State variable stability analysis of multi-loop PWM controlled DC/DC regulators in light and heavy mode

Abstract

Stability analysis and transient response predictions of PWM controlled DC/DC regulators are now feasible in both continuous and discontinuous mode A linear equivalent continuous model of the power stage is firstly established for the boost and the buck converter by means of state variable representation for each of the elementary structure occuring within one sampling period. This equivalent model turns out to be of first order for the discontinuous mode and of 2nd order for the continuous mode. A general computer program has been implemented for the derivation of such a model and for the stability analysis and transient response of multiloop regulators. Special emphasis has been given to the boost converter in light conduction mode operation whether an AC feedback loop is included or not. The existence of the non-minimum phase effect associated with such a regulator for a heavy operation mode is shown to be dependent of the sampling frequency.