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 transformer, configured to output a voltage of a second pulsating waveform based on the voltage of the modulated first pulsating waveform; a second rectification unit, configured to rectify the voltage of the second pulsating waveform and output a voltage of a third pulsating waveform; a filter unit, configured to filter the voltage of the third pulsating waveform and output a second direct current, DC; a controllable switch, configured to control whether the filter unit operates; a first charging interface, configured to apply the voltage of the third pulsating waveform or the second DC to a battery of a device via a second charging interface of the device when the first charging interface is coupled with the second charging interface, wherein the second charging interface is coupled with the battery; a sampling unit, configured to sample an output voltage and/or an output current of the second rectification unit to obtain a voltage sampling value and/or a current sampling value; a control unit, coupled with the sampling unit, the switch unit, and the controllable switch respectively; the control unit being configured to control the controllable switch to cause the filter unit to a) operate, so as to output the second DC via the first charging interface; and b) stop operating, so as to output the voltage of the third pulsating waveform via the first charging interface; the control unit being configured to output the control signal to the switch unit to adjust a duty ratio of the control signal based on the voltage sampling value and/or the current sampling value, whereby the voltage of the third pulsating waveform or the second DC meets charging requirements, wherein the control unit is further configured to communicate with the device via the first charging interface to determine a charging mode, the charging mode comprising a quick charging mode and a normal charging mode, and wherein the controllable switch and the filter unit are coupled in series and then coupled with a first output end of the second rectification unit, the control unit being further configured to control the controllable switch to switch on when determining the charging mode as the normal charging mode, to output the second DC and control the controllable switch to switch off when determining the charging mode as the quick charging mode, to output the voltage of the third pulsating waveform. 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 transformer, configured to output a voltage of a second pulsating waveform based on the voltage of the modulated first pulsating waveform; a second rectification unit, configured to rectify the voltage of the second pulsating waveform and output a voltage of a third pulsating waveform; a filter unit, configured to filter the voltage of the third pulsating waveform and output a second direct current, DC; a controllable switch, configured to control whether the filter unit operates; a first charging interface, configured to apply the voltage of the third pulsating waveform or the second DC to a battery of a device via a second charging interface of the device when the first charging interface is coupled with the second charging interface, wherein the second charging interface is coupled with the battery; a sampling unit, configured to sample an output voltage and/or an output current of the second rectification unit to obtain a voltage sampling value and/or a current sampling value; a control unit, coupled with the sampling unit, the switch unit, and the controllable switch respectively; the control unit being configured to control the controllable switch to cause the filter unit to a) operate, so as to output the second DC via the first charging interface; and b) stop operating, so as to output the voltage of the third pulsating waveform via the first charging interface; a) operate, so as to output the second DC via the first charging interface; and b) stop operating, so as to output the voltage of the third pulsating waveform via the first charging interface; the control unit being configured to output the control signal to the switch unit to adjust a duty ratio of the control signal based on the voltage sampling value and/or the current sampling value, whereby the voltage of the third pulsating waveform or the second DC meets charging requirements, wherein the control unit is further configured to communicate with the device via the first charging interface to determine a charging mode, the charging mode comprising a quick charging mode and a normal charging mode, and wherein the controllable switch and the filter unit are coupled in series and then coupled with a first output end of the second rectification unit, the control unit being further configured to control the controllable switch to switch on when determining the charging mode as the normal charging mode, to output the second DC and control the controllable switch to switch off when determining the charging mode as the quick charging mode, to output the voltage of the third pulsating waveform.