What are the components of the lithium-ion battery protection board?

2021-08-20 09:40:26 0

Lithium-ion battery protection board composition

IC chip, MOS switch, and some microcapacitors and microresistances are also added. The purpose of controlling ic is to protect the battery. If the protection condition is reached, the mos is controlled to open or close (such as the battery reaches the protection conditions of overcharge, overdischarge, short circuit, overcurrent, etc.), and the purpose of the mos tube is to switch. It is controlled by the control ic.

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The reason why lithium-ion batteries (rechargeable) need to be protected is determined by their own characteristics. Because the material of the lithium-ion battery itself determines that it cannot be overcharged, over-discharged, over-current, short-circuited, and ultra-high temperature charging and discharging, the lithium battery components of the lithium-ion battery will always appear with an exquisite protection board and a current fuse. The protection function of lithium-ion battery is usually completed by the protection circuit board and PTC. The protection board is composed of electronic circuits, which can accurately monitor the voltage of the battery cell and the current of the charging and discharging circuit under the environment of -40°C to +85°C.

The working principle of the protection board

1. Overcharge protection and overcharge protection recovery

When the battery is charged and the voltage exceeds the set value VC (4.25-4.35V, the specific overcharge protection voltage depends on the IC), VD1 flips to make Cout low, T1 ends, and charging stops. When the battery voltage drops to VCR (3.8-4.1V, the specific overcharge protection recovery voltage depends on the IC) When Cout becomes high, T1 is turned on and charging continues, and VCR must be a fixed value less than VC to prevent frequent jumps.

2. Over-discharge protection and over-discharge protection recovery

When the battery voltage drops to the set value VD (2.3-2.5V, the specific overcharge protection voltage depends on the IC) due to discharge, VD2 reverses, after a short time delay, Dout becomes low and T2 ends. Discharge stops. When the battery is placed in charge, the internal OR gate is flipped to make T2 turn on again to prepare for the next discharge.

3. Over current and short circuit protection

When the charging and discharging loop current of the circuit exceeds the set value or is short-circuited, the short-circuit detection circuit acts to turn off the MOS tube and the current is cut off.