I know these two circuits can both realize the ac-dc conversion. I just want to know which one is more efficient. I mean with the same input source which circuit can obtain a higher output power (it does not matter the load resistances are different), assuming the load a resistor. I think the full wave voltage doubler will output a higher power due to a reduced diode forward drop, although the output volatge is doubled. Anyone can help me to compare them? Thanks a lot.