Design And Implementation Of A Cascaded And Protection Circuit For Charging And Discharging Multi-cell Li-ion Batteries In Series

Lithium-ion batteries have gradually replaced other types of batteries such as nickel tin batteries or nickel metal hydride batteries and become the most popular high-energy batteries because of the advantages of small size and mass,high energy density,long life,no pollution and so on.In addition,lithium-ion batteries are not only widely used in the smart mobile phone,laptop,pad,cameras and other portable electronic products,but also can be used as the power source of the electric bicycles,battery cars and electric vehicles and other transports.Due to the unique characteristics of lithium batteries,over charge,over discharge,over current and other abnormal conditions will affect the life and performance of the battery,the serious situation will lead to lithium battery combustion,explosion and other safety incidents in the application.Futhermore,lithium batteries are widely used in a variety of forms.For example,a single lithium battery can supply power to the mobile phone,and lithium batteries in series can be used for power tools.A design method of SOC for charging and discharging protection of multi-cell lithium batteries in series with cascade stage is presented in this paper according to these characteristics of lithium battery and its application.In this method,the voltage divider network and the amplifier are used to complete the conversion from high voltage to low voltage,and realize three series lithium battery protection system,which contains the protection function of lithium battery in the charging and discharging,as well as the function of cascading.Besides,the design is implemented from the circuit module design and simulation to the system design and simulation,and then to the final chip manufacturing and testing to verify the feasibility of the circuit design.The key circuits of the chip is analyzed and described,including: band gap reference circuit,the battery voltage sampling circuit,current reference circuit,disconnection protection circuit,cascade circuit and so on.As these circuits are integrated in a single chip,which reduces the cost and increases reliability.This design achieves protection chip of three cells lithium batteries in series with 0.18?m BCD process,and the test results show that this design realizes the functions including over charge,over discharge,over current protection and cascade stage.In addition,the chip consumes only 21.6?A at normal state and 0.2?A in sleep state,which meets the requirements of low power consumption of the lithium battery.