應用於電腦電源之電壓調節器控制架構建模與設計

Modeling and Design of Voltage Regulator Control Schemes for Computer Power Applications

陳景然(Ching-Jan Chen)

指導教授 ： 陳德玉

國立臺灣大學/電機資訊學院/電機工程學研究所/博士(2011年)

https://doi.org/10.6342/NTU.2011.01081

摘要

運算設備例如個人電腦與筆記型電腦已成為電源供應器產業的一個主要市場。為了滿足運算設備中的各種電源需求，許多直流轉直流電壓調節器(VR)被用來提供各個裝置的電源，例如中央處理器、繪圖處理器與輸出入電源。由於運算設備的進步，電壓調節器的電源需求越來越嚴峻。除此之外，電壓調節器的轉換效率改善一直是重要的研究課題，近幾年來對於重載乃至於輕載時的高轉換效率要求更加重視，傳統的控制架構無法達到上述的要求，因此新的控制架構紛紛被提出以解決這些問題。面對高效率的要求，目前有兩個主要的趨勢。一是適應性電壓定位(AVP)架構；一是使用固定導通時間控制取代傳統定頻控制，以增加輕載轉換效率。本論文的焦點在對兩個最近提出的控制架構發展解析模型並提出設計準則。這兩個控制架構分別是高增益峰值電流控制(HGPCC)及改進的固定導通時間漣波控制(RBCOT Control)。高增益峰值電流控制具有相電流平衡及每週期過電流保護的優點，且可以提供精確的適應性電壓定位以減少中央處理器電源損耗。改進的固定導通時間漣波控制具有下列優點:快速暫態響應、較少的元件需求、精確輸出電壓及輕載時有高轉換效率。
由於這兩個新控制架構的脈波寬度調變架構的特性，傳統的小信號平均模型無法使用於此。在本論文中，使用改進的平均模型方法來對高增益峰值電流控制建模；使用描述函數(Describing Function)方法來對改進的固定導通時間漣波控制建模。根據模型，本論文提出設計的準則以達到預期的控制特性。模擬與實驗的結果驗證了模型及穩定條件的準確度。

關鍵字

電壓調節器 ； 適應性電壓定位 ； 峰值電流控制 ； 輸出阻抗 ； 固定導通時間漣波控制 ； 描述函數 ； 穩定度條件

並列摘要

Computing devices such as personal computers and laptop computers have become a major market for power supply industry. To meet the various power requirements of a computing device, a variety of DC/DC voltage regulators (VR) are used to power loads such as central processing unit (CPU), graphic processing unit, and I/O power. Due to the advancement of computing devices, the power requirements of VRs have become more and more stringent. Besides, VR efficiency has always been an important research topic. In recent years, the mandate for higher efficiency, not only for the full load but also for the light-load condition, has become even more critical. Conventional control schemes cannot meet such requirements; therefore, novel control schemes are proposed to solve the problems. There are two major trends to meet the high efficiency requirement. One is to use adaptive-voltage positioning (AVP) scheme. The other is to use constant on-time controller, instead of conventional constant-frequency controller, to increase the efficiency at light load. The focus of the dissertation is to develop analytical models and provides the design guideline of two recently-reported control schemes: high-gain peak current control (HGPCC) scheme and the modified ripple-based constant on-time (RBCOT) control. HGPCC scheme has the advantages of phase-current balancing and cycle-to-cycle over current protection. Besides, the scheme can be designed to achieve accurate AVP for CPU power loss reduction. The modified RBCOT control has the advantages of fast transient response, small components count requirement, accurate output voltage, and high efficiency at light-load.
Because of the fundamental difference in the pulse-width modulation schemes used in the two new control schemes, the conventional small-signal average model does not apply. In developing the models, a modified average modeling approach is used for the HGPCC scheme, and the describing function approach is used for the RBCOT scheme. Based on the model, design guidelines are given to achieve prescribed control characteristics. Simulation and experimental results confirm the proposed models and the accuracy of the stability criteria.

並列關鍵字

Voltage regulator (VR) ； Adaptive voltage positioning (AVP) ； peak current control ； output impedance ； Ripple-based constant on-time (RBCOT) control ； Describing function ； Stability criteria

參考文獻

[1] F. C. Lee, P. Barbosa, P. Xu, J. Zhang, B. Yang, and F. Canales, “Topologies and design considerations for distributed power system applications,” in Proc. IEEE, vol. 89, no. 6, pp. 939–950, 2001.

Available at http://focus.ti.com/docs/solution/folders/print/563.html

[4] C.-J. Chen, D. Chen, C.-S. Huang, M. Lee, and E. K.-L. Tseng, "Modeling and design considerations of a novel high-gain peak current control scheme to achieve adaptive voltage positioning (AVP) for DC power converters," IEEE Trans. Power Electronics, vol. 24, pp. 2942-2950, 2009.

[5] C.-J. Chen, D. Chen, M. Lee, and E. K.-L. Tseng, "Design and modeling of a novel high-gain peak current control scheme to achieve adaptive voltage positioning for DC power converters," in Proc. IEEE Power Electronics Specialist Conference (PESC), 2008, pp. 3284-3290.

[6] C.-J. Chen, D. Chen, C.-W. Tseng, C.-T. Tseng, Y.-W. Chang, and K.-C. Wang, "A novel ripple-based constant on-time control with virtual inductor current ripple for Buck converter with ceramic output capacitors," in Proc. IEEE Applied Power Electronics Conference and Exposition (APEC), 2011, pp. 1488-1493.