Stability Effect of Different Modulation Parameters in Voltage-Mode PWM Control for CCM Switching DC–DC Converter

Abstract

In order to guide the parameters design of voltage-mode controlled switching dc-dc converter, taking continuous conduction mode (CCM) buck converter as an example, the discrete iterative-map model for six possible evolutions is established. Based on which, the dynamical behaviors of different pulse-width modulation (PWM) parameters on voltage-mode controlled buck converter are revealed via bifurcation diagrams. In addition, the closed-loop z-domain transfer function and the corresponding stability boundary equations are derived. Meanwhile, the operating regions with varying circuit parameters for different PWM methods can be estimated and divided by the boundary equations, which can provide guidance for stability control. The research results indicate the nonlinear phenomena, such as period window, Hopf bifurcation, period-doubling bifurcation, chaos and so on, exist in the voltage-mode controlled buck converter. Dual-edge modulation (symmetrical dual-edge or asymmetrical dual-edge) shows more stable performance than single-edge modulation (leading-edge or trailing-edge) under certain circuit parameters. Moreover, there are two similar but different Hopf bifurcation phenomena in the voltage-mode controlled buck converter. The existence and difference of them are theoretically analyzed by eigenvalues and Poincare sections. Finally, simulation waveforms and experimental results are given to verify the theoretical analysis.