A control circuit of a power converter includes a sensing circuit, a ramp signal generator, an error amplifier, a comparator and a PWM circuit. The sensing circuit, coupled to a first output circuit, provides a current sensing signal. The ramp signal generator, coupled to the sensing circuit, receives the current sensing signal to provide a ramp signal. The error amplifier receives a reference voltage and an output feedback voltage of the power converter to provide an error amplification signal. The comparator, coupled to the ramp signal generator and the error amplifier, provides a control signal according to the ramp signal and the error amplification signal. The PWM circuit, coupled between the comparator and the first output circuit, receives the control signal and provides a PWM signal to control the first output circuit. The ramp signal generator adjusts a slope of the ramp signal according to the current sensing signal.