Voltage limiter for Cockroft/ walton cap charger

mahela007

Hello,
I'm trying to design a capacitor charging circuit using a Cockroft-walton voltage doubler circuit.
My mains voltage is ~220 Volts and the output would be 220*2 = 440.
My capacitors are rated for 500V which means that they can be charged safely to about 400V.

Is there a circuit which would allow me to limit the voltage coming in to the voltage doubler to [an upper limit of] exactly 200 volts ? The output of this voltage limiting circuit must also be AC, otherwise the voltage doubler wouldn't work.

I've also read this thread which is focused on the voltage multiplier part of this question.
http://www.physicsforums.com/showthread.php?t=412640