A power converter includes a ramp generating unit, a first comparator, a second comparator, and a pulse width modulation (PWM) signal generating unit. The ramp generating unit provides a ramp signal. The first comparator receives the ramp signal and a control signal to provide a normal operation control signal. The second comparator receives the ramp signal and the control signal to provide a dynamic response control signal. The PWM signal generating unit generates a PWM signal according to the normal operation control signal or dynamic response control signal. When the control signal is higher than a threshold of ramp signal, the second comparator provides the dynamic response control signal to the PWM signal generating unit to control it to adjust a duty cycle of the PWM signal.