Research And Design Of Piezoelectric Energy Harvesting Circuit Based On Synchronous Switch Harvesting On Capacitors

With the rapid development of wireless sensor networks,a series of low-power implantable or wearable devices have appeared on the market.The size and life of traditional batteries have become a major bottleneck in extending the life of devices.Therefore,people are considering adopting transducers to achieve the collection of external energy.Energy harvesting technology can use the external natural energy to convert it into electrical energy for continuous power supply.Among many external energy sources,vibration energy has the advantages of high energy density and wide range of sources.Therefore,this paper chooses to use piezoelectric transducers to achieve vibration energy harvesting.Piezoelectric transducers can use vibration to generate AC signals through piezoelectric effect.Based on the research of the cantilever piezoelectric vibration energy harvesting interface controlled circuit,this paper proposes a cold-start piezoelectric energy harvesting system with synchronous switch harvesting on capacitors to efficiently improve energy conversion efficiency,and uses the converted energy to power the entire system,which has two working situations before and after the synchronous switch harvesting on capacitors interface controlled circuit.The paper mainly works from the following aspects:?1?Firstly,the academic research of domestic and foreign scholars was investigated,the advantages and disadvantages of different piezoelectric energy harvesting interface controlled circuits and the design improvements were introduced in detail.Then the fundamental of piezoelectric transducer is introduced,and the corresponding piezoelectric effects and equations are analyzed.The physical structure and electrical structure of the cantilever piezoelectric transducer are proposed.This paper focuses on analyzing the working process of traditional full-bridge rectifier,synchronous electrical charge extraction circuit,series-synchronous switch harvesting on inductor circuit,parallel-synchronous switch harvesting on inductor circuit,and synchronous switch harvesting on capacitors circuit,and derives the output voltages and output power respectively and compares them.?2?This paper proposes and designs an synchronous switch harvesting on capacitors cold-start piezoelectric energy harvesting system,to achieve self-power supply in the system without external voltage.The whole system mainly includes active AC-DC rectifier,high-voltage module,controlled module and cold-start module.The circuit diagram of each module is described in detail and its working principle is analyzed.The internal power supply of the entire system is provided by the output energy storage capacitor.When V_DDdoes not reach the working voltage,the interface controlled circuit does not work,and the system works as a full-bridge rectifier.The cold-start circuit is turned on to increase the open circuit voltage.When V_DDreaches,each module of the interface controlled circuit is started,which greatly improves the energy conversion efficiency,and the cold-start circuit is closed.?3?Appropriate system circuit parameters were set according to the theoretical model with Cadence's Spectre.This paper performs functional simulation for each module,and the waveform diagram of the system's flipping efficiency was obtained.Compared with other interface controlled circuits,synchronous switch harvesting on capacitors cold-start piezoelectric energy harvesting circuit can reduce the design area while increasing the flipping efficiency.The simulation results show that the flipping efficiency of voltage V_PThas reached 66.36%.The output power ratio reaches 5.5 times under the open-circuit voltage of 4.5V,much higher than that using inductive rectification technology,and the function of cold-start self-power supply can be realized.