In order to prevent lithium batteries from affecting battery life in abnormal conditions such as overcharge, overdischarge, and overcurrent, lithium battery protection devices are usually used to prevent abnormal conditions from damaging the battery.

　　At present, the application of lithium batteries is becoming more and more extensive. From mobile phones, MP3, MP4, GPS, toys and other portable devices to gas meters that require continuous data storage, the market capacity has reached hundreds of millions per month. In order to prevent the lithium battery from affecting the battery life in abnormal conditions such as overcharge, overdischarge, and overcurrent, lithium battery protection devices are usually used to prevent abnormal conditions from damaging the battery.

　　The circuit principle of the lithium battery protection device is shown in Figure 1, which is mainly realized by the battery protection control IC and the external discharge switch M1 and the charge switch M2. When the P+/P- terminal is connected to the charger and the battery is charged normally, M1 and M2 are in the conducting state; when the control IC detects abnormal charging, the M2 is turned off to terminate the charging. When the P+/P- terminal is connected to the load and the battery is discharged normally, both M1 and M2 are turned on; when the control IC detects abnormal discharge, M1 is turned off to terminate the discharge.