The balanced working principle of lithium iron battery protection chip and lithium battery protection board

　　The balanced working principle of lithium iron battery protection chip and lithium battery protection board. The lithium iron battery is mainly composed of two large parts, the battery cell and the protective plate PCM. The battery core is mainly composed of positive electrode material, negative electrode material, electrolyte, diaphragm and casing, while the protective board is mainly composed of protection chip (or management chip), MOS tube, resistor, capacitor and PCB board.

　　Working principle of iron lithium battery protection chip

　　The lithium iron phosphate battery circuit has overcharge protection, over-discharge protection, over-current protection and short-circuit protection. Only by understanding the working principles of these basic protection chips can we better design lithium iron phosphate battery packs and even assist the quality department in analyzing abnormal batteries or circuits. The reason why lithium iron phosphate battery (rechargeable type) needs protection is determined by its own characteristics. Since the material of the lithium battery itself determines that it cannot be overcharged, overdischarged, overcurrent, short-circuited, or charged and discharged at ultra-high temperatures, the lithium battery components will always appear with a delicate protective board and a current fuse.

　　The protection function of lithium iron batteries is usually completed by a protection circuit board and current devices such as PTC. The protection board is composed of electronic circuits and can accurately monitor the voltage and charge and return circuit of the battery core at all times in an environment of -40°C to +85°C. current, and timely control the on-off of the current loop; PTC prevents severe damage to the battery in high-temperature environments.

　　1. Introduction to the main components in the working principle of the protection chip: IC: It is the core of the protection chip. It first samples the battery voltage, and then issues various instructions through judgment. MOS tube: It mainly functions as a switch.

　　2. The protection chip works normally: the MOS tube on the protection chip may be in the off state at first. After the battery is connected to the protection chip, the MOS tube must be triggered first, and then the P+ and P- terminals will have output voltage. The common triggering method is to use a The wire short-circuit B- and P-.

　　3. Protection chip overcharge protection: Connect P+ and P- to a power supply higher than the battery voltage. The positive pole of the power supply is connected to B+ and the negative pole of the power supply is connected to B-. After the power supply is connected, the battery starts charging. The current direction is as shown in the figure. The flow current of I1 shown starts from the positive terminal of the power supply, flows through the battery, D1, and MOS2 to the negative terminal of the power supply (MOS1 is short-circuited by D1 at this time). The IC samples the battery voltage value through the capacitor. When the battery voltage reaches 4.25v, the IC Send an instruction to make pin CO low level. At this time, the current starts from the positive pole of the power supply, flows through the battery, D1, and reaches MOS2. Since the gate of MOS2 is connected to CO, it is also low level. MOS2 is turned off, and the entire loop is shut down. Shut down, the circuit plays a protective role.

　　4. Protection chip over-discharge protection: After connecting a suitable load to P+ and P-, the battery begins to discharge. The current direction is such as I2. The current flows from the positive electrode of the battery through the load, D2, and MOS1 to the negative electrode of the battery (at this time MOS2 is short-circuited by D2); when the battery is discharged to 2.5v, the IC samples and sends an instruction to turn off MOS1, the circuit is disconnected, and the battery is protected.

　　5. Overcurrent protection: After connecting a suitable load to P+ and P-, the battery begins to discharge. The current direction is such as I2. The current flows from the positive electrode of the battery through the load, D2, and MOS1 to the negative electrode of the battery. (At this time, MOS2 is D2 short circuit); when the load suddenly decreases, the IC samples the voltage generated by the sudden increase in current through the VM pin. At this time, the IC samples and issues an instruction to turn off MOS1, open the loop, and the battery is protected.

　　6. Short circuit protection: After an empty load is connected to P+ and P-, the lithium iron phosphate battery begins to discharge. The current direction is such as I2. The current flows from the positive electrode of the battery through the load, D2, and MOS1 to the negative electrode of the battery. (At this time, MOS2 is connected by D2. Short circuit); the IC samples the voltage generated by a sudden increase in current through the VM pin. At this time, the IC samples and issues an instruction to turn off MOS1, disconnect the circuit, and protect the battery.

　　Lithium battery protection board balancing working principle

　　The lithium battery protection board is to protect the charge and discharge of the series-connected lithium battery pack; when fully charged, it can ensure that the voltage difference between each single cell is less than the set value, achieving even charging of each single cell of the lithium battery pack, effectively improving It improves the charging effect in series charging mode; simultaneously detects the overvoltage, undervoltage, overcurrent, short circuit, and overtemperature status of each single cell in the battery pack to protect and extend the service life of the battery; undervoltage protection ensures that each single battery Avoid battery damage due to over-discharge during discharge use.

　　Lithium battery protection board balancing principle Commonly used balancing charging technologies include constant shunt resistance balancing charging, on-off shunt resistor balancing charging, average battery voltage balancing charging, switched capacitor balancing charging, buck converter balancing charging, inductor balancing charging, etc.

　　When charging a group of lithium batteries in series, each battery should be charged evenly, otherwise the performance and life of the entire group of lithium iron phosphate batteries will be affected during use. However, the existing single-cell lithium battery protection chips do not include the balanced charge control function. The balanced charge control function of the multi-cell lithium battery protection chip requires an external CPU; it is implemented through serial communication with the protection chip, which increases the complexity of the protection circuit. degree and design difficulty, reducing system efficiency and reliability, and increasing power consumption.

　　According to the needs of the application, the balancing principle of lithium battery protection board can realize protection and equal charging of power lithium battery packs of any structure and voltage level after changing the protection chip model and series number, and the power level of switching devices and energy consumption components in the circuit. .

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