Synchronized switch charge constrained conditioning circuit for electrostatic energy harvesting

Electrostatic energy harvesting conditioning circuits usually rely on triangular or rectangular shaped energy cycles. While the former enables significant converted energy, its complexity raises significant issues in realistic applications. Rectangular cycles can be implemented using purely passive components but feature limited conversion abilities. This study bridges the gap between these two approaches, presenting a semi-passive technique consisting of charging and discharging the transducer synchronously with the structure motion, using controlled switches that can be easily implemented while ensuring triangular cycles. Theoretical analysis and experimental validation of such an electrostatic energy harvesting circuit with synchronized controlled switches confirm that this technique provides a simple configuration while ensuring the efficiency of the triangular cycle. To validate the proposed circuit design, a system was employed featuring a rotating metallic variable capacitor designed to mechanically open two magnetic reed switches. This system seamlessly integrates with the devised circuit. The total energy converted by the entire system is estimated to be approximately 1 μJ per cycle, considering a storage component comprising a precharged 1 μF capacitor at 60 V. Yet, results demonstrated that efficiently transferring this energy to the storage stage requires transducers with low losses. While in the presented experimental test an off-the-shelf generic transducer showed high losses, resulting in only 24 nJ per cycle to be harvested, it is believed that specific high quality electrostatic device can benefit from this approach for efficient energy harvesting systems. [Display omitted] •High efficiency, low complexity electrostatic energy harvester circuit is proposed.•It relies on a hybrid approach between triangular and rectangular energy cycles.•The circuit works using resonant charge and discharge.•The proposed circuit bridges the gap between efficiency and simplicity.•Mechanical switches allow cost-effective experimental validation.