
source at the harmonics.
Tom, look at it this way... Draw the square wave, assuming capacitive
coupling so it has a zero crossing. Then draw the same signal but invert
the negative going half to positive, which is what the full wave diode
doubler would do.
You wind up with a positive voltage, but with VERY narrow negative spikes.
So, a square wave into a diode doubler will produce only a small amount of
the second harmonic. You'd be better off running the input square wave
through a lowpass of some sort and then doubling it.
Given a sine wave input, there is a fair amount of negative going signal
and that is what produces the high energy content of the second harmonic.
Jim Pennell
N6BIU