A Refined Nonlinear Averaged Model for Constant Frequency Current Mode Controlled PWM Converters

Existing nonlinear averaged models for current programmed converters are based on a steady-state formulation of the current mode control law. Although reasonably accurate at the lower frequencies (f << fswitching), these models tend to break down well before sampled-data effects nullify the assumptions underlying state-space averaging. Moreover, the SPICE implementation of the large-signal models is often plagued by a multitude of simulation problems. In this paper, a refined duo-model model for current programmed PWM converters is presented which exhibits improved high frequency accuracy over previous formulations and whose SPICE implementation remains, thus far, remarkably free of simulation problems. The large-signal transient response predicted using the refined average model is shown to be virtually indistinguishable, in an average sense, from that predicted using a pulse-by-pulse simulation.