In this paper, the nonlinear dynamics of PWM-type converters is studied. The sampled-data approach is applied to the periodic modeling and stability analysis of switching converters. The period-one and period-two modeling for the converter dynamics is proposed to predict the occurrence of the corresponding bifurcations and used to analyze the stability of converter circuits. The example study of buck converters is presented to demonstrate the feasibility of the methodological approach proposed in this paper. Applying to buck converters, the period-doubling bifurcation is found to exhibit as the input voltage varies, which might produce a series of period-doubling bifurcations and then result in a chaotic motion. Furthermore, the system stability of buck dynamics is studied and evaluated.