ohh sorry for this... That's the grammer problem ,I haven't increased the voltage just used a different source providing 3.3volts with more current. Actually English is not my native language 
. I have done the wiring as given in library's example codes i.e.
Arduino UNO:- MFRC522:-
9 RST
10 SDA(SS)
11 MOSI
12 MISO
13 SCK
I have checked the wiring many times and it seems to be fine.