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锂电池充电器的设计介绍根据其尺寸，重量和能量储存优点，锂- 离子可再充电电池正在被用于许多的应用领域。这些电池已经被考虑为优先的电池于手提式计算机的应用,移置 NiMH 和 NiCad电池,而且行动电话正在飞快地成为锂电池的第二个主要的市场。 理由是明显的。 锂- 离子的电池提供很多的好处对与终端消费者。 对于手提式计算机来说,锂- 离子电池在相同条件和大小并减少重量的情况下能够提供比 NiCad 和 NiMH更为持久的电力。 相同的优点对于蜂窝电话更是真实的。一个电话能被做得更小和更轻如果使用李- 离子的电池的话而不牺牲续航时间。 当锂- 离子的电池费用降下来的话,甚至更多的应用将会转变到这一个更轻巧和更小巧的技术上来。当消费者一直要求方便的时候，市场的趋势表明一个持续不断的增长在所有的可再充电的电池中。 根据以前市场的资料大约在 1997年的时候表明大约二亿个锂-离子电芯将会被装船运送,相比较于 600 百万 个NiMH的电芯 。 然而,有必要说明的是三个NiMH 的电芯相当于一个锂- 离子的电芯在被包裹为电池包装的时候。 因此，真实的体积对两者来说是非常接近一样的。1997年也被标记为第一年锂- 离子作为电池类型用于在大多数的手提式的计算机中, 移置 NiMH 为高端领域中。 资料显示1997年在欧洲和日本电池电芯市场表现出一个变化对于锂- 离子在多数的电话的应用中。锂- 离子的电池是一种令人兴奋的电池技术必须给于高度的关注。要想 了解这些新的电池，这设计引导者解释这些原则，要价需求以及符合这些需求的线路。随着越来越多的手持式电器的出现，对高性能、小尺寸、重量轻的电池充电器的需求也越来越大。电池技术的持续进步也要求更复杂的充电算法以实现快速、安全的充电。因此需要对充电过程进行更精确的监控，以缩短充电时间、达到最大的电池容量，并防止电池损坏。AVR 已经在竞争中领先了一步，被证明是下一代充电器的完美控制芯片。Atmel AVR 微处理器是当前市场上能够以单片方式提供Flash、EEPROM 和10 位ADC的最高效的8 位RISC 微处理器。由于程序存储器为Flash，因此可以不用象MASK ROM一样，有几个软件版本就库存几种型号。Flash 可以在发货之前再进行编程，或是在PCB贴装之后再通过ISP 进行编程，从而允许在最后一分钟进行软件更新。EEPROM 可用于保存标定系数和电池特性参数，如保存充电记录以提高实际使用的电池容量。10位A/D 转换器可以提供足够的测量精度，使得充好后的容量更接近其最大容量。而其他方案为了达到此目的，可能需要外部的ADC，不但占用PCB 空间，也提高了系统成本。AVR 是目前唯一的针对象 “C”这样的高级语言而设计的8 位微处理器。AT90S4433 参考设计就是用 “C”写的，说明用高级语言进行软件设计是多么的简单。C 代码似的此设计很容易进行调整以适合当前和未来的电池。而ATtiny15 参考设计则是用汇编语言写的，以获得最大的代码密度。现代消费类电器主要使用如下四种电池： 密封铅酸电池 (SLA) 镍镉电池 (NiCd) 镍氢电池(NiMH) 锂电池(Li-Ion)在正确选择电池和充电算法时需要了解这些电池的背景知识。密封铅酸电池(SLA) 密封铅酸电池主要用于成本比空间和重量更重要的场合，如UPS和报警系统的备份电池。SLA 电池以恒定电压进行充电，辅以电流限制以避免在充电过程的初期电池过热。只要电池单元电压不超过生产商的规定( 典型值为2.2V)， SLA 电池可以无限制地充电。镍镉电池(NiCd) NiCd 电池目前使用得很普遍。它的优点是相对便宜，易于使用；缺点是自放电率比较高。典型的NiCd 电池可以充电1,000 次。失效机理主要是极性反转。在电池包里第一个被完全放电的单元会发生反转。为了防止损坏电池包，需要不间断地监控电压。一旦单元电压下降到1.0V 就必须停机。NiCd 电池以恒定电流的方式进行充电。镍氢电池(NiMH) 在轻重量的手持设备中如手机、手持摄象机，等等镍氢电池是使用最广的。这种电池的容量比NiCd 的大。由于过充电会造成NiMH 电池的失效，在充电过程中进行精确地测量以在合适的时间停止是非常重要的。和NiCd 电池一样，极性反转时电池也会损坏。NiMH 电池的自放电率大概为20%/ 月。和NiCd 电池一样，NiMH 电池也为恒定电流充电。锂电池 (Li-Ion) 和本文中所述的其他电池相比，锂电池具有最高的能量/ 重量比和能量/ 体积比。锂电池以恒定电压进行充电，同时要有电流限制以避免在充电过程的初期电池过热。当充电电流下降到生产商设定的最小电流时就要停止充电。过充电将造成电池损坏，甚至爆炸。电池的安全充电现代的快速充电器( 即电池可以在小于3 个小时的时间里充满电，通常是一个小时) 需要能够对单元电压、充电电流和电池温度进行精确地测量，在充满电的同时避免由于过充电造成的损坏。充电方法SLA 电池和锂电池的充电方法为恒定电压法要限流； NiCd 电池和NiMH 电池的充电方法为恒定电流法，且具有几个不同的停止充电的判断方法。最大充电电流最大充电电流与电池容量(C) 有关。最大充电电流往往以电池容量的数值来表示。例如，电池的容量为750 mAh，充电电流为750 mA，则充电电流为1C (1 倍的电池容量)。若涓流充电时电流为C/40，则充电电流即为电池容量除以40。过热电池充电是将电能传输到电池的过程。能量以化学反应的方式保存了下来。但不是所有的电能都转化为了电池中的化学能。一些电能转化成了热能，对电池起了加热的作用。当电池充满后，若继续充电，则所有的电能都将转化为电池的热能。在快速充电时这将使电池快速升温，若不及时停止充电就会造成电池的损坏。因此，在设计电池充电器时，对温度进行监控并及时停止充电是非常重要的。停止充电的判别方法电池的不同应用场合及工作环境限制了对判断停止充电的方法的选择。有时候温度不容易测得，但可以测得电压，或者是其他情况。本文以电压变化率(-dV/dt) 为基本的判断停止充电的方法，而以温度和绝对电压值为辅助和备份。但是本文所描述的硬件支持以下讲述的所有的方法。t 时间这是决定何时停止充电的最简单的方法。通常用于快速充电时的后备方案。有时也作为普通充电 (14 - 16 小时) 方法的基本方案。适用于各种电池。V 电压当电压超出上限时停止充电。通常与恒定电流充电配合使用。最大电流由电池决定，通常为1C。为了防止充电时电流过大导致电池过热，此时电流限制是非常关键的。这个方法是锂电池的基本充电和停止方案。实际锂电池充电器往往在达到最大电压之后还继续进行第二阶段的充电，以达到100% 的电池容量。对于NiCd 电池和NiMH 电池本方法可以作为后备的判断停止充电方案。-dV/dt 电压变化率这个判断停止充电的方法利用了负的电压变化率。对于某些类型的电池，当电池充满后继续充电将导致电压的下降。此时本方案就非常合适了。这个方法通常用于恒定电流充电，适用于对NiCd 电池和NiMH 电池的快速充电。I 电流当充电电流小于某个预先设定的数值时停止充电。通常用于恒定电压充电法。适用于SLA电池和锂电池。T 温度绝对温度可以作为NiCd 电池和NiMH电池停止充电的依据，但是更适合于作为备份方案。温度超出设定值时任何电池都得停止充电。dT/dt 温度上升速率快速充电时温度的变化率可以作为停止充电的依据。请参考电池生产商的规范(NiCd电池的典型值为1oC/min) 适用于NiCd 电池NiMH 电池。DT 超出环境温度的温度值当电池温度和环境温度之差超过一定门限时需要停止充电。此方法可以作为NiCd 电池和SLA 电池停止充电的方案。在寒冷环境中充电时这个方法比绝对温度判定法更好由于大多数系统往往只有一个温度探头，只好将充电之前的温度作为环境温度。dV/dt = 0 零电压差这个方法与-dV/dt 方法极其类似，而且在电压不会再升高的情况下更准确。 适用于NiCd电池和NiMH 电池。本参考设计完全实现了电池充电器设计的最新技术，可以对各种流行的电池类型进行快速充电而无须修改硬件，从而围绕单个硬件平台实现一个完整的充电器产品系列。只需要将新的充电算法通过ISP 下载到处理器的FLASH 存储器就可以得到新的型号。很显然，这种方法可以大大缩短新产品上市的时间，而且只需要库存一种硬件。本设计提供完整的适合SLA、NiCd、NiMH 和Li-Ion 电池的库函数。