A Highly Efficient Integrated Piezoelectric Energy Harvesting Circuit With Wide Input Frequency Range

With the development of science and technology and the increase of people's living standards,demanding for wearable smart devices and micro portable electronic devices are more and more high,efficient energy harvesting and management are the foundation that the equipments can be widely used.Energy of the natural is expected to become an important source of energy for small portable electronic devices and wearable smart devices.The vibration energy has become a hot spot and focus on the field of energy harvesting because of its universality and high energy density.In order to improve the vibration energy,harvesting efficiency and conversion efficiency,it is key that the highly efficient vibration energy harvesting system with wide frequency input signal.Due to the parasitic capacitor and the parasitic resistance in the piezoelectric sensor model,it can cause the problem of low energy harvesting efficiency.As a traditional full bridge rectifier,the current source will change the direction from positive to negative or from negative to positive every half period.When the current source direction changes,it will firstly release the electric charges which have been charged into the parasitic resistance in the previous cycle,and then reversely charge.Because the diode threshold is very high,the charges of the parasitic capacitor will be discharged to the next part of circuit only once they reach a certain amount,which results in a large amount of charges wasted.The simple enhance of the efficiency of the rectifier conversion is not enough.Therefore,the high conversion efficiency and the improvement of energy harvesting efficiency need to be satisfied at the same time.Because of different energy sources having different energy frequency,to obtain a wide range frequency energy sources is an important aspect of obtaining more energy.Based on the above considerations,this paper presents a wide input high efficiency energy harvesting circuit for piezoelectric applications.This circuit consists of the wide efficient energy harvesting circuit,the intermittent energy management circuit based on the switched capacitor,the off-chip capacitor LDO with ultra-low quiescent current.In this paper,the rectifier using P-SSHI technology to improve the efficiency of the rectifier power extracting power from the piezoelectric sensor.The use of active diodes instead of the traditional diode reduces the conduction voltage drop,which improves the efficiency of rectifier conversion.The voltage across the piezoelectric sensor is used to control the closing time of switches in the P-SSHI branches.By using a zero-current input comparator to improve the non-ideal effect of the comparator and therefore decrease the comparative leakage problem,and the input frequency is improved by improving the comparator performance.P-SSHI rectifiers achieve the circuit's self-powered by themselves without the need for additional power.The energy management circuit uses the switching capacitor to collect the energy outputted from the rectifier.When this energy reaches a certain volume,it will be transported to supplies the next stage of the LDO circuit,and it will use the intermittent working way to ensure the stable output to the post-stage circuit of the whole system.The capacitorless LDO circuit can switch between bipolar and tertiary cascade structures according to the load size.It satisfies extremely low power consumption,high stability,and good transient response.Based on the application background of wireless body network,a highly efficient piezoelectric energy harvesting circuit is proposed to improve the frequency range of the captured input signal.The high efficiency energy harvesting rectifier circuit based on synchronous switching inductance circuit is presented.The design is based on high speed and low power amplifier to broaden the frequency range of the input signal.Based on selfpowered technology,the wide frequency input signal and high energy conversion efficiency rectifier circuit have been reasonable compromised.Finally,the paper layout is fabricated in SMIC 0.18?m standard CMOS process;the proposed rectifi ers were simulated using Spectre software.The overall layout area is 1.1mm×1.1mm and the core part of the area is only 0.39mm×0.31 mm.The simulation results show that the designed rectifier can operate at a high voltage flip efficiency and work at the input signal frequency of 20Hz-5KHz.In particular,at an input frequency of 225 Hz,the voltage flip efficiency is over 80%,and the power obtained is 4.5 times than that of the full bridge rectifier under the same conditions.The bandgap reference circuit and off-chip capacitorless LDO are both achieved low power consumption.The entire circuit intermittently operates at 1.8V.The PCE of the whole circuit reaches about 80%.