Hi,
many thanks for the links and explanation. Unfortunately my ideas are not that clear... :grin:
I knew how the circuits in those links you gave me work, they are standard voltage doubler as you said.
Now please look at Bo's circuit, it has a cap and diode in series... I just can't understand how the cap can charge with that diode in series... circuits in those links show the diode placed between the other diode and the output... I can post a picture of what I mean if you want.
I even simulated that circuit and it looks that the output voltage is not correct...
Thanks,
Frank