The design of the lithium battery chargerIntroductionLi-Ion rechargeable batteries are finding their way into many applications due to their size, weight and energy storage advantages.These batteries are already considered the preferred battery in portable computer applications, displacing NiMH and NiCad batteries, and cellular phones are quickly becoming the second major marketplace for Li-Ion. The reason is clear. Li-Ion batteries offer many advantages to the end consumer. In portable computers,Li-Ion battery packs offer longer run times over NiCad and NiMH packs for the same form factor and size, while reducing weight. The same advantages are true for cellular phones. A phone can be made smaller and lighter using Li-Ion batteries without sacrificing run time. As Li-Ion battery costs come down, even more applications will switch to this lighter and smallertechnology. Market trends show a continual growth in all rechargeablebattery types as consumers continue to demand the convenience of portability. Market data for 1997 shows that approximately 200 million cells of Li-Ion will be shipped, compared to 600 million cells of NiMH. However, it is important to note that three cells of NiMH are equivalent to one Li-Ion cell when packaged into a battery pack. Thus, the actual volume is very close to the same for both. 1997 also marked the first year Li-Ion was the battery type used in the majority of portable computers, displacing NiMH for the top spot. Data for the cellular market showed a shift to Li-Ion in the majority of phones sold in 1997 in Europe and Japan.Li-Ion batteries are an exciting battery technology that must be watched. To make sense of these new batteries, this design guide explains the fundamentals, the charging requirements andthe circuits to meet these requirements.Along with more and more the emergence of the handheld electric appliances, to the high performance, baby size, weight need of the light battery charger also more Come more big.The battery is technical to progress to also request continuously to refresh the calculate way more complicatedly is fast with the realization, safety of refresh.Therefore need Want to carry on the more accurate supervision towards refreshing the process, to shorten to refresh time and attain the biggest battery capacity, and preventfrom the battery Bad.The AVR has already led the one step in the competition, is prove is perfect control chip of the next generation charger. The microprocessor of Atmel AVR is current and can provide Flash, EEPROM and 10 ADCses by single slice on the market Of 8 RISC microprocessors of the tallest effect.Because the saving machine of procedure is a Flash, therefore can need not elephant MASK ROM Similar, have a few software editions a few model numbers of stock.The Flash can carry on again to weave the distance before deliver goods, or in the PCB Stick after pack carry on weaving the distance through an ISP again, thus allow to carry on the software renewal in the last one minute.The EEPROM can used for conservancy mark certainly coefficient and the battery characteristic parameter, such as the conservancy refreshes record with the battery that raise the actual usage Capacity.10 A/ Ds conversion machine can provide the enough diagraph accuracy, making the capacity of the good empress even near to its biggest capacity. And other project for attaining this purpose, possible demand the ADC of the exterior, not only take up the space of PCB, but also raised the system Cost.The AVR is thus deluxe language but 8 microprocessors of the designs of unique needle object C currently.The AT90S4433 reference The design is with C to write, the elucidation carries on the software designs is what and simple with the deluxe language.Code of C this design is very Carry on adjust easily to suit current and future battery.But the ATtiny15 reference design then use edit collected materials the language to write of, with Acquire the biggest