延長電池壽命已經成為電池供電可攜式裝置設計者努力改善的一個課題。加大電池容量是一個普遍但成本會增加的方式，如何用系統的觀點來減少耗電量則是一個有效而且低成本的方法。本文是依據有效利用各元件省電模式的觀念來顯著減少個人數位助理 (PDA, Personal Digital Assistant) 的整體消耗功率。在我們的實驗中，我們量測Dell AXIM X50 PDA的每個功率軌道(power rail)上的電流來探究每個功率軌道消耗多少的功率。實驗是用以下三種狀況來執行：執行一個WMV檔案、閒置、關機。本文指出了把元件安置在合適的低功率模式對於預防不必要功率消散的重要性。實驗結果顯示中央處理器(CPU)在PDA關機時應該被切換到深睡眠模式(deep sleep mode)而不是睡眠模式(sleep mode)。把CPU切換到deep sleep mode所節省的功率相當於增加16.9個百分比的電池壽命。

Extending the battery lifetime has been an important topic that all the battery-powered portable device designers struggle to improve. Enlarging the battery capacity is one common but cost-plus way to achieve this goal. How to reduce power in terms of system viewpoint is one of the most effective ways to reduce power with minimal cost increased. Our work is based on the concept that effectively utilizing the power saving mode of each component to reduce whole power consumption by a significant amount in a Personal Digital Assistant (PDA). In our experiments, we measured the current of each power rail of a Dell AXIM X50 PDA to explore how much power is consumed by each power rail. Experiments were performed in 3 different conditions: Play a WMV file, idle, and system off. In this paper we pointed out the importance of placing components in the appropriate lower power states to prevent from unnecessary power dissipation. It showed that CPU should be switched to deep sleep mode instead of sleep mode when PDA is turned off. The power saved by switching the CPU to deep sleep mode can extend 16.9 percent of the PDA battery lifetime.

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