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Fully autonomous piezoelectric energy harvesting interface circuit utilizing low profile nonlinear switching technique

2020
Çiftci, Berkay
Energy scavenging from ambient vibration sources via piezoelectric transducers offers a promising solution to power microelectronic devices. Energy extraction from harvesters is conducted with full-bridge rectifiers (FBRs) whose performances are affected harshly due to intrinsic capacitance of harvester requiring continuous charging. Conventional nonlinear switchingtechniques proposed in literature overcome problems associated with standard AC/DC converters. Nonetheless, they require large external components to achieve decentconversion efficiencies and output powers. This obstructs miniaturization trend inmicro-fabricated wireless sensor networksand limits their application area. The aim of this work is to implement a low-profile autonomous interface circuit that can harvest energy from MEMS piezoelectric transducers and deliver power to electronic loads. In the first design, a unique low-cost fully autonomous interface circuit using novel SSHCItechnique is proposed to reduce overall system volume. New two-step voltage flipping with optimalflipping time detection enables Synchronized Switch Harvesting on Capacitor-Inductor (SSHCI) circuit to use inductors in the range of tens of ȝH¶s forvoltage flipping. Thisshrinks system volume significantly. Fabricated IC is able to attain 6.14x output power improvement over ideal FBRs and 90.1% power n the first design, a unique low-cost fully autonomous interface circuit using novel SSHCItechnique is proposed to reduce overall system volume. New two-step voltage flipping with optimalflipping time detection enables Synchronized Switch Harvesting on Capacitor-Inductor (SSHCI) circuit to use inductors in the range of tens of ȝH¶s forvoltage flipping. Thisshrinks system volume significantly. Fabricated IC is able to attain 6.14x output power improvement over ideal FBRs and 90.1% power conversion efficiency.Secondly, maximum power point tracking (MPPT) circuit integrated with SSHCI is implementedto eliminate load dependency. Inductor sharing between SSHCI and MPPT allows them to employ the same low-prolife inductorfor operation which decreases system cost.Occasional refreshment of optimum battery voltage sensing makes system invulnerable to input excitation changes of PEH. SSHCI-MPPT achieves 5.44x power extraction improvement and 83% efficiency while providing load independency.