Abstract: A charger system which includes a power adapter, an enhanced USB cable and a linear charger. The power adapter includes a two-way voltage divider. The two-way voltage divider receives a reference voltage through a first end and divides the reference to generate a default voltage level, or additionally receives a current request signal through a second end. The enhanced USB cable is coupled to the power adapter for transmitting the adapter output voltage. The linear charger is coupled to the transmission cable to receive the adapter output voltage. Wherein, the power adapter identifies whether the enhanced USB cable is a compliant cable or not, and identifies whether the charger is a compliant charger or not according to the presence of a current request signal. Wherein, the power adapter folds back the output voltage at a current limit level according to the charger current request signal.