Operation-based signal-flow AC analysis of switching DC-DC converters in CCM and DCM

Ensuring stable operation is perhaps one of the most challenging aspects of designing a power-supply circuit because the load is dynamically unpredictable and widely variable. Unfortunately, the nonlinear dynamics of switch-mode converters accentuate these difficulties, especially when considering conventional analytical techniques rely on abstract mathematics to describe ac switching events that convey little operational insight into the circuit. This paper proposes an operation-based signal-flow ac analysis approach that is both sufficiently general to apply to most switched-inductor converters in continuous- and discontinuous-conduction modes (CCM and DCM) and insightful enough to derive directly from the waveforms of the circuit, not from the system of differential equations that govern them. To this end, after presenting the technique, the paper applies it to a relatively simple topology like the buck converter to prove its efficacy and then to a more complex counterpart like the non-inverting buck-boost converter to show the ease with which a more complicated system can be analyzed.