A duty cycle generator for generating a duty cycle signal to a power converter is disclosed. The duty cycle generator includes a first inverter, a second inverter, a signal protection unit including an input terminal coupled to the duty cycle signal for generating a break pulse to generate a protected duty cycle signal, a comparator for comparing a triangle-wave signal with a comparison signal to generate a comparison result, a NOR gate for generating a reset signal according to the comparison result and the protected duty cycle signal, an SR-latch for outputting a turn-on signal according to the clock signal and the reset signal, and an AND gate for generating the duty cycle signal according to the inverted clock signal and the turn-on signal.