Modeling of control loop behavior of magamp post regulators

Abstract

Small-signal control models are presented for a magamp switching-mode post regulator. Two commonly used current reset schemes are considered: an external reset scheme and a self-reset scheme. Models for both continuous and discontinuous modes of operation are presented. It is mathematically shown that the open-loop gain is a two-pole, single-zero transfer function for continuous-mode operation and a single-pole function for discontinuous-mode operation. The equations for predicting the loop gains for both types of reset circuits are derived and verified experimentally. It is shown that the loop gain characteristics of a magamp regulator depend on power circuit parameters, the reset circuit parameters, and the saturable reactor parameters. Therefore, in a normal design procedure of a magamp, if the design parameters of the saturable reactor are changed, a corresponding change of the compensation network must be made to optimize the control performance. The models presented provide the designer with a tool to facilitate the feedback loop design of a voltage-mode magamp post regulator.<>