Design Of Programmable Charge-Discharge Protection Circuit For Cascaded Multi-Cells Lithium Battery Packs

With the advantages of high specific energy,high discharge performance,long life and no memory effect,Lithium-ion batteries have become the most excellent and widely used secondary batteries.However,it is necessary to take more complex management and protection to ensure the perfect performance and security due to its structural characteristics.In addition,it is common to cascade multiple battery packs to generate higher voltage in high-voltage applications.Thus,the research on cascaded charge-discharge protection circuit for multi-cells lithium battery packs is really important for protecting cascaded lithium battery packs.If the internal protection thresholds of lithium battery protection circuit are programmable,it can be widely used in various application environments and the flexibility of which can be greatly improved.Therefore,a programmable cascaded five-cells lithium battery protection circuit is designed and validated for cascade applications of multiple lithium battery packs.By communicating with the external MCU without integrated ADCs,the protection circuit can realize the flexible configuration of the internal thresholds,so that the circuit can adapt to various application requirements.In addition,the protection circuit integrates a cascade charging equalization function to ensure the consistency of cell voltage during charging and improve the service life of cells.For application of a single battery pack,the cells above the equalization threshold are equalized in the charging process to eliminate the cell voltage inconsistency.For cascade applications,it can eventually achieve simultaneous equalization of multiple battery packs through the transmission of equalization information between adjacent protection circuits during charging process.In addition,the designed protection circuit integrates low-power broken line detection module which can reliably detect the broken lines of cells and take protective measures.The broken line detection function avoides the security risks caused by the failure detection of cell voltage,thus improving the reliability of voltage detection.In order to realize the above protection circuit,a five-cells lithium battery charge-discharge protection IC is designed by using 0.18 um BCD technology.The feasibility and reliability of the circuit design is verified in both the simulation of the circuit module and the simulation of the whole system.In addition,the key circuit modules of the IC are analyzed and described in detail.The main involved modules are as follows: high-precision bandgap reference circuit,cascade charging equalization circuit,battery voltage detection circuit,low-power broken line detection circuit and so on.