Lithium ion battery handset battery charger present situation and prospect
August 8, 2008 – 7:53 pmAuthor Email: zhh@ httc.com.cn
[abstract]The lithium ion battery’s superperformance, causes it in the portable product (handset, notebook, PDA and so on) the application is getting more and more widespread, uses in the lithium ion battery’s battery charger in designing and in the function also day by day consummates. This article mainly introduced the lithium ion battery handset battery charger’s market present situation, the prospects for development, as well as present popular circuit design.
[key word]Lithium ion battery, battery charger
First, introduction
The lithium ion battery has the high energy load ratio and the energy volume compared to, non-memory effect, but the recharge number of times are many, the service life is long, the price is also getting more and more low. Its these characteristics promoted the portable product to develop to a smaller lighter direction, cause to select the single-node lithium ion battery power supply the product to be also getting more and more.
The lithium ion battery’s deficiency lies to battery charger’s request is quite harsh, is high to protection circuit’s request. Its request’s charge way is the constant flow constant pressure way, for the effective use battery capacity, must the lithium ion battery charge to the greatest voltage, but has pressed the charge to be able to create the battery damage, this requests the high control precision (precision to be higher than 1%). Moreover, needs to carry on pre-sufficiently regarding the voltage excessively low battery, charge termination examination besides voltage examination, but must use other aiding method achievement to prevent the sufficient reserve measure, like the examination battery temperature, the definition duration of charging, is the battery provides the additional protection. Thus it can be seen realizes the safe highly effective charge control into lithium ion battery promotion application bottleneck.
The lithium battery battery charger’s essential requirements are the specific charging current and the charging voltage, thus guaranteed that the battery charges safely. Increases the other charge auxiliary function is to improve the battery life, simplifies battery charger’s operation, after including has given the electric discharge battery use trickling charge, the battery voltage examination, the input current limit, the charge complete, shuts off battery charger, battery partial discharges, the automatic start charge and so on. All or part these functions may realize in the charge chip, certainly, may also using ASIC, establish separately the component, or realizes in microprocessor’s foundation with the software.
Second, domestic handset battery charger market conditions
At present, in market handset battery charger great variety, but also has the many quality inferior certified products. Spot-checked in the result at last year product quality country surveillance, nearly 40% factory production’s battery charger will be unqualified. Its subject matter appears in: With exchange network source’s connection, power source post harassment voltage, radiation harassment field intensity and charging voltage several aspects. Moreover, some aspects and so on product’s low temperature performance, rated capacity, electric discharge performance, safekeeping of security performance have the quality problem. These quality question will affect handset’s normal use, will also affect handset’s service life, will be serious when also possibly will injure the consumer.
Now in the market the discovery has some fake and shoddy handset battery portable battery charger. Because these battery chargers the price is low, carries conveniently, many handset user is willing to use these battery chargers to come to the battery to carry on the charge. The inferior battery charger in fact is one does not have the security guarantees simple transformer, because the interior lacks guarantee security and so on protection circuit spare parts, thus weight original installation light many. But in fact, because present’s handset battery uses the lithium ion battery or the nickel hydrogen battery makes the electricity core, to battery charger’s voltage, the electric current characteristic and the safekeeping of security has the very high request. Because these fake and shoddy battery chargers design simply, uses the inferior material, the processing method is rough, has the very big harm to the handset battery’s performance and the life. Protection circuit’s battery charger, because cannot guarantee time the charge electric current stability, will thus have burns out the danger which the battery will even explode.
At present the handset battery charger mainly has the travel battery charger, the place type battery charger and the vehicle carries the battery charger. The factory production’s original installation travel battery charger and the place type battery charger, in the design uses more and more precise protection circuit or the switching circuit design, to battery’s charge good protective function. The vehicle carries the battery charger to be possible to facilitate the user on the automobile is the handset charge, an end insertion cigar lighter, another end connection handset, but not suitably in automobile medium and long-term charge, because in the automobile the temperature is high.
Third, handset battery charger’s market trend
1. At present, the handset battery charger may divide into the single cavity shape and the double trough battery charger, the list grooved battery charger is coming under the double grooved attack. The double grooved battery charger besides has the slow charge, the rapid charge rate, the electric discharge and the nickel cadmium, the nickel hydrogen battery concurrently sufficient standard function, but also has the partial products to have the automatic temperature control and the voltage control, has taken strict precautions against the sufficient new function, thus the consumer should favor in chooses the double trough battery charger.
