What is the principle of lithium iron phosphate battery protection circuit?

There are also two types of lithium iron phosphate batteries, one is a rechargeable secondary battery, which we call lithium iron phosphate batteries, which are generally used in our previous notebook computers, mobile phones, PDAs and other relatively expensive products, and the other This is a non-rechargeable primary battery, also known as lithium iron phosphate battery, which is generally used in portable electronic products with low power consumption. When the lithium iron phosphate battery is in normal use, the internal chemical energy and electric energy of the battery are mutually converted, but if we overcharge, overdischarge or overcurrent, it will cause the internal chemical energy of the lithium iron phosphate battery to have side reactions, and then it will be in the process of use. It seriously affects the performance and service life of the battery, and a large amount of gas may appear, causing the internal pressure of the battery to rapidly increase and then explode. It is to guard against these problems, so there is a protection circuit inside the lithium iron phosphate battery. This protection circuit is composed of two MOS transistors V1 and V2 and a control IC plus some resistance-capacitance components. The control chip is responsible for testing the battery voltage and loop current, and controls the gates of the two MOS and MOS transistors in the circuit. To the switch, it controls the turn-on and turn-off of the charging circuit and the discharging circuit respectively. C3 is the delay capacitor. This circuit looks simple. In the normal state of the battery, the CO and DO of N1 in the circuit are both at high potential. All MOS transistors are in the conducting state, and the lithium iron phosphate battery can be charged and discharged freely. In the process of overcharging the lithium iron phosphate battery, if the charger circuit is out of control, when there is no protection circuit, the lithium iron phosphate battery will continue to be charged with constant current after the voltage exceeds 4.2. When the voltage exceeds 4.3V, the negative chemical reaction of the battery will be Exacerbated, it will cause battery damage or safety issues. But in the lithium iron phosphate battery with protection circuit, when the control chip tests that the battery voltage reaches a value set inside the chip, the CO pin will be converted from high potential to zero voltage, and V2 will be switched from on to off , Thereby cutting off the charging circuit, so that the charger can no longer charge the battery, playing a protective role. And because V2 has its own diode VD2, the battery can discharge the external load through the diode. In order to guard against misjudgment of the chip, there is a buffer time between when the lithium iron phosphate battery voltage exceeds a value set by the chip and turning off the MOS transistor. This time is determined by C3. According to the standard, it is generally set to 1 second. The over-discharge operation is critical. After the chip tests that the battery voltage is lower than a certain set value, the voltage of DO changes from high potential to zero voltage, and V1 turns from on to off, thus cutting off the discharge circuit. The lithium iron phosphate battery cannot Discharge the load, but V1 has its own diode VD1, so the charger can charge the lithium iron phosphate battery through this diode. Overcurrent protection relies on the V-pin on the chip to test the loop current. If the current reaches the set value, V1 will automatically flip and cut off. Short-circuit protection means that when the instantaneous current of the battery is judged to be greater than a certain value, the short-circuit protection mechanism will be automatically triggered, DO will be reversed, and V1 will be turned off. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to use the sweeping robot lithium battery correctly?