Research On Power Management Circuit Of Electromagnetic Vibration Energy Harvesters

The vibration energy harvester,converting the ambient vibration energy into electric energy,has the advantages of long life and non-pollution,and is an ideal power source for the wireless sensor node.However,since the output of the vibration energy harvester is low-powered alternating current,it is difficult to directly supply power to the wireless sensor node.Therefore,it is of great significance to carry out the research of efficient power management circuit.According to characteristics of electromagnetic vibration energy harvester developed by the research group in the early stage,this paper proposes a completely autonomous power management circuit scheme,and establishes the interface circuit model of the harvester,and completes the design of each module circuit.Through the simulation and experiment,the components were selected.The power management circuit was designed and fabricated.The performance of the circuit was tested.The harvester and designed circuit fully driven a medium-distance wireless temperature and humidity sensor node.The main work of the thesis is as follows:(1)Analyze the research status of electromagnetic vibration energy harvester and power management circuit at home and abroad,and clarify the applicable objects of different circuit structures,which provides ideas for designing power management circuit.(2)The impact-based electromagnetic vibration energy harvester was developed in our previous work.Based on the analysis of the structure and electrical output characteristics of the harvester,the overall design scheme of power management circuit,completely autonomous,was determined.Two sets of coils were,respectively,used to power the energy storage branch and the switch control branch.It achieves the purpose of self-powered supply.Impedance matching is performed by DC-DC converter,which improves the charging power of the harvesting system to the capacitor;(3)Based on the nonlinear model of electromagnetic vibration energy harvester,the nonlinear interface circuit model of the harvester is constructed.The numerical simulation is carried out by using MATLAB.The output performance is analyzed,under different excitation conditions.It provides a theoretical basis for the design of subsequent circuits.(4)The function and implementation of each circuit module was analyzed in detail.The macro model of device was selected.The function of each module was verified by the circuit simulation software(LTspice/Pspice).Complete the selection of circuit components and design the printed circuit board;(5)If the same electromagnetic vibration energy harvester prototype is used to drive a medium-distance wireless temperature and humidity sensor node.Experiments show that,when the frequency and acceleration of the base excitation are 8Hz and 0.3g,the charging power of the two-stage power conditioning circuit is 4.8mW,and the efficiency is 41.7%.Compared to the standard energy harvesting circuit,the charging efficiency of the two-stage power conditioning circuit is increased by 172% and 28%,respectively,at 0.3g and 0.4g acceleration.When the two circuits supply power to the node,the waiting time for the intermittent operation of the node is 66 s and 32 s,respectively,and the waiting time of the latter is reduced by 51%.