具機械波無線充電功能之超音波換能器能量採集電路設計與實作

Abstract

本論文提出一個超音波換能器能量採集介面電路，此電路適用於機械波無線電能傳輸系統的接收端。超音波換能器由壓電材料組成，利用壓電效應使電能與機械能互相轉換。不過受限於壓電材料的電學特性，傳統能量採集方法效率不佳，且效率受負載端影響。 本論文利用同步擷取電荷方法，設計一個能量採集介面電路與控制電路。此電路開關的時刻與超音波換能器電壓振盪峰值同步，每一次開關的動作，可以擷取所有接收端超音波換能器內的能量。控制電路偵測超音波換能器的電壓訊號，並且控制同步擷取電荷電路開關的時刻。理論分析使用同步擷取電荷方法採集效率是傳統方法最大採集效率的四倍。最後實驗結果顯示，使用同步擷取電荷方法最大採集效率約是傳統方法最大採集效率的兩倍。

This thesis presents an ultrasonic transducer energy harvester interface circuit. This circuit can apply to the receiver of wireless power transmitter system with mechanical wave. The ultrasonic transducer is made of piezoelectric material, which can convert between electrical and mechanical energy. However, the performance of conventional energy harvesters are limited by the electrical characteristic of the piezoelectric, which leads to low efficiency. In addition, the harvested power of it will be affected by the load variation. This thesis utilizes the synchronized electrical charge extraction technique to design and implement an energy harvester interface circuit. The switching of the circuit is synchronous with the peak of the vibration from the ultrasonic transducer. Once the switching is closed, the circuit extracts the energy stored in the ultrasonic transducer. The control circuit detects the voltage of the ultrasonic transducer and controls the instance and duration of the switching. The synchronized electrical charge extraction method increases the harvested power of by 400% in theoretical analysis. Finally, the experiment result shows that the synchronized electrical charge extraction method increases the harvested power by 200%.