Title: 具快速暫態反應及適應性相位控制技術的電流模式直流/直流降壓電源轉換器
Fast Transient Technique and Adaptive Phase Margin Control for Current Mode DC-DC Buck Converters
Authors: 李昱輝
Lee, Yu-Huei
陳科宏
Chen, Ke-Horng
電控工程研究所
Keywords: 直流/直流轉換器;快速暫態反應控制;適應性相位;極零點補償相銷;穩定度;內嵌式補償;DC-DC converter;fast transient control;adaptive phase margin;pole-zero cancellation;stability;on-chip compensation
Issue Date: 2008
Abstract: 在消費性電子產品中,尤以手持式產品的應用上,需求越來越廣泛。擁有高效能與小型化的電源轉換器日趨重要。為了有效使用有限的電池能量,電源管理系統為晶片系統中非常重要的一環。故本文提出一個運用於切換式電源轉換器的技術,以期在此切換式電源轉換器的暫態響應和穩態響應,都能夠有最好的效能表現。
本論文所提出的內容,則是運用密勒等效電流來充放此誤差放大器的輸出電容,來達到電容放大的功用,使整合進IC內部的小電容相當於大的系統補償電容,讓整體電路減少一樣外部原件進而降低成本和得到較佳的表現水準。因為此電容放大的技術,以致於在穩定系統反應時,可以讓系統保持在一個穩定的操作狀態。而當系統在負載瞬間改變的暫態階段,一旦穩壓器瞬間遭受到大負載電流的改變而需要快速穩壓時,即可將一部分的密勒等效電流用來快速充放誤差放大器輸出電容上的電荷,等同於是將原本的穩定的密勒補償大電容還原成本來的小電容,以達到電壓快速反應回穩之效果,亦可以避免震盪的發生。而且此額外的密勒等效電流原本即為誤差放大器輸出電流的一部分,完全沒有增加額外的功率消耗。
另外提出動態零點的補償。當負載瞬間變動進入暫態響應階段時,用頻率的角度來解釋,等於是把系統的頻寬瞬間拉大,讓整個系統的反應快速,以達到電壓快速回穩的功效。因此我們用上了負載相關的動態零點補償,使系統在暫態時零點能夠依據當時的負載狀況,移到不同的最佳化位置,以確保在加大系統頻寬反應速度時,依然保持應有的系統穩定度,來達到整個系統最佳化的情形。另外,在穩態系統響應時,動態負載相關零點補償也可以確實抵銷掉系統的極點,使整個系統近似一單極點系統確實達到大頻寬和最佳穩定度的功效。
本論文所提出的方法運用於電流模式直流/直流降壓轉換器上,並用台灣積體電路公司三五微米製程來實現。實驗結果顯示本論文的方法在不增加太多額外的功率消耗的前提下,顯著的加強了系統的暫態響應和穩定度。
This paper proposes a fast transient (FT) control with adaptive phase margin (APM) to achieve good transient response of current-mode DC-DC buck converters at any load condition. Thus, the overshoot/undershoot voltage and the transient recovery time are effectively reduced. Owing to the load-dependent output pole of the current-mode buck converters, the operation of a load-dependent compensation pole-zero pair is designed to be moved to a higher frequency at transient period and back to an optimum position for pole-zero cancellation in steady state. Therefore, an adaptive phase margin is always maintained at a suitable value in all load conditions for achieving good transient responses. In other words, the compensation pole-zero pair is adapted to the load current to extend the system bandwidth and get the optimum phase margin. Experimental results demonstrate the improved transient performance at transient period and good phase margin in steady state. The overshoot/undershoot voltage is smaller than 60mV and the transient period is shorter than 12μs as the load current suddenly changes from 100mA to 500mA, or vice versa. Compared with the conventional design without any fast transient technique, the performances of undershoot voltage and recovery time are enhanced 45 % and 85 %. With the proposed technique, the performance of the current-mode buck DC-DC converter is improved significantly.
URI: http://140.113.39.130/cdrfb3/record/nctu/#GT079612522
http://hdl.handle.net/11536/41839
Appears in Collections:Thesis