charging current to the battery 500 an input terminal of the mixer u 1 is coupled to an output terminal of the second error amplifier u 3 to receive the result of comparing currents an output terminal of the mixer u 1 is coupled to a feedback terminal of the power management ic 100 via the feedback resistor rf the mixer u 1 outputs a feedback signal to the power management ic 100 the capacitor c 1 and the third resistor r 3 are coupled in series and are coupled to the second resistor r 2 in parallel a conducting end of the feedback resistor rf is coupled between the second resistor r 2 and the third resistor r 3 so that a voltage of the feedback signal to the power management ic can be adjusted for example the first error amplifier u 2 acquires the charging current to the battery 500 from the sampling resistor rs and outputs an amplified charging current to the second error amplifier u 3 the second error amplifier u 3 compares the amplified charging current with the analog signal representing the preset value of current the second error amplifier u 3 then outputs the result of comparing the levels of current to the mixer u 1 as the result of comparing amounts of current if the charging current to the battery 500 is higher than the preset value of current the second error amplifier u 3 outputs a higher voltage to the power management ic 100 and the power management ic 100 decreases the output power if the charging current to the battery 500 is lower than the preset value of current the second error amplifier u 3 outputs a lower.