A power adapter, comprising: a first rectification unit, configured to rectify an input alternating current and output a voltage of a first pulsating waveform; and a switch unit, configured to modulate the voltage of the first pulsating waveform according to a control signal; a high-frequency transformer with a primary side and a secondary side, configured to output a voltage of a second pulsating waveform based on the voltage of the modulated first pulsating waveform, wherein the first rectification unit is connected to a primary side of the high-frequency transformer without a primary electrolytic capacitor; a second rectification unit, configured to rectify the voltage of the second pulsating waveform and output a voltage of a third pulsating waveform; a first charging interface, coupled with the second rectification unit without a secondary electrolytic capacitor and configured to be coupled with a second charging interface of a device, wherein the second charging interface is coupled with a battery of the device; and a control unit, coupled with the first charging interface and the switch unit, and configured to output the control signal to the switch unit, to communicate with the device via the first charging interface to obtain a voltage of the battery when the second charging interface is coupled with the first charging interface, and to apply the voltage of the third pulsating waveform to the battery via the second charging interface when adjusting the duty ratio of the control signal to make a peak voltage of the voltage of the third pulsating waveform to be greater than the voltage of the battery. a first rectification unit, configured to rectify an input alternating current and output a voltage of a first pulsating waveform; and a switch unit, configured to modulate the voltage of the first pulsating waveform according to a control signal; a high-frequency transformer with a primary side and a secondary side, configured to output a voltage of a second pulsating waveform based on the voltage of the modulated first pulsating waveform, wherein the first rectification unit is connected to a primary side of the high-frequency transformer without a primary electrolytic capacitor; a second rectification unit, configured to rectify the voltage of the second pulsating waveform and output a voltage of a third pulsating waveform; a first charging interface, coupled with the second rectification unit without a secondary electrolytic capacitor and configured to be coupled with a second charging interface of a device, wherein the second charging interface is coupled with a battery of the device; and a control unit, coupled with the first charging interface and the switch unit, and configured to output the control signal to the switch unit, to communicate with the device via the first charging interface to obtain a voltage of the battery when the second charging interface is coupled with the first charging interface, and to apply the voltage of the third pulsating waveform to the battery via the second charging interface when adjusting the duty ratio of the control signal to make a peak voltage of the voltage of the third pulsating waveform to be greater than the voltage of the battery.