Abstract
Triboelectric nanogenerator (TENG), a class of mechanical to electrical energy transducers, has emerged as a promising solution to self-power Internet of Things (IoT) sensors, wearable electronics, etc. The use of synchronous switched energy extraction circuits (EECs) as an interface between TENG and battery load can deliver multi-fold energy gain over simple-minded Full Wave Rectification (FWR). This paper presents a detailed analysis of Parallel and Series Synchronous Switched Harvesting on Inductor (P-SSHI and S-SSHI) EECs to derive the energy delivered to the battery load and compare it with the standard FWR (a 3rd circuit) in a common analytical framework, under both realistic conditions, and also ideal conditions. Further, the optimal value of battery load to maximize output and upper bound beyond which charging is not feasible are derived for all the three considered circuits. These closed-form results derived with general TENG electrical parameters and first-order circuit non-idealities shed light on the physics of the modeling and guide the choice and design of EECs for any given TENG. The derived analytical results are verified against PSpice based simulation results as well as the experimentally measured values. In our experiments, P-SSHI and S-SSHI circuits are found to provide 1.18 and 8.59 fold per-cycle energy gain over the standard FWR circuit at 15 V battery load, respectively.
Highlights
One of the major challenges faced by today’s ever-expanding field of mobile electronics, Internet of Things (IoT), implantables, and wearable electronics is limited onboard battery lifetime
Our work provides the analytical models for PARALLEL SYNCHRONOUS SWITCHED HARVESTING ON INDUCTOR (P-SSHI) and Synchronous Switched Harvesting on Inductor (S-SSHI) circuits to help guide the energy extraction circuits (EECs) design, such as determining optimal load voltage to maximize energy extraction. [33] designed the P-SSHI circuit for a Triboelectric nanogenerator (TENG) paired with a parallel capacitor that provides an additional degree of controlling the variation between max to min capacitance ratio
The commercial inductor used in the Parallel Synchronous Switched Harvesting on Inductor (PSSHI)/S-SSHI circuit was modeled as a series L-RL for simulation with frequency-dependent inductance and resistance values obtained experimentally using the LCR meter at the respective L-CT resonance frequencies of States I and II: ωdI and ωdII
Summary
One of the major challenges faced by today’s ever-expanding field of mobile electronics, Internet of Things (IoT), implantables, and wearable electronics is limited onboard battery lifetime. Our work provides the analytical models for P-SSHI and S-SSHI circuits to help guide the EEC design, such as determining optimal load voltage to maximize energy extraction. Our work studies both the SSHI circuits for varying battery loads commonly encountered in the practical IoT applications; uses convenient automated electronic switches for physical implementation, and demonstrates the desired match between the experimental, simulated, and the derived analytical Ecycle results. The analytical derivations include the computation of the optimal value of the battery load to maximize output and upper bound beyond which the charging becomes infeasible, providing additional insights into the 3 EECs. Our analytical derivations and experimental verification are provided for the most generalized case: ‘‘ContactSeparation’’ mode TENGs, in which the internal capacitance varies with time so that the ratio of maximum to minimum TENG capacitances β ≥ 1. The diode’s on-state voltage drop (VD) is the third analytically modeled non-ideality in our setup
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