I am from India, my cousin bought PS 3 from USA. It is designed for 110v power. In India we have 220V.

My question:  Do i need to purchase 220v to 110v converter or 110v to 220v converter?

You want to convert 220v to 110v to power your ps3 so you want a 220v to 110v, Id google it.

You need step-down transformer 220V->110V. AFAIK all PS3 models are universal, working in the range of 110-220V, but you better check it.

From dailytech.com:

"The entire power supply is built into the PlayStation 3. The Xbox 360 requires an external "brick" that can be swapped out depending on the local regulations for electronic devices. 

The US and Japan uses 110-120V, 60Hz adaptors.  We have confirmation from SCEA now that the power supply inside the Playstation 3 is, in fact, universal. The power supply supports 100 to 240 volts at 50 to 60 Hertz, which is useable in all modern power grids -- including Europe.

Although European markers require a different physical plug for their infrastructure, there is no need to replace the power supply."

Thanks guys.. I appreciate your quick responses.