A system has a processor, a battery charging circuit, a voltage regulating circuit and a control circuit. The control circuit provides digitalized feedback signals representative of circuit parameters of the battery charging circuit and circuit parameters of the voltage regulating circuit to the processor and receives a first information and a second information from the processor. The processor is able to adjust its operating states in response to the digitalized feedback signals. The control circuit controls the battery charging circuit in response to the circuit parameters of the battery charging circuit and the first information received from the processor, and the control circuit controls the voltage regulating circuit in response to the circuit parameters of the voltage regulating circuit and the second information received from the processor.