Unified prediction of slow and fast scale instabilities by means of complementary design-oriented models

Average models are commonly used to describe switching power converter dynamics because of their design-oriented perspective, despite the fact that they are not well suited to predict the so-called fast-scale period-doubling instabilities. Conversely, such fast-scale instabilities occurrence can be predicted by mathematical discrete-time recurrent maps which capture all the dynamics of converter, but lack a design-oriented perspective. Recently a design-oriented index based on the ripple magnitude at the input of the PWM modulator has been proposed to predict fast-scale instabilities. This paper addresses the combination of both complementary design-oriented models to predict instability boundaries, thereby providing a unified prediction framework of slow and fast-scale instability occurrence to characterize the influence of each parameter upon the global converter stability. Both analytical as well as frequency-domain graphical approaches are presented.