A piezoelectric harvesting interface with capacitive partial electric charge extraction for energy harvesting from irregular high-voltage input

A fully integrated piezoelectric energy harvesting interface is proposed for harvesting energy from irregular human motion. To handle irregular pulse inputs generated by the piezoelectric transducer (PZT), the proposed harvesting interface includes a wake-up controller that activates the harvesting interface only when human motion is detected and deformation is applied on the piezoelectric material, thereby keeping static power loss low. The PZT output voltage is increased to its peak voltage by removing any type of external load capacitance seen by the PZT during its deformation. Once the peak voltage is detected, a multi-voltage conversion-ratio-based switched-capacitor circuit is activated to transfer PZT-generated energy to the battery in multiple ratio steps to maximize the conversion efficiency, with the help of a carefully designed harvesting controller. To deal with open-circuit voltages (V_OCS) higher than the maximum voltage tolerated (V_MAX) by available technology, capacitive partial electric charge extraction is activated every time the PZT output voltage approaches the V_MAX. The proposed harvesting interface extracts 3.37 times more energy than a conventional full-bridge rectifier-based harvesting scheme.