降壓型電壓穩壓器的分析與設計

Abstract

近年來，隨著科技的快速發展和不斷創新，大量由電池供電的可攜式電子產品進入我們的日常生活中，如個人數位助理、手機、MP3隨身聽、數位相機和筆記型電腦等等。如何延長電池的使用壽命，就成了所有工程師的熱門話題。而使用具有高轉換效率的電源管理系統是延長電池使用壽命的有效方法之一。 交換電容式電壓轉換器具有高轉換效率，但是通常並沒有電壓調節功能，使得輸出電壓不夠精確，而且在其電路架構中，它是使用功率電晶體當作開關不斷地切換，因此具有輸出電壓漣波。而低壓降線性穩壓器的輸出電壓並沒有漣波，但是當輸入電壓與輸出電壓的電壓差越大時，轉換效率會越低。因此，本論文提出一個交換電容式電壓轉換器串接低壓降線性穩壓器的降壓型穩壓器架構，結合此兩種架構的優點，提供一組穩定之可調節式的雙輸出電壓。 交換電容式電壓轉換器具有兩種分數型式的電壓增益，通過控制功率開關電晶體的狀態，使系統具有1倍、2/3倍和1/2倍三種工作模式。本論文設計的降壓型穩壓器可將輸入電壓(2.5V~5V)轉換成固定的輸出電壓(1.8V或2V)，其可供應的最大負載電流可達到150毫安培。整個電路設計是藉由HSPICE軟體，透過TSMC 0.25um 1P5M BCD製程進行模擬。

In recent years, with the rapid development and innovation of technology, more and more battery-powered portable electronic products are introduced to our daily live, such as PDAs, cell phones, MP3 players, digital cameras, notebooks and so on. How to make battery lifetime longer is an urgent research topic for circuit designers. Especially, using high conversion efficiency power management systems is one of effective methods to prolong the battery life. The switched capacitor voltage converters have high efficiency, but they have poor accuracy and stability. Besides, the use of power transistors as a switch to change or discharge frequently to result in the output voltage has a neglected ripple. On the other hand, low dropout regulators ideally have no output voltage ripple, but the conversion efficiency will be greatly deteriorated when the input and output voltages have larger voltage difference. Therefore, in this paper a low dropout regulator is connected in series with the switched capacitor voltage converter is presented to behave as the pre-regulator for supplying the next step-down converter to achieve high conversion efficiency. The advantages of these two architectures are merged to provide a set of stable and dual adjustable output voltages. The switched capacitor voltage converter contains two types of fractional gain to step down the supply voltage and through controlling the switches composed of the power MOSFETs makes the converter have three work modes including 1X, 2/3X, and 1/2X. This buck regulator can convert a varied input voltage (2.5V~5V) to a fixed output voltage (1.8V or 2V) and the maximum output load current is up to 150mA. The implementation circuits are simulated by HSPICE in TSMC 0.25um 1P5M BCD process of CMOS technology.