Simulation of Control Characteristics of Current-Mode DC-DC Boost Converters

在電流控制模式直流-直流電源轉換器中有二個回授路徑，分別為電壓回授路徑及電流回授路徑，根據其小信號模型得到二組迴路增益方程式，分別為 及 ，由這二個迴路增益方程式可以瞭解整個電源轉換器的系統是否穩定工作，而要得到穩定的的系統就必須瞭解電壓回授路徑及電流回授路徑，也必須由這二個路徑與 及 來設計出穩定的電源轉換器，其中 可透過測量的方式得到，但 多年來無法經由測量或模擬的方法獲得，且 也是系統穩定度的指標，近年雖然在已經有人探討過利用SIMPLIS軟體來模擬得到Buck Converter的 ，由於Boost Converter的架構與Buck Converter 不同，且Boost Converter具有正零點(Positive Zero)，正零點在頻率響應的觀點對穩定度有很大的影響，因此瞭解右半平面零點對 及 的影響是重要的；本論文重點為利用SIMPLIS模擬Boost Converter之 及其它重要參數，並以實驗方法驗證結果。 本論文的主旨在於探討SIMPLIS模擬結果的正確性，雖然由數學計算式搭配MATHCAD軟體可得到 頻率響應中的交越頻率(Crossover Frequency)及相位邊限 (Phase Margin)，但由於數學方程式是在理想狀態下推導出來的，並未考慮MOSFET導通電阻、運算放大器(Operation Amplifier)頻寬及延遲(Delay)之效應，故透過SIMPLIS軟體模擬能將實際情況考慮進去，且不需額外推導方程式，此結果尤其對近年來高頻之DC Converter發展有益，因為控制頻寬要求愈來愈高，故本論文利用改變MOSFET的導通電阻來驗證SIMPLIS軟體不但能與數學方程式計算結果相符，更進一步的確定透過SIMPLIS軟體模擬的迴路增益(Loop Gain)是可以相信的。There are two feedback loops, Voltage Control Loop and Current Control Loop, in Current Mode DC-DC Converter. According to Small Signal Model, two groups of Loop-gain function can be obtained, and they are T1 and T2. It can be verified by these two groups of Loop-gain function that whether the whole system is working under stable and reliable condition. In order to build up a stable and reliable system, Voltage Control Loop and Current Control Loop are essential to be understood. Hence, a reliable converter can only be hence designed through T1 and T2, together with Voltage Control Loop and Current Control Loop. In which, T2 can be easily obtained by measurement; however, T1 has yet long been obtained by any measurement or simulation. Most importantly, T1 has been the benchmark of system reliability. In recent years, many researchers make effort to use SIMPLIS software to obtain simulated T1 of Buck Converter, yet this method cannot be applied in Boost Converter since the structure of Boost Converter is different from Buck converter, let alone that Boost Converter has the feature of Position Zero. Position Zero has great influence to reliability from to view of Frequency Response. Therefore, to understand right plane Zero is important to effect of T1 and T2. This dissertation aims to make use of SIMPLIS to simulate T1 in Boost Converter and other important parameters. Then the simulation result will be cross-verified by experiments. The purpose of this dissertation is to research the accuracy of simulation result of SIMPLIS. Although by collocating mathematic equation and MATHCAD, Crossover Frequency and Phase Margin can be obtained in T1 Frequency Response, this method does not consider the influence of MOSFET Turn on Resistance, Operation Amplifier, and Delay based on the reason that mathematic equation is designed under perfect conditions. Therefore, by SIMPLIS simulation, real conditions will be considered into equation in addition to no demand of extra equation. The result is importantly beneficial to recent DC Converter development in high frequency since demand of controlling bandwidth is increasing dramatically. To conclude, this dissertation purpose is to use the change of MOSFET Turn on Resistance to examine and verify that SIMPLIS can prove the accuracy of the result made by mathematic equation and also make it convincing that Loop Gain made by SIMPLIS simulation is reliable.口試委員會審定書 ................................. i 誌謝 ............................................. ii 中文摘要 ........................................ iii 英文摘要 ..........................................iv 目錄 ............................................. vi 圖目錄 ......................................... viii 表目錄 .......................................... xii 符號表 ......................................... xiii 第一章 緒論 ...................................... 1 1.1 研究動機與目的 ................................ 1 1.2 本論文焦點 .................................... 4 第二章 電流控制模式方法與分析 .................... 5 2.1 簡介 .......................................... 5 2.2 電流控制型小信號模型及轉移函數方式 ........... 10 2.2.1 電壓控制模式 ............................... 10 2.2.2 電流控制模式 ............................... 12 2.3 T1、T2及轉移函數方程式之回顧 ................. 18 2.4 內部迴路方程式Fin ............................ 20 2.5 穩定度 ....................................... 23 2.6 斜率補償 ..................................... 28 第三章 模擬與實驗結果 ........................... 31 3.1 硬體電路 ..................................... 31 3.2 補償器設計 ................................... 35 3.3 量測T2 ....................................... 38 3.3.1 頻率響應分析儀 ............................. 38 2.2.2 量測Loop Gain T2 之線路 .................... 38 3.4 SIMPLIS模擬T2、T1及Fin ....................... 40 3.4.1 模擬T2 ..................................... 40 3.4.2 模擬T1及Fin ................................ 44 3.5 模擬結果與數學模型的比較 ..................... 49 第四章 結論與未來展望 ........................... 54 3.1 結論 ......................................... 54 3.2 未來展望 ..................................... 54 參考文獻 ..........................................5