An electronic device includes a sampling circuit and a summing circuit coupled with the sampling circuit. The sampling circuit samples a pulse width of a first input pulse of a PWM input signal since a first time point on a rising edge of a clock pulse of a clock signal. The summing circuit generates a first output pulse of a PWM output signal since a second time point on a falling edge of the clock pulse. A pulse width of the first output pulse is a summation of the pulse width of the first input pulse and a pulse width of a second input pulse of the PWM input signal, and the second input pulse is the next pulse after the first input pulse.