Introduction to the working principle of Li-ion battery charging protection IC

The protection circuit of the lithium ion battery is to ensure the safety in such overcharge and discharge situations and prevent the deterioration of the characteristics. The protection circuit of the lithium ion battery is composed of a protection IC and two Power-MOSFETs. The protection IC during this period is to monitor the battery voltage; when there is overcharge and discharge, the external Power-MOSFET is switched to protect the battery. The functions of the protection IC are: (1) overcharge protection, (2) overdischarge protection, ( 3) Over current/short circuit protection. The protection actions of these three functions are described below. When the lithium-ion battery is overcharged, the electrolyte in the battery will be decomposed, causing the temperature to rise and the generation of gas, which causes the pressure to rise and may cause the risk of spontaneous combustion or explosion. Lithium-ion battery protection The intention of the IC is to prevent the occurrence of overcharging. The principle of overcharge protection IC: Under the scene of overdischarge, the electrolyte will decompose and cause the deterioration of the battery characteristics, which will cause a decrease in the number of recharges. The lithium ion battery protection IC is used to protect it from overdischarge and reach the protection action. When the lithium-ion battery is connected to the charger, and the voltage of the lithium-ion battery is higher than the over-discharge voltage at this time, the over-discharge protection function can be released. In addition, for the situation of pulse discharge, over-discharge detection has a delay time to prevent this kind of malfunction. Because of unknown reasons (when discharging or the positive and negative electrodes are accidentally touched by metal objects), an overcurrent or short-circuit current occurs. To ensure safety, make it discharge intermittently. The principle of the current protection IC: the formula is: assuming V-u003d0.2V, Rds(on)u003d25m, the size of the protection current is the same as Iu003d4A, and it is necessary to set a delay time for the overcurrent detection to prevent sudden accidents. When current flows in, a malfunction will occur, causing a malfunction of the protection. Generally, after an overcurrent occurs, if the element of the overcurrent can be removed (for example, immediately separated from the load..), it will return to its normal condition, and normal charging and discharging operations can be performed again. In addition to the above-mentioned lithium-ion battery protection IC functions, there are now some new functions worthy of our attention. Take the Ricoh lithium-ion battery protection IC exclusively represented by Dawnrays as an example---R5426 when connected to the charger while charging Suddenly an overcurrent occurs (the charger is damaged), that is, overcurrent detection occurs during charging. At this time, Cout will be High'Low and PowerMOS will be ON'OFF to reach the protection action. Note: Vdet4 is -0.1V (2) Shorten the test time: (A) When we open the DSpin of R5426, the delayTIme is shown in the specification; (B) When we connect the DSpin of R5426 to VDD, this time The delayTIme will only be 1/90; (C) When we connect the DSpin of R5426 to Vim (minu003d1.2V, maxu003dVDD-1.1V), the delayTIme can be ignored at this time. (3) Latch mode during overcharge: Li-ion battery has been repeatedly charging and discharging, charging and discharging. PowerMOS Gate will be High/Low repeatedly, which may make the MOSFET heat up. It is also related. The life of the battery constitutes an introduction, which shows the importance of LatchMode. Assuming that the protection circuit has LatchMode when the overcharge protection is detected in the lithium battery, the MOSFET will not become hot, and the safety is relatively improved. After detecting the overcharge protection, as long as there is a charger connected to the battery pack, the situation at this time and the lock mode when the overcharge is reached, therefore, although the voltage of the lithium-ion battery drops by one value, no recharging will occur To relieve this situation, simply remove the charger and connect the load to restore the charging and discharging situation. (4) Reduce the protection circuit components: wrap the delay capacitor for overcharge and short circuit protection into the protection IC (A) High precision of overcharge protection; (B) Reduce the current consumption of the protection IC to achieve the purpose of over discharge protection ; (C) Over-current/short-circuit protection needs to have low detection voltage and high precision requirements; (D) Finish withstand voltage, when it reaches the protection, its quiescent current consumption must be small (0.1uA), some batteries In the process of storage, the voltage may be as low as 0V due to too long storage or abnormal reasons, so the protection IC needs to be able to charge at 0V. In terms of packaging, it is now gradually moving from SOT23-6 to SON6. In the future, there will be CSP Packages and even COB products appearing to meet the current focus on frivolity and shortness. It is not necessary to protect ICs for all functions. For use, a single protection can be developed according to different lithium-ion battery data (such as: as long as the overcharge protection or overdischarge protection function), which can greatly reduce the cost and space, which is not a merit for us. Statement ：Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete.