1. Lithium-ion battery protection board
When the cell voltage is between 2.5V and 4.3V, the first and third pins of DW01 both output high level (equal to the power supply voltage), and the second pin voltage is 0V. At this time, the voltage of the 1st and 3rd pins of DW01 will be applied to the 5th and 4th pins of 8205A respectively. The two electronic switches in 8205A are in the conducting state because their G poles are connected to the voltage from DW01, that is, Both electronic switches are on. At this time, the negative pole of the cell is directly connected to the P- terminal of the protection board, and the protection board has a voltage output.
2. The over-discharge protection control principle of the protection board
When the cell is discharged through the external load, the voltage of the cell will gradually decrease, and the DW01 will monitor the voltage of the cell in real time through the R1 resistor. When the voltage of the cell drops to about 2.3V, DW01 will consider the cell voltage In the state of over-discharge voltage, the output voltage of pin 1 is immediately disconnected, so that the voltage of pin 1 becomes 0V, and the switch tube in 8205A is turned off because there is no voltage on pin 5. At this time, the B- of the battery cell and the P- of the protection board are in a disconnected state
The lithium-ion battery protection board is in an overdischarged state and has been maintained. After the P and P- of the protection board are indirectly charged with the charging voltage, DW01 stops the over-discharge state immediately after detecting the charging voltage through B-, and outputs a high voltage on the 1st pin again, so that the over-discharge control tube in the 8205A is turned on, That is, the B- of the cell and the P- of the protection board are reconnected, and the cell is directly charged by the charger.
3. Protection board overcharge protection
When the battery is normally charged by the charger, as the charging time increases, the voltage of the cell will become higher and higher. When the voltage of the cell rises to 4.4V, the DW01 will consider that the voltage of the cell has been in the state of overcharge voltage. , then immediately disconnect the output voltage of the 3rd pin, so that the 3rd pin voltage becomes 0V, and the switch tube in the 8205A is turned off because the 4th pin has no voltage. At this time, the B- of the battery cell and the P- of the protection board are in a disconnected state. That is, the charging circuit of the battery cell is cut off, and the battery cell will stop charging. The protective plate is overcharged and remains on.
Wait until the P and P- of the protection board are indirectly discharged to the load, so although the overcharge control switch is turned off, the forward direction of the internal diode is the same as the direction of the discharge loop, so the discharge loop can be discharged. When it is placed below 4.3V, DW01 stops the overcharge protection state and outputs high voltage at pin 3 again, so that the overcharge control tube in 8205A is turned on, that is, the B- of the battery cell and the protection board P- are reconnected , the battery can be charged and discharged normally.