Large-current short-circuit protection circuit for lithium battery pack

By designing a high-current short-circuit protection circuit for lithium battery packs that includes a power MOSFET and a turn-off delay branch, and utilizing adjustable capacitors and resistors in conjunction with a lithium battery protection chip, rapid protection against high-current short circuits is achieved. This solves the problems of high cost, complexity, and instability in existing technologies, and provides flexible short-circuit delay adjustment and simplified circuit design.

CN223487852UActive Publication Date: 2025-10-28DONGGUAN SANKE ELECTRONIC TECH CO LTD
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Patent Information

Application Number
CN202422965637.6
Authority / Receiving Office
CN · China
Patent Type
Utility models(China)
Current Assignee / Owner
Filing Date
2024-12-03
Publication Date
2025-10-28
Estimated Expiration
2034-12-03

AI Technical Summary

Technical Problem

Existing short-circuit protection circuits for lithium battery packs cannot effectively protect large-capacity battery packs. Existing solutions are costly, complex, or unstable, and cannot meet the protection requirements for high-current short circuits.

Method used

The circuit design employs a power MOSFET and a turn-off delay branch, combined with adjustable capacitors and resistors, to achieve rapid turn-off via a discharge drive signal provided by a lithium battery protection chip. This simplifies the circuit structure and avoids the need for a microcontroller system and software control.

Benefits of technology

It achieves effective protection against high-current short circuits, simplifies circuit design, reduces costs, provides flexible short-circuit delay adjustment, adapts to the personalized needs of different cell capacities, and avoids damage to MOSFETs and fire risks.

✦ Generated by Eureka AI based on patent content.

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Abstract

The utility model discloses a lithium battery pack large-current short-circuit protection circuit, which comprises a power tube Q2 and a turn-off delay branch, the grid electrode of the power MOS tube Q2 is connected with a discharge driving voltage through a resistor R15 and a resistor R11, the resistor R15 is connected with the resistor R11 in series, and the source electrode of the Q2 is connected with the positive electrode of a battery; the turn-off delay branch comprises MOS (Metal Oxide Semiconductor) tubes Q3 and R20, MOS tubes Q5 and R21, a triode Q4, and diodes D3, C10 and R23; the drain electrode of the Q3 is connected with the drain electrode of the Q2 and one end of the R20, the source electrode of the Q3 is connected with the negative electrode of the battery, the drain electrode of the Q5 is connected with the other end of the R20, the source electrode is connected with the base electrode of the triode Q4 through the R21, and the collector electrode of the triode Q4 is connected with the point A; the positive electrode of the diode D3 is connected with the point A, and the negative electrode is connected with the grid electrode of the Q5, the capacitor C10 and the resistor R23. The circuit is simple in structure, ingenious in design, low in cost, good in flexibility and capable of meeting individual requirements.
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Description

Technical Field

[0001] This utility model belongs to the field of lithium battery pack protection technology, and in particular relates to a high-current short-circuit protection circuit for lithium battery packs. Background Technology

[0002] Commonly used garden tools, two-wheeled vehicles, and three-wheeled vehicles use new energy lithium battery packs. When the large-capacity lithium battery pack is powered on, the charging through the large capacitor of the equipment controller is equivalent to a short circuit, causing sparks to fly. This often results in damage or even destruction of the internal MOSFETs. Even if the MOSFETs break down, they can still charge and discharge, but during use, the MOSFETs are prone to overheating and catching fire, burning the equipment and property.

[0003] Currently available short-circuit protection circuits for lithium battery packs are only suitable for small-capacity battery packs. The second approach uses transient voltage regulators (TVS) for suppression protection, and the third uses complex MCU program control. However, the shortcomings are: the first approach can only protect small-capacity batteries; the second approach using TVS is costly, requires a large number of units, occupies a significant amount of space, and is highly unstable, failing to provide 100% protection; and the third approach involves complex program control and high time investment. Summary of the Invention

[0004] Purpose of the invention: In order to solve the problem that lithium battery packs are prone to spontaneous combustion during charging and discharging due to short circuits in the prior art, this utility model provides a high-current short circuit protection circuit for lithium battery packs.

