Design Of Driver Chip For LED Emergency Lamp With Power Supply

Emergency lights with their own power supply have a potential life-saving effect and are an important safety feature in modern buildings.Emergency lamps with their own power supply usually use lithium batteries as power supply and LEDs as lighting sources.Due to its special application environment,in the application circuit of LED emergency lights with its own power supply,it is necessary to have three major functions: emergency conversion,lithium battery management,and LED constant current drive.In the past application circuits,multiple general-purpose chips were often used to achieve the above functions,making the application circuit of emergency lights complex and costly.With the continuous development of chip technology,highly integrated driver chips can be used to replace complex application circuit systems.To this end,this thesis designs a high-reliability professional chip with power LED emergency light,which builds the emergency detection circuit,LED driver circuit and lithium battery management circuit into a chip,which improves the integration of the special driver chip for LED emergency light with power supply,and also makes the offchip circuit of the chip simpler.The thesis gives the system design scheme of the chip,and makes a detailed design analysis of the circuit module of the following three parts,the first is to optimize and improve the circuit structure,and propose an emergency detection circuit that is not affected by the battery voltage to improve the accuracy of the detection results.The second is to use CC-CV charging method to charge the lithium battery,the charging current varies from 90 m A to 180 m A,and the charging current can be adjusted by peripheral resistors.Extended life of backup lithium batteries.Third,in order to improve the stability of LED lighting,NMOS type LDO circuit is used to achieve the purpose of constant current driving LED,and the driving current is 2.5A.In the design process,combined with the workflow and design requirements of the chip,a delay circuit is added to the chip,and the lithium battery can start to supply power only after the emergency detection circuit sends an effective control signal for a period of time,effectively avoiding the emergency detection circuit from misjudging the mains power supply status.At the same time,the chip also adds over-temperature protection,over-discharge protection and other functions to protect the lithium battery from damage,improve the chip integration and system reliability.Under the 0.18 μ m BCD process,Cadence software is used to complete circuit design and simulation verification,and complete the chip Layout design.The simulation results show that the 90 m A-180 m A charging current,2.5 A drive current,2.7 V undervoltage protection lockout threshold,and 150?C overtemperature protection all meet the expected indicators of the design.