The protection circuit of the lithium solar cell consists of a protection IC and two power MOSFETs. The protection IC monitors the battery voltage and switches to an external power MOSFET in the event of overcharge and discharge. Its functions include overcharge protection, overdischarge protection and Overcurrent/Short Circuit Protection.
Overcharge protection device.
The principle of the overcharge protection IC is as follows: when an external charger is charging a lithium solar cell, it is necessary to stop charging in order to prevent the internal pressure from rising due to temperature rise. At this time, the protection IC needs to detect the voltage of the battery. When it reaches (assuming that the overcharge point of the battery is), the overcharge protection is guaranteed, and the power MOSFET is turned on and off, and then the charging is turned off.
In addition, attention must be paid to overcharge detection malfunction due to noise, so as not to be judged as overcharge protection. Therefore, the delay time needs to be set, and the delay time cannot be less than the noise duration.
A battery protection circuit will take the battery out of the circuit if the load current is too high. Battery protection ICs typically use MOSFETs to switch lithium cells in and out of circuit. Lithium cells of the same age and part number can be paralleled and share one protection circuit.