................unless you use really huge capacitors and a high frequency drive waveform.How much current?
Capacitive voltage doublers only work well for small currents.
The triplers in TV sets didn't run particularly hot - the diodes in the early ones were long paxolin tubes full of hundreds of little selenium rectifier pellets.... and are prepared to have very low efficiency.
In most SMPSU topologies - the output side capacitor has nothing to do with conversion, its simply a LPF.I meant that in the way of this conundrum http://www.smpstech.com/charge.htm In the first picture lets say you have 1F at 1v which is 0.5J of total energy, but after the switch closes you get twice 1F at 0.5V = 0.125J so total energy of 0.25J. When you charge a capacitor by paralleling it with another capacitor, you lose half or less of the energy in the resistance.
That is also why step down SMPS uses an inductor as well as acapacitor, instead of just doing PWM into a capacitive load.