The disclosure concerns a power supply circuit comprising a voltage converter receiving an external voltage and outputting an internal voltage; a first switch and a second switch connected between an output of the voltage converter and a constant voltage source; a resistor provided between the first switch and the second switch, and dividing the internal voltage; a comparator including a first input unit, a second input, and an output which is connected to the voltage converter; a reference voltage source supplying a reference voltage to the first input; a feedback feeding back a voltage divided by the resistor to the second input from a node between the first switch and the second switch; a setting voltage source, to the second input; a third switch connected between the setting voltage source and the second input; and a control signal generator controlling the first switch, the second switch, and the third switch.