Research And Realization Of Electric Field Energy Harvesting Power Supply For Low Voltage Power Line

With the rapid development of wireless sensor networks,various wireless sensor nodes powered by batteries will consume a lot of energy and cannot operate stably for a long time.The emergence of energy harvesting technology and ultra-low-power chip devices provides a self-powered solution for low-power nodes.Under certain conditions,a new type of power supply that harvests environmental energy and converts it into applicable electrical energy can make low-power wireless nodes work indefinitely.Among them,the power line electric field energy is one of the very stable and reliable environmental energy.In this thesis,according to the theory of displacement current and analysis of the internal capacitance of the electric field energy harvester(EFEH),the equivalent circuit model of the collector is established.A double-layer copper foil plus ground structure is proposed to reduce the internal capacitive of EFEH and increase the charging power of the energy storage capacitor.Then,combined with the power consumption analysis of the device,the corresponding rectifier circuit,switch circuit and output voltage regulator circuit are designed to realize the reasonable and efficient storage and application of the collected energy.Finally,an ultra-low-power wireless temperature sensing node was developed and used to verify the practical performance of electric field energy harvesting power supplies(EFEHPS).The main work of this thesis is as follows:1)According to the displacement current theory,the equivalent circuit model of the EFEH is established in the space loop.Theoretically analyze the main capacitance calculation method of the EFEH,and derived that the conversion conductor film is proportional to the capacitance of the conductive core.The capacitance of the induction plate to ground is positively related to the size of the induction plate and negatively related to the distance from the ground.2)In order to optimize the structure of the EFEH,Maxwell was used to simulate and analyze the structure of the EFEH.An equivalent simulation model is established on the two-dimensional plane,and the voltage,displacement current density and average power density of the central position of the storage capacitor are used as the evaluation criteria.By comparison,it is found that the conductor film plus the induction plate structure is superior to the parallel plate capacitor structure.Further research found that the average power density of the center of the simulated energy storage capacitor can reach 84.59 u W/m2 when connected to the ground.The double-layer conductor film plus the structure of the ground connection can increase the average power density to 137 u W/m2.3)In order to realize the storage,management and application of weak energy,combined with the power consumption analysis of the components,a switching circuit without auxiliary power supply and an efficient 3.3V regulated output circuit are designed.In the end,the energy of 2.47 m J was obtained in 280 s.During the cycle of charging and discharging,the charging power was 8.8u W and the energy utilization efficiency was 60.9%.4)An ultra-low power wireless temperature sensing node was developed to test the actual performance of EFEHPS.The energy consumption of the node running once is reduced to 0.663 m J.The EFEHPS and nodes are used to observe the 24-hour temperature change of the indoor environment.The test results show that the wireless temperature sensor node powered by the EFEHPS works normally.