[0005] Technical solution: A high-current short-circuit protection circuit for a lithium battery pack, including a power MOSFET Q2 and a turn-off delay branch. The gate of the power MOSFET Q2 is connected to the discharge drive voltage through resistors R15 and R11. Resistors R15 and R11 are connected in series. The connection point of resistors R15 and R11 is defined as point A. The source of the power MOSFET Q2 is connected to the positive terminal of the battery.

[0006] The turn-off delay branch includes MOSFET Q3, current-limiting resistor R20, MOSFET Q5, resistor R21, transistor Q4, diode D3, capacitor C10, and resistor R23. The drain of MOSFET Q3 is connected to the drain of power MOSFET Q2 and one end of current-limiting resistor R20. The source of MOSFET Q3 is connected to the negative terminal of the battery. The drain of MOSFET Q5 is connected to the other end of current-limiting resistor R20, and its source is connected to the base of transistor Q4 through resistor R21. The collector of transistor Q4 is connected to point A. The anode of diode D3 is connected to point A, and its cathode is connected to the gate of MOSFET Q5, one end of capacitor C10, and one end of resistor R23. The other ends of capacitor C10 and resistor R23 are both grounded.

[0007] Furthermore, it also includes diode D4, MOSFET Q6, capacitor C11, resistor R24 ​​and resistor R25. The positive terminal of diode D4 is connected to point A, the negative terminal of diode D4 is connected to the gate of MOSFET Q6, one end of capacitor C11 and one end of resistor R24, the drain of MOSFET Q6 is connected to the battery status lock signal, the source is connected to one end of resistor R25, and the other ends of capacitor C11, resistor R24 ​​and resistor R25 are all grounded.

[0008] Furthermore, it also includes capacitor C9 and resistor R22. Capacitor C9 and resistor R22 are connected in parallel. One end of capacitor C9 is connected to the base of transistor Q4, and the other end is grounded along with the emitter of transistor Q4.

[0009] Furthermore, the capacitance of capacitor C10 is adjustable, and the resistance of resistor R23 is adjustable.

[0010] Furthermore, the capacitance of capacitor C11 is adjustable, and the resistance of resistor R24 ​​is adjustable.

[0011] Furthermore, it also includes a freewheeling diode ZD1 and a resistor R16. The positive terminal of the freewheeling diode ZD1 is connected to the source of the MOSFET Q3 and the negative terminal of the battery, and the negative terminal of the freewheeling diode ZD1 is connected to the gate of the MOSFET Q3. The resistor R16 is connected in parallel with the freewheeling diode, and the gate of the MOSFET Q3 is connected to the charging drive voltage.

[0012] Furthermore, the discharge driving voltage is provided by the lithium battery protection chip.

[0013] Furthermore, the lithium battery protection chip is a CW1053.

[0014] Compared with existing technologies, the lithium battery pack high-current short-circuit protection circuit provided by this utility model does not require a microcontroller circuit system or software control system; the circuit structure is simple and ingeniously designed, realizing power-on or short-circuit protection of the battery pack, with sufficient cost advantages, convenient and clear to use, and the short-circuit shutdown time is adjustable, with good flexibility. Customers can customize the appropriate short-circuit delay time and power-on charging time of the controller capacitor according to their own cell capacity curve to meet personalized needs. Attached Figure Description

[0015] Figure 1 Schematic diagram of a high-current short-circuit protection circuit for lithium battery packs;

[0016] Figure 2 This diagram illustrates the connection between the lithium battery protection chip and the high-current short-circuit protection circuit of the lithium battery pack. Detailed Implementation

[0017] The present invention will be further explained below with reference to the accompanying drawings and specific embodiments.

[0018] A high-current short-circuit protection circuit for lithium battery packs, such as Figure 1 As shown, it includes a power MOSFET Q2 and a turn-off delay branch. The gate of the power MOSFET Q2 is connected to the discharge drive voltage through resistors R15 and R11. Resistors R15 and R11 are connected in series. The connection point of resistors R15 and R11 is defined as point A. The source of the power MOSFET Q2 is connected to the positive terminal of the battery.

