An adaptive charging voltage generator of a mobile device charger configured for charging a mobile device, the adaptive charging voltage generator comprising: a power receiving interface arranged to operably receive a DC voltage and a cable current supplied by a power source unit of the mobile device charger from a cable of the mobile device charger; a terminal communication interface arranged to operably transmit a charging voltage and a charging current to a connection terminal detachably connected to the mobile device and to operably receive a communication signal (X1B; X2B) generated by the mobile device from the connection terminal; a buck converter, coupled between the power receiving interface and the terminal communication interface, arranged to operably receive the DC voltage and the cable current from the power receiving interface and to operably generate the charging voltage and the charging current, wherein the charging voltage is lower than the DC voltage while the charging current is greater than the cable current; and a charging voltage control circuit, coupled with the terminal communication interface and the buck converter, arranged to operably control the buck converter according to the communication signal (X1B; X2B) and at least one of the charging voltage and the charging current outputted from the buck converter; characterized in that the charging voltage control circuit is further coupled with the power receiving interface, and arranged to operably control the power source unit through the power receiving interface and the cable according to at least one of the charging voltage and the charging current outputted from the buck converter. a power receiving interface arranged to operably receive a DC voltage and a cable current supplied by a power source unit of the mobile device charger from a cable of the mobile device charger; a terminal communication interface arranged to operably transmit a charging voltage and a charging current to a connection terminal detachably connected to the mobile device and to operably receive a communication signal (X1B; X2B) generated by the mobile device from the connection terminal; a buck converter, coupled between the power receiving interface and the terminal communication interface, arranged to operably receive the DC voltage and the cable current from the power receiving interface and to operably generate the charging voltage and the charging current, wherein the charging voltage is lower than the DC voltage while the charging current is greater than the cable current; and a charging voltage control circuit, coupled with the terminal communication interface and the buck converter, arranged to operably control the buck converter according to the communication signal (X1B; X2B) and at least one of the charging voltage and the charging current outputted from the buck converter; characterized in that the charging voltage control circuit is further coupled with the power receiving interface, and arranged to operably control the power source unit through the power receiving interface and the cable according to at least one of the charging voltage and the charging current outputted from the buck converter.