由於可攜式電子產品的設計朝向多功能智慧型手機發展，將多功能的晶片整合至單一系統上，電源管理晶片的發展因為高轉換效能的技術已經趨於飽和，另一方面，由於可攜式電子產品大部分時間都是使用者攜帶於身邊，因此使用的安全性是當前相當重要的課題。
因應輸出負載異常時之電源保護系統，在本論文為設計一個具有過電流保護機制及過負載除頻之降壓穩壓器，其中提出精準電感電流偵測電路取得電感電流變化，適當調整功率電晶體導通週期，調節輸出功率得以控制最大輸出功率點，相較於傳統的降壓穩壓器，則具有較安全而更低能耗之特性。
此具過電流保護偵測及過載除頻之降壓穩壓器是以TSMC 0.18 um 3.3 V 1P6M CMOS製程實現，此晶片的工作電壓範圍為2.5 V ~ 4.5 V，操作頻率為1 MHz，提供1 V的輸出電壓轉換，在外部電感10 uH以及外部電容10 uF情況下，轉換時間為50 us，而可供應負載電流範圍為0.05 A~0.5 A，而轉換效能可達到91.3%，線性調節度為5.83 mV/V，負載調節度為0.04048 mV/mA，而晶片面積為1.44 mm2。

Portable electronic devices are toward to the multi-function intelligent cell phone. Since all functions are integrated in one system, the power management is very important. Currently, the high efficiency power device design has been developed very well. According to most of the time, the electronic device is placed in the pockets; the safety issues are more and more critical. As a result, the power management device with high reliability has become an important research topic.
In case of protection when abnormal conditions, the current mode buck converter was implemented by current protection and over load frequency divider. In the thesis, high accuracy L sensing circuit is proposed to get the variation inductor current then adjust the duty cycle of power fet to control the max power points, compare to traditional converters, this thesis provides higher reliability and lower power consumptions.
A high accuracy current sensing protection and over load frequency divider have implemented with TSMC 0.18 um 3.3 V 2P4M CMOS process. Measurement results show that the buck converter can be operated at 1 MHz with supply voltage from 2.5 V to 4.5 V. The output voltage step up at 1 V with 10 uH inductor and 10 uF capacitor. The maximum conversion power efficiency for load current from 50 mA to 500 mA is up to 91.3%. The load regulation and line regulation are 0.04048 mV/mA and 5.83 mV/V, respectively. The chip area is 1.44 mm2.

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