Introduction to the working principle of lithium battery protection board

　　1. Lithium battery protection board over-discharge protection control principle:
　　When the battery is discharged through the external load, the voltage of the battery will gradually decrease, and the voltage inside the DW01 will be monitored in real time through the R1 resistor. When the voltage of the battery drops to about 2.3V, the DW01 will consider the voltage of the battery. When the voltage is over-discharged, the output voltage of the first pin is immediately turned off, so that the voltage of the first pin becomes 0V, and the switch tube in the 8205A is turned off due to the absence of voltage on the fifth pin. At this time, the B- of the battery cell and the P- of the protection board are in an open state. That is, the discharge circuit of the battery cell is cut off, and the battery cell will stop discharging. The protection board is in an overdischarged state and remains there. After the P and P- protection voltages of the protection board are indirectly charged, the DW01 immediately stops the overdischarge state after detecting the charging voltage by B-, and re-outputs the high voltage on the first pin, so that the overdischarge control tube in the 8205A is turned on. That is, the B- of the battery cell and the P- of the protection board are reconnected, and the battery cell is directly charged by the charger.
　　2. The normal working process of the lithium battery protection board is:
　　When the cell voltage is between 2.5V and 4.3V, the first pin and the third pin of DW01 output a high level (equal to the power supply voltage), and the second pin voltage is 0V. At this time, the voltage of the first leg and the third pin of DW01 will be respectively added to the 5th and 4th legs of 8205A, and the two electronic switches in 8205A will be in the on state due to the voltage of the G12 being connected to the voltage from DW01. Both electronic switches are on. At this time, the negative pole of the battery cell and the P-end of the protection board are equivalent to direct communication, and the protection board has a voltage output.
　　3. Lithium battery protection board overcharge protection control principle:
　　When the battery is normally charged by the charger, as the charging time increases, the voltage of the battery will become higher and higher. When the voltage of the battery rises to 4.4V, the DW01 will assume that the voltage of the battery is in an overcharged state. Immediately disconnect the output voltage of pin 3, so that the voltage of pin 3 becomes 0V, and the switch tube in 8205A is turned off because there is no voltage on pin 4. At this time, the B- of the battery cell and the P- of the protection board are in an open state. That is, the charging circuit of the battery core is cut off, and the battery core will stop charging. The protection board is in an overcharged state and remains there. Wait until the protection board P and P- indirectly discharge the load, so although the overcharge control switch is closed, but the internal diode is in the same direction as the discharge circuit, so the discharge circuit can discharge, when the voltage of the battery When it is placed below 4.3V, DW01 stops the overcharge protection state and re-outputs the high voltage on pin 3, so that the overcharge control tube in the 8205A is turned on, that is, the battery B- and the protection board P- are connected again. The battery can perform normal charging and discharging.