Peak and average current controls - Simulation techniques and comparison

摘要

This paper presents a non-linear simulation model of the peak current control (PCC) and the average one (ACC) applied to a buck converter and valid both for DC and AC analyses, and transient simulations. Scope of the present paper is to give an idea on how to build a large signal ACC or PCC model for any converter topology. Small signal models gives a lot of interesting insight into the dynamical properties of the control loops, but when position of poles and zeroes does depend on the operating point (as in the PCC case), they can fail to predict the time-domain response of the controlled system to large signal excitations. Another reason for large signal models is the practical need of predicting how the real circuit performs when the circuit non-idealities are taken into account (e.g. like presence of input filters, low pass characteristic of real current sensors, actual rise/fall and delay times of PWM comparator - ACC - or flip-flop - PCC -, possible saturation of the control or power stages, etc). The correct DC starting point is evaluated before running the transient switching model, allowing for a faster and accurate prediction of transient events.