Battery-Less Power Management Circuit Powered by a Wearable Piezoelectric Energy Harvester

Abstract

A system that aims to manage the energy harvested from the finger movement using a glove-type garment is proposed. For this, five polyvinylidene difluoride (PVDF) film-type sensors are mounted on different interphalangeal joints of the fingers. A 68 μF/25 V ceramic capacitor is used as a storage device. A battery-less power management circuit (PMC) is proposed to isolate the capacitor from the load to reduce the current consumption while charging. When the voltage across the capacitor reaches a threshold voltage, the user decides when to transfer the energy to the electronic load. To test the proposed system, the harvested and conditioned energy is used to power both the PMC and a battery-less cardiac pulse detection circuit, achieving an autonomy of 20 s. This time depends on the voltage stored in the capacitor and the current consumption of the load. Using the proposed wearable system, it is possible to store up to 700 μJ in the capacitor when a subject manipulates a computer or a cellular phone for 10 min. The proposed system is not limited to the activities presented herein because it can harvest the biomechanical energy from any activity that involves finger movements.