>     Actually, the easiest way to do what you want is to charge a _single_
>     capacitor to 12V across the input supply, then switch both capacitor
>     poles so the -ve end is now connected to the +ve input supply, and the
>     +ve end of the cap is now at 24V.  Dump this voltage to another cap
>     and you have your 24V output.
>
>     Note that because of various circuit losses, at 1A you are unlikely to
>     get a full 24V output.


Because you are using a capacitor, the currents will be very high when the
cap is connected, and the resulting I^2R losses are rather high.

The output voltage can't get to 24 except at zero load.  If there's a
significant
load, then you get into a problem where you have to have a large ripple
in order to transfer any power. If the output cap only droops 1V, then the
max
charge you can transfer is .5 * C  (The V^2 term reduces to 1)

The C then has to be HUGE, and it has to be charged FAST, which means
lots of I, and the I^2R losses go through the roof.


An inductive boost switcher would be a lot more efficient. I've done a 60W
boost switcher from 16V - 32V in about 2sq in that isn't even hardly warm.