A fully integrated split-electrode synchronized-switch-harvesting-on-capacitors (SE-SSHC) rectifier for piezoelectric energy harvesting with between 358% and 821% power-extraction enhancement

Along with the development of the Internet of Everything (IoE), miniaturized piezoelectric vibration-energy harvesters have drawn significant recent interest as a means of harvesting ambient kinetic energy to power wireless sensors. As the energy generated by a piezoelectric transducer (PT) cannot be directly used, an interface circuit is needed to rectify the generated power and provide a stable supply. Full-bridge rectifiers (FBR) are widely used due to their simplicity despite their low energy efficiency. Recently, various interface circuits have been reported [1-5] to improve power efficiency, such as the SSHI (Synchronized Switch Harvesting on Inductor) rectifier. However, most of these reported circuits require large inductors to achieve good performance, and these inductors significantly increase the system volume, counter to the requirement for system miniaturization. Although a flipping-capacitor rectifier was proposed in [2] to flip voltages using on-chip capacitors, it was designed for high frequency (>100kHz) ultrasonic energy transfer applications and does not work with PTs with a large internal capacitor CP since the values of the capacitors required are too large for on-chip implementation. Another inductorless circuit, named SSHC (synchronized switch harvesting on capacitors), was recently proposed in [1] (Fig. 8.9.1); however, the required switched-capacitor (SC) values must equal CP to achieve optimal performance and this limits the on-chip implementation for PTs with large CP capacitance.