Abstract: An integrated circuit for a power supply circuit that generates an output voltage, and that includes: a transformer including primary and secondary coils, first and second transistors controlling a current of the primary coil, and a resonant circuit including the primary coil and a first capacitor. The integrated circuit controls the first and second transistors. The integrated circuit includes: a voltage generator circuit supplying a first current to a second capacitor, and to generate a first voltage at the second capacitor; a driving signal output circuit outputting a driving signal for driving the first and second transistors, based on the first voltage and a feedback voltage corresponding to the output voltage; and a control circuit controlling the voltage generator circuit such that, when the output voltage drops and a derivative of the feedback voltage at a time point is greater than a predetermined value, the first current increases and then decreases.