Circuit design of three/four-section series protection for rechargeable lithium battery

LC03-3.3 SOP8 TVS Static Protection 3.3V

Overview:
Rechargeable lithium batteries have been widely used in many fields due to their unique performance advantages. With the development of the lithium ion rechargeable battery industry, the protection system will play an increasingly important role as an integral part of it. . This article will introduce a system design method that can realize three/four-section series protection of Rechargeable Lithium Battery with practical examples. The system subtly implements the various protection functions required through simple and effective circuit design.

The following is a combination of practical examples to introduce the specific design of the three- or four-section series protection system for rechargeable lithium batteries!

The protection system uses Seiko's three- or four-cell series lithium-ion rechargeable battery dedicated charging and discharging protection ICS-8254 to build a first-class protection. The S-8254 series has built-in high-precision voltage detection circuit and delay circuit for high-accuracy voltage detection for each cell, enabling single-section overcharge protection and single-section over-discharge protection. It also has three-stage overcurrent detection function, which can be externally connected. The overcharge detection delay time, the overdischarge detection delay time, and the overcurrent detection delay time 1 (the overcurrent detection delay time 2 and the overcurrent detection delay time 3 are set inside the chip) are set. The system uses Seiko's S-8244 series built-in high-precision voltage detection circuit and delay circuit for lithium-ion rechargeable battery secondary protection dedicated IC to achieve single-stage secondary charging protection of the battery, the protection delay time can pass the capacitance of the external capacitor To set it up.

S-8254 can realize three-cell series or four-series series switching through the SEL terminal; S-8244 short-circuits the fourth battery voltage detecting terminal VCC3 and VSS through resistor R22, which can be used as the second stage when three batteries are used in series. protection.

Implementation of various protection functions
The S-8254 series charging and discharging protection voltage and overcurrent detection voltage are advanced units of 50mV. The S-8244 series overcharge detection voltage is 5mV as the advanced unit. The system can select the appropriate model according to the needs of different occasions. . Taking the protection system of Figure 1 as an example, S-8254AAVFT and S-8244AAPFN are used as protection ICs to specify the implementation process of each protection function.

Figure 1 is a schematic diagram of the protection system when four batteries are used in series (please read the PDF for details)