具有智能热调整功能的单片线性锂离子电池充电器IC研究与设计

【作者】 李涛峰；

【导师】 李平；

【作者基本信息】 电子科技大学 ， 微电子学与固体电子学， 2007， 硕士

【摘要】 锂离子电池由于体积小、重量轻、能量密度高和循环寿命长等优点,在便携式设备中得到了广泛的应用。由于锂离子电池的使用寿命与锂离子电池充电器的充电方法密切相关,充电器必须安全、快速、效率高。本文分析了锂离子电池的化学原理、常用充电方法以及这些充电方法对锂离子电池性能的影响,考虑到IC的成本,采用CMOS工艺设计了一款具有智能热调整功能的单片线性锂离子电池充电器IC。本文设计的线性锂离子电池充电器IC在恒流/恒压充电模式的基础上,增加了涓流充电模式和智能热调整模式。在充电初期若锂离子电池电压很低时(小于2.485V),充电器IC采用涓流模式对电池充电,实现对电池的修复和保护;一旦电池电压上升到大于2.485V,IC采用恒流模式对电池充电,实现快速充电的目的;当电池电压上升到最终充电电压4.1V或4.2V时,IC采用恒压模式对电池充电,确保电池被充满。在恒流充电阶段,当电源电压高而电池电压低时,充电器IC产生的高功耗导致IC温度急剧上升,在温度上升到约105℃时,IC会进入智能热调整模式工作;智能热调整模式使充电电流减小并维持IC的温度不变,在保护IC的同时兼顾了充电速度。此外,本文增加了电源状态和电池状态检测,不间断的检测电源电压和电池的充电电压、充电电流和温度,以确保充电器的正常工作和在充电过程中电池的正常工作,实现了对充电过程的智能化控制。采用用户可编程的方式设计充电器IC的充电电流、充电时间和电池最终充电电压等参数,实现了与用户的交互式管理。本文通过HSPICE对充电器IC进行了容差分析,仿真结果证实充电器IC的充电电流和锂离子电池最终充电电压等关键参数对器件参数随工艺角的变化不敏感,对电源电压在4.5V至6V范围内的变化和对温度在-40℃至125℃范围内的变化也不敏感。电池最终充电电压的最坏情况在基准电压未进行微调时为4.1/4.2V±0.8%,在基准电压进行微调后为4.1/4.2V±0.4%。更多还原

【Abstract】 Li-ion battery is widely used in the portable application for its light weight, small size, high energy density and long life. Because the method of charging affects the Li-ion battery’s life, charger must have the qualities of safety, reliability, fast speed and high efficiency. The chemic theory of Li-ion battery is studied in this paper. Based on the analysis of impacts on the performance of Li-ion battery with different charging methods and the consideration of cost, a monolithic linear Li-ion battery charger IC with intelligent thermal regulation is designed by CMOS process.The trickle charge mode and intelligent thermal regulation are added in the constant- current/constant-voltage charge mode in this paper. At the beginning of charge cycle, if the battery voltage is low (below 2.485V), the IC goes into trickle charge mode to bring the cell voltage up to a safe level for charging. The IC goes into the fast charge constant-current mode once the battery voltage rises above 2.485V. When the battery approaches the final float voltage, the charge current begins to decrease and the charge cycle switches to constant-voltage mode. The constant-voltage mode guarantees that the battery is fully charged. In the constant-current mode, the junction temperature rises rapidly for the excessive power dissipation when the input voltage is high and the battery voltage is low. When the temperature rises to about 105℃, the charge cycle goes into the intelligent thermal regulation mode. The IC can be protected in the charge proceeding because thermal regulation decreases the charge current and maintains the charger’s temperature. Besides, the battery under and over temperature protection block, the battery status detection module, and the power supply status detection module are also added to the IC to ascertain that the IC works correctly. The methods above realize the intelligent control of the charging process. As to the charge current, the total charge time and the final float voltage design adopts programmable form to realize interactive management with users.The HSPICE tolerance simulation results prove that the IC can work correctly and its work is not sensitive to the change of process corner, power supply voltage in the range of 4.5V to 6V, temperature in the range of -40℃to 125℃. The final floating voltage of battery in the worst case is 4.1/4.2V±0.4% when the voltage reference is trimmed and 4.1/4.2V±0.8% when the voltage reference is not trimmed.更多还原