System and method for protecting a power converter. The system includes a duty-cycle detection component configured to receive a modulation signal, determine a first duty cycle corresponding to a first period of the modulation signal, compare the first duty cycle with a threshold duty cycle, and generate a duty-cycle comparison signal. Additionally, the system includes a threshold generator configured to receive the duty-cycle comparison signal and generate a threshold signal corresponding to a second period of the modulation signal, the second period being after the first period, and a comparator configured to receive the threshold signal and a first signal and to generate a first comparison signal. The first signal is associated with an input current for a power converter. Moreover, the system includes a pulse-width-modulation component configured to receive the first comparison signal and generate the modulation signal for adjusting the input current for the power converter.