# An Adaptable Interface Conditioning Circuit Based on Triboelectric Nanogenerators for Self-Powered Sensors

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## Abstract

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## 1. Introduction

^{2}and their volume energy density has reached 490 kW/m

^{3}[8]. When compared with other energy generators, the TENG has high efficiency, low fabrication cost, and high output voltage. These advantages make TENG more suitable for self-powered wireless sensors and the wearable devices. Some studies of TENG have shown that charging efficiency decays quickly after several charging cycles, the maximum voltage of the energy storage device is much smaller than the open-circuit voltage of the TENG, regardless of the energy conversion efficiency of the TENG [9]. Also, the TENG has poor load capacity because of its high output impedance. In order to convert the output voltage of the TENG to a stable DC voltage and increase the energy-storage efficiency, an interface conditioning circuit is essential. Some studies have shown that the DC-DC circuit is effective in working as a conditioning circuit that can stabilize the output voltage successfully [10,11]. However, maximizing the power extraction from TENG is still unresolved, so impendence matching is a major consideration in circuit design and also it is the most efficient way to increase the output power. The fully-integrated self-powered wireless sensor node contains TENGs, which is an interface conditioning circuit, energy storage elements, and load circuits (wireless sensor node).

## 2. Modeling of TENG

_{0}represents the maximum energy value that a single charge cycle can provide determined by the power supply, ${P}_{avr}\left({C}_{L}\right)$ indicates average $P\left({C}_{L}\right)$ in one cycle, so the parameter $\mathsf{\alpha}\left({P}_{avr}\right)$ is used to characterize the average charge efficiency. As shown in Figure 2e,f, for a certain n, $\mathsf{\alpha}\left({P}_{avr}\right)$ gets the maximum value corresponding to an optimal value of β, and for a certain β, $\mathsf{\alpha}\left({P}_{avr}\right)$ gets the maximum value corresponding to an optimal value of n. Consider the following two points: (a) capacitor leakage or capacitance capacity is limited; (b) charging time is limited. So, according to the limitations of the actual application, select the optimal n and β.

## 3. Results and Discussion

## 4. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

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**Figure 1.**(

**a**) Structure diagram of a Tribo-electric-Nano-generator (TENG). (

**b**) Output voltage waveform of TENG in one working cycle without any load. (

**c**) Open-circuit voltage of TENG. (

**d**) Equivalent SPICE model of TENG. (

**e**) Load voltage curve while the capacitor ranging from 22 pF to 10 μF is loaded. (

**f**) Load voltage curve while the resistor ranging from 0.1 kΩ to 9.1 MΩ is loaded.

**Figure 2.**(

**a**) Impedance matching circuit using coupling inductance. (

**b**)

**i**: Equivalent primary circuit of the coupling inductance;

**ii**: The equivalent secondary circuit of the coupling inductance;

**iii**: Charge a capacitor via a rectifier bridge. (

**c**) Voltage curves of the ${C}_{L}$ and ${C}_{s}$ when ${C}_{L}/{C}_{s}$ changes from 1 to 10. (

**d**) Power curves of the ${C}_{L}$ and ${C}_{s}$ when ${C}_{L}/{C}_{s}$ changes from 1 to 10. (

**e**) Average charge efficiency diagram (β ranges from 0 to 1000). (

**f**) Average charge efficiency diagram (β ranges from 1000 to 8000).

**Figure 3.**(

**a**) Voltage simulation curves of the secondary inductance (Vsec), primary inductance (Vpri), the oscillator (Vosc). (

**b**) Simulation curve of charging process. (

**c**) Experiment curve of charging process. (

**d**) Comparison to charge a capacitor via a rectifier bridge and conditioning circuit. (

**e**) Maximum voltage of the storage capacitor and the required time. (

**f**) When resistive load is connected, load voltage and output voltage of the primary inductance.

**Figure 4.**(

**a**) An environmental energy harvesting system based on TENG. (

**b**) The interface conditioning circuit for TENG. (

**c**) Physical picture of the interface conditioning circuit. (

**d**) An application of the environmental energy harvesting system based on TENG and the interface conditioning circuit.

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## Share and Cite

**MDPI and ACS Style**

Hu, Y.; Yue, Q.; Lu, S.; Yang, D.; Shi, S.; Zhang, X.; Yu, H.
An Adaptable Interface Conditioning Circuit Based on Triboelectric Nanogenerators for Self-Powered Sensors. *Micromachines* **2018**, *9*, 105.
https://doi.org/10.3390/mi9030105

**AMA Style**

Hu Y, Yue Q, Lu S, Yang D, Shi S, Zhang X, Yu H.
An Adaptable Interface Conditioning Circuit Based on Triboelectric Nanogenerators for Self-Powered Sensors. *Micromachines*. 2018; 9(3):105.
https://doi.org/10.3390/mi9030105

**Chicago/Turabian Style**

Hu, Yongshan, Qiuqin Yue, Shan Lu, Dongchen Yang, Shuxin Shi, Xiaokun Zhang, and Hua Yu.
2018. "An Adaptable Interface Conditioning Circuit Based on Triboelectric Nanogenerators for Self-Powered Sensors" *Micromachines* 9, no. 3: 105.
https://doi.org/10.3390/mi9030105