Dual lithium battery protection circuit

Abstract

The utility model discloses a kind of double-section lithium battery protection circuit, the positive and negative pole B+ of double-section lithium battery, B- is connected by positive and negative pole charging terminal P+ respectively, P- charges, there is three-terminal fuse F1 in series on positive pole charging line, there is charging MOS tube group, discharging MOS tube group in series on negative pole charging line;The lithium battery protection circuit includes protection chip U1, U2;Protection chip U1 collects the voltage B1 of each cell of lithium battery, B+, connects the on-off of control charging MOS tube group, discharging MOS tube group, and then control the charge-discharge of lithium battery;Protection chip U2 collects the voltage B1 of each cell of lithium battery, B+, connects the on-off of control three-terminal fuse F1.The utility model has adopted the double protection framework formed by protection chip U1 and U2.U1 is responsible for traditional charge-discharge MOS tube group control, realizes overcharge, overdischarge, overcurrent etc. basic protection;U2 is specifically used for controlling three-terminal fuse F1 in series on positive pole charging line.

Description

Technical Field

[0001] This utility model relates to the field of lithium-ion battery technology, and in particular to a dual-cell lithium battery protection circuit. Background Technology

[0002] Lithium-ion batteries are widely used in portable electronic devices, power tools, and electric vehicles due to their advantages such as high energy density, long lifespan, high rated voltage, strong power handling capability, low self-discharge rate, light weight, and good adaptability to high and low temperatures. However, under abnormal operating conditions such as overcharging, over-discharging, overcurrent, short circuit, or excessive temperature, the safety and stability of lithium batteries face severe challenges, posing risks of thermal runaway, combustion, and even explosion. Therefore, lithium batteries typically require dedicated protection circuits to monitor battery status in real time and take protective measures such as cutting off the charging and discharging circuit in abnormal situations to ensure safe battery operation.

[0003] Traditional lithium battery protection circuits typically use a single protection chip to achieve basic voltage and current monitoring and control functions. However, as application scenarios demand higher discharge current capabilities from battery systems (e.g., supporting discharge currents of 15A and above) and increasingly stringent safety and reliability requirements, such simple circuits may lack sufficient protection capability and reliability when dealing with faults such as MOSFET breakdown under high current conditions. For example, if a MOSFET bank in the charging / discharging circuit experiences a short circuit due to breakdown, failure to quickly and effectively interrupt the fault could lead to circuit failure or more serious safety issues.

[0004] Therefore, there is an urgent need in this field for a lithium battery protection circuit solution that can adapt to high-current application scenarios and provide a faster and more reliable protection mechanism when the MOSFET fails. Utility Model Content

[0005] The purpose of this invention is to provide a dual-cell lithium battery protection circuit that can adapt to high-current application scenarios and provide a faster and more reliable protection mechanism when the MOSFET fails.

[0006] The technical solution of this utility model is: A dual-cell lithium battery protection circuit is provided. The positive and negative terminals B+ and B- of the dual-cell lithium battery are connected to the positive and negative charging terminals P+ and P- for charging, respectively. A three-terminal fuse F1 is connected in series on the positive charging line, and a charging MOSFET group and a discharging MOSFET group are connected in series on the negative charging line. The lithium battery protection circuit includes protection chips U1 and U2. Protection chip U1 collects the voltages B1 and B+ of each cell of the lithium battery and controls the on / off state of the charging MOSFET group and the discharging MOSFET group, thereby controlling the charging and discharging of the lithium battery. Protection chip U2 collects the voltages B1 and B+ of each cell of the lithium battery and controls the on / off state of the three-terminal fuse F1. The protection chips U1 and U2 are R5460N222AA-TR-FE and R5438L305BA, respectively.

[0007] Preferably, the charging MOS transistor group includes multiple charging MOS transistors connected in parallel, and the discharging MOS transistor group includes multiple discharging MOS transistors connected in parallel.

[0008] Preferably, the charging MOS transistor group and the discharging MOS transistor group are connected in parallel with capacitors C11 and C12 connected in series.

[0009] Preferably, the protection chips U1 and U2 are both powered by the positive terminal of a lithium battery.

[0010] Preferably, the protection chip U2 controls the on / off state of the three-terminal fuse F1 via a MOS transistor.

[0011] The advantages of this utility model are: 1. This utility model adopts a dual protection architecture consisting of protection chips U1 and U2. U1 is responsible for the traditional charging and discharging MOSFET group control, realizing basic protection such as overcharge, over-discharge, and overcurrent; U2 is dedicated to controlling the three-terminal fuse F1 connected in series on the positive charging line. When the MOSFET group fails due to accidental breakdown or other reasons, the three-terminal fuse can quickly act to completely cut off the charging circuit, greatly improving the safety redundancy and reliability of the battery system, and effectively preventing serious accidents caused by single-point failure.

[0012] 2. The circuit scheme of this utility model is based on a high-performance chip combination design and has a specially optimized discharge circuit, which can stably support high current discharge of up to 15A, meeting the needs of application scenarios such as power tools and high-end drones that have strict requirements for high power output. Attached Figure Description

[0013] The present invention will be further described below with reference to the accompanying drawings and embodiments: Figure 1 This is a schematic diagram of the dual-cell lithium battery protection circuit of this utility model. Detailed Implementation like Figure 1 As shown, the dual-cell lithium battery protection circuit of this utility model is connected to a dual-cell lithium-ion battery pack (the cell voltages are B1 and B+, the total positive terminal of the battery pack is B+, and the total negative terminal is B-), and is used to safely charge and discharge through the charging terminals (P+, P-). The dual-cell lithium battery protection circuit of this utility model has the following main components. Protection chip U1: Model R5460N222AA-TR-FE. Its main function is to monitor the voltage (B1 and B+) of each cell in the battery pack and output control signals accordingly to control the on / off state of the charging MOSFET group and discharging MOSFET group connected to the negative charging line, thereby realizing basic overcharge, over-discharge, and overcurrent protection.

