小面積無放大器之數位控制鋰電池充電器

Abstract

鋰電池具備了高能量密度、高循環壽命、高電壓、以及不具記憶效應，因此在攜帶式裝置上，鋰電池是最好的選擇。然而，鋰電池的安全性相當重要，過度充電會損毀鋰電池之物理結構，甚至會導致爆炸。本論文實現兩種不同架構之鋰電池充電器，並提供定電流充電及定電壓充電之功能。 第一個作品為一個以類比低壓降穩壓器為基礎的鋰電池充電器。其具有簡單的電路架構及達到很小的電流漣漪，並且利用二極體形式的NMOS確保定電流和定電壓充電模式轉換時之穩定度。本作品以台積電0.35μm CMOS製程實現，輸入電源為5 V，最後輸出電壓穩在4.2 V，定電流充電之電流為600 mA而晶片面積為1.94 mm^(2)。 第二個作品提出全新數位控制架構，實現一個小面積無放大器之數位控制鋰電池充電器。由於使用數位控制技巧，此充電器省去所有類比電路，並減少高功率電晶體的大小，由此達到小面積且設計簡單化的效果。此外，數位控制之架構也讓此作品擁有更好的製程擴展性。此設計以台積電0.35μm CMOS製程實現，輸入電源為5 V，最後輸出電壓穩在4.2 V，定電流充電電流為600 mA而晶片面積僅0.768 mm^(2)。

Lithium-ion (Li-Ion) batteries have high energy density, high cycle life, and no memory effect. Therefore, Li-Ion batteries are the most suitable battery for portable devices. However, the safety of Li-Ion battery is very important. Over discharging and over charging may damage the physical structure of Li-Ion batteries, resulting in reduced battery life or even explosion. In this thesis, two compact Li-Ion battery chargers are proposed with different topologies, and provide essential charging operations including constant-current (CC) and constant-voltage (CV) modes. The first work is an analog LDO-based Li-Ion battery charger. This work features a simple circuit structure and achieves low current ripple. A diode-connected NMOS is used to ensure the stability during the transition from the CC to CV modes. This work is fabricated in TSMC 0.35-µm CMOS process with a 5-V power supply. The output voltage is 4.2 V, and the current in the CC mode is 600 mA with an area of 1.94 mm^(2). In the second work, an area-efficient, amplifier-less Li-Ion battery charger with a novel digitally-controlled architecture is proposed. Owing to the digitally-controlled technique, the proposed charger eliminates all analog circuits and reduces the size of the power transistor. Hence, the proposed charger features a simple circuit structure and a small chip area. Additionally, the nature of digital control suggests that the proposed charger has better process scalability. This work is implemented in the TSMC 0.35-µm CMOS process with a 5-V power supply. The output voltage is 4.2 V, and the charging current in the CC mode is 600 mA with an area of only 0.768 mm^(2).