Lithium-ion batteries (rechargeable) are protected due to their characteristics. Due to the material of the lithium-ion battery itself, it cannot be charged and discharged by overcharge, overdischarge, overcurrent, short circuit and ultra-high temperature, so the lithium-ion battery components of the lithium-ion battery generally have a protection circuit.
The protection function of the lithium-ion battery is usually to complete the protection of the circuit board. The protection board is controlled by the electronic circuit to accurately monitor the voltage and current of the battery cell in the environment of -40℃+85℃. ;
The protection board should have overcharge protection, overdischarge protection and overcurrent protection functions. The basic circuit consists of a voltage detection IC and two MOS tubes connected in series on the battery. The IC detects the battery terminal voltage and the MOS tube terminal voltage.
Lithium-ion battery protection boards generally include control ICs, MOS switches, resistors, capacitors and auxiliary equipment NTC, ID memory. In the control of the integrated circuit, under normal circumstances, it controls the conduction of the MOS switch, and the cell communicates with the external circuit. When the battery voltage or circuit current exceeds the specified value, it immediately (tens of milliseconds) controls the MOS switch to protect the safety of the cell. . NTC negative temperature coefficient resistor, when the ambient temperature rises, its resistance value decreases, and the electrical equipment or charging equipment is used to respond in time to control the internal discontinuous and discontinuous charge and discharge. ID memory is usually a single-line interface memory. ID is the abbreviation of identity, it means identity. It stores information such as battery type and production date. Product traceability and usage constraints can be brought into play.
It is generally required to control (IC) test the current and voltage of the battery voltage control and charging and discharging circuits at 25°C~85°C, the C-MOS switch tube is turned on under normal conditions, and the battery and protection circuit board In the battery voltage circuit or operating the current control IC in the preset value comparison circuit, within 15~30ms (different control ICs and C-MOS have different processing times), the CMOS is turned off, the battery is closed or the charging and discharging circuit is used to ensure that the user and the battery safety.
The basic protection functions of a single battery are as follows:
1. Overcharge protection and overcharge protection recovery
When the battery is charging, the voltage exceeds the set value VC (4.25-4.35v, the specific overcharge protection voltage depends on the IC), the overcharge monitoring signal Cout becomes low, the overcharge switch MOS tube is disconnected, and the charging is interrupted. When the battery voltage drops to the set value of the recorder (3.8--4.1v, the specific overload protection recovery voltage depends on the IC), the overload signal becomes a high level, and the overcharge switch MOS tube conduction charge continues, which is necessary for the recorder less risk than a fixed value to prevent frequent jumps.
2. Over-release protection and over-release protection recovery
When the battery voltage drops due to the set value of discharge VD (2.3--2.5V voltage depends on the specific charge protection IC), the discharge Dout monitoring signal, with a short time delay, makes it a low level, Dout releases the MOS tube and turns off , the discharge gap, when the battery is responsible for the internal or reverse gate again, so that the MOS tube conducts and prepares for the next discharge.
3. Overcurrent and short circuit protection
When the current of the charging and discharging circuit exceeds the set value or is short-circuited, the short-circuit detection circuit turns off the MOS tube and the current is cut off.
