DC power source determination circuitry for use with an adapter

A method comprising:

• receiving DC power from a DC power source, at an adapter which is in an external casing separate from a portable computer, and outputting a regulated DC voltage (Vout) from the adapter to the portable computer;
• comparing, in the adapter, a magnitude of a voltage of the DC power with a reference magnitude of a reference voltage (Vref) to identify what type of DC power source is supplying the DC power to the adapter;
• outputting a data signal (Vdata) having a first value along with the regulated DC voltage to the portable computer when the magnitude of the voltage of the DC power is greater than the reference magnitude which identifies that the DC power source is an airplane power source;
• and
• outputting the data signal (Vdata) having a second value along with the regulated DC voltage to the portable computer when the magnitude of the voltage of the DC power is less than the reference magnitude which identifies that the DC power source is an automobile power source.

A power supply system, comprising:

• an adapter device to receive DC power from an external DC power source, and to output a regulated DC voltage, the adapter device including:
• DC source determination circuitry to receive the DC power from the external DC power source and compare, in the adapter device, a magnitude of a voltage of the DC power with a reference magnitude of a reference voltage in order to determine a type of external DC power source that is supplying the DC power,
• wherein when the magnitude of the voltage of the DC power is greater than the reference magnitude, a data signal having a first value indicative of the external DC power source being an airplane power source is output along with the regulated DC voltage, and when the magnitude of the voltage of the DC power is less than the reference magnitude, the data signal having a second value indicative of the external DC power source being an automobile power source is output along with the regulated DC voltage;
• and
• a portable computer having control circuitry to receive the data signal and the regulated DC voltage.