具適應性電壓位置控制之電壓調整器之分析與設計

Abstract

適應性電壓位置(Adaptive voltage position, AVP)控制已被應用在微處理器電源供應器中的多相式電壓調整器，適應性電壓位置可以提高電源轉換器的效率同時降低輸出電容的使用量。本論文主要便是探討適應性電壓位置的控制電路分析。 適應性電壓位置控制與一般電源電路使用的非適應性電壓位置控制最大的不同在於控制迴路的設計法則，由於控制迴路會影響閉迴路之輸出阻抗，所以具適應性電壓位置控制的控制器必須設計控制迴路來達到所謂固定輸出阻抗的需求。控制迴路除了影響閉迴路之輸出阻抗之外，也會影響其他閉迴路之特性如輸入電壓調整率及控制穩定度，因此，必須利用較準確的數學模型來設計所需之固定輸出阻抗並同時滿足其他特性。 本論文中將會分析名為AVP+的新型適應性電壓位置設計。為了深入探討控制迴路性能，例如控制迴路穩定度、輸出阻抗以及輸入電壓調整率，AVP+控制的電壓調整器的小訊號模型已被推導出來，且經由實驗和模擬已證明了此項模型可做為小訊號分析基礎。這是先前從未被研究探討的。 本文將以AVP+ 控制與另一個常用的適應性電壓位置控制(在此稱作AVP- control)及電流模式控制(Current-mode control)作比較，對於目前輸出電容朝小型化的發展，使用陶瓷電容和高頻切換已成為現在的主流趨勢。本文也針對此種條件做分析比較。經由分析及模擬能證明AVP+控制相對於AVP-控制是能得到較佳的穩定度及輸出阻抗特性，所以AVP+控制是比較符合電壓調整器的未來特性需求。

Adaptive voltage positioning (AVP) technique has been used in multiphase voltage regulators for microprocessor power applications. It is a control scheme to increase the energy efficiency and reduce the output capacitor size of a DC power converter. The focus of the dissertation is on the control aspect of the AVP schemes. The design philosophy of AVP control is very different from that of a conventional DC power converter. In such a design, the converter output impedance must be designed to be a prescribed constant value with respect to frequency. As a result, the control loop gain must be shaped in certain way to accomplish AVP. Besides the issue of output impedance, the issues of line regulation and control stability must also be considered at the same time. Without a detailed mathematical model, this is very hard to achieve. In this dissertation, a novel scheme introduced in recent years, called AVP+, was for the first time analyzed. Small signal model was developed from which compensator design can be accomplished. The model has been verified by simulations and experiments. Comparisons were made of this scheme with two well-known conventional schemes, the current-mode scheme and the AVP- scheme. Compared to conventional AVP schemes, the AVP+ scheme provides better stability margin, better output impedance performance while maintaining good line regulation. This is especially true for the case of using ceramic output capacitors and high switching frequency, which is the prevailing trend of high-performance voltage regulators.