交錯臨界模式轉換器之同步截止電壓型主控調變控制法則

Abstract

本論文提出一開回路後緣同步電壓模式(Synchronized-OFF voltage-mode, SFVM)主控調變(Master-made-modulated, M3)控制法則，用於二相主僕控制交錯式臨界模式升壓轉換器功因校正電路。多相交錯式功因修正器常應用於功率密度需求的產品，如薄型電視或伺服器等等。文中將針對目前交錯式臨界模式升換器的操作原理以及同步控制方法先作分析，由於變頻操作，要將二台臨界模式升壓轉換器交錯工作極為複雜，而在已知的問題中發現，電流發散的不穩定問題會發生在高輸入電壓的情況，傳統設計使用鎖相回路會造成額外的設計成本和系統複雜度。本論文提出之SFVM-M3控制法則可以即時調整僕轉換器(Slave unit)的導通時間，藉以補償相位差，使二相維持180度相移以達到輸入電流最佳化，並且不需要任何相位補償控制的回路。SFVM-M3控制法則不同於傳統的閉回路鎖相控制，或是利用電流模式控制，其為一開回路控制方法，有效地簡化控制電路，即能在每週期中作補償(cycle-by-cycle)。論文最後提出一類比控制電路來模擬SFVM-M3的可行性，並且實作一台200 W，利用數位控制器實現的平台來作驗證。

In recent years, interleaving of converter modules has become an attractive approach to increase converter output power capability. To do so for converters with constant-switching-frequency operation, it is relatively easy and that has been implemented in many commercial practical products. However, for converters with variable-switching-frequency operation, conventional interleaving scheme presents a problem. In this dissertation, this issue is addressed. There are schemes reported that solves such problems but those are often suffering from increased circuit complexity, and/or additional sensing requirements that increases the overall cost. This problem is analyzed from which new control scheme is proposed in the dissertation. A synchronized-off voltage-mode master-made-modulation (SFVM-M3) scheme is proposed to address this issue while retaining the basic advantages of voltage mode control. While the proposed scheme has wider practical implication, the focus in this dissertation is to apply this scheme to a critical mode (CRM) power factor correction (PFC) circuit which becomes popular choice in recent years in medium power (about 200 Watts) applications. In a critical mode PFC, it’s a constant on-time variable frequency switching and, therefore, it presents an interleaving problem. The proposed scheme is an elegant approach to solve this problem. Simulations and experiments are conducted to verify the proposed control scheme in the dissertation. The combination of critical mode PFC power modules and the proposed control scheme makes it an attractive approach to higher power PFC applications.