A power adapter configured to output a voltage with a pulsating waveform, comprising: a full-bridge rectifier circuit, configured to rectify an input alternating current and output a first voltage with a first pulsating waveform; a switch unit, configured to modulate the first voltage according to a control signal and output a modulated first voltage to a transformer, and to perform a chopping modulation on the first voltage with the first pulsating waveform; the transformer, configured to output a second voltage with a second pulsating waveform according to the modulated first voltage, wherein the full-bridge rectifier circuit is connected to a primary winding of the transformer without electrolytic capacitor; a second rectifier, connected to a secondary winding of the transformer, configured to rectify the second voltage to output a third voltage with a third pulsating waveform; a first charging interface, coupled to the second rectifier without electrolytic capacitor, configured to apply the third voltage to a battery in a device via a second charging interface of the device when the first charging interface is coupled to the second charging interface, in which the second charging interface is coupled to the battery; a sampling unit, configured to sample a voltage and current outputted by the second rectifier to obtain a voltage sampling value and a current sampling value; and a control unit, coupled to the sampling unit and the switch unit respectively, and configured to output the control signal to the switch unit, and to adjust a duty ratio of the control signal according to the current sampling value and/or the voltage sampling value, such that the third voltage meets a charging requirement of the device. a full-bridge rectifier circuit, configured to rectify an input alternating current and output a first voltage with a first pulsating waveform; a switch unit, configured to modulate the first voltage according to a control signal and output a modulated first voltage to a transformer, and to perform a chopping modulation on the first voltage with the first pulsating waveform; the transformer, configured to output a second voltage with a second pulsating waveform according to the modulated first voltage, wherein the full-bridge rectifier circuit is connected to a primary winding of the transformer without electrolytic capacitor; a second rectifier, connected to a secondary winding of the transformer, configured to rectify the second voltage to output a third voltage with a third pulsating waveform; a first charging interface, coupled to the second rectifier without electrolytic capacitor, configured to apply the third voltage to a battery in a device via a second charging interface of the device when the first charging interface is coupled to the second charging interface, in which the second charging interface is coupled to the battery; a sampling unit, configured to sample a voltage and current outputted by the second rectifier to obtain a voltage sampling value and a current sampling value; and a control unit, coupled to the sampling unit and the switch unit respectively, and configured to output the control signal to the switch unit, and to adjust a duty ratio of the control signal according to the current sampling value and/or the voltage sampling value, such that the third voltage meets a charging requirement of the device.