Then at the input we must have at least 18.3V at 12V because: 12V*18.3 = 220v*1 So you have to wind the step up transformer 12v to 220v but input winding must be capable to bear 20A. ???.(electronic schematic added 11/08) 12V to 120V Inverter - Have you ever wanted to run a TV, stereo or other appliance while on the road or camping?