Integrated circuit and power supply circuit

A power supply circuit configured to generate an output voltage from an input voltage thereof, to apply the output voltage to a load, the power supply circuit comprising:

• a transformer including a primary coil, a secondary coil, and an auxiliary coil;
• a transistor configured to control an inductor current flowing through the primary coil;
• a first capacitor;
• a first diode configured to charge the first capacitor, based on a voltage across the auxiliary coil, upon turning off of the transistor;
• a booster circuit configured to generate a boost voltage, based on the voltage across the auxiliary coil;
• a first charging circuit configured to charge the first capacitor;
• and
• an integrated circuit configured to control switching of the transistor, the integrated circuit including
• a first terminal configured to receive a voltage across the first capacitor as a power supply voltage,
• a second terminal configured to receive a feedback voltage corresponding to the output voltage,
• a driving signal output circuit configured to output a driving signal to change a switching period of the transistor, based on the feedback voltage,
• a driver circuit configured to drive the transistor in response to the driving signal, and
• a determination circuit configured to determine whether the power supply voltage drops below a first voltage, wherein
• the first charging circuit is configured to charge the first capacitor based on the boost voltage, when the power supply voltage is lower than the first voltage.

A power supply circuit configured to generate an output voltage from an input voltage thereof, to apply the output voltage to a load, the power supply circuit comprising:

• a transformer including a primary coil, a secondary coil, and an auxiliary coil;
• a transistor configured to control an inductor current flowing through the primary coil;
• a first capacitor;
• a first diode configured to charge the first capacitor, based on a voltage across the auxiliary coil, upon turning off of the transistor;
• a determination circuit configured to determine whether a voltage across the first capacitor drops below a first voltage;
• a booster circuit configured to generate a boost voltage, based on the voltage across the auxiliary coil;
• a first charging circuit configured to charge the first charging circuit, based on the boost voltage, when the voltage across the first capacitor is lower than the first voltage;
• and
• an integrated circuit configured to control switching of the transistor, the integrated circuit including
• a first terminal configured to receive the voltage across the first capacitor as a power supply voltage,
• a second terminal configured to receive a feedback voltage corresponding to the output voltage,
• a driving signal output circuit configured to output a driving signal to change a switching period of the transistor, based on the feedback voltage, and
• a driver circuit configured to drive the transistor in response to the driving signal.