基于便携机的锂离子蓄电池充电器的设计

Design of the lithium-ion battery charger based on portable computer

为了满足不同便携式计算机中锂离子蓄电池组对充电器的需求,介绍了如何运用锂离子蓄电池专用充电控制芯片MAX745进行充电器的设计。首先介绍了该充电控制芯片的拓朴结构及锂离子蓄电池所要求的先进行恒流充电后进行恒压充电的控制机理;后阐述了针对不同电池组的要求进行充电电压、充电电流及最小输入电压等参数的设计,以实现对1～4节任意相串的锂离子蓄电池组进行充电的目的。由于MAX745芯片内含国际上先进的同步整流技术,工作频率为300kHz、最大充电电流可达4A、充电电压精度高于0.75%,所以此充电器不但可快速、精确地完成对锂离子蓄电池组的充电,而且其转换效率高达90%以上。实际应用证明,用MAX745控制芯片设计的充电器电路简洁、安全、可靠,能满足便携式计算机所需的大电流、高精度、体积小、质量轻的要求。

In order to meet the requirement of the lithium-ion battery in diverse portable computers to the charger, it introduced the method of how to design a charger using the lithium-ion battery appropriative charge control chip MAX 745. Firstly, it introduced the topological structure of the charge control chip, and the mechanism of first constant current charge and then constant voltage charge which is required by the lithium-ion battery. Then it explained how to design the parameters as charge voltage, charge current and minimum input voltage etc.for the requirement of diverse batteries. And then we can charge whatever lithium-ion battery in series of 1-4 cells. In the MAX 745 chip, there is the most advanced technique of synchronous rectifier in the world with the frequency of 300 kHz, the charge voltage precision up to 75% and 4 A of charge current. So the charger can not only fleetly and accurately complete the charge of the lithium-ion battery, but also reach the switch efficiency of 90% above. It is proved in practice that the charge circuit designed with the MAX 745 charge control chip is concise, safe and reliable. It can satisfy the requirement of large current, high precision, small volume and light weight by portable computers.