Piezoelectric Energy-Harvesting Interface Using Split-Phase Flipping-Capacitor Rectifier With Capacitor Reuse for Input Power Adaptation

• Published in: IEEE journal of solid-state circuits 2020-08, Vol.55 (8), p.2106-2117
• Main Authors: Chen, Zhiyuan, Law, Man-Kay, Mak, Pui-In, Zeng, Xiaoyang, Martins, Rui P.
• Format: Article
• Language: English
• Subjects: Adaptation; Capacitor reuse; Capacitors; CMOS; Complexity theory; Converters; Energy conversion efficiency; Energy harvesting; Inductors; Interfaces; maximum output power improving rate (MOPIR); Maximum power tracking; multiple-voltage-conversion ratio (MVCR); Open circuit voltage; Phases; piezoelectric energy harvesting (PEH); Piezoelectricity; Rectifiers; split-phase flipping-capacitor rectifier (SPFCR); switched-capacitor dc-dc converter; Switches; Switching circuits; Very large scale integration; Voltage control
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2020.2989873

This article proposes a split-phase flipping-capacitor rectifier (SPFCR) to resolve the hard tradeoff between the number of capacitors and the energy-extraction efficiency for capacitive piezoelectric energy-harvesting (PEH) interfaces. By splitting the capacitor usage into multiple phases, this article can achieve the most number of flipping phases using the same number of capacitors when compared with the state of the art. We also relaxed the implementation complexity by removing insignificant SFPCR flipping phases without sacrificing the energy-harvesting efficiency. To improve further the input power adaptation, the flipping capacitors are reconfigured as a multiple-voltage-conversion-ratio (MVCR) switched-capacitor dc-dc converter during the non-flipping period without using extra passives. Maximum-power-point tracking (MPPT) is also accomplished using the full-bridge rectifier (FBR) fractional open-circuit voltage ( V_{{\text {OC}, \text {FBR}}} ) to relax the voltage-tolerance requirements. Fabricated in 0.18- \mu \text{m} CMOS, the proposed 21-phase SPFCR PEH interface demonstrates a measured maximum output power improving rate (MOPIR) of up to 9.3 \times with V_{D}= 0.12 V (6.5 \times with V_{D}= 0 V) when compared with the conventional FBR interface over an equivalent FBR input power range ( P_{{\text {in, FBR}}} ) from 0.15 to 5.57 \mu \text{W} .