What is the MOS and what's function of it ?
The MOS tube is a voltage control element. You only need to add the voltage required by its voltage control element to make it conduct. Its conduction is just like the transistor is in a saturated state, and the voltage drop of the conduction junction is minimum. This is what is often said to be a switching function. Remove this control voltage and terminate.
We know that the MOS tube plays a role in voltage stabilization for the entire power supply system, but the MOS tube cannot be used alone. It must be combined with an inductive coil, a capacitor, and other filter voltage stabilizing circuits to exert sufficient advantages.
The PWM (widened modulator, pulse width modulator) chip on the main board generates a pulse waveform with adjustable width, so that the two MOS tubes can be turned on in turn. When the voltage of the load separation (such as the voltage required by the CPU) is to be reduced, the switching function of the MOS tube begins to work, and the external power supply charges the inductor and reaches the required rated voltage. When the voltage of the load in parallel increases, the external power supply is supplied by the switching function of the MOS tube, and the inductance releases the previously charged energy.
At this time, the inductance becomes a "power supply" and continues to supply power to the load. The energy stored in the inverter inductance is continuously consumed, and the voltage distributed by the load is gradually reduced again, and the external power source needs to be charged again through the switching function of the MOS tube. In this way, the process of charging and discharging is carried out continuously, so as to form a stable voltage, and the voltage corresponding to the load will never increase or decrease.
The function of the mos tube is that when the battery protection board is working normally, the control signal controls the MOS tube to open, and the terminals P+ and P- of the battery pack output the voltage for the load. At this time, the power MOS tube has been in the on state, the power loss is only the conduction loss, and there is no switching loss. The total power loss of the power MOS tube is not high, and the temperature rise is small, so the power MOS tube can work safely. However, when the load is short-circuited, the short-circuit current suddenly increases from several tens of amperes to several hundred amperes due to the small loop resistance and the strong discharge capacity of the battery. In this case, the power MOS tube is easily damaged.
The role of the mos tube is in the battery protection board-voltage protection overcharge and overdischarge. This depends on the material of the battery. This may seem simple, but in terms of details, there is still experience.