Fully digital hysteretic modulator for DC-DC switching converters

This paper presents an alternative modulation approach for digitally controlled DC-DC switching converters, which exploits the natural jittering activity of a digital hysteretic feedback loop in order to provide an effective increase in resolution. The proposed structure replaces conventional high-resolution digital pulse-width modulators (DPWM) or sigma-delta based (ΣΔ-DPWM) solutions with a single, fully-digital block featuring reduced complexity, high resolution, and improved noise performance and small-signal dynamic characteristics, enabling the design of accurate, high-bandwidth digital feedback loops with minimum hardware resources. A stochastic modeling approach is developed for the proposed structure, which allows the derivation of a simple and effective switching frequency control criterion. Analysis, simulation and experimental tests are shown to validate the properties of the proposed digital hysteretic modulator.