Research And Design Of Charge And Discharge Protection Circuit For Single Lithium Battery

With the advent of the intelligent age,a variety of portable electronic products have greatly enriched and facilitated people's lives.The market of portable power has reached unprecedented progress,driving the development of rechargeable batteries.Owing to its eco-friendly character and high energy density,lithium batteries are often used as rechargeable batteries.Nevertheless,the internal substances of lithium batteries will be damaged under abnormal conditions such as overcharge and overdischarge that causes combustion and explosion in serious cases and leads to security incidents.Therefore,when charging and discharging,protection circuit is provided in lithium battery pack to monitor and protect its charging and discharging process.The protection circuit should be needed when Lithium batteries charge and discharge in order to facilitate the monitoring and protection of the charging and discharging process.Under this circumstances,a protection circuit for single lithium battery was researched and designed in this thesis.The main work of this thesis includes the following:Firstly,based on the analyzing basic functions and working status,the system architecture of the protection circuit of lithium battery was identified.Secondly,based on SMIC 0.18?m BCD process,a MOS bandgap voltage reference(BGR)circuit was designed by adopting piecewise curvature temperature-compensated technique and the pre-regulator technique for the charging and discharging protection circuit of single lithium battery.Simulation results showed that the designed BGR achieved the temperature coefficient of 3.1ppm/? in the temperature range from-40? to 125? and the power supply rejection ratio(PSRR)of-102 dB at 10 kHz.Thirdly,these function modules of charging and discharging protection circuit for lithium battery,which include over-temperature protection circuit,overcharge and overdischarge voltage comparator,over-current protection circuit,oscillator circuit,frequency divider circuit and logic control circuit,were designed in SMIC 0.18?m BCD process.Hysteresis comparator structure was adopted for overcharge and over-discharge voltage comparator,and its detection accuracy reached ±30mV.In order to prevent the influence of high temperature on the safety and stability of the circuit,the protection circuit stopped working when the temperature exceeded 106?.Finally,the system of lithium battery charge and discharge protection circuit was designed,and the whole protection circuit was simulated in SMIC 0.18 um BCD process.Simulation results showed that the protection circuit had the functions of overcharge and overdischarge,overdischarge current and short circuit protection.