The lithium battery protection board is generally composed of IC, MOSFET, resistor, capacitor and corresponding circuit. Its working principle is different according to the use of IC, voltage, etc. The circuit and parameters are different. The protection board has two core components: a protection IC, which is a precise comparator to obtain reliable protection parameters; the other is a MOSFET connected in series in the main charge and discharge circuit as a high-speed switch to perform protection actions.
Take DW01 with MOS tube 8205A as an example:
1. Method of activating the protection board: When the protection board P+ and P- have no output and are in the protection state, you can short-circuit B- and P- to activate the protection board. In this case, Dout and Cout will be in a low level (the two ports of the protection IC are high-level protection, low-level normal state) to open the two MOS switches to activate.
2. The normal working process of the lithium battery protection board: When the battery cell voltage is between 2.5V and 4.3V, the 1st and 3rd pins of DW01 both output high levels (equal to the power supply voltage), and the voltage of the second pin is 0V. At this time, the voltage of pin 1 and pin 3 of DW01 will be added to pin 5 and pin 4 of 8205A respectively. The two electronic switches in 8205A are both in the on state because their G poles are connected to the voltage from DW01, that is, both electronic switches are in the open state. At this time, the negative pole of the battery cell is directly connected to the P- terminal of the protection board, and the protection board has voltage output.
