Comparative Analysis of Double-Stage Interfaces for Electromagnetic Energy Harvesters Generating Impulsive Voltages.

An emerging class of electromagnetic energy harvesters, primarily designed to scavenge energy from human motion, sea waves, or sporadic mechanical vibrations, generates impulsive voltage waveforms rather than conventional sinusoidal ones. For such harvesters, usually employed for powering wireless sensor network nodes, this paper presents an in-depth investigation of double-stage AC/DC conversion interfaces aimed at evaluating and comparing their performance in energy extraction. Closed-form expressions are derived for widely adopted topologies consisting of full-bridge or voltage doubler rectifiers followed by DC/DC converters that exhibit either constant-voltage or constant-resistance behavior at their input terminals. The derived expressions provide valuable design insight, showing that no topology is universally preferable under all operating conditions; therefore, design guidelines are provided to support the selection and optimization of the most appropriate configuration. The analytical results show good agreement with measurements performed on interface prototypes assembled using off-the-shelf components, with a relative error below 4% at the maximum-energy points for all the tested configurations. The experimental validation confirms the accuracy of the developed models and their practical relevance for the analysis and design of interfaces for impulsive electromagnetic energy harvesters.