A power adapter. The power adapter comprises an electric energy conversion unit (20) and a clamping unit (21). The electric energy conversion unit (20) is used for performing alternating-current-to-direct-current conversion on alternating-current electric energy, or for performing direct-current conversion on pulsed direct-current electric energy formed after the alternating-current electric energy is rectified; and the clamping unit (21) is connected to an input end and an output end of the electric energy conversion unit (20), so as to control, when the difference value between an input end voltage and an output end voltage of the electric energy conversion unit (20) is greater than or equal to a first difference value, the electric energy conversion unit to reduce an output voltage. The present invention improves the adaptability of the power adapter used in external power supply environments having different quality, and improves the working stability of the power adapter. (FIG. 1)