Question

How Dc voltage can be boost up?

Answer 1

there are electronic circuits which can do "voltage doubling" and the like, I think. Of course, you could also convert the dc to ac, boost the ac and then go back to dc. I don't know whether this IS done, and my electronics is about as crappy as mot other things, but without more info that's what I'd guess. I've heard of the circuit called a "DIODE PUMP" as well.
http://perendis.webs.com

Answer 2

for a source of "AC" to be diode pumped to obtain a high dc voltage, an ASTABLE MULTIVIBRATOR or "FLIP FLOP" can be used I think. Used in ratemeters and cars and things, apparently.

Answer 3

@radar

Answer 4

https://en.wikipedia.org/wiki/Boost_converter