Asymmetric Instability Conditions for Peak and Valley Current Programmed Converters at Light Loading

Three types of bifurcations (instabilities) in the DC-DC converter under valley current mode control (VCMC) are analyzed, which is an extension of a recent paper on the peak current mode control (PCMC). The three bifurcations are border-collision, period-doubling, and saddle-node bifurcations. The corresponding critical (instability) conditions are derived. The derived conditions divide the parameter space into different operating modes. Contrary to the general belief that the critical conditions for VCMC and PCMC are symmetric with respect to the duty cycle D=1/2, most critical conditions are actually asymmetric. The dynamics symmetry is converter, bifurcation, loading, and parameter dependent, verified by bifurcation diagrams and time-domain simulations. The VCMC boost converter has rich dynamics and it is extensively analyzed.