A Generalized Large/Small Signal Average PWM Converter Model 1999-01-2597
A generalized pulse-width modulated (PWM) DC-DC converter model utilizing SPICE-oriented techniques that provide both large and small signal converter parameterizations is presented. The modeling method features the development of a unified variable duty cycle generator concept (s) and, in association with an average model of a PWM switched inductor, simulates current programmed and/or voltage-mode-controlled converters. The technique provides transient, DC, and small-signal behavior simulation in continuous conduction and discontinuous conduction operating modes (CCM and DCM) using a SPICE model behavioral scheme that is applicable to all PWM topologies. The model development comprises a partitioning of the PWM power stage into two elements: (1) a first element comprising an I-V characterization of the PWM switched inductor, derived in terms of large signal average ON/OFF duty cycle functions and (2) a novel second element (i.e., duty cycle generator) that explicitly solves the control-to-duty-cycle functionality by taking into consideration input/output voltage, output current, compensation slope factors, and DCM/CCM boundary conditions.