Research On Self-powered Synchronous Charge Extraction And Voltage Flip Circuit

With the development of energy conversion and microelectronics,it is possible to convert vibrations in the environment into electrical energy more effectively to supply power for lowpower wireless sensor nodes.Piezoelectric energy harvesting has the advantages of easy integration,easy miniaturization and immunity to electromagnetic interference,and is widely used in the field of vibration energy collection.In this thesis,an implementation scheme of synchronous charge extraction and voltage inversion circuit(SCEVI)is proposed.Firstly,according to the working principle of standard circuit,SECE circuit and SCEVI circuit,it is verified by Matlab that the SCEVI circuit gets the highest output power and the output power of SCEVI and SECE are independent of the load under constant displacement conditions.When the voltage flip coefficient is 0.5 and the Buck-Boost conversion efficiency is 0.65,the output power of the SCEVI circuit is about 1.3 times of the SECE and is about 3.3 times of the maximum output power of standard circuit.The characteristics of the three circuits under the condition of constant excitation force are verified.The standard circuit is suitable for strong coupling,and the SECE and SCEVI are suitable for energy collection under weak coupling or medium coupling.Then,since the vibrations in real life mostly meet the constant displacement conditions,based on the high efficiency of the SCEVI circuit and the characteristics of output power has nothing to do with the load,an implementation scheme of the self-powered SCEVI circuit is given and how to select components is discussed.The self-powered SCEVI circuit includes SCEVI interface circuit,switch control circuit and self-powered three modules.The on-time of the switch control circuit can be adjusted by the resistor,and the circuit can accurately detect the voltage peak of the piezoelectric element and conform to the switching control timing of the SCEVI.Self-powered modules are composed of full bridge rectifier circuit and half bridge rectifier circuit.The self-sufficient energy solution is achieved by collecting the energy generated by the second piezoelectric piece to supply power to the switch control circuit.After that,the feasibility of the designed SCEVI circuit is verified by LTspice simulation.Compared with standard circuit and SECE circuit(including passive SECE circuit and SECE circuit based on displacement detection),the output power of SCEVI circuit is about 4 times of the standard circuit,2.5 times of the self-powered SECE,and 1.4 times of the SECE circuit which is based on displacement detection.Finally,energy harvesting experimental device is built to verify the reliability of the SCEVI circuit designed in this paper and compare the output power of the three circuits.The output power of SCEVI circuit is 1.2 times of SECE circuit and 2.04 times of the standard circuit.The output power of the SECE and SCEVI circuits has little correlation with the load,and the SCEVI output power is greater than the SECE.