近年來多媒體可攜式產品應用越來越廣泛，所以需要高轉換效率的電源轉換器來提升電池的使用壽命，在本篇論文中，提出一個類比變頻控制電路，其會根據負載條件來調整穩壓器的切換頻率，進而達到最佳化功率轉換的效果。相對傳統固定頻率操作的穩壓器，此最佳化頻率控制方法，不僅能改善輕載時的功率轉換效率，同時也使得穩壓器在重載時的消耗功率得以減少，切換頻率與負載之間的轉換曲線，則是透過評估切換式穩壓器的功率消耗模型得到的，本論文則整合此電路至一電流型降壓穩壓器中，以驗證此方法。
由模擬驗證的結果，此穩壓器能操作500KHz在負載範圍為10mA到600mA，且輸入電壓可以從2.4V到3.6V，輸出電壓可以從0.6V到3.3V。當輸入電壓由2.4V變化到3.3V時，輸入電壓調節率為0.625%V/V；負載電流由100mA變化到600mA時，負載電流調節率為0.12%V/A，此穩壓器的最大轉換效率為95.6%。使用本論文所提出的方法，能使穩壓器在負載600mA的條件下還能改善2.2mW。所設計的電流型降壓穩壓器是使用0.35μm 1P4M 3.3V混合訊號互補式金氧半製程來製作。晶片整體面積約為1.22mm2，而控制器的面積約為0.18 mm2。

Recently, the consumer market of portable electronic devices are in widespread demand. In general, these portable devices are often powered by batteries and require high-efficiency switching DC-DC converters to extend the life time of batteries. In this thesis, an analog variable-frequency controller (VFC) circuit, which receives the load current information and generates the required switching frequency to optimize efficiency, is proposed. Compares with conventional fixed 500KHz PWM control, the efficiency is improved not only in light load but also in heavy load. The optimal relationship of switching frequencies versus load currents can be obtained by evaluating the power-loss models of switching converters. In this thesis, an analog VFC circuit has been integrated into current mode buck switching regulator to verify the performance.
Verification show the proposed converter can operate at 500KHz during the load current from 10mA to 600mA. Supply voltage of the converter is 2.4V~3.6V and output voltage of the converter is 0.6V~3.3V. Line regulator=0.625%V/V when Vin=2.4V~3.3V. Load regulator=0.12%V/A when Iload=100mA~600mA. The maximum efficiency of the converter is 95.6%. The proposed method can improve 2.2mW at 600mA load current. The current mode buck switching regulator has been fabricated with 1P4M 0.35μm 3.3V polycide CMOS process and measured 1.22mm2 with the controller measured 0.18 mm2.

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