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 pulsewidth modulators (DPWMs) or sigma–delta-based (ΣΔ- DPWM) solutions with a single, fully digital block featuring reduced complexity, high resolution, improved noise performance, and small-signal 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.