用於電池電源的DC-DC轉換器動態調整研究

Abstract

行動裝置的電池電量耗盡之際電壓會急劇下降，此時內部DC-DC電源轉換器若能正常工作，則可延長裝置使用時間。額外爭取到的使用時間可供系統進行緊急處置，如存檔備份等，然而這需要DC-DC轉換器有較低的輸入電壓範圍。 由於DC-DC轉換器的小信號轉移函數會隨著電池輸入電壓降低而改變；因此設計轉換器的補償器時，則需考慮以最差狀況之轉移曲線為對象來進行補償設計。又傳統上補償器採固定極零點方式，因此DC-DC轉換器運作在電池額定電壓附近時，其響應自然不是最理想。不幸的是，在百分之七八十的電池工作時間內，其輸出電壓都分佈在電池額定電壓附近。 因此固定極零點式補償器若以電池額定電壓所對應之轉換器轉移曲線來進行補償設計，則大部份工作時間內可擁有高的頻寛及較大之低頻增益。然而電池電壓大幅下降之際，由於特性曲線偏移可能導致不穩定，或是鏈波擴大，特別是Boost電路。 若能動態調整依上述原則所設計的DC-DC轉換器，使其輸入電壓較低時，依然能維持一定品質電源輸出，便可在電池低電壓時有效爭取額外時間進行緊急處置；另一方面，電池電壓正常輸出時，DC-DC轉換器可擁有較好的響應。 本論文將著重於研究分析使用於行動裝置的DC-DC轉換器之低電壓動態參數調整，特別是Boost電路；以期在更低輸入電壓的範圍下，維持一定品質電源輸出，並且有效爭取電池使用時間。

When battery service life of mobile device will run out, battery output voltage will drop immediately. At this moment, if DC-DC converter still works, device gains an external service life and has a short time to do emergency handling, such as to backup files. This needs a lower input voltage range of DC-DC converter. Small signal transfer functions of DC-DC converters varies when battery input voltage is dropping. In this case, a fixed pole-zero compensator design should consider the worst-case of transfer function. For this reason, DC-DC converters will not work in best condition at battery rated output voltage. Unfortunately, output voltage of battery distributes around battery rated output voltage during 70~80% of battery life. A compensator is designed for a transfer function of rated battery voltage, it will have a higher bandwidth and DC-gain. But this kind of converter, especially for boost circuit would be unstable if the battery voltage drops lower. If DC-DC converter could dynamically adjust parameters of compensator, we could gain a little to emergency handling when battery voltage is low. On the other hand, DC-DC converter has a good output performance when in battery rated output voltage. This paper will focus on the dynamic tuning analyses of DC-DC converter when input voltage is lower, especially for boost circuit.