Switching control circuit and power supply circuit

A switching control circuit for a power supply circuit that generates, for an output capacitor, an output voltage at a target level from an alternating current (AC) voltage inputted to the power supply circuit, the power supply circuit including

• an inductor configured to receive a rectified voltage corresponding to the AC voltage,
• a first transistor configured to control an inductor current flowing through the inductor, the first transistor having a parasitic capacitor, and
• a second transistor provided between the inductor and the output capacitor,
• the switching control circuit being configured to complementarily switch the first transistor and the second transistor, the switching control circuit comprising:
• a time period output circuit configured to output a first time period in which the inductor current changes from a predetermined value to a first value smaller than the predetermined value, with the first transistor being off and the second transistor being on;
• and
• a drive signal output circuit configured to output a first drive signal to switch the first transistor and a second drive signal to switch the second transistor,
• the drive signal output circuit being configured to
• output the second drive signal to turn off the second transistor, in response to the first time period having elapsed since the inductor current has reached the predetermined value with the first transistor being off, and
• output the first drive signal to turn on the first transistor, in response to a second time period having elapsed after the lapse of the first time period, and
• the second time period being determined based on a resonant period of the parasitic capacitor of the first transistor and the inductor, and being a time period in which a voltage level of an output electrode of the first transistor drops to a predetermined level.