The function of the lithium battery protection board is to prevent the lithium battery from being overcharged or overdischarged and play a corresponding protective role. If there is a protective plate, the battery itself can be well protected. If not, the lithium battery itself is easily damaged, and the second is a safety hazard. This is no joke. Of course, if the protective plate is not used, because the internal resistance is small, the use time may be a little longer and the price is cheaper, but personally, safety is still the first.
The circuit and parameters of the lithium battery protection board are different according to the use of IC, voltage, etc. The following is an explanation of DW01 with MOS tube 8205A:
1. The normal working process of the lithium battery protection board is: when the cell voltage is between 2.5V and 4.3V, the first and third pins of DW01 both output a 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 a 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 an 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. At 2.3V, DW01 will think that the cell voltage is in the state of over-discharge voltage, and immediately disconnect the output voltage of pin 1, 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. That is, the discharge circuit of the cell is cut off, and the cell will stop discharging. The protection board is in an overdischarged state and remains there. 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. Overcharge protection control principle of lithium battery protection board: 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, DW01 It will be considered that the cell voltage has been in the state of overcharged voltage, and the output voltage of pin 3 will be disconnected immediately, so that the voltage of pin 3 will become 0V, and the switch tube in 8205A will be 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 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 cell and the protection board P- are reconnected , the battery can be charged and discharged normally.
4. Short-circuit protection control process: Short-circuit protection is a limit form of over-current protection. Its control process and principle are the same as over-current protection. Short-circuit protection is equivalent to adding a small resistance between PP- (about 0Ω) so that the load current of the protection board reaches more than 10A instantaneously, and the protection board immediately performs overcurrent protection.
Post time: Jun-30-2022