Study And Design Of Low Power High Precision Protection Chip For Multi-cell Li-ion Battery

Lithium batteries are widely used in portable electronic equipment and large electric products due to their low cost,high capacity,and no pollution.However,when the lithium battery is working in over-charging,over-discharging,over-current,short circuit,high or low temperature,it can deteriorate the characteristics of the lithium battery.Therefore,each lithium battery requires a corresponding protection chip to provide charge-discharge protection,which will ensure the safe use of the battery and prolong its service life.However,the lithium battery protection chips currently researched in China have the disadvantages of low accuracy,large power consumption,and low function integration.To solve the shortcomings of domestic lithium battery protection chips,in this thesis a lithium battery protection chip is designed that has certain advantages in chip power consumption and detection accuracy,based on the GF(Global Foundries)0.18?m BCD process.The chip supports 3 lithium battery series detection protection,and integrates three major protection functions including voltage protection,current protection and temperature protection.The voltage protection module is responsible for over-charge and over-discharge protection,the current protection module performs charge and discharge over-current and discharge short-circuit protection,and the temperature module protects the high and low temperature of the lithium battery.The chip also provides a delay clock and disables 0V charging function.In order to reduce the system power consumption,dynamic power control and time division multiplexing technology are adopted to reduce the dynamic power consumption of the system.A subthreshold characteristic low-power comparator is designed to all protection functions detected,and a low-power voltage sampling circuit is designed to reduce the series lithium-ion battery voltage sampling power.Simulation results show that the temperature protection dynamic average current is 300 n A,the current protection dynamic average current is 100 n A and the voltage protection dynamic average current is 1.77?A.In terms of improving detection accuracy,a resistor trimming network is designed to improve the temperature detection accuracy.Temperature compensation for the negative voltage generated by the charging current is designed to improve its current detection accuracy.A high-precision delay circuit is designed to improve the voltage detection delay time accuracy.The layout area of the proposed lithium battery protection chip is 1029?m?1205?m.Simulation results show that over-charge protection accuracy is ±22m V,over-discharge protection accuracy is ±17m V,charge overcurrent protection accuracy is ±14m V,discharge overcurrent protection accuracy is ±7m V,temperature protection accuracy is ±1?.The whole chip has a static working current of 10?A,and sleep current is 3?A.The function and performance of the chip meet the design goal,and there are some advantages on accuracy,power consumption,and multi-functional integration as compared with the current lithium battery protection chips currently researched in China.