適用於壓電能量擷取系統的同步電荷擷取整流器與脈衝頻率調變直流降壓轉換器

Synchronous electric charge extraction rectifier and pulse frequency modulation buck convertor for piezoelectric energy harvesting system

謝宇傑(Yu-Chieh Hsieh)

指導教授 ： 吳文中

國立臺灣大學/工學院/工程科學及海洋工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201701995

摘要

隨著物聯網時代的來臨，人類身邊將會有無數個無線感測器，幫助人們掌控週遭環境的狀況。這些感測器的供電將是一項重要的議題，若使用電池供電，除了會使這些感測器的運作受限於電池壽命外，廢棄電池也可能對環境造成汙染。為了解決這些問題，我們可以將壓電元件安裝在如馬達、引擎等振動源周遭，以擷取環境中振動的能量，為這些感測器裝置供電。
壓電元件的輸出為交流形式，因此需要透過介面電路作適當的電能處理才能為負載供電。介面電路通常包含一個整流器與一個直流轉換器。整流器負責將元件輸出的能量整流並暫存至儲能電容中，直流轉換器負責將儲能電容中的能量轉換為穩定的直流電源。
本論文將針對不同整流介面電路進行分析、提出同步電壓反轉與電荷擷取整流架構(SICE)，並設計一個整流器晶片與一個直流降壓轉換器晶片。晶片皆使用台積電0.25 μm高壓CMOS製程製作。
整流器晶片使用同步電荷擷取整流架構(SECE)，做到提升系統輸出功率、使輸出功率與負載無關、能利用高電壓輸出之微型壓電元件組成自供電系統以及具有緩啟動功能等四個設計目標。根據模擬結果，本電路在使用電流振幅為30 μA、頻率120 Hz、寄生電容為6.7 nF之壓電元件做為輸入時，輸出功率可達53 μW。與標準界面電路相比，本整流器晶片提供261 %之輸出功率增益。
直流降壓轉換器晶片設計操作於電感電流不連續模式，並使用數位脈衝頻率調變控制，達到低控制功耗與高輕載效率的目標。根據量測結果，此轉換器在輸入電壓為5 V時的最高效率為82.8 %，而輕載(負載電流10 μA)時的效率大於75 %，輸出電壓在1.8 V至1.92 V間，可用來為感測器模組等負載供電。

關鍵字

物聯網 ； 壓電能量擷取 ； 同步電荷擷取整流器 ； 直流降壓轉換器

並列摘要

With the advent of “Internet of Things (IoT)”, there will be numerous wireless sensors around human kinds to help us monitor different status of the environment. Powering these wireless devices is an important issue. If the wireless sensors are powered by batteries, the reliability and performances of the device will be limited by battery lifetime. Furthermore, batteries can cause serious pollution if they are not recycled properly. To overcome these issues, piezoelectric energy harvesters can be installed around vibration sources to harvest energy from ambient vibrations and power IoT devices.
The output from a piezoelectric energy harvester is in alternating current (AC) form, and needs to be transformed into direct current (DC) form to supply electronic devices by an interface circuit. An interface circuit usually consists of a rectifier and a DC/DC convertor. The rectifier is used for rectifying the output from the harvester from AC to DC form and storing output energy into a buffer capacitor. The DC/DC convertor is used for converting the energy in the buffer capacitor into a stable DC power supply with proper voltage level to power electronic devices.
In this thesis, we analyze different kinds of rectifying interface circuit, propose a synchronous inversion and charge extraction (SICE) rectifier topology, and design a rectifier chip and a DC/DC buck convertor chip. Both chips are implemented in a TSMC 0.25 μm HV CMOS process.
The rectifier adopts synchronous electric charge extraction (SECE) technique to boost output power and being load independent. It can be powered solely by a piezoelectric harvester and has cold start-up function. According to simulation results, this chip has an output power of 53 μW when operating with a piezoelectric harvester with current amplitude 30 μA, operating frequency 120 Hz and internal static capacitance 6.7 nF. Compared to the standard interface circuit, this chip provides 261% output power gain.
The DC/DC buck convertor adopts digital pulse frequency modulation (PFM) control and operates in discontinued current mode (DCM) operation to achieve the design goals of low control power and good light load efficiency. According to the measurement results, this chip has a peak efficiency of 82.8 % with 5 V input voltage, and the light load (output current 10μA) efficiency is over 75 %. The chip has an output voltage of 1.8 V ~ 1.92 V, and can be used to power sensor modules and other IoT electronic devices required 1.8 V power supply.

並列關鍵字

Internet of Things ； Piezoelectric energy harvesting ； SECE ； Buck convertor

參考文獻

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