Lithium battery protection board (BMS) protection function is usually accomplished by the protection circuit board and PTC and other current devices in concert. The protection board is composed of electronic circuits, which accurately monitor the voltage of the battery cell and the current of the charging and discharging circuit at all times under the environment of -40℃ to +85℃, and timely control the on/off of the current circuit; the protection board usually includes control IC, MOS switch, resistor, capacitor and auxiliary devices FUSE, PTC, NTC, ID, memory, etc. Among them, the control IC, under all normal conditions, controls the MOS switch on to make the core conductive with the external circuit, and when the core voltage or circuit current exceeds the specified value, it immediately controls the MOS switch off to protect the safety of the core.
Under normal condition, Vdd is high level, Vss, VM is low level, DO, CO is high level, when Vdd, Vss, VM any one parameter change, DO or CO end level will be changed.
1、Overcharge detection voltage: In the normal state, Vdd is gradually raised to the voltage between VDD and VSS when the CO terminal changes from high level to low level.
2、Overcharge release voltage: In the charging state, Vdd gradually decreases to the voltage between VDD-VSS when the CO terminal changes from low level to high level.
3、Over-discharge detection voltage: In the normal state, Vdd gradually decreases to the voltage between VDD-VSS when the DO terminal changes from high level to low level.
4、Over-discharge release voltage: In the over-discharge state, Vdd gradually rises to the voltage between VDD-VSS when DO terminal changes from low level to high level.
5、Overcurrent 1 detection voltage: In the normal state, VM gradually rises to the voltage between VM-VSS when DO changes from high level to low level.
6、Overcurrent 2 detection voltage: In the normal state, VM rises from OV to DO from high level to low level with a speed of more than 1ms and less than 4ms, when the voltage between VM and VSS.
7、Load short circuit detection voltage: In the normal state, the VM rises from OV at a rate of more than 1μS and less than 50μS to the voltage between VM-VSS when the DO terminal changes from high level to low level.
8、Charger detection voltage: In the over-discharge state, VM gradually decreases with OV to the voltage between VM-VSS when DO changes from low to high level.
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