Modeling of control loop behavior of magamp post regulators

Small signal-control models are presented for a magnetic amplifier switching-mode post regulator for SMPS applications. Two commonly used current reset schemes are considered; an external reset scheme and a self-reset scheme. It is mathematically shown that the open-loop gain is a two-pole, single-zero transfer function for continuous-mode operation and is a single pole transfer function for discontinuous mode operation. The equations for predicting the open-loop gains for both types of reset circuits are derived and verified experimentally. It is shown that the open-loop gain characteristics of a magnetic-amplifier regulator depends on power circuit parameters, the reset-circuit parameters, and the saturable reactor parameters. Models for both continuous mode and discontinuous modes of operation that provide designers with useful tools for designing a compensation network for the feedback error amplifier are presented