902030 lipo battery.On the Self Protection Function of Lithium Batteries

　　Lithium ion batteries are widely used rechargeable batteries, which have the advantages of high single unit operating voltage, small size, light weight, high energy density, long cycle life, fast and sufficient charging in a short period of time, and wide allowable discharge temperature range. In addition, lithium-ion batteries have advantages such as low self discharge current, no memory effect, and no environmental pollution. Its global supply and lithium battery suppliers are continuously increasing. According to a market research company report, the global supply of lithium rechargeable batteries in 2007 increased by 17% compared to the previous year. With the expansion of the usage of lithium-ion batteries, the charge and discharge protection of lithium-ion batteries has become increasingly important. With the increase of lithium battery suppliers, the safety of lithium battery power supply equipment is currently the most concerned issue, so its protection is very important. The protection of lithium batteries mainly includes overcharging protection, over discharge protection, over current and short circuit protection, etc.

　　1. Overcharge protection

　　When the charger overcharges the lithium battery, in order to prevent the internal pressure from rising due to temperature rise, the charging state needs to be terminated. For this purpose, the protective device needs to monitor the battery voltage. When it reaches the overcharging voltage of the battery, the overcharging protection function is activated and charging is suspended.

　　2. Overdischarge protection

　　In order to prevent the over discharge state of lithium-ion batteries, when the voltage of the lithium battery is lower than its over discharge voltage detection point, the over discharge protection is activated, the discharge is stopped, and the battery is kept in a low quiescent current standby mode.

　　3. Overcurrent and short circuit protection

　　When the discharge current of a lithium-ion battery is too high or a short circuit occurs, the protection device will activate the overcurrent protection function.

　　4. Protection of multi section lithium circuits

　　The rated voltage of a single lithium-ion battery is 3.6V, which cannot meet the needs of high-voltage power supply scenarios. Therefore, multiple lithium-ion batteries need to be used in series. To this end, various manufacturers of power management and control integrated circuits have launched their own multi section lithium battery (battery pack) protection integrated circuit chips. The characteristic of these products is to monitor the charging and discharging status of 3 or 4 lithium batteries, which can achieve overcharging, discharging, and overcurrent protection.

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