Switching control circuit and power supply circuit

A switching control circuit for controlling a power supply circuit that generates an output voltage from an alternating current (AC) voltage inputted thereto, the power supply circuit including

• an inductor configured to receive a rectified voltage corresponding to the AC voltage,
• a transistor configured to control an inductor current flowing through the inductor,
• the switching control circuit being configured to control switching of the transistor, the switching control circuit comprising:
• a storage circuit;
• and
• an arithmetic circuit, the arithmetic circuit including a first arithmetic unit configured to calculate a first time period, which is from when the transistor is turned off to when the inductor current reaches a predetermined value, based on
• a first voltage corresponding to the rectified voltage,
• a second voltage corresponding to the output voltage, and
• the inductor current upon turning on of the transistor.

A power supply circuit that generates an output voltage from an alternating current (AC) voltage inputted thereto, the power supply circuit comprising:

• an inductor configured to receive a rectified voltage corresponding to the AC voltage;
• a transistor configured to control an inductor current flowing through the inductor;
• a first arithmetic circuit configured to calculate a first time period, which is from when the transistor is turned off to when the inductor current reaches a predetermined value, based on
• a first voltage corresponding to the rectified voltage,
• a second voltage corresponding to the output voltage, and
• the inductor current upon turning on of the transistor;
• and
• a drive circuit configured to
• cause the transistor to be on in a second time period corresponding to the second voltage, and
• cause the transistor to be off in the first time period.