Integrated circuit and power supply circuit

An integrated circuit for a power supply circuit configured to generate an output voltage of a target level from an input voltage thereof, the power supply circuit including a coil and a transistor configured to control a current flowing through the coil, the integrated circuit being configured to drive the transistor, the integrated circuit comprising:

• a determination circuit configured to determine whether a predetermined time period has elapsed since a power supply voltage of the integrated circuit rises to a first predetermined level;
• an oscillator circuit configured to output an oscillator signal, the oscillator signal
• having a first frequency, a second frequency higher than the first frequency, and a third frequency lower than the first frequency,
• changing in a first range from the first frequency to the third frequency based on the output voltage, before lapse of the predetermined time period, and
• changing in a second range from the third frequency to the second frequency based on the output voltage, after the lapse of the predetermined time period;
• and
• a driver circuit configured to
• switch the transistor responsive to the oscillator signal that changes in the first range, in the predetermined time period, and
• switch the transistor responsive to the oscillator signal that changes in the second range, after the lapse of the predetermined time period.

A power supply circuit configured to generate an output voltage of a target level from an input voltage thereof, the power supply circuit comprising:

• a coil;
• a transistor configured to control a current flowing through the coil;
• and
• an integrated circuit configured to drive the transistor, the integrated circuit including
• a determination circuit configured to determine whether a predetermined time period has elapsed since a power supply voltage of the integrated circuit rises to a first predetermined level,
• an oscillator circuit configured to output an oscillator signal, the oscillator signal
• having a first frequency, before lapse of the predetermined time period, and
• changing in a range at least from the first frequency to a second frequency higher than the first frequency, based on the output voltage, after the lapse of the predetermined time period, and
• a driver circuit configured to switch the transistor responsive to the oscillator signal, so as to gradually increase an on period of the transistor, in the predetermined time period, and switch the transistor responsive to the oscillator signal, after the lapse of the predetermined time period.