The principle of overprotection of lithium batteries.
The protection circuit of the lithium-ion battery consists of a protection IC and two power MOSFETs. The protection IC monitors the battery voltage and switches to an external power MOSFET in the event of overcharge and discharge. Its functions include overcharge protection, overdischarge protection and Over current/short circuit protection.
Overcharge protection device.
The principle of the overcharge protection IC is as follows: When the external charger is charging the lithium battery, in order to prevent the internal pressure from rising due to the temperature rise, the charging needs to be stopped. At this time, the protection IC needs to detect the battery voltage, and when it reaches (assuming that the battery's overcharge point is), the overcharge protection is turned on, the power MOSFET is turned off, and then the charging is turned off.
In addition, you must also pay attention to the overcharge detection error caused by noise, so as not to be judged as overcharge protection. Therefore, the delay time needs to be set, and the delay time cannot be less than the noise duration.
Over discharge protection device.
When the discharge is too much, the performance of the lithium battery will deteriorate due to the decomposition of the electrolyte, and the number of charging times will decrease. The use of lithium battery protection IC can avoid the occurrence of excessive discharge and realize the protection of the battery.
Principle of over-discharge protection IC: In order to prevent the over-discharge of the lithium battery, suppose the lithium battery is connected to the load. When the voltage of the lithium battery is lower than its over-discharge voltage detector (assumed to be), the over-discharge protection will be turned on to enable the power MOSFET Change from open to disconnected, disconnected discharge to avoid over-discharge and keep the battery in a standby state, that is, only μA over-discharge current.
The protection circuit of the lithium-ion battery consists of a protection IC and two power MOSFETs. The protection IC monitors the battery voltage and switches to an external power MOSFET in the event of overcharge and discharge. Its functions include overcharge protection, overdischarge protection and Over current/short circuit protection.
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