Patent ID: 7453171

Claim:
An adapter device, comprising: a DC/DC adapter, located in an external casing to a portable computer having a power supply, to receive DC power from an external DC power source, and output a regulated DC voltage (V out ) to the portable computer; and DC source determination circuitry, in the adapter device, to receive the DC power from the external DC power source and compare a magnitude of a voltage of the DC power with a reference magnitude of a reference voltage (V ref ) in order to determine what type of external DC power source is supplying DC power, wherein when the magnitude of the voltage of the DC power is greater than the reference magnitude, a data signal (V data ) having a first value indicative of the external DC power source being an airplane power source is output to the portable computer 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 (V data ) having a second value indicative of the external DC power source being an automobile power source is output to the portable computer along with the regulated DC voltage.