A DC/DC converter converts an input DC voltage to an output DC voltage and charges a battery. The DC/DC converter includes: a DC/DC controller, operable for generating a driving signal according to a target value for the output voltage and a first detection signal indicative of the output voltage level to control switching circuitry and to adjust the output voltage level; and a battery charging controller, coupled to the DC/DC controller and the battery, that is operable for receiving the first detection signal indicative of the output voltage level and a second detection signal indicative of a battery voltage level, and for generating a loop control signal according to the first detection signal and the second detection signal to adjust the target value for the output voltage, wherein the difference between the first detection signal and the second detection signal indicates the amount of a battery charging current.