code density.An electric appliances of the modern consumption mainly uses as follows four kinds of batteries:1.Seal completely the sour battery of lead( SLA)2.The battery of NiCd3.The NiMHhydrogen battery( NiMH)4.Lithium battery( Li- Ion)At right choice battery and refresh the calculate way need to understand the background knowledge of these batteries. Seal completely the sour battery( SLA) of lead seals completely the sour battery of lead to mainly used for the more important situation of the cost ratio space and weights, such as the UPS and report to the police the backup battery of the system.The battery of SLA settles the electric voltage to carry on , assist limits to avoid with the electric current at refresh the process of early battery lead the heat.Want only the electricity .The pond unit electric voltage does not exceed the provision( the typical model is worth for the 2.2 Vs) of produce the company, the battery of SLA can refresh without limit.The battery of NiCd battery of NiCd use very widespread currently.Its advantage is an opposite cheapness, being easy to the usage;Weakness is from turn on electricity the rate higher.The battery of NiCd of the typical model can refresh 1,000 times.The expired mechanism mainly is a pole to turn over.The first in the battery pack drive over.The unit that all turn on electricity will take place the reversal.For preventfroming damage the battery wrap, needing to supervise and control the electric voltage without a break.Once unit electric voltage Descend the 1.0 Vs must shut down.The battery of NiCd carries on refresh in settling the electric current by forever . The NiMH hydrogen battery( NiMH) holds to shoot the elephant machine such as the cellular phone, hand in the hand that the importance measure hold equipments, the etc. NiMHhydrogen battery is an usage the most wide.This kind of battery permit.The quantity is bigger than NiCds.Because lead to refresh and will result in battery of NiMH lose efficacy, carry on measuring by the square in refresh process with.Stop is count for much in fit time.Similar to battery of NiCd, the pole turn over the battery also will damage.Battery of NiMH of from turn on electricity the rate and is probably 20%/ month.Similar to battery of NiCd, the battery of NiMH also settles the electric current to refresh .Other batteries says compare in lithium battery( Li- Ion) and this texts, the lithium battery has the tallest energy/ weight to compare to compare with energy/ physical volume.Lithium batterySettle the electric voltage to carry on refresh with , want to have the electric current restrict to lead the heat in the early battery of refresh the process by avoid at the same time.When refresh the electric currentDescend to produce the minimum electric current of the enactment of company will stop refresh.Leading to refresh will result in battery damage, even exploding.The safety of the battery refreshes the fast charge machine( namely battery can at small be filled with the electricity in 3 hours, is usually a hour) demand of the modern.Can to the unit electric voltage, refresh the electric current and the battery temperatures to carry on to measure by the square, avoid at the time of being filled with the electricity because of leading to refresh.Result in of damage.Refresh the method SLA battery and lithium batteries refreshes the method to settle the electric voltage method to want to limit to flow for the ever ; The battery of NiCd and battery of NiMHs refresh the method.Settle the electric current method for the ever , and have severals to stop the judgment method for refresh differently.Biggest refresh the electric current biggest refresh the electric current to have relation with battery capacity( C).Biggest usually refresh the