恒流_恒压充电方式的锂电池充电器芯片_英文_

第28卷　第7期2007年7月

半　导　体　学　报

C HIN ES E J OU RNAL O F S EM ICON

D U C TO RS

Vol.28　No.7

J uly ,2007

›Corresp onding aut hor.Email :chenc @

　Received 22J a nuary 2007,revised ma nuscript received 5March 2007

Z 2007Chinese Institute of Elect ronics

Chip Design of Li 2Ion B attery Charger Operating in

Constant 2Current/Constant 2V oltage Modes

Chen Chen ›and He Lenian

(I nstit ute of V L S I Desi gn ,Zhej iang Universit y ,Hangz hou 310027,Chi na )

Abstract :A design f or a L i 2ion battery charger IC t hat can operate in a constant curre nt 2consta nt voltage (CC 2

CV )charge mode is p rop osed.In t he CC 2CV charge mode ,t he charger IC p rovides a consta nt charging current at t he beginning ,a nd t he n t he charging curre nt begins t o decrease bef ore t he battery voltage reaches its final value.Af ter t he battery voltage reaches its final value and remains consta nt ,t he charging current is f urt her reduced.This app roach p revents charging t he battery wit h f ull curre nt near its saturated voltage ,w hich can cause heating.The novel design of t he core of t he charger IC realizes t he p rop osed CC 2CV charge mode.The chip was impleme nted

in a CSM C 016

μm CMOS mixed signal p rocess.The experimental results verif y t he realization of t he p rop osed CC 2CV charge mode.The voltage of t he battery af ter charging is 411833V.

K ey w ords :L i 2ion battery charger ;consta nt current 2constant voltage charge modes ;CMOS analog circuit EEACC :1205

C LC number :TN 401 Document code :A Article I

D :025324177(2007)0721030206

1　Introduction

Lit hium 2ion batteries have become t he mo st widely used rechargeable batteries due to t heir many advantages.Research o n charge management circuit s is meaningf ul for p ractical use.The Li 2ion battery charger IC developed in several p hases.In order to avoid t he overheating of batteries during t he charging p rocess ,t he earliest charger IC only supplied a constant but small charging current ,and was terminated manually.It required a long time to complete a charge cycle.Moreover ,manual termi 2nation lowers t he reliability ,because it may result in inefficient charge or overcharge.Cope et al.[1]p ropo sed a charging app roach t hat uses a constant ,large charging current to shorten t he charge time.However ,a large charging current not only makes a battery susceptible to overcharge ,but may also o 2verdrive t he available chemical reactions in t he bat 2tery ,resulting in heating and finally reducing t he capacity and cycle life of t he battery.

The charge met hod wit h constant current 2con 2stant voltage (CC 2CV )modes [2,3]has been employed as an improvement over t he constant current ap 2proach.U nder t his arrangement ,a constant current

is applied until t he battery voltage rises to a p rede 2termined value ,i.e.,t he sat urated voltage ,and t hen t he charge current gradually decreases while t he battery voltage remains constant.When t he current reaches a minimum value ,t he charge cycle is complete.This approach is more p recise t han t he constant current approach.The characteristic grap h of t he CC 2CV approach is illust rated in Fig 11(a ).Nevert heless ,t his approach also has disadvanta 2ges.When t he battery voltage is near it s sat urated value ,t he quantity of materials available for chemi 2cal reactions inside t he battery is low.If a large charging current is still supplied to t he battery ,t he fast charge may cause t he reaction rate to exceed t hat allowed by t he concent ration of t he reactant s.This will result in over 2heating of t he battery.

To solve t his problem ,we propose an im 2p roved CC 2CV charge met hod.In t his met hod ,t he charging current begins to decrease before t he bat 2tery voltage reaches it s final value ,as illust rated in Fig 11(b ).After t he battery voltage reaches it s fi 2nal value and remains stable ,t he charging current is f urt her reduced.The charging current begins to decrease around 4.1V when t here is sufficient re 2actant.Thus ,overheating of t he battery caused by t he chemical reaction rate exceeding