An adapter comprising: a power conversion unit, configured to convert an input alternating current to obtain an output voltage and output current of the adapter; a voltage feedback unit, having an input end coupled to the power conversion unit, the voltage feedback unit being configured to detect the output voltage of the adapter to generate a voltage feedback signal, the voltage feedback signal being configured to indicate whether the output voltage of the adapter reaches a set target voltage; a current feedback unit, having an input end coupled to the power conversion unit, the current feedback unit being configured to detect the output current of the adapter to generate a current feedback signal, the current feedback signal being configured to indicate whether the output current of the adapter reaches a set target current; and a power adjustment unit, having an input end coupled to an output end of the voltage feedback unit and to an output end of the current feedback unit, and an output end coupled to the power conversion unit, the power adjustment unit being configured to receive the voltage feedback signal and the current feedback signal and control the output voltage and output current of the adapter to remain unchanged when the voltage feedback signal indicates the output voltage of the adapter reaches the set target voltage or when the current feedback signal indicates the output current of the adapter reaches the set target current, wherein the adapter further supports a main charging mode, which is a constant-current mode, in which the target voltage is the maximum voltage the adapter allows to output under the main charging mode and the target current is set to a current corresponding to the main charging mode; wherein the power adjustment unit is configured to adjust the output current of the adapter to the corresponding current of the main charging mode based on the current feedback signal, wherein the current higher than the corresponding current is peak clipped, and control the output voltage of the adapter to not exceed the maximum voltage the adapter allows to output under the main charging mode when the voltage feedback signal indicates the output voltage of the adapter has reached the maximum voltage; and wherein in said main charging mode, the output current of the adapter is a pulsating direct current. a power conversion unit, configured to convert an input alternating current to obtain an output voltage and output current of the adapter; a voltage feedback unit, having an input end coupled to the power conversion unit, the voltage feedback unit being configured to detect the output voltage of the adapter to generate a voltage feedback signal, the voltage feedback signal being configured to indicate whether the output voltage of the adapter reaches a set target voltage; a current feedback unit, having an input end coupled to the power conversion unit, the current feedback unit being configured to detect the output current of the adapter to generate a current feedback signal, the current feedback signal being configured to indicate whether the output current of the adapter reaches a set target current; and a power adjustment unit, having an input end coupled to an output end of the voltage feedback unit and to an output end of the current feedback unit, and an output end coupled to the power conversion unit, the power adjustment unit being configured to receive the voltage feedback signal and the current feedback signal and control the output voltage and output current of the adapter to remain unchanged when the voltage feedback signal indicates the output voltage of the adapter reaches the set target voltage or when the current feedback signal indicates the output current of the adapter reaches the set target current, wherein the adapter further supports a main charging mode, which is a constant-current mode, in which the target voltage is the maximum voltage the adapter allows to output under the main charging mode and the target current is set to a current corresponding to the main charging mode; wherein the power adjustment unit is configured to adjust the output current of the adapter to the corresponding current of the main charging mode based on the current feedback signal, wherein the current higher than the corresponding current is peak clipped, and control the output voltage of the adapter to not exceed the maximum voltage the adapter allows to output under the main charging mode when the voltage feedback signal indicates the output voltage of the adapter has reached the maximum voltage; and wherein in said main charging mode, the output current of the adapter is a pulsating direct current.