本論文提出一套適用於LLC諧振式電源轉換器之變頻控制架構的小訊號分析方法。為了暸解在變頻機制下，LLC諧振式電源轉換器的控制訊號之頻率特性，其控制對輸出電壓的小訊號轉移函數與其極、零點的組成迄待推導與分析。因此，本文提出一植基於頻率調變與解調概念之理論架構對LLC 諧振式電源轉換器進行小訊號分析。
由於變頻控制機制的頻率變化可視為一頻率調變之訊號，此訊號經過LLC諧振槽與全橋整流電路可達到頻率解調之效果，並將輸入控制訊號之變化在輸出端還原。故此，經由頻率調變之概念推導出頻率調變訊號之通式後，將其代入頻率解調過程所造成之衰減與增益，便可得到LLC諧振式電源轉換器之控制對輸出電壓的小訊號轉移函數。再者，輔以SIMPLIS®電路模擬軟體，此分析方法與所推導出轉移函數可被驗證。此外，藉由簡化過的控制對輸出電壓轉移函數可整理出系統之極、零點組成元件，據此分析出合適的元件參數設計方法。
最後，實作一576W之全橋LLC諧振式電源轉換器雛型電路，並以增益/相位分析儀PSM1735建構一量測平台，俾以驗證本論文所提出分析方法的可行性。

This thesis presents the small-signal analysis of the full-bridge LLC resonant converter with the variable-frequency control. In order to determine the frequency characteristics of the full-bridge LLC resonant converter, the control-to-output transfer function and corresponding poles and zeros need to be derived. Therefore, a novel small-signal analysis using the concept of frequency modulation (FM) and frequency demodulation (FDM) is proposed.
The variable-frequency control scheme can be treated as a frequency modulator because the small-signal perturbation causes frequency variation. Then, the FM signal can be demodulated by the LLC resonant tank and the full-wave rectifier to the load. Therefore, the control-to-output transfer function can be derived. With the further simplification of the derived transfer function, the poles and zeros can be obtained to predict the frequency characteristics. Based on the derived transfer function, the Bode diagrams can be plotted by Mathcad® to compare with the SIMPLIS® simulation results.
Finally, a prototype circuit of the 576W full-bridge LLC resonant converter is built to validate the derived transfer function through the gain/phase measurement station which is constructed by using the gain/phase analyzer, PSM1735.

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