A power adapter, comprising: a first rectification unit, configured to rectify an input alternating current and output a voltage of a first pulsating waveform; a transformer; a synthesize unit, including two controllable switching circuits constituted by an electronic switching device and a control module, which is adopted to control the electronic switching device and which can optionally be located outside of the synthesize unit in a control unit, configured to synthesize a voltage of a second pulsating waveform and a voltage of a third pulsating waveform to output the second AC, alternating current, by switching the electronic switching circuits, wherein an absolute value of a peak voltage of a positive half of each cycle of the second AC is greater than an absolute value of a peak voltage of a negative half, wherein the second AC is applied to a battery of a device; a sampling unit, configured to sample a voltage of the second AC to obtain a voltage sampling value; a modulation and control unit, configured to modulate the voltage of the first pulsating waveform according to the voltage sampling value and to apply the voltage of the modulated first pulsating waveform to a primary side of the transformer, and the transformer being configured to convert the voltage of the modulated first pulsating waveform to the voltages of the multiple pulsating waveforms, such that the second AC meets a charge requirement, wherein further the transformer comprises a primary winding, a first secondary winding, and a second secondary winding, and wherein the transformer is configured to output the voltage of the second pulsating waveform via the first secondary winding according to the voltage of the modulated first pulsating waveform, and to output the voltage of the third pulsating waveform via the second secondary winding according to the voltage of the modulated first pulsating waveform. a first rectification unit, configured to rectify an input alternating current and output a voltage of a first pulsating waveform; a transformer; a synthesize unit, including two controllable switching circuits constituted by an electronic switching device and a control module, which is adopted to control the electronic switching device and which can optionally be located outside of the synthesize unit in a control unit, configured to synthesize a voltage of a second pulsating waveform and a voltage of a third pulsating waveform to output the second AC, alternating current, by switching the electronic switching circuits, wherein an absolute value of a peak voltage of a positive half of each cycle of the second AC is greater than an absolute value of a peak voltage of a negative half, wherein the second AC is applied to a battery of a device; a sampling unit, configured to sample a voltage of the second AC to obtain a voltage sampling value; a modulation and control unit, configured to modulate the voltage of the first pulsating waveform according to the voltage sampling value and to apply the voltage of the modulated first pulsating waveform to a primary side of the transformer, and the transformer being configured to convert the voltage of the modulated first pulsating waveform to the voltages of the multiple pulsating waveforms, such that the second AC meets a charge requirement, wherein further the transformer comprises a primary winding, a first secondary winding, and a second secondary winding, and wherein the transformer is configured to output the voltage of the second pulsating waveform via the first secondary winding according to the voltage of the modulated first pulsating waveform, and to output the voltage of the third pulsating waveform via the second secondary winding according to the voltage of the modulated first pulsating waveform.