There is provided a power supply circuit. A switching regulator is configured to drop a battery voltage to a first specific voltage. A series regulator includes a switching element and a capacitor connected at an output stage of the switching element. The series regulator is configured to drop the first specific voltage to a second specific voltage and output the second specific voltage. A control circuit is configured to adjust an amount of electric charge to be accumulated in the capacitor according to a voltage value of the first specific voltage.