What are the main components and functions of the lithium battery protection board?

Society is progressing, and all walks of life are also facing new opportunities and challenges. Especially the electrical industry is booming and the development is unprecedented! In the past, people’s expectations were 'light telephonesElectricity is indispensable in life, and it can be seen everywhere and used all the time (such as mobile phones, electric vehicles, household appliances, etc.). Because of this, this has also brought a lot of flowers to the rechargeable battery industry. As the core component of each lithium battery, the battery protection board plays a key role in protecting the lithium battery and can be used by everyone who is busy. Rest assured, rest assured. Lithium battery protection board has such an important function and it has such a great effect on people. Therefore, it is very important to understand some common sense of lithium battery protection board. Today, I will share with you the main components and parts of lithium battery protection board. Its function? As shown in the figure

R1: Reference power supply resistance, which forms a voltage divider circuit with the internal resistance of the IC to control the level inversion of the internal overcharge and overdischarge voltage comparators, generally in the resistance value It is 330Ω and 470Ω. When the package form (that is, the length and width of the standard component are used to indicate the size of the component, such as the 0402 package mark, the length and width of this component are 1.0mm and 0.5mm respectively), it will be marked with a number Its resistance value, such as the number mark 473 on the chip resistor, means that its resistance value is 47000Ω or 47KΩ (the third digit means the digit with 0 after the first two digits).

R2: Over-current, short-circuit detection resistor, through the detection of VM terminal voltage to control the current of the protection board, poor welding, damage will cause the battery to over-current, short-circuit without protection, the general resistance value is 1KΩ, 2KΩ more .

R3: ID identification resistor or NTC resistor or both.

1. The resistance is a black patch in the protection board, and its resistance can be measured with a multimeter. When the package is large, its resistance will be indicated by numbers. The method is as described above, of course, the resistance value Generally there are deviations, and each resistor has a precision specification. For example, if the 10KΩ resistance specification is +/-5% accuracy, the resistance value is within the range of 9.5KΩ -10.5KΩ. C1, C2: Since the voltage at both ends of the capacitor cannot change suddenly, it acts as an instant voltage stabilization and filtering.

2. The capacitor is a yellow patch in the protection board. There are many types of 0402 packages, and there are also a few 0603 packages (1.6mm long, 0.8mm wide); the resistance value is generally infinite or MΩ when tested with a multimeter Level; Capacitor leakage will cause large self-consumption, and there is no self-recovery in short-circuit. FUSE: Ordinary FUSE or PTC (abbreviation of Positive Temperature Coefficient, meaning positive temperature coefficient), to prevent unsafe high current and high temperature discharge from occurring. Among them, PTC has a self-recovery function.

3. FUSE is generally a white patch in the protection board. The FUSE provided by LITTE will mark the character DT on FUSE, which means the rated current that FUSE can withstand. For example, it means that the rated current of D is 0.25 A, S are 4A, T is 5A, etc.

U1: Control IC; all functions of the protection board are realized by the IC by monitoring the voltage difference between VDD-VSS and the voltage difference between VM-VSS and controlling the C-MOS to perform switching actions.

Cout: Overcharge control terminal; the switch of MOS tube is controlled by the gate voltage of MOS tube T2.

Dout: Over-discharge, over-current, short-circuit control terminal; control the switch of MOS tube through the gate voltage of MOS tube T1.

VM: Over-current, short-circuit protection voltage detection terminal; realize circuit over-current and short-circuit protection by detecting the voltage of VM terminal (U(VM)u003dI*R(MOSFET)).

4. The IC in the protection board is generally a 6-pin package. The method of distinguishing the pins is: the first pin is marked on the package body near the black dot, and then counterclockwise Rotation is the 2nd, 3rd, 4th, 5th, and 6th pins; if there is no black dot mark on the package body, then the lower left of the characters on the package body is the first pin, and the remaining pins are analogously counterclockwise) C-MOS: Field effect switch tube; the implementer of the protection function; continuous welding, false welding, false welding, and breakdown will cause unprotected battery, no display, low output voltage and other undesirable phenomena.

5. CMOS is generally an 8-pin package in the protection board. It is composed of two MOS tubes, which are equivalent to two switches, which control overcharge protection and overdischarge and overcurrent respectively. , Short circuit protection; the method of distinguishing its pins is the same as that of IC. Under normal conditions of the protection board, Vdd is high, Vss, VM are low, Dout, Cout are high; when any parameter of Vdd, Vss, VM is changed, the level of Dout or Cout will occur Change, at this time the MOSFET performs the corresponding actions (opening and closing the circuit), so as to realize the protection and recovery function of the circuit.