In a power source circuit including a switching circuit 8 as a power conversion circuit for converting by a switching operation at least one of a frequency and a voltage of an alternating voltage from an alternating power source 2 via a pair of supply lines 3 and 4, one supply line 3 includes a fuse 5 as an excess current protection element, and between a ground line 10 and one supply line 3, a first line bypass capacitor 6 is connected. Between the ground line 10 and another supply line 4, a second line bypass capacitor 7 is connected, and another supply line 4 includes an inductor 9. With this configuration, an unbalanced state of the circuit due to the excess current protection element is reduced so as to restrain the common mode noise.