2. Because along with handset type’s day-by-day increase, each kind of battery charger the type is different, the power source port’s size is not same, thus cannot exchange the use, has brought inconveniently to the consumer. The standard battery charger, is refers to may connect all handset bottom end power point. (port) the battery charger. Moreover, the production handset’s power source port will unify to be suitable for the standard battery charger’s specification. Thus, the consumer will not need when each time to trade the handset simultaneously purchases the new battery charger. Thus it can be seen, the battery charger while from the sitting which to directions and so on portable, double-trough type develops, also starts to standardized, the universalized direction to develop.
3. The handset battery charger waits for an opportunity the power consumption to reduce becomes in a battery charger’s design process important link gradually. Compares in the beforehand battery charger, from now on will produce the product will further reduce while each function perfect will wait for an opportunity the power consumption. In order to achieve this goal, may design one to judge the AC adapter whether to connect the load (handset) IC, when has not connected the load, (2 levels of electric circuits) cuts on the high impedance electric circuit the AC adapter’s direct-current output side. Through adopts this measure may reduce largely waits for an opportunity when 2 level of electric circuit’s current sinkings (to be possible to achieve dozens of μA). Moreover, but may also, in the input exchanges the 100V side (1 level of electric circuits) to establish the cut electric circuit. When has not connected the load, reduces supplies for the direct-current output side (2 levels of electric circuits) the power through the switch cut electric circuit, thus reduced power consumption.
4. in the present market’s majority of battery chargers, are only aim at the lithium battery or the nickel hydrogen battery charge, but along with the market development, the automatic diagnosis two kind of batteries carries on the corresponding charge advancement the battery charger to occupy the mainstream gradually. May distinguish the lithium battery or the nickel hydrogen battery’s place automatically sufficient energy “prevents the lithium electricity electric discharge malfunction”, if in sufficient lithium battery time was not careful that according to arrived at place sufficient on “to put the push-button”, the good place sufficient might recognize is a lithium battery, will therefore not make the electric discharge movement; The difference place is sufficient, then gives the heck with carries on the electric discharge, this will create the lithium battery life the buckle.
Fourth, handset battery charger’s design requirements
At present some big factory production’s handset battery charger has the following characteristic: The wide scope AC input or the multi-country voltage may elect; Has the current limiting protection, the electric current short circuit and the counter-sufficient protection line design; The volume is small, the weight is light; Automatic, rapid charge rate, after filling the electricity, automatic cutout and so on. Moreover, some battery chargers also have the automatic diagnosis lithium ion, the nickel hydrogen, the nickel cadmium cell group; Has the electric discharge function; LED charge condition demonstration; Low noise; Characteristics and so on simulation microcomputer control system.
Use intelligent control battery charger module diagram general as follows:
Fifth, handset battery charger work flow
At present the handset battery charger’s work flow is generally:
1. Examines battery’s voltage, if is lower than a threshold voltage, must carry on the trickling charge;
2. When the battery imitates to certain voltage (general establishment is 2.9V), carries on the full current charge;
3. When the battery voltage achieves the initialization voltage (lithium ion battery is generally 4.2V), starts the constant pressure charge, simultaneously the charging current reduces;
4. When the electric current reduces gradually to the stipulation value, the charging-up ended.
Take American TI Corporation’s BQ2057 as the example, its charge flow is as follows:
Except the above flow description, it also has the battery temperature monitoring which may elect, examines the battery temperature continuously using the battery temperature sensor, when the battery temperature surpasses the hypothesis scope BQ2057 closure to battery charge. Moreover, the charge condition recognition may realizes by the output LED indicating lamp or with the master controller connection, has recharges automatically, minimum current characteristics and so on termination charge, low power loss dormancy.
Generally speaking, when in constant pressure charge conclusion undercurrent charging-up, electric current size generally for constant flow charge when electric current 1/10. At present in the lithium ion battery charger’s design, had finished after the handset charge as a result of some kind of factor electric discharge situation, but designed specially examined the electric circuit, once examined the battery voltage to reduce, (see above will start the charging-up chart).
Its model’s charge pattern like chart shows:
In summary, arises suddenly the development which along with the portable product advances vigorously, particularly handset’s popularization, as well as the lithium ion battery’s widespread application, the lithium ion battery charger’s design and the function are facing the further improvement. Regarding the numerous battery charger Manufacturer, designs the function to consummate, the safe practical battery charger as soon as possible, can earlier occupy the leading position in the market, the grab opportunity.