[0014] Protection chip U2: Model R5438L305BA. Its main function is to monitor the cell voltage (B1 and B+), but its output is used to control the on / off state of the three-terminal fuse F1 connected in series with the positive charging line as a backup safety protection.

[0015] Power switch section: MOSFET group: In the negative terminal path (B- to P-) of the battery, there is a charging MOSFET group Q2, Q4, Q6, Q8 and a discharging MOSFET group Q1, Q3, Q5, Q7, consisting of four MOSFETs connected in parallel. This parallel design is designed to share large currents (e.g., 15A), reduce on-resistance and heat loss, and improve reliability. The gate of the MOSFET group is controlled by the protection chip U1.

[0016] Three-terminal fuse F1: A three-terminal fuse F1 is connected in series in the positive charging path (B+ to P+) of the battery. This is a fuse whose melting can be controlled by an external signal. Its control terminal is controlled by the protection chip U2 (usually driven by an intermediate MOSFET).

[0017] Power supply and auxiliary circuits: The power supply pins (VDD) of protection chips U1 and U2 are both connected to the positive terminal B+ of the lithium battery, and are directly powered by the battery, ensuring that the protection circuit can work as long as the battery has voltage.

[0018] At both ends of the charging MOSFET group and the discharging MOSFET group, there is an RC absorption circuit or filter circuit consisting of capacitors C11 and C12 connected in series, which is used to absorb the voltage spikes generated when the MOSFETs are switched and improve the stability of the circuit.

[0019] Under normal conditions, protection chips U1 and U2 continuously monitor the cell voltage, which is within the normal range.

[0020] The U1 output control signal keeps both the charging and discharging MOSFETs in the conducting state.

[0021] The U2 output control signal keeps the three-terminal fuse F1 in the open state.

[0022] At this point, current can smoothly flow through the P+ and P- terminals to charge or discharge the battery.

[0023] Overcharge / over-discharge / overcurrent occurs (normal protection): When chip U1 detects that the battery voltage exceeds the overcharge threshold, falls below the over-discharge threshold, or the current exceeds the overcurrent threshold, it will immediately shut down the corresponding MOSFET group (e.g., shut down the charging MOSFET during overcharging and the discharging MOSFET during over-discharging), cutting off the circuit and achieving the first layer of protection.

[0024] Backup protection under MOSFET breakdown fault (key feature of this invention): Assuming the circuit operates under a high current of 15A, the charging MOSFETs may short-circuit due to unexpected causes (such as surge current or overheating), losing their switching function. In this case, U1 alone cannot cut off the charging circuit, and the battery faces the risk of continuous overcharging.

[0025] The protection chip U2 continuously monitors the voltage. Due to the breakdown of the MOSFET, the charging circuit cannot be effectively cut off, and the battery voltage will continue to rise abnormally (or enter other abnormal states).

[0026] Once U2 detects this fault, it will immediately output a control signal to trigger the three-terminal fuse F1 to blow.

[0027] When F1 melts, the positive charging path is physically and permanently cut off, thereby forcibly terminating the charging process and preventing the battery from being damaged by overcharging or causing a safety accident, thus achieving a crucial second layer of protection.

[0028] In summary, this invention achieves flexible and recoverable conventional protection by controlling the MOSFET with U1, and provides a rigid, ultimate safety barrier by controlling the three-terminal fuse with U2. The two work together to greatly improve the safety redundancy and reliability of lithium battery protection circuits, especially in high-current applications.

[0029] The above embodiments are only for illustrating the technical concept and features of this utility model, and are intended to enable those skilled in the art to understand the content of this utility model and implement it accordingly. They should not be construed as limiting the scope of protection of this utility model. All modifications made in accordance with the spirit and essence of the main technical solution of this utility model should be included within the scope of protection of this utility model.

Claims

1. A dual-cell lithium battery protection circuit, wherein the positive and negative terminals B+ and B- of the dual-cell lithium battery are connected for charging via positive and negative charging terminals P+ and P- respectively, a three-terminal fuse F1 is connected in series on the positive charging line, and a charging MOSFET group and a discharging MOSFET group are connected in series on the negative charging line; characterized in that, The lithium battery protection circuit includes protection chips U1 and U2; protection chip U1 collects the voltages B1 and B+ of each cell of the lithium battery and connects to control the on / off state of the charging MOSFET group and the discharging MOSFET group, thereby controlling the charging and discharging of the lithium battery; protection chip U2 collects the voltages B1 and B+ of each cell of the lithium battery and connects to control the on / off state of the three-terminal fuse F1. The protection chips U1 and U2 are R5460N222AA-TR-FE and R5438L305BA, respectively.

2. The dual-cell lithium battery protection circuit according to claim 1, characterized in that, The charging MOS transistor group includes multiple charging MOS transistors connected in parallel, and the discharging MOS transistor group includes multiple discharging MOS transistors connected in parallel.

3. The dual-cell lithium battery protection circuit according to claim 2, characterized in that, The charging MOSFET group and the discharging MOSFET group are connected in parallel with capacitors C11 and C12 connected in series.

4. The dual-cell lithium battery protection circuit according to claim 1, characterized in that, The protection chips U1 and U2 are both powered by the positive terminal of a lithium battery.

5. The dual-cell lithium battery protection circuit according to claim 1, characterized in that, The protection chip U2 controls the on / off state of the three-terminal fuse F1 via a MOS transistor.

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