Research On Power Management Circuit Of Low Power Piezoelectric Energy Harvester

With the development of sensing technology,the application of wireless sensor nodes is becoming more and more widespread.The use of piezoelectric energy harvesting systems to power wireless sensor nodes has received much attention.The micro-miniature piezoelectric energy harvester with a capacitive internal impedance normally works at a low frequency,thus has a weak output power.It is not possible to directly power wireless sensor nodes.For piezoelectric energy harvesters with an output power of only microwatts,by using a traditional power management circuit to transfer and store the piezoelectric energy,the current flowing into the rectifying and charging circuit is weak.The loss of the rectifier diode is large and the output power of the circuit is low at weak current.Therefore,it is necessary to design a power management circuit for a low-power piezoelectric energy harvester,which can efficiently store weak energy,then release it instantaneously,and drive a wireless sensor node.This paper presents an inductor energy storage power management circuit.The energy of the piezoelectric element is transferred and stored into the high-Q inductor by using the up-conversion impedance matching technology.The energy of the inductor is continuously accumulated and increased.When the energy of the inductor reaches the maximum,it is released into the rectifying and charging circuit by controlling the energy storage switch.The rectifying and charging circuit can obtain a higher charging current and reduce the conduction loss of the rectifier diode.This paper theoretically analyzes the process of energy storage of the inductor,the relationship between the energy storage current of the inductor and the average charging power of the circuit,and the influence of the distributed capacitance of the inductor on the average charging power.In this paper,a high-Q honeycomb inductor with a low distributed capacitance is produced.Compared with an ordinary winding inductor,the circuit using the honeycomb inductor can increase the charging power by 16.3%.At the input power of 1-10μW,the average charging power of the proposed circuit is increased by 15%-98% and 144%-367%,respectively,compared with the traditional up-conversion circuit and the standard rectifier circuit.Therefore,the inductor energy storage management circuit can efficiently store the weak energy produced by the piezoelectric energy harvester into the storage capacitor.In order to achieve efficient self-powered power management for piezoelectric energy harvesters,two self-powered management circuits are designed and analyzed in this paper.The first one is a self-powered power management circuit using a traditional linear regulated auxiliary power supply.The piezoelectric voltage is rectified and filtered into a dual-polarity power supply,providing a stable power voltage for the control module of the power management circuit.However,the power consumption of the power auxiliary circuit by the self-powered method is high.In order to reduce power consumption,another intermittent self-powered power management circuit is designed.The self-powered power supply circuit does not use filtering capacitors and directly provides pulsating DC power supply for the active devices.And the self-powered auxiliary circuit works at the peak point of the piezoelectric voltage.The working time of the auxiliary circuit can be greatly reduced,thereby the average power consumption of the self-powered auxiliary circuit can be effectively reduced.Compared with the first self-powered management circuit,the second self-powered management circuit can significantly reduce the power consumption of the auxiliary circuit and efficiently store more energy in the storage capacitor.Finally,this paper introduces the hardware design of the self-powered wireless sensor node system and tests the power supply of the wireless sensor node.The proposed power management circuit can drive the wireless sensor node.