Analyze the working principle of battery circuit

How the battery circuit works The working principle of the battery circuit This circuit has the functions of overcharge protection, overdischarge protection, overcurrent protection and short circuit protection. The working principle is analyzed as follows: 1. Under normal circumstances, the CO and DO pins of N1 both output high voltages in the circuit, and the MOSFETs are in the on state. The battery can be charged and discharged freely. In this case, the current consumption of the protection circuit is Class A, generally less than 7barA. 2. The charging method required for lithium battery overcharge protection is constant current/constant voltage charging. In the initial stage of charging, constant current charging is used. In the process of battery charging, if the charger circuit is out of control, the battery voltage will exceed 4.2v and continue to be charged with constant current. At this time, the battery voltage will continue to rise. When the battery voltage is 4.3v, the chemical side reaction of the battery will increase, causing damage to the battery or safety problems. In the battery protection circuit, when the control IC detects that the battery voltage reaches 4.28V (control integrated circuits with different values, the integrated circuits have different values), the company's pin goes from high voltage to zero voltage, V2 conducts to close, and then blocks the charging circuit. The charger can no longer charge the battery, charging protection effect. At this time, due to the presence of the V2 body diode VD2, the battery can discharge the external load through this diode. There is also a delay time between the detection of the 4.28v battery voltage by the control IC and the turn-off statement of the V2 signal. The delay time is selected by C3, and is generally set to about 1 second to prevent misidentification due to interference. 3. During the discharge process, the voltage of the over-discharge protection battery will gradually decrease as the discharge process progresses. When the battery voltage drops to 2.5v, the capacity is completely reduced. During the battery discharge process, when the control IC detects that the battery voltage is lower than 2.3V, the value of the selected control integrated circuit, different integrated circuits have different values), the pin is made from high voltage zero voltage V1 from conduction to shutdown, and then blocked In addition, the discharge circuit and battery can no longer discharge the load and the purpose of over-discharge protection. At this time, due to the presence of the body diode VD1 of V1, the charger can charge the battery through the diode. Since the over-discharge protection cannot reduce the battery voltage, the current consumption of the protection circuit is required to be very small. At this time, the control IC will enter a low power consumption state, and the power consumption of the entire protection circuit will be less than 0.1a. There is also a delay between the control IC detects that the battery voltage is lower than 2.3v and the V1 signal is reported. The delay time is selected by C3, and is generally set to about 100 milliseconds to prevent interference with misidentification. 4. Due to the chemical characteristics of lithium batteries, battery manufacturers stipulate that the maximum discharge current of lithium batteries cannot exceed 2C (Cu003dbattery capacity/hour). When the battery discharges more than 2C current, it will cause permanent damage to the battery or cause safety problems. In the normal load discharge process of the cell, the discharge current passes through a series of two MOSFETs. Due to the on-resistance of the MOSFET, it will attack the voltage at both ends. The voltage Uu003dI*RDS*2, RDS is a MOSFET stimulated, and the impedance controls the IC pin. The test voltage value of V-, if the load is abnormal due to some reason, the loop current increases, when the ocean current is U>0.1V (the value of the selected control integrated circuit, different ICs have different values), do the foot The high voltage turns to zero voltage, so that V1 is switched from on to off, and then the discharge circuit is blocked, so that the current in the circuit is zero, which plays the role of overcurrent protection. There is also a delay time between the detection of overcurrent in the control IC and the turn-off of the V1 signal. The delay time is selected by C3, generally about 13 milliseconds, to prevent interference with misidentification. In the above control process, the overcurrent detection value not only depends on the control value of the control IC, but also depends on the conduction impedance of the MOSFET. When the conductive resistance of the MOSFET is large, the overcurrent protection value of the same control IC is small. 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 post: How long is the service life of the UPS power lithium battery?