3 circuit optimize your charger design
[introduction] dear, where is my charger? Current and character, this may be the commonnest problem in the life. Of the century hand in, batteries (the batteries that is based on lithium ion especially) of cost reduce and of function rise, drove batteries power supply store can mix of portable equipment grow steadily. In addition, because super capacitor has distinctive quality, use increasingly also at all sorts of application.
Plumbic acerbity batteries is a technology that already had 150 years of histories, still use extensively at car of car, wheelchair, footplate, golf cart and UPS up to now (UPS) system. Once energy is extinct, these store can equipment must charge afresh. 2019, the whole world charges IC shipment volume is 1.16 billion, predict to reached growth 1.72 billion 2024, year increase rate is 8.6% , quite healthy. Income is mixed for 518.1 billion dollar respectively 735.4 billion dollar, compound year of increase rate for 7.3% . Graph 1 showed this one trend, its come from OMDIA ” market of power source IC dogs – 2019 ” .
Graph 1. The whole world charges IC market
To the demand of course of development of boat of more electric power, longer add or run time, the demand rises store can the tension that equipment uses. For example, robot, unmanned aircraft, dynamoelectric tool and the lithium ion cell that use in a lot of other things pile to had increased from 9 battery unit many (most 12) batteries is unit. Caboodle of batteries of ion of lithium of a 12 core can offer the voltage of the biggest 50.4 V. Below rating of identical electric current, the add boat time of 12 core batteries is 12 times of 1 core batteries. Or, can 12 batteries paralell connection in order to gain higher power, but this kind of method can make electric current increases 12 times. Taller electric current can bring about more conduction loss, because this is unfavorable,use shunt-wound cell.
Belt reserve the lash-up illume of batteries, UPS reserves the industrial system such as power source, HVAC uses 24 VDC power source, although come with 24 V batteries,offer for these systems reserve power source. However, according to IEC 61131-2 and IEC 60664-1 standard, 24 VDC power source can rise below transient state condition to voltage of 60 V peak value.
Below a kind of any circumstances, equipment asks charger solution can get used to taller batteries voltage, can bear the taller input voltage during transient state incident.
Charger has a lot of develop to attack structure. Linear charger reduces the voltage difference between power source and batteries through power switch. Lowest of efficiency of this kind of charger, because become when the voltage difference between power source and batteries is very big, power switch can consume a large number of power. Step up charger goes to the voltage step up that comes from power source batteries voltage. This kind of develop attacks voltage of structural demand power supply under batteries voltage. Step-down charger undertakes step-down to coming from the voltage of power source, ask voltage of batteries of prep above of power source voltage. Step up – step-down charger can use prep above or charge for batteries under the power source voltage of batteries voltage. This kind of develop attacks the structure needs 4 power switch (step-down develop attacks to need two only) , and efficiency is general not tall.
Efficiency of charger of synchronous commutate step-down is highest, it is the key of the article. Graph 2 showed circuit of charger of step-down of a general and synchronous commutate. Nowadays, most step-down charger falls in relatively inferior voltage move. The rated input voltage of a lot of charger is 28 V only, some are 40 V. If allow ± ,the inputs voltage adjustment and 2 V step-down charger of 10% is pressed fall, so the charger of rating 28 V can be batteries of 5S lithium ion to pile only actually (the biggest) charge. We will study a new 60 V inputs charger IC series, its support charges higher voltage — batteries voltage is as high as 52 V (or batteries piles ion of 12 core lithium) , and can bear the input voltage twinkling of 65 V changes.
Graph 2. Charger of step-down of general and synchronous commutate
Of charger wait for machine electric current to answer very low in order to save the sources of energy. Energy Star? The regulation bides his time power comsumption is 30 MW or fewer mobile phone charger and other and small-sized charger are 5 stars. One star is applied to bide one’s time power comsumption is 300 MW or taller charger, other bit class applies to interpose at both the other charger between. Energy Star aims to reduce the power comsumption of individual charger, these charger also won’t unplug mostly when be not used come down. In any specific time, the whole world has join of more than 1 billion this kind of charger to arrive electrified wire netting.
