IEEE Trans Biomed Circuits Syst. 2011 Apr;5(2):131-7. doi: 10.1109/TBCAS.2011.2106125.
The demand for greater battery life in low-power consumer electronics and implantable medical devices presents a need for improved energy efficiency in the management of small rechargeable cells. This paper describes an ultra-compact analog lithium-ion (Li-ion) battery charger with high energy efficiency. The charger presented here utilizes the tanh basis function of a subthreshold operational transconductance amplifier to smoothly transition between constant-current and constant-voltage charging regimes without the need for additional area- and power-consuming control circuitry. Current-domain circuitry for end-of-charge detection negates the need for precision-sense resistors in either the charging path or control loop. We show theoretically and experimentally that the low-frequency pole-zero nature of most battery impedances leads to inherent stability of the analog control loop. The circuit was fabricated in an AMI 0.5-μm complementary metal-oxide semiconductor process, and achieves 89.7% average power efficiency and an end voltage accuracy of 99.9% relative to the desired target 4.2 V, while consuming 0.16 mm(2) of chip area. To date and to the best of our knowledge, this design represents the most area-efficient and most energy-efficient battery charger circuit reported in the literature.
在低功率消费电子产品和可植入医疗设备中，对更大电池寿命的需求对小型可充电电池的管理提出了提高能源效率的要求。本文介绍了一种超紧凑的模拟锂离子（Li-ion）电池充电器，具有很高的能源效率。本文提出的充电器利用亚阈值运算跨导放大器的 tanh 基函数，在无需额外的面积和功耗控制电路的情况下，平稳地在恒流和恒压充电模式之间转换。用于充电结束检测的电流域电路无需在充电路径或控制环路中使用精密感测电阻器。我们从理论和实验上表明，大多数电池阻抗的低频极点-零点特性导致模拟控制环路的固有稳定性。该电路采用 AMI 0.5-μm 互补金属氧化物半导体工艺制造，实现了 89.7%的平均功率效率，与所需的 4.2 V 目标相比，端电压精度为 99.9%，同时消耗的芯片面积为 0.16 mm(2)。据我们所知，到目前为止，这一设计代表了文献中报道的最节省面积和最节能的电池充电器电路。
