低功率儲能系統之回授式升壓型轉換器設計與實現

Abstract

為了使微小能量能夠被有效收集，本文設計出以直流對直流轉換器為主架構的回授式儲能電路，主要是以數百μW到數mW等級的微小能量為收集目標，並使用超級電容當作能量儲存元件。所欲收集的能量源因為功率低，所以產生電壓也較小，因此直流對直流轉換器的部份是使用Boost Converter。系統使能量可以有效轉換的原理，是藉由將輸入電壓的分壓經過比較器後，在比較器輸出端產生Boost Converter上MOSFET的開關控制訊號來控制電路，使得不穩定的能量源電壓經過儲能電路後能夠穩定在固定電壓，進而提高儲能元件的儲存效率。

本文是以實現硬體電路的方式來完成儲能系統，電路設計初始條件是以微型發電機所產生的不穩定電壓源當做輸入，而設計目標是在系統輸出端產生儲能元件的額定電壓並對儲能元件進行充電。設計出來的電路可依據不同的輸入電壓來調整直流對直流轉換器上MOSFET開關的開關控制訊號其duty cycle，而Boost Converter上MOSFET開關的控制訊號duty cycle則會影響轉換器的電壓增益，藉此達到穩定輸出電壓、提高儲能效率的結果。

This paper presents an energy harvesting circuit, and designs a feed-forward circuit which is based on DC-to-DC Converter. This research collects the power range which is from hundred scale of μW to several mW. The circuit utilizes a super capacitor as the storage element. Since the power and voltage of energy sources are low, the Boost Converter is adopted to raise the voltage level. What make energy transfer effectively is the MOSFET control signal which is created by comparing the reference voltage and the saw-tooth voltage. This control signal controls the MOSFET of Boost Converter to make unstable power source steadier.

This paper realizes the energy harvesting system by hardware circuit. Although the input is an unstable power source, the converter will output a stable voltage as a result. The circuit can adjust the duty cycle of MOSFET which is on the DC to DC converter by various input voltage. And the change of control signal’s duty cycle will affect the voltage gain of converter. By above proceedings, there are steady output voltage and effective results.