The present invention relates to a power supply circuit that can intermittently operate when its load is small and therefore can reduce current consumption at a sleep mode. The power supply circuit for receiving an input voltage at an input terminal, converting the input voltage to an output voltage and outputting the output voltage to a load connected to an output terminal comprises: a power supply circuit unit; an output current detecting circuit unit; and an output voltage detecting circuit unit; whereby the output supply voltage detecting circuit unit makes the power supply circuit unit operate when the detected voltage becomes equal to or lower than a predetermined value, and thereby the power supply circuit unit performs intermittent operations.