A Unified Sampled-Data Small-Signal Model for a Ripple-Based COT Buck Converter With Arbitrary Ripple Injection Network

In this paper, we present a novel and unified small-signal modeling technique for Pulse-Width Modulated (PWM) DC-DC Buck converters with Ripple-Based Constant On-Time (RBCOT) control. In fact, despite the spread of RBCOT-based converters in several applications requiring tight dynamic performances and a low architectural complexity, their description through small-signal models is not always as reliable as that of fixed-frequency PWM control architectures, and a general and exact modeling framework is not well established. The proposed methodology is grounded on the DC-DC converter state-space representation and thus, differently from other modeling techniques, it permits to fully characterize the dynamic behavior of generic RBCOT converter topologies with arbitrary complex power stage and ripple injection networks. As a case study, we derive the small-signal model for a Buck converter embedding a widely used ripple injection network in industrial applications. The validity of the theoretical results is confirmed through direct comparison with SIMetrix/SIMPLIS simulations and experimental measurements in practical application scenarios, confirming the accuracy of the model even well beyond the converter switching frequency.