The Design Of A Piezoelectric Energy Harvesting System With Wide Input Range

In the application of ultra-micro vibration energy harvesting, the output voltage of piezoelectric transducer ranges from tens of millivolt to hundreds of millivolt. In order to capture all kinds of vibration energy in the environment as much as possible, firstly, the energy harvesting system should have a power extracting circuit to make sure that more energy harvested by transducer can be delivered to the input terminal of rectifier; secondly, the rectifier should have the properties of low input voltage threshold, wide input range and high conversion efficiency; finally, the output power of piezoelectric transducer ranges from tens of microwatt to hundreds of microwatt, the energy varies with environment and cannot continuous power DCDC converter load, so a energy management unit which can manage the harvested energy should be attached to the rectifier.Based on the abovementioned factors, a highly efficient piezoelectric energy harvesting system with wide input range is proposed in this paper, which consists of a highly efficient power extracting circuit with synchronous switch, an active charge pump rectifier and a intermittent energy management circuit. The proposed power extracting circuit has two synchronous switches, therefore simplify the circuit structure of switch control signal. the rectifier adopts two stage charge pump structure to obtain a high output DC voltage; and the adoption of active diode based on unbalanced biased comparator reduce voltage drop along rectify path, and solve the reverse leakage current problem occurred in conventional active diode; two low power consumption common-gate comparators reduce the input voltage threshold. Energy management circuit collects the harvested energy and delivers it to the following DCDC converter when the harvested energy can power the DCDC converter, the intermittent operation model can ensure the rectify system provide a proper power to DCDC converter.The model of piezoelectric transducer is firstly introduced in this paper, and several rectifiers are represented in the following. Then the operation states of the proposed charge pump rectifier are described. The design of proposed energy harvesting system is described in chapter 3. Based on SMIC 0.18?m standard CMOS technology, the proposed circuits are simulated and verified.The simulation results show that this system can rectify AC signal whose frequency ranges from 20Hz-3k Hz, amplitude ranges from 0.32V-1.5V. The DC output voltage range is 0.8V-1.2V. the max output current can reach 5.5m A. The power efficiency is more than 70%, and the peak efficiency is 81% when the input amplitude is 0.8V and input frequency is 200 Hz.