内容简介：: 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 hour can be to stop refresh.Please consult the norm that the battery produces the company( battery of NiCdOf typical model be worth for the 1 oC/ min) the be applicable to the battery of NiCd and battery of NiMHs.Need to stop refresh when the DT outrun the temperature value of the environment temperature to be the bad battery temperature and the environme

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