Stability Analysis of Series-Capacitor Buck Converters With Different Phase Shift Strategies via Filippov's Method

Carrier phase shift (CPS) and switching signal phase shift (SSPS) are two commonly used switching delay methods for modulation in series capacitor buck converters (SCBC). This paper studies the nonlinear behavior of the SCBC under CPS and SSPS using the Filippov-based stability analysis method. Closed-form monodromy matrices of the SCBC are developed, incorporating the phase shift effects. Both fast and slow timescale stability are studied through eigenvalue analysis of the monodromy matrix. The findings reveal that different phase shift strategies result in the same steady-state behavior but different stability regions and even distinct bifurcation instability behaviors. Finally, experimental results confirm the correctness of the theoretical analysis.