Lithium battery protection board’s composition and working principle

Composition of Lithium Battery Protection Board

1, control ic, 2, switch tube, in addition to some micro-capacitance and micro-resistance and composition. Control ic use is the protection of the battery, such as the protection conditions to control mos to disconnect or close (such as the battery to achieve overcharge, over discharge, short circuit, overcurrent, and other protection conditions), where the use of mos tube is the use of the switch, by the control ic open control.

The reason why the lithium-ion battery should be protected is determined by its own characteristics. Because the lithium-ion battery itself material determines that it can not be overcharged, overdischarged, overcurrent, short circuit and ultra-high temperature charging and discharging, so the lithium-ion battery components will always follow a delicate protection plate and a current fuse appear. The protection function of lithium-ion battery is usually accomplished by the protection board and PTC. The protection board is composed of an electronic circuit that accurately monitors the voltage of the battery cell and the current of the charging and discharging circuit at all times under the environment of -40℃ to +85℃.

The working principle of the protection board

1、Overcharge protection and overcharge protection recovery

When the battery is charged so that the voltage exceeds the set value VC (4.25-4.35V, the specific overcharge protection voltage depends on IC), VD1 flips so that Cout goes low, T1 cuts off and charging stops. When the battery voltage falls back to VCR (3.8-4.1V, the specific overcharge protection recovery voltage depends on IC), Cout goes high and T1 turns on and charging continues, VCR must be less than VC a fixed value to prevent frequent jumps.

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

When the battery voltage decreases to the set value VD (2.3-2.5V, the specific overcharge protection voltage depends on IC) due to discharge, VD2 flips, and after a short time delay, Dout becomes low, T2 cuts off and discharge stops, when the battery is put on charge, the internal or gate is flipped and T2 conducts again to prepare for the next discharge.

3、Over-current, short-circuit protection

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

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