Four aspects analyze the working principle of lithium-ion battery protection board

The lithium-ion battery protection board has two core components: a protection IC, which is based on an accurate comparator to obtain reliable protection parameters; in addition, the MOSFET string is used for high-speed switching in the main charging and discharging circuit for protection purposes. 1. The normal working process of the lithium ion battery protection board is as follows: When the battery voltage is between 2.5v and 4.3v, the first and third pins of DW01 both output high level (equal to the power supply voltage), and the second pin voltage It is 0V. At this time, the voltages of the first pin and the third pin of DW01 are applied to the fifth pin and the fourth pin of the 8205A, respectively. Since the G poles of the two electronic switches in the 8205A receive the voltage of DW01, they are in the on-off state, that is, both electronic switches are in the open state. At this time, the negative electrode of the battery is directly connected to the p terminal of the protection board, and the protection board has a voltage output. 2. Protection board over-discharge protection control principle: when the battery is discharged through an external load, the battery voltage will slowly decrease, and the internal resistance of R1DW01 will monitor the battery voltage in real time. When the battery voltage drops to 2.3VDW01, it will be considered that they are discharging Voltage battery voltage, immediately disconnect the output voltage of pin 1 and pin 10V. In 8205, a switch tube is turned off because there is no voltage for 5 feet. At this time, the B- of the battery is disconnected from the P- of the protection board. In other words, the battery's discharge circuit is cut off, and the battery will stop discharging. The protection board is in an over-discharge state and remains in an over-discharge state. P and p-indirect are on the protective board after the charging voltage. After DW01, the over-discharge state is immediately stopped. The charging voltage detects B-, and then the high-voltage output is on the first pin. In this way, the over-discharge control tube has been carried out for 8205 years. The B-cell is connected to the P-protection board, and the battery is charged directly by the charger. 3. Protection board overcharge protection and control principle: When the battery charger passes normally and the charging time increases, the battery voltage will become higher and higher. When the battery voltage rises to 4.4V, DW01 will think that they are at the charging voltage battery voltage , Immediately disconnect the output voltage of 3 feet, make 3 feet 0V voltage, in 8205, a switch tube by 4 feet without voltage is turned off. At this time, the B- of the battery is disconnected from the P- of the protection board. In other words, the battery's charging circuit is cut off, and the battery will stop charging. The protective plate was charged, and it has been so. After waiting for the P, P-indirect protection board to discharge the load, when the charge control switch tube is turned off, but its internal diode has a discharge circuit with the same forward direction and direction, so the discharge circuit discharges. When the battery voltage input is less than 4.3V, DW01 stops charging protection The output voltage is 3 feet high, so that the 8205 charging control conduction pipeline, that is, the battery BP- and the protection board are replaced, and the battery can be charged and discharged normally. 4. Protection board short-circuit protection and control principle: In the process of external discharge protection board, two 8205 years, an electronic switch is not equivalent to two mechanical switches, but equivalent to two small resistances, called conduction resistance of 8205, each The conduction resistance of a switch is about 30 meters/U03a9, and a total of about 60 meters/U03a9. The G voltage is actually to directly control the on-resistance of each switch. When the V voltage is greater than 1 gram, the on-resistance of the switch is very small. (A few milliohms), which is equivalent to the switch is closed. When the voltage of G is less than 0.7V, the on-resistance of the switch tube is very large (several meters), which is equivalent to a switch. The voltage UA is the voltage appearing by the 8205A conductive internal resistance and the discharge current. When the load current increases, UA must increase. ua0.006l×IUA is also known as the tube pressure drop of 8205A, and UA can simply represent the discharge current. When it rises to 0.2v, the load current is considered to have reached the limit value, so the first pin of the output voltage is stopped, so the first pin becomes the voltage of 0v and the discharge control tube is closed in 8205, and the discharge circuit of the battery is cut off , And the discharge control tube is closed. In other words, the maximum output current allowed by DW01 is 3.3a, which realizes over-current protection. 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: Compared with lead-acid batteries, which lithium-ion batteries are safer?