本研究提出一基於分切合整數位控制之隔離型雙級降壓直流/直流轉換器，其電路架構前級為降壓型轉換器(buck converter)，後級為全橋轉換器(full-bridge converter)搭配倍流整流電路(current-doubler rectifier)。其中全橋轉換器則採用相移切換方式(phase-shift switching)，達到零電壓導通以降低切換損失。本研究提出分切合整數位控制(D-Σ digital control)應用於直流/直流轉換器中，基於此控制法，轉換器允許寬電感值變化，即使電感值隨著電流變大而衰減，仍能避免電流發生振盪，並準確追蹤電流命令。本論文詳細推導出用於直流/直流轉換器之分切合整數位控制法則，且修正過去分切合整數位控制僅能應用於連續電流導通模式(CCM)之限制，使轉換器即使於不連續導通模式(DCM)下仍能夠穩定提供負載需求。
傳統常見應用於直流/直流轉換器之控制法如尖峰電流控制(peak current-mode control)與平均電流控制(average current-mode control)。尖峰電流控制容易因電流峰值與平均值差異造成輸出電壓穩態誤差。而當負載瞬間抽載時，平均電流控制因電流內迴路存在低通濾波器之緣故，動態響應速度慢，本論文亦模擬驗證了分切合整數位控制相較於上述兩傳統控制法，擁有更低之系統穩態誤差以及更快之動態響應速度。最後本研究實現一部額定功率2.6 kW，輸出電壓26 V之直流/直流轉換器，同時亦驗證分切合整數位控制應用於直流/直流轉換器之特點與可行性。

This thesis presents design and implementation of an isolated two-stage dc/dc converter with division-summation (D-Σ) digital control. The first stage is a buck converter, and the second stage is a full-bridge converter with current-doubler rectifier which is controlled with phase-shift switching method. Therefore, the primary-side power devices can achieve zero voltage switching. With D-Σ digital control, the converter is allowed to have wide inductance variation caused by high current flowing through inductor, and to track current reference precisely for achieving tight output voltage regulation. This paper derives D-Σ control law for dc/dc converter in detail, and initiates the application of D-Σ control in DCM operation.
The major contributions of this paper is: this research applies D-Σ digital control on dc/dc converter unprecedentedly, and verify that the control can reduce steady-state error as compared with peak current-mode control and achieve faster dynamic response over average current-mode control. Moreover, it presents a modified D-Σ control law for DCM operation to enables the applicability of the control in both CCM and DCM operation. Last, the research implements a high voltage step-down dc/dc converter with input voltage 600 V, output voltage 26 V and power rating 2.6 kW.

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