Design Of Multi-input Piezoelectric Vibration Energy Harvesting Circuits

With the rapid development of the Internet of Things in recent years,wireless sensor network are widely used in environmental monitoring,wearable smart devices,security monitoring and other fields.Traditional wireless sensor network nodes use battery power supply,and the battery will have shortcomings such as limited life,easy to cause environmental pollution and high replacement cost.Therefore energy harvesting from environment is becoming an efficient solution to provide power supply for the sensor network nodes.Light energy,thermal energy,vibration energy and electromagnetic energy are four main ambient energy sources.Among them,piezoelectric vibration energy has attracted extensive research interest due to its large energy density and extensive advantages.In this thesis,by analyzing the AC characteristics,energy transmission characteristics of the piezoelectric element,and the main factors affecting system efficiency,a self-powered synchronous charge extraction circuit is proposed.Using unpowered peak detector to realize the function of selfpower supply.However,the proposed circuit has the problem of switching phase delay,so the peak detection structure is employed,and a low phase delay synchronous charge extraction circuit is proposed to reduce the energy loss caused by the phase delay in the switch.Based on the theoretical analysis of the two circuits,simulation and experiments are performed.The experimental results show that the energy harvesting power of the LPD-SECE circuit is 3.10 times the maximum power of the standard energy harvesting circuit,which is 4% higher than the SP-SECE circuit.Because the energy captured by a single piezoelectric element is limited and the inductor is inactive during most of time in one cycle in a synchronous charge extraction circuit,high efficiency multi-piezoelectric capture based on synchronous charge extraction energy harvesting circuit based on synchronous charge extraction(EM-SECE)circuit is proposed.The proposed circuit is based on the LPD-SECE circuit structure.It contains multiple piezoelectric energy acquisition modules,in which each module contains an independent peak detection structure.It utilizes a single inductor’s asynchronous time-division multiplexing and synchronous inductor sharing to implement multiple vibration energy harvesting,and the theoretical analysis,simulation and experiment are performed.The experimental results show that under the same experimental conditions,the energy harvesting power of the single piezoelectric EM-SECE circuit is 3.10 times the maximum power of the standard energy capture circuit,and the energy harvesting power of the dual piezoelectric EM-SECE circuit is 0.97 times of the total energy of two single piezoelectric EM-SECE.