A power adapter includes a regulation device, which includes a division circuit, a reference circuit, and an impedance regulation circuit. The division circuit includes a first reference terminal and a second reference terminal. The second reference terminal is connected to an output terminal of the regulation device. The reference circuit includes a third reference terminal connected to the first reference terminal, and the reference circuit outputs a stable reference voltage via the third reference terminal, to provide the stable reference voltage for the first reference terminal. The impedance regulation circuit is connected to the first reference terminal, to provide equivalent impedance for the first reference terminal. The impedance of the equivalent impedance changes in a way corresponding to changes in the current flowing through the output terminal.