A Nanopower Synchronous Charge Extractor IC for Low-Voltage Piezoelectric Energy Harvesting With Residual Charge Inversion

The paper presents a power converter for piezoelectric energy harvesting implementing a modified version of a synchronous electrical charge extraction with quiescent current as low as 160 nA. The input energy is increased of more than 200% for weak vibrations, by inverting the residual charge left on the capacitance of the transducer after each energy extraction. Moreover, a power management policy, named two-way energy storage, is introduced in order to improve significantly the efficiency of the energy harvesting system in battery-less systems during the startup phase, when the energy storage is fully depleted. The converter behaves as a buck-boost converter, and the measured peak efficiency is 85.3%. The IC has been designed in a 0.32-mu m microelectronic technology from STMicroelectronics in an active area of 0.95mm(2).