| With the development and progress of science and technology,lithium batteries,as the main power source of new energy vehicles,are also constantly upgrading and innovating.In order to avoid the performance and service life of the battery pack affected by overcharge and overdischarge and improve the safety of the lithium battery,it is necessary to use the battery management system(BMS)to monitor the use status of the lithium battery pack in real time.As an important component of the battery management system,the performance of the front-end acquisition largely determines the safety and reliability of the lithium battery pack.Therefore,it is of great significance to study the high-precision front-end acquisition technology of battery management chip.Through the research and analysis of the system architecture and module composition of the battery management chip,this paper studies the key technologies of multi-cell series lithium battery front-end acquisition.Aiming at the high-precision front-end acquisition requirements of the chip,the voltage sampling technology and charge-discharge current sampling technology of the series battery pack are studied.Through the research of high voltage sampling architecture,a high precision operational amplifier voltage conversion circuit is designed,which improves the voltage sampling accuracy of 7～14 series lithium batteries.At the same time,in order to improve the current sampling accuracy of lithium battery charging and discharging,a low offset chopper fully differential operational amplifier circuit is designed to reduce the influence of operational amplifier offset on sampling accuracy.Aiming at the charging drive function requirements of the chip,a low power sensitivity charging drive circuit is designed based on the low-side parallel architecture,which enables the charging MOSFET to maintain stable drive in the power supply voltage range of 14V～63V.Aiming at the protection function requirements of the chip,the charging state detection technology and load open circuit detection technology are studied to improve the safety of the series battery pack.Based on 0.35μm BCD process,the system circuit design and layout design of the chip are completed.The overall circuit layout area is 3.5×2.7mm2.The results show that the maximum error of voltage sampling is 1.25mV in the overall circuit verification of the chip.When the current sampling input is 10mV,the maximum error of current sampling is 375μV.When the current sampling input is 160mV,the maximum error of current sampling accuracy is 1.836%.The battery management chip circuit designed in this paper meets the design requirements,and can realize the high-precision front-end acquisition,charging drive control and protection requirements of the chip. |
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