Research On High Efficiency Power Capture And Management Circuit For Piezoelectric Energy Harvester

With the rapid development of the wireless sensor network,the power supply requirements for the wireless sensor nodes constituting the network are getting higher and higher.The traditional power supply method is to use equipment such as batteries for power supply,but it requires manual maintenance and replacement,which increases the cost and also brings environmental pollution.Using piezoelectric energy harvesters to convert vibration energy in the environment into electrical energy is an effective way to solve the problem of self-powering of wireless sensor nodes.The output of the piezoelectric energy harvester is alternating current,which cannot directly supply power to the load,so it is necessary to design a corresponding power capture and management circuit.On the basis of analyzing the output characteristics of different types of piezoelectric energy harvesters,this paper designs two power capture and management circuits.The first power capture and management circuit uses a full-wave rectifier circuit to achieve energy capture,including a rectifier bridge,a full CMOS structure reference source,and a power management circuit.The rectifier bridge adopts the PMOS cross-coupling structure to greatly reduce the conduction voltage drop,the full CMOS reference source provides the reference voltage and reference current for the circuit,the power management circuit provides the load with a 1.8V stable voltage and controls the load to work intermittently.The circuit is taped out using HHGrace 110nm CMOS process,the layout area is 0.6mm2,and the chip is packaged in the form of QFN32.Under the vibration conditions of 40Hz frequency and 4g acceleration amplitude,the measured energy extraction power of the chip is 234μW,the load works once every 3s,and the power supply voltage is 1.8V when the load is working.Although the full-wave rectification power capture circuit has a simple structure and is easy to implement,the maximum power extraction cannot be achieved in capturing the output power of the piezoelectric energy harvester with a two-stage vibration structure.Therefore,a synchronous electric charge extraction circuit is used in the second power capture and management circuit to achieve power capture,including cold start,peak detection,comparator multiplexing,and gate drive circuit modules.Among them,the comparator multiplexing circuit uses only one comparator to complete the switching of multiple working states such as circuit vibration detection,zero-crossing detection,and reverse current detection,which effectively reduces circuit power consumption and layout area.The circuit adopts HHGrace 110nm CMOS process for design,and the layout area is 0.75mm2.Under the simulation conditions of constant-type and shock-type vibration excitation,it is found that the energy extraction power of the synchronous electric charge extraction circuit is 3.01 times and 4.57 times that of the full-wave rectifier circuit,respectively,which effectively improves the energy extraction power.