Novel developments in the study of nonlinear phenomena in power factor correction circuits

Boost power factor correction (PFC) converter with average current mode control is a nonlinear system due to the effects of the multiplier and a large variation of the duty ratio. Although stability analysis must be studied depending on nonlinear model, most prior researches attempted to put some assumptions to force this nonlinear system to be linear. As a result the practical dynamics and the nonlinear phenomena were disregarded. In this paper, two nonlinear phenomena are detected in the prior stable regions: period-doubling bifurcation and chaos. Stability maps are introduced at different loads to clarify the power factor and also the instability regions. It is made clear that instability regions enlarge as the operation moves toward light loads. A novel method to judge the system stability is introduced depending on the phase plane trajectory where the horizontal axis is the input line current and the vertical axis is the output voltage or its ripple. The symmetry around the vertical axis in the phase plane curve assures the system stability. On the other hand, the symmetry around the horizontal axis improves the system power factor. Therefore, period-doubling bifurcation can be known by two asymmetrical loops around the vertical axis in the phase plane trajectory. Chaos can be known by multi loops in the phase plane trajectory. The dynamics of period-doubling instability is understood from the instantaneous power behavior. Stability can be judged from the first transient cycles of the instantaneous powers waveforms. Bifurcation map is developed to determine the accurate minimum output capacitance value that assures the system stability at all cases. Experimental results confirm the simulated and analytical results with a very good matching.