固定導通時間控制多相降壓型轉換器之均流迴路分析與設計

Abstract

定導通時間控制(COT)的多相降壓型轉換器被廣泛使用於需要高效率和低電壓高輸出電流的應用中，為了避免熱的問題並且提高效率，需要均流迴路來平衡每一相的電感電流，然而，在以前的文獻中都沒有完整的分析以及研究如何設計均流迴路的參數。 在本論文中，對上述的轉換器控制方法進行了許多層面的分析，首先，推導了具有均流迴路的固定導通控制的每一相電感電流分佈方程式，由推導出來的式子，可以看出不同元件的參數對電感電流分佈的影響。其次，利用蒙地卡羅方法(Monte Carlo methods)的結果，可以知道如何挑選元件的誤差範圍以及如何設計均流回路的參數來符合均流的規範。然後，推導了均流迴路的小訊號模型，它可以用來分析均流迴路的穩定度以及暫態時的響應狀況，另外，也探討了均流迴路與電壓回路的關係，這些分析提供了設計均流迴路時的依據。最後，透過實測結果驗證了所提出的小訊號模型。

Multi-phase buck converter configuration with constant on-time (COT) control scheme has been widely used in many high-efficiency, low-voltage high-current computer power applications. To avoid thermal issue and increase efficiency, a current balance control scheme is required to balance per-phase inductor currents. However, it lacks comprehensive analysis and design of current balance loop in literature. In this thesis, analyses are performed for several aspects of the above-mentioned converter-controller configuration. First, per-phase D.C. current equations are derived for COT control scheme with current balance loop. From the equations, the relation between component parameters and current distribution can be obtained. Second, Monte Carlo results give a reference to choose mismatch range of component and design current balance loop parameter to meet the current balance specification. Third, small-signal models are developed which can be used to predict stability and transient response performance. Besides, the relation between the current balance loop and the voltage regulation loop is discussed. The analytical results provide a design guideline of the current balance loop. Finally, the proposed model was verified with experimental results.