Lithium battery protection board working principle and functional use analysis

Lithium battery protection board usually includes control IC, MOS switch and auxiliary device NTC, ID memory and so on. Among them, the control IC controls the MOS switch to turn on under all normal conditions, so that the cell can communicate with the external circuit, and when the cell voltage or loop current exceeds the specified value, it immediately controls the MOS switch to turn off to protect the safety of the cell . Lithium battery protection board IC: control MOS: switch NTC: negative temperature coefficient resistance (the higher the temperature, the smaller the resistance), which is used for mobile phone protection. ID: used for decoding (identification resistance) resistance: used for current limiting and sampling. Capacitor: used for instantaneous voltage stabilization, used for filtering. Fuse: blown or fuse, melted when short-circuited, unrecoverable. Ptc: Professionals usually refer to PTC devices for short For PTC, the PTC in battery products can guard against the occurrence of battery high temperature discharge and unsafe high current. According to the battery voltage, current density characteristics and use environment, PTC has special requirements. It is a very important component in battery pack products, and it bears an important mission for battery safety. Its performance and quality are also an important factor of battery pack performance and quality. When an overcurrent occurs in the circuit, the heat generated by the large current flowing through the polymer resettable fuse is sufficient to melt the polymer resin matrix and expand its volume, thus cutting off the chain-like conductive path formed by the conductive particles, resulting in the polymer resetting fuse The impedance rises rapidly, and it is used to protect the circuit from overcurrent. After the fault is eliminated, the resin cools and crystallizes again, the volume shrinks, the conductive particles re-form the conductive path, and the device returns to low impedance, so some people call it a recoverable fuse or Resettable fuse. 1. The function of the lithium battery protection board: overcharge protection: when the battery cell voltage rises to a certain value (below 4.4V), the protection board will cut off the charging circuit. Over-discharge protection: When the cell voltage drops to a certain value (above 2.2V), the protection board will cut off the discharge circuit. Short circuit protection: When the positive and negative ends of the battery are short-circuited, the circuit can be quickly cut off to protect the battery. Overcurrent protection: When the battery output current exceeds a certain value (about 2A), the protection circuit will cut off the output loop. Other auxiliary functions: There are usually NTC, identification resistor and decoding chip on the protection board. The main purpose is to ensure that the battery can be charged and used normally with the host and the original charger. 2. The coordination use of lithium battery protection board includes the following points: (1) Overcharge detection voltage: Under normal conditions, Vdd gradually increases to the voltage between VDD and VSS when the CO terminal changes from high level to low level. (2) Overcharge release voltage: In the charging state, Vdd gradually decreases to the voltage between VDD and VSS when the CO terminal changes from low level to high level. (3) Overdischarge detection voltage: Under normal conditions, Vdd gradually decreases to the voltage between VDD and VSS when the DO terminal changes from high level to low level. (4) Overdischarge release voltage: In the overdischarge state, Vdd gradually rises to the voltage between VDD and VSS when the DO terminal changes from low level to high level. (5) Overcurrent 1 detection voltage: In the normal state, VM gradually rises to the voltage between VM and VSS when DO changes from high level to low level. (6) Overcurrent 2 detection voltage: In the normal state, VM rises from OV to the voltage between VM and VSS when the DO terminal changes from high level to low level at a speed of 1ms or more and 4ms or less. (7) Load short-circuit detection voltage: Under normal conditions, VM starts from OV and rises to the voltage between VM and VSS when the DO terminal changes from high to low at a speed of 1μS or more and 50μS or less. (8) Charger detection voltage: In the over-discharge state, VM gradually decreases with OV to the voltage between VM and VSS when DO changes from low level to high level. (9) Current consumption during normal operation: Under normal conditions, the current (IDD) flowing through the VDD pin is the current consumption during normal operation. (10) Over-discharge current consumption: In the discharge state, the current (IDD) flowing through the VDD terminal is the over-current discharge current consumption. 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.