The Study Of Self-powered System Based On Electret Nanogenerator

With the fast development of sensor technology,integrated circuit technology and communication technology,‘Internet of Things’(Io T)and wearable electronics have become the hotspots of research currently.However,there are certain limitations in supplying through traditional energy storage devices(batteries and capacitors,etc.),which restricts the development of Io T and wearable devices.At present,harvesting environmental or human-motion energy to power wearable devices or Io T nodes for sustainable operation has become one of the effective methods to solve the power problem.As a new type of electromechanical transducer,electret nanogenerators have the advantages of strong flexibility,simple packaging,low cost and light weight,and is widely used in the collection of environmental energy.Therefore,in the development and popularization of the Io T,electret nanogenerators are expected to be used to develop self-powered systems to replace traditional power supply methods.However,in order to embed electret nanogenerators into electronic system for practical applications,there are two problems need to be solved:(1)The traditional contact-separation mode electret nanogenerator has poor compactness,low space utilization rate,and energy conversion rate needs to be improved.(2)Electret nanogenerators usually have high output peak voltages and low peak currents,which cannot directly drive electronic devices,and needs to be converted by an energy management circuit.In order to solve the above problems,a new type of dielectric multilayered electret nanogenerator is designed in this thesis,which remarkably enhance the output charge density of the nanogenerator.Then,we design a self-powered system based on the electret nanogenerator,which achieves higher energy collection efficiency and can drive electronic devices.The main research contents are as follows:1.A new type of high-performance dielectric multilayered electret nanogenerator is designed.By embedding a dielectric film(polyvinylidene fluoride)with high permittivity into air gaps,the output charge density of the nanogenerator can be improved effectively.At the same time,in order to solve the problems of low output and unstable performance of single-layer devices,an innovative electret nanogenerator design was demonstrated,which can realize the enhancement of output power while the area is kept constant by manufacturing a multi-layer unit on a single flexible substrate.After testing,the output charge density of the electret nanogenerator at a frequency of 2 Hz and an excitation force of 10 N can reach 468μC/m~2.Moreover,the output performance of this device does not show significant reduction after 8000 cycles of testing.2.The output characteristics of the electret nanogenerator is studied through simulation software.We discuss the governing equation of the electret nanogenerator and establish the equivalent circuit model to analyze the output electrical characteristics and cycles for energy output of the electret nanogenerator in this section.Finally,two power management strategies are compared and analyzed.3.An innovative and efficient self-powered power management circuit based on the electret nanogenerator is proposed,which is able to power wireless sensor nodes without any additional power.This solution is based on a‘two-path’approach,the electret nanogenerator first charges the small capacitor C_s through path-1 to supply the power for path-2.The power management circuit in path-2 effectively transmits the energy of the electret nanogenerator to capacitor C_b.By the startup control circuit,the two paths can be switched on/off in different states.The test result shows that the power conversion efficiency of the circuit from alternating current(AC)to direct current(DC)exceeds 68%,and the stored energy is increased by 1800 times compared with the standard circuit.Finally,a self-powered energy system is proposed,which consists of a dielectric multilayered electret nanogenerator,a power management circuit,and a‘Bluetooth Low Energy’(BLE)device.This work provides a general power management strategy for electret nanogenerators,undoubtedly improves the practical value of electret nanogenerators and lays a good foundation for their further application.