Although lead is acerbity,batteries, lithium ion batteries and super capacitor are store can equipment, but their charge / discharge character is apparently different. We will inspect these character, discuss every to charge characteristicly solution. A good batteries charger can offer good batteries performance and durable sex, charge below disadvantage especially when.
Plumbic acerbity batteries is existent the oldest can charge batteries, invented by é of French doctor Gaston Plant 1859. After 150 years, it is used extensively still at cart of car of car, wheelchair, footplate, dynamoelectric bicycle, golf and UPS system.
Plumbic acerbity batteries must slow charge. The model charges time is 8 to 16 hours. Batteries must from beginning to end with charging condition stores, undertake complete saturation charges to be changed to preventing sulfate regularly crucial. Normally the practice is plumbic acid inside about 8 hours batteries charges to 70% , next reoccupy undertakes 8 hours the most important complemental charge. If plumbic acerbity batteries often accepts complete saturation to charge to be changed in order to prevent sulfate, charge to also be no problem partly. Make batteries long be in float to charge condition won’t cause damage.
Find ideal charge voltage is restricted to be worth crucial. Tall voltage (prep above 2.45 V/ is unit) can produce good batteries performance, but because the board bar on positive electrode board is corroded, battery service life can shorten. Low voltage is restricted to be worth can cause negative plate sulfate to change. Temperature also can affect batteries voltage, temperature coefficient model is worth C of ° of the 5 MV/ that it is – (0.028 V of unit of every battery of F of every 10 ° ) . Good charger must compensate this temperature coefficient, it is in order to prevent cell when high temperature overcharge or in the undercharge when microtherm.
For example, MAX17702 (refer to a graph 3) it is a complete plumbic acid batteries charger controller, the input of design support 4.5 V to 60 V voltage limits. This parts of an apparatus is offerred efficient (more than 97% ) , solution of tall voltage, synchronous step-down, can charge for group of acerbity batteries of lead of 12 V/24 V/48 V. Graph 4a and 4b showed its charge cycle and charge efficiency.
Graph 3. Controller of charger of high-pressured lead acerbity batteries
Acid of graph 4a.MAX17702 lead charges periodic
Graph 4b.MAX17702 charge efficiency
Density of energy of plumbic acerbity batteries is low, do not suit portable equipment. Portable equipment needs lithium battery.
Because weight is mixed gently high energy density, lithium ion batteries is the is used at drive of portable application, heavy industry, report and satellite cell that accepts generally.
The maintenance of lithium ion batteries workload is very few. This kind of batteries does not have memory effect, do not need intended and complete discharge to be able to maintain kilter. But it needs to protect circuit, batteries piles interior and charger to all need, in order to prevent short circuit, fill too, hot out of control and excessive discharge. If lithium ion batteries maintains below in 1.5 V/ unit a week or longer, produce branch shape crystal possibly, influence security.
To prevent excessive discharge, buy batteries protects position of Morpheus of park of circuit general batteries inside. Store below discharge condition when batteries, make from discharge voltage drop comes when cut off, can produce afore-mentioned situations. Groovy charger regards such batteries as cannot use, batteries bag is discarded normally. Charger of advanced lithium ion is had wake up character or ” charge beforehand ” function, the lithium ion batteries that can enter Morpheus state to be being entered as a result of excessive discharge charges. Charging beforehand in mode, the charging current with charger very small application arrives with promoting voltage security between 2.2 V/ unit and 2.9 V/ unit, activation thereby protective circuit, begin to charge normally next.
During charging normally, lithium ion charger with constant current constant voltage (CCCV) mode moves. Charging current is constant, when voltage achieves set to be restricted to be worth, rise no longer. When achieving voltage to be restricted to be worth, batteries saturation, electric current drops batteries cannot till reassume charges further, charge right now stop. Every batteries has threshold value of his small electric current.
