Research On Energy Acquisition And Optimization Of Wire Magnetic Field And Power Management Circuit

With the development of Nano technology,a variety of low-consumed electronic components have emerged successively.In the field of wireless sensor network,various wireless sensor nodes are developed to apply energy harvesting technology to wireless sensor networks,thus the energy harvesting power supply can be provided continuously to the low-power nodes to realize the autonomous operation.In this thesis,according to the law of electromagnetic induction,the model of the energy-obtaining coil is established.A double-ring magnetic core structure is proposed to optimize the magnetic circuit and improve the equivalent magnetic permeability of the magnetic core,and new magnetic field energy harvester is designed.Through series matching capacitor,a larger acquisition power is achieved.The energy storage method combining the super capacitor and the lithium battery is used to reasonably store and release the electric energy by designing the power management circuit.The main work of this thesis includes:Firstly,according to the electromagnetic theory analysis,the model of the energy coil is established.The relationship between the output voltage of the energy coil and the parameters of the magnetic core is deduced.The output voltage of the energy coil can be increased by increasing the current of the wire,the equivalent relative permeability of the magnetic core,the area of the magnetic core and the number of turns of the energy coil,or reducing the inner diameter of the magnetic core.Secondly,considering the practicability,the core needs to be designed as an open mode,but this design will bring about larger magnetic leakage.This thesis uses the electromagnetic field simulation software Ansoft Maxwell to simulate and analyze the core,and the influence of air gap on the magnetic induction strength,equivalent permeability and magnetic resistance of the core is mainly studied.A double-ring magnetic core structure is proposed,which reduces the magnetic resistance of the magnetic circuit and improves the equivalent magnetic permeability of the magnetic core without changing the cross-sectional area of the magnetic core.Through test and analysis,it is proved that the double toroidal core structure proposed in this paper can effectively reduce the magnetic leakage caused by the air gap,When the wire current is 5A,the average magnetic induction intensity reaches 78.6mT,when the wire current is 10 A,the output power of the energy take-up coil is increased by 53%.Furthermore,in order to reduce the dead zone of energy supply,this thesis adopts the energy storage mode combining supercapacitor and lithium battery,and designs the power management circuit to make the circuit charge and discharge orderly.According to the output characteristics of the energy-obtaining coil,capacitance matching is performed to resonate the circuit,Further Improve the Collection Efficiency of Energy Source.The experimental results show that when the wire current is 10 A,after the capacitor is matched,the acquisition efficiency is 2.23 times higher than that of unmatched capacitors,and the charging time of the supercapacitor from 0 to 4.5 Volt is reduced by 50%.Finally,in order to meet the requirements of low power consumption,the main control,RF,and sensor were selected and the sleep program was designed.Then,the designed wireless sensor node was used to test the performance of the power supply.The experimental results show that the wireless sensor node powered by the energyharvesting power supply works well.