Cascaded High-precision Multi-string Lithium Battery Protection Chip Design

Lithium-ion batteries are favored by users due to their small size,light weight,high energy density,long service life,and pollution-free.They have gradually replaced batteries of other material types and become mainstream products on the market.Lithium-ion batteries are not only applicable to portable electronic equipment and large power tools,but also have certain applications in the fields of space exploration and deep-sea exploration.However,due to the characteristics of lithium batteries,abnormal conditions such as excessively high or low battery voltages and excessive working currents may occur in various applications,which severely shortens the life of lithium batteries,greatly reduces the power supply capacity,and even explosion in serious cases.Therefore,it is of great significance to monitor the safety of lithium batteries during its operation.Based on the complex and changing application environment of lithium batteries,this paper designs a cascadable high-precision multi-string lithium battery protection chip.The protection chip can achieve overcharge protection,over discharge protection,overcurrent protection,and short-circuit protection during the charging and discharging process of seven series lithium batteries,and multiple chips can be stacked for use.The chip uses the short characteristics of the op amp to realize the conversion relationship from battery voltage to current and then to the sampling voltage,which properly solves the problem of high battery voltage and undetectability.The cooperation of the highprecision hysteresis comparator and the delay module enables accurate detection of the battery working status.The internal high-performance reference module and linear voltage regulator module provide a strong guarantee and prerequisite for the accurate work of the system.The control module logically processes the protection signal and the release signal,and outputs corresponding control signals in different circumstances.The level-shifting circuit and the driving circuit ensure that the control signals effectively act on the chip's peripheral circuits.The cascading function makes the chip not limited to applications in a certain field,but also has greater practical significance in protecting the chip.This article designs and simulates the circuit based on the 0.5um BCD process.The overcharge protection threshold voltage of the designed lithium battery protection chip is 4.2V,the overcharge protection release threshold voltage is 4.0V;the overdischarge protection threshold voltage is 2.3V,the overdischarge protection release threshold voltage is 3V;The overcurrent protection threshold voltage is 100 m V,and the short-circuit protection threshold voltage is 500 m V.After simulation verification,the error of each protection function in this design is within 10 m V,and the delay error is within 10 us.The circuit works stably and performs well,meeting the design requirements.Compared with the same type of lithium battery protection chip,this design has higher detection accuracy and a wider range of applications.