An adaptor is provided for connecting an EV/PHEV charging system to a grounded extension cord that may be plugged into a conventional NEMA receptacle. A proximity detection switch is provided within the adaptor. A pulse width modulated signal is limited by the control logic to limit the current provided to the vehicle charging system so that the current drawn by the system does not exceed the current carrying capacity of the extension cord. The adaptor has a NEMA plug on one side and a J1772 connector receptacle on another side.