Thanks guys for your help and inputs. 
I would like to correct6 confusions!
I have Luminous Inverter cum UPS at my home so I dont need UPS. But my worry is if someday the inverter doesnt work or its backup is finished and my AIO PC is ON, then it'll suddenly switch off. So I want a power backup device for such kind of situation which can give a little power to shut down my PC.

I would like to correct6 confusions!
I have Luminous Inverter cum UPS at my home so I dont need UPS. But my worry is if someday the inverter doesnt work or its backup is finished and my AIO PC is ON, then it'll suddenly switch off. So I want a power backup device for such kind of situation which can give a little power to shut down my PC.