Actively Controlled Synchronized-Switch Harvesting on Inductor for Piezoelectric Transducers

Vibrational energy harvesting by means of piezoelectric transducers has been of particular interest in recent years for powering autonomous, wireless devices. In this context, a non-linear treatment of piezoelectric voltage greatly enhances electromechanical conversion. This paper presents an ultra-low power circuit implementation of the technique called Synchronized Switch Harvesting on Inductor (SSHI). The circuit detects the zero-current condition through the rectifier with a series shunt resistor and a nano-power comparator. Simulations show that the maximum power extracted is approximately 6.7 times greater than with a passive rectifier. The estimated overall consumption of the circuit components is 4 µA. The measured voltage flip efficiency is between 91% and 94%.