The principle of the lithium battery pack protection board and the four functions of the lithium battery protection circuit. The lithium battery protection board is composed of electronic components and PCB. It is a circuit board that is ready to monitor the voltage of the battery cell and the current of the charging and discharging circuit under a certain temperature and humidity environment, and to control the on and off of the current circuit in time. Let's talk about the principle of the lithium battery pack protection board and the four functions of the lithium battery protection circuit.

Lithium battery pack protection function

The protection function of the lithium battery pack is usually completed by the protection circuit board and current devices such as PTC. The protection board is composed of electronic circuits, which can accurately monitor the voltage of the battery cell and the charging and discharging circuit under the environment of -40℃ to +85℃. It can control the on and off of the current loop in time; PTC prevents severe damage to the battery under high temperature environment.

Ordinary lithium battery protection boards usually include control ICs, MOS switches, resistors, capacitors and auxiliary devices FUSE, PTC, NTC, ID, memory, etc. Among them, the control IC controls the MOS switch to turn on under all normal conditions to make the cell and the external circuit conduct, and when the cell voltage or loop current exceeds the specified value, it immediately controls the MOS switch to turn off to protect the cell’s Safety.

When the protection board is normal, Vdd is high, Vss and VM are low, DO and CO are high. When any parameter of Vdd, Vss, VM is changed, the level of DO or CO will be Changes.

Principle of Lithium Battery Pack Protection Board

The reason why the lithium battery pack needs protection is determined by its own characteristics. Because the material of the lithium battery pack determines that it cannot be overcharged, overdischarged, overcurrent, short circuited, and ultra-high temperature charged and discharged, the lithium battery components will always appear with a delicate protection board and a current fuse.

The protection function of lithium battery is usually completed by a protection circuit board and current devices such as PTC. The protection board is composed of electronic circuits, which can accurately monitor the voltage of the battery cell and the charging and discharging circuit at all times under the environment of -40°C to +85°C. Current, timely control the on and off of the current loop; PTC prevents severe damage to the battery in high temperature environments.

Ordinary lithium battery protection boards usually include control ICs, MOS switches, resistors, capacitors and auxiliary devices FUSE, PTC, NTC, ID, memory, etc. Among them, the control IC controls the MOS switch to turn on under all normal conditions to make the cell and the external circuit conduct, and when the cell voltage or loop current exceeds the specified value, it immediately controls the MOS switch to turn off to protect the cell’s Safety.

Four functions of lithium battery protection circuit

1. Overcharge protection

The principle of the overcharge protection IC is that when an external charger is charging a lithium battery, the charging state must be terminated in order to prevent the internal pressure from rising due to temperature rise. At this time, the protection IC needs to detect the battery voltage, and when it reaches 4.25V (assuming the battery overcharge point is 4.25V), it activates the overcharge protection, turns the power MOS from on to off, and then stops charging.

In addition, you must also pay attention to the malfunction of overcharge detection 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 shorter than the duration of the noise.

2. Over discharge protection

In the case of over-discharge, the electrolyte is decomposed to cause deterioration of battery characteristics and reduce the number of recharges. The use of lithium battery protection IC can avoid the occurrence of excessive discharge and realize the battery protection function.

3. Over current protection

Over current or short circuit caused by unknown reasons (when discharging or the positive and negative electrodes are touched by metal objects), in order to ensure safety, it must be stopped immediately

When the discharge current is too large or a short circuit occurs, the protection IC will activate the over (short circuit) current protection. At this time, the over current detection uses the power MOSFET's Rds(on) as an inductive impedance to monitor its voltage drop. If the overcurrent detection voltage is higher than the specified overcurrent detection voltage, the discharge will stop. Similarly, the overcurrent detection must have a delay time to prevent malfunction when a sudden current flows in.

4. Short circuit protection

Prevent the battery from catching fire and explosion due to careless operation, directly connecting the positive and negative poles to ensure the safety of use and transportation.

The above is the principle of the lithium battery pack protection board and the four functions of the lithium battery protection circuit. In addition, the lithium battery protection board also has functions such as power detection, remaining capacity display, battery working status display, and communication remote control. When testing the protection board of the lithium battery pack, be sure to connect the cable before plugging in the protection board. Plugging in the protection board may cause the protection board to burn out.