An adaptive charging voltage generator of a mobile device charger includes: a power receiving interface for receiving a DC voltage and a cable current from a cable; a terminal communication interface for transmitting a charging voltage and a charging current to a connection terminal of the mobile device charger and for receiving a communication signal generated by the mobile device from the connection terminal; a buck converter for receiving the DC voltage and the cable current from the power receiving interface and for generating 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 buck converter and configured for controlling the buck converter according to the communication signal.