Patent ID: 8225111

Claim:
An external power supply of an electronic product, comprising: a switch coupled to modulate an output of the power supply with information encoded to identify the power supply to the product, wherein the output of the power supply includes no more than two conductors to transfer the information encoded to identify the power supply and to transfer power from the power supply to the product; and a controller coupled to provide a command signal to the switch in response to an encoder and a sense signal that senses the output of the power supply, wherein the encoder provides the information to identify the power supply to the electronic product, wherein the controller includes: an oscillator, wherein the encoder is coupled to modify the operation of the oscillator; an error amplifier coupled to receive a reference signal and the sense signal, wherein the encoder is coupled to modify a value of the reference signal; and switching logic that produces the command signal in response to the oscillator, the encoder, and the error amplifier.