electric current to mean with the number of the battery capacity.For example,The capacity of the battery for 750 mAhs, refresh the electric current as 750 mAs, then refresh the electric current as 1 C(1 times battery capacity).IfThe electric current to flow refresh is a C/40, then refreshing the electric current for the battery capacity in addition to with 40.Lead the hot battery refresh is the process that the electric power delivers the battery.Energy by chemical reaction conservancy come down.But is not all.The electric powers all convert for the sake of the chemistry in the battery ability.Some electric power conversions became the thermal energy, having the function of the heating to the battery.When electricity.After pond be filled with, if continue to refresh, then all electric powers conversion is the thermal energy of the battery.At fast charge this will make the battery.Heat quickly, if the hour of can not compare with stop refresh and then will result in battery damage.Therefore, while design the battery charger, to the temperature.It is count for much that carry on the supervision combine to stop refresh in time.The discretion method battery stopped refresh of different and applied situation and work environment limitted to the choice of the method that the judgment stop refresh.The sometimes temperature allow of no.Measure easily, but can measure electric voltage, or is other circumstances.This text takes the electric voltage variety rate(- dV/ dt) as the basic judgment to stopThe method for refresh, but with the temperature and absolute electric voltage be worth for assistance and backup.But the hardware support that this text describe speaks as follows.The method of the havings of say.Time of t this method that is the decision when stop refresh most in brief.Usually used for spare project of the hour of fast charge.Sometimes also be .Refresh(14- 16 Hour) basic project of the method.Be applicable to various battery.Stop refresh when the electric voltage of V be the electric voltage to outrun the upper limit.Usually with the forever settle the electric current refreshes the match usage.The biggest electric current is decide by the battery, usually For the 1 C.For preventfroming refresh the electric current leads to causes battery lead greatly hot, the restrict of the electric current at this time very key.This method Is a lithium battery basic to refresh and stop project. The actual lithium battery charger usually still continues into after attain biggest electric voltage Go the second stage refresh, to attain 100% battery capacity. For battery of NiCd and battery of NiMHs are originally method can Be the spare judgment stops refreshing the project. - The method exploitation that this judgment of the dV/ dt electric voltage variety rate stops refresh negative electric voltage variety rate.For the battery of some types, be the battery to be filled with the subsequence Refreshing continuously will cause electric voltage descend. At this time this project was very fit.This method usually useds for the ever to settle the electric current to refresh, Be applicable to to the fast charge of the battery of NiCd and battery of NiMH. The electric current of I is to refresh the electric current small in a certain the number that set in advance stop refresh. Usually used for the ever to settle the electric voltage to refresh the method.Be applicable to the SLA Battery and lithium battery.The T temperature absolute zero can be the basis that battery of NiCd and battery of NiMHs stop refresh, but even suited for to be the backup project.Any battery for temperature to outrun initial value have to stop refresh.The basis that the dT/ dt temperature rising velocity fast charge variety rate of the temperature of hou