當降壓型轉換器工作於類連續導通模式，其控制對輸出轉移函數中只會產生一個極點，使得系統補償後具有比連續導通模式較快的暫態響應，此特性與不連續導通模式相同，且應用功率可以高於不連續導通模式。類連續導通模式最常用之控制方法為固定參考電流控制，此控制需要電流感測元件以決定飛輪時間，然而此控制工作於輕載時，因為飛輪時間太長，導致系統效率低落。本論文提出一類連續導通降壓型轉換器之動態飛輪時間控制晶片以解決上述問題。本論文提出之動態飛輪時間控制是利用回授訊號控制飛輪時間，使飛輪時間在暫態時隨著負載變化而進行動態調變，因此不需要額外使用電流感測元件。本控制晶片在輕載時會減少飛輪電流值，且在極輕載時進入不連續導通模式，將飛輪電流值降為零，使降壓型轉換器的輕載效率提升。最後，本控制晶片使用TSMC 0.25 μm CMOS 高壓製成實現並將其應用於一輸入電壓12 V，輸出電壓3.3 V，輸出功率為6.6 W的降壓型電源轉換器以驗證此控制晶片之可行性。

The buck converter operating in pseudo-continuous conduction mode (PCCM) increases the ability of current handling compared with discontinuous conduction mode (DCM). Same as DCM operation, the control-to-output transfer function of PCCM buck converter exhibits a single pole, which make the transient response faster than that of CCM operation. The most commonly used control for PCCM buck is constant reference current (CRC) control, which needs sensing device to determine the freewheeling time. However, CRC control suffers from low efficiency under light load condition because of long freewheeling time. In this thesis, the dynamic freewheeling-time (DFT) control for PCCM buck converter is proposed to solve the issue mentioned above. The proposed DFT control uses feedback signal to determine the freewheeling time, which make the freewheeling time vary with load condition at transient state. Therefore, the sensing device is needless in DFT control. The proposed DFT control decreases the freewheeling current value under the light load condition. Furthermore, the proposed DFT control can operate in DCM at very light load condition and the freewheeling current is zero. Thus, the light load efficiency of buck converter can be improved. Finally, this controller is fabricated with TSMC 0.25 μm CMOS high voltage mixed signal general purpose process, and applied to an input voltage of 12 V, output voltage of 3.3 V, and output power of 6.6 W buck converter to verify the feasibility of proposed control IC.

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