The invention discloses an adapter. A mobile terminal is charged through a data line, and a source end connector is used for receiving required charging
voltage and required charging current from the mobile terminal. A
control unit is used for obtaining the charging
voltage and the charging current. The
control unit is used for comparing the charging
voltage and the charging current with the required charging voltage and the required charging current respectively, and a
control signal is generated when the charging voltage and the charging current are different from the required charging voltage and the required charging current. A PWM (Pulse-Width Modulation) driving module is used for adjusting an output pulse
signal according to the
control signal so as to control the start frequency of a switch unit and change a third
alternating current, and thus the charging voltage and the charging current are adjusted to the required charging voltage and the required charging current. In the charging process of the adapter, the adapter outputs voltage and current matched with the required charging voltage and the required charging current of the mobile terminal, and thus the charging effect of the mobile terminal is better.