A Novel High-Accuracy Inductor-Current Estimator for Digitally-Controlled Synchronous DC-DC Buck Converters

This paper presents a novel digital inductor-current estimator for digitally-controlled current-ripple-based synchronous DC-DC buck converters. The estimator features high accuracy, which is imperative for current-ripple control that requires precise estimation of instantaneous DC and inductor ripple currents in both the discontinuous and continuous conduction modes. The estimation method indirectly determines the currents by constructing a digital representation of the voltage across the inductor, rendering it applicable in both conduction modes. This method is more accurate and simpler than conventional methods that estimate DC and inductor ripple currents directly in each conduction mode. Compared to state-of-the-art methods, the proposed estimator achieves an average DC current estimation error that is ≥5.7× smaller and an inductor ripple current estimation error that is ≤ 1.90% over various load conditions.