Lithium batteries are generally composed of a battery cell, a battery protection board, and a casing. The protection board includes the battery protection ic. During the normal use of lithium batteries, the internal chemical positive reaction of the mutual conversion of electric energy and chemical energy, but under certain conditions, such as overcharging, over-discharging and overcurrent will cause chemical side reactions inside the battery. After this side reaction is intensified, it will seriously affect the performance and service life of the battery and may produce a large amount of gas, which will cause the internal pressure of the battery to rapidly increase and then explode, causing safety problems. Therefore, all lithium-ion batteries need a protection circuit, that is Battery protection ic is used to effectively monitor the charging and discharging status of the battery, and to shut off the charging and discharging circuit under certain conditions to prevent damage to the battery.
1. Commonly used battery protection IC
1.TI series: BQ29700 (single section), BQ294707 (2/4 section), BQ771809 (2/5 section)
2. Seiko (Japan) series: S8261x (single section), S8232X (double section)
3. Ricoh (Japan) series: R5400, R5402, R5421, R5426 (single section)
4. The Beauty of Beauty (Japan) Series: MM3077 (single section), MM1414 (3/4 section)
5. Fortune (Taiwan) series: DW01+, DW01-, FS312F, FS326 series (single section), FS3332 (double section)
6. Xinde (Taiwan) series: CS213 (single section)
7. Vimicro (Beijing) series: VM7021 (single section)
8. Silan (Hangzhou) series: SC451 (single section)
2. Lithium battery protection IC working mode
(1) Auto Release (self-recovery) version
Overcharge protection: When the charger is charging the battery, the battery voltage will rise slowly. When it reaches Vdet1, the protection IC will act. At this time, the level of Cout will change from high to low to make the charger Can not continue to charge the battery cell, so as to achieve the protective effect.
Release the protection conditions
Method 1: When the battery cell voltage is lower than Vrel1 when the charger is connected, the charger will charge the battery again.
Method 2: As long as the charger is reconnected, the charging will continue (when the overcharge protection is entered, the protection will be released by unplugging the charger).
Note: When the charger is connected, as long as any of the above conditions is met, the Cout level will change from low to high, so as to release the protection.
Over-discharge protection: When the battery is discharged through the load, the battery cell voltage will continue to drop below Vdet2, the protection IC will perform a protection action, at this time the Dout pin will change from high level to low level, thereby turning off the Mosfet and turning off the power The core cannot continue to discharge the load.
Release the protection conditions
Method 1: When the charger is connected, the protection can be released as long as it is higher than Vdet2. Method 2: When the charger is not connected, the battery cell voltage must be higher than Vrel2 to release the protection
: When the charger is connected or the cell voltage is higher than Vrel2, Dout will change from low level to high level so that the Mosfet can be turned on and the cell can continue to discharge the load.
(two) Latch Mode (locked) version
Overcharge protection: When the charger is charging the battery, the battery voltage will rise slowly. When it reaches Vdet1, the protection IC will act. At this time, the level of Cout will change from high to low to make the charger Can not continue to charge the battery cell, so as to achieve the protection effect.
Release the protection conditions
Two conditions must be met to release the protection (Cout changes from low level to high level)
1. The battery cell voltage is lower than Vdet12, the charger must be removed
Over-discharge protection: When the battery is discharged through the load, the battery cell voltage will continue to drop below Vdet2, the protection IC will perform a protection action, at this time the Dout pin will change from high level to low level, thereby turning off the Mosfet and turning off the power The core cannot continue to discharge the load.
Unprotection condition: connect the charger to release the protection.