When ionic batteries is charging, lithium should keep cool from beginning to end. Lithium ion batteries cannot admit overmuch charge. Accordingly, monitoring batteries temperature reachs his to charge voltage is mixed with ensuring batteries is healthy safety is very important. Good charger must include these character.
Graph 5 gave out the example of charger of batteries of advanced lithium ion. MAX17703 is controller of charger of an efficient, tall voltage, synchronism, step-down, the wide input of design support 4.5 V to 60 V voltage limits. This parts of an apparatus is most batteries caboodle offerred ion of 12 core lithium to charge thoroughly solution.
Graph 5. Circuit of charger of batteries of ion of lithium of advanced tall voltage
Accurate CCCV charging current is offerred when this parts of an apparatus is 1 ％ of 4 ％ of ± and ± respectively / voltage. When charging current reduces threshold value of ending electric current, charger enters complement to charge condition; After ending timer cycle ends, charger is exited charge condition. Should output electric depress at charging when threshold value voltage, charger is started charge periodic. This is a very strong character, can let stay for long in charge a batteries that go up hold full report position, and won’t consume too much electric power, and accord with Energy Star requirement. This parts of an apparatus can detect and batteries of pretreatment deepness discharge, use charge beforehand character wakes up his. To provide more protection, this parts of an apparatus can detect batteries temperature, make charge to be able to undertake inside formulary temperature limits only. It still has an input short circuit to protect character, use at batteries discharge preventing when inputting accident short circuit. Graph 6 those who showed MAX17703 charge periodic.
Batteries of ion of graph 6.MAX17703 lithium charges periodic
Super capacitor has a few distinct advantages than batteries, because this is used increasingly at all sorts of application. Super capacitor works according to electrostatic principle, without chemical reaction, avoided the life problem related as chemical as batteries memory. Its are tall durable sex allows millions second fill / discharge circulates, service life is as long as 20 years, than batteries tower above an amount class. Its are low impedance support charges quickly and discharge, a few seconds achievable. Additional, it still has the capacity that carries charge for long moderately, all these makes super capacitor suits to need to fill the application that discharge circulates quickly very much. Super capacitor still can be used with batteries paralell connection, the application that power of instantaneous peak value transmits needs during holding load is changed thereby.
Of super capacitor fill discharge to ask charger can handle big electric current circularly quickly, charging in the process with constant current (CC) mode works smoothly, charge to begin possibly from 0 V, once reach final output value, criterion with constant voltage (CV) mode works. In tall voltage application, a lot of super capacitor establish ties together, need charger will manage tall input and output voltage.
MAX17701 (refer to a graph 7) it is an efficient, tall voltage, synchronism, step-down controller of super capacitance charger, charge for big electric current only and design, can come in 4.5 V the input voltage limits of 60 V (the job inside VDCIN) . Output voltage but process designing, limits comes for 1.25 V (VDCIN – 4 V) . This parts of an apparatus uses exterior N-MOSFET to provide side of input power source ” logistic or ” function, prevent super capacitor discharge to return input end. Graph 8 showed simple but electric current is very tall charge curve.
Graph 7. Tall voltage, big electric current is super capacitance charger
Graph 8.MAX17701 super capacitance charges curve
Of batteries power supply store can grow steadily with the use of portable equipment. To the demand of course of development of boat of more electric power, longer add or run time, the demand rises batteries to pile use tension. In the industrial system application of power source of use 24 VDC, tension of 60 V peak value can see below transient state condition. Traditional charger solution inputs in the limit of with 28 V mostly. Step-down of synchronism of profit from tall voltage charges develop attacks structure, the new-style charger solution of ADI company can realize taller batteries to pile voltage and charge efficiency.
Plumbic acerbity batteries, lithium radical batteries and super capacitor are store can equipment, have very different charge / discharge is characteristic, need special charger ability to obtain best charge solution. Advanced batteries charger still provides sufficient protection in order to ensure batteries function and durable sex, charge below disadvantage especially when. These also get settlement in newer charger solution.
(origin: Yadenuo semiconductor)
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