Li-ion battery protection IC working principle and development prospects

The working principle of lithium-ion battery protection IC When an external charger is charging a lithium-ion battery, in order to prevent the internal pressure from rising due to temperature rise, it is necessary to terminate the charging condition. At this time, the protection IC needs to detect the battery voltage, when it reaches 4.25V ( Assuming that the battery overcharge point is 4.25V) and the overcharge protection is activated, the PowerMOS is turned ON'OFF to stop charging. In addition, for overcharge detection, the malfunction due to noise must also be paid attention to, so as not to be judged as overcharge protection, so the delay time is set, and the delaytime cannot be shorter than the noise time. 1. Overcurrent protection during charging. When an overcurrent occurs suddenly when the charger is connected for charging (such as the charger is damaged), the circuit will immediately perform overcurrent detection. At this time, Cout will change from high to low, and the power MOSFET will be switched from on to off. Realize the protection function. V-u003dIu0026TImes; Rds(on)u0026TImes; (I is the charging current; Vdet4, the overcurrent detection voltage, Vdet4 is -0.1V) 2. The lock mode during overcharging usually protects the IC after a delay in overcharging protection Time, then the power MOSFET will be cut off to achieve the purpose of protection. When the voltage of the lithium-ion battery drops to the release point (overcharge hysteresis voltage), it will recover, and then continue to charge→protect→discharge→charge→discharge . The safety problem in this state will not be effectively solved. The lithium-ion battery will always repeat the action of charging→discharging→charging→discharging, and the gate of the power MOSFET will be in the alternating state of high and low voltage repeatedly, which may cause the MOSFET to change Heat can also reduce battery life, so the lock mode is very important. If the lithium battery protection circuit has a lock mode when the overcharge protection is detected, the MOSFET will not become hot, and the safety is relatively improved. After the overcharge protection, as long as the charger is connected to the battery pack, it will enter the overcharge lock mode at this time. At this time, even if the voltage of the lithium-ion battery drops, there will be no recharging. Remove the charger and connect the load to restore the charging and discharging state. 3. Reduce the size of the protection circuit components. The delay capacitor for overcharge and short-circuit protection is integrated into the protection IC to reduce the size of the protection circuit components. Protection IC development prospects As mentioned above, the future protection IC will further improve the precision of detection voltage, reduce the current consumption of the protection IC, and improve the function of preventing malfunctions. At the same time, the high withstand voltage of the charger connection terminal is also the focus of research and development. In terms of packaging, SOT23-6 has gradually shifted to SON6 packaging. In the future, there will be CSP packaging and even COB products to meet the current emphasis on thin, thin and short. In terms of functions, protection ICs should not integrate all functions. A single protection IC can be developed based on different lithium-ion battery materials, such as only overcharge protection or overdischarge protection, which can greatly reduce cost and size. Of course, the single crystal of functional components is the unchanging goal. For example, mobile phone manufacturers are currently moving towards a two-chip chipset composed of peripheral circuits such as protection ICs, charging circuits, power management ICs, and logic ICs. However, the open-circuit impedance of the power MOSFET is currently required. It is difficult to integrate with other ICs. Even if a single chip is made with a special technology, the cost will be too high. Therefore, it will take some time to solve the single crystal protection of IC. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: Introduction to the correct charging and discharging methods of polymer lithium ion batteries