To provide a power supply circuit where turning-on and/or turning-off of power supply voltage is adjustable in accordance with the ON state of a power source switch and/or the OFF state of a power source switch.

The power supply circuit is provided with DC-DC conversion means (110, 110a and 110b) for converting an inputted DC power supply voltage supplied through a power supply switch to a desired voltage and timing control means (120, 130 and 140) for controlling the timing of turning-on, or the timing of turning-off, or both by using a reference voltage which the DC-DC conversion means uses internally. The timing control means includes an amplifier for amplifying the reference voltage, a timing generating means which is actuated in accordance with the output of the amplifier so as to generate a timing signal for controlling the timing, and a means for switching the output of the DC-DC conversion means in accordance with the timing signal.