Design And Verification Of A Charger For Single Cell Li-ion Battery

With the popularization of smart portable electronic devices such as mobile phones,Li-ion batteries are widely used because of their high energy density,high voltage,no pollution,long using life,no memory effect,and quick charging speed.Simultaneously,efficient,fast and reliable Li-ion battery charging technology has been increasingly demanded by market nowadays.Based on the widespread application of power management ICs,and with the background of key scientific research projects undertaken by the CAD Research Institute of Xidian University,this article mainly focuses on the research of related theory of Li-ion battery charging and designs a power management IC as single-cell Li-ion batteries'charger.XD8268,the charger for Li-ion battery designed in this thesis,adopts segmented CC/CV charging method,of which the charging process includes precharging,constant current charging and constant voltage charging.When the battery voltage is low,the battery is precharged with a small current,so that the excessively discharged battery can be repaired and protected.Then,a huge constant current will be used to charge the battery so that the time of CC charging process can decrease.Finally,constant voltage mode will work to ensure that the battery is charged to full.This three-stage charging method has the advantages of fast speed,high efficiency,and good safety.XD8268 adopts the structure of Buck DC-DC converter plus linear Charger.Firstly,the Buck DC-DC makes its output a little higher than the voltage of battery,and the linear charger charges the battery through the output of Buck DC-DC that is only a small voltage difference between the output and the battery.The advantage of this structure is that it combines the advantages of a switch-mode charger and a linear charger,achieving high charging efficiency,high charging accuracy and low system complexity simultaneously.On the other hand,as the capacity of battery used in portable electronic devices become larger and every single portable electronic device has more functions,power dynamic path management(DPM)during charging becomes more and more meaningful.Power dynamic path management allows the user to run more applications and programs on the device during charging,without being limited by the charger's output current limit.XD8268 is manufactured through 0.5?m 1P3M 5V/20V BCD process of Dongbu HiTek in South Korea.Cadence EDA integrated circuit design tool and Spectre simulation platform are used for simulating verification.WaveView Analyzer Version is used to observe and analyze the simulation results.Cadence layout design tool is used to draw the layout of this chip.After the IC is taped out,of which the die's area is 1.7?1.9 mm~2,special PCB and testing platform are used to verify the functions and performance of this IC.The testing results indicate that XD8268 runs well.During the 2A CC mode,the error of charging current is less than 4.6%and the peak power efficiency is 88.2%,which shows XD8268's performance is excellent.