[0019] The turn-off delay branch includes MOSFET Q3, current-limiting resistor R20, MOSFET Q5, resistor R21, transistor Q4, diode D3, capacitor C10, and resistor R23. The drain of MOSFET Q3 is connected to the drain of power MOSFET Q2 and one end of current-limiting resistor R20. The source of MOSFET Q3 is connected to the negative terminal of the battery. The drain of MOSFET Q5 is connected to the other end of current-limiting resistor R20, and its source is connected to the base of transistor Q4 through resistor R21. The collector of transistor Q4 is connected to point A. The anode of diode D3 is connected to point A, and its cathode is connected to the gate of MOSFET Q5, one end of capacitor C10, and one end of resistor R23. The other ends of capacitor C10 and resistor R23 are both grounded.

[0020] It also includes diode D4, MOSFET Q6, capacitor C11, resistor R24 ​​and resistor R25. The positive terminal of diode D4 is connected to point A, the negative terminal of diode D4 is connected to the gate of MOSFET Q6, one end of capacitor C11 and one end of resistor R24, the drain of MOSFET Q6 is connected to the battery status lock signal, the source is connected to one end of resistor R25, and the other ends of capacitor C11, resistor R24 ​​and resistor R25 are all grounded.

[0021] It also includes capacitor C9 and resistor R22. Capacitor C9 and resistor R22 are connected in parallel. One end of capacitor C9 is connected to the base of transistor Q4, and the other end is grounded along with the emitter of transistor Q4.

[0022] The capacitance of capacitor C10 and the resistance of resistor R23 are both adjustable. The capacitance of capacitor C11 and the resistance of resistor R24 ​​are also adjustable. A larger resistance value results in a slower voltage drop across the corresponding capacitor. The delay time and the required recovery time after protection can be selected as needed.

[0023] It also includes a freewheeling diode ZD1 and a resistor R16. The positive terminal of the freewheeling diode ZD1 is connected to the source of the MOSFET Q3 and the negative terminal of the battery, and the negative terminal of the freewheeling diode ZD1 is connected to the gate of the MOSFET Q3. The resistor R16 is connected in parallel with the freewheeling diode, and the gate of the MOSFET Q3 is connected to the charging drive voltage.

[0024] The discharge drive voltage is provided by the lithium battery protection chip, which can be implemented using the CW1053 chip or other chips with the same function. Figure 2The diagram shows the connection between the lithium battery protection chip and the high-current short-circuit protection circuit of the lithium battery pack. Pin CO16 is the gate control pin of the charging MOS; pin VM15 is the battery status locking pin; and pin DO14 is the gate control pin of the discharging MOS.

[0025] like Figure 2 As shown, the working process is as follows: Pin 14 (DO) of the protection chip outputs a discharge drive signal to drive the turn-off delay branch. The discharge drive voltage output by DO is current-limited by resistor R11 and then drives the power MOSFET Q2 to conduct. When voltage P+ is short-circuited or strikes P-, or when a capacitive load is applied, the voltage passes through MOSFET Q3, the freewheeling diode, and then through resistor R20, which limits the current. This then drives MOSFET Q5 and resistor R21 to quickly turn on transistor Q4, ultimately forcibly turning off the power MOSFET Q2 to prevent it from burning out due to excessive current. The DO drive voltage charges capacitor C11 through diode D4, turning on MOSFET Q6. When Q2 is turned off due to current cutoff or overcurrent, capacitor C11 keeps Q6 conducting, charging the large capacitor inside the controller or device through resistor R25. The charging time is determined by capacitor C11 and resistor R24. The driving voltage DO charges capacitor C10 through diode D3. Once fully charged, MOSFET Q5 turns on. When capacitor C10 is discharged by R23, MOSFET Q5 turns off, and transistor Q4 is cut off due to the loss of driving voltage. Power MOSFET Q2 then resumes normal conduction. This circuit effectively prevents short-circuit overcurrent from burning out power MOSFET Q2. Furthermore, the short-circuit delay time is adjustable from 50µs to the second level; combined with the transistor, it enables rapid turn-off, which is faster and more effective than MCU control. The circuit is simple and cost-effective.

Claims

1. A high-current short-circuit protection circuit for a lithium battery pack, characterized in that, Includes power MOSFET Q2 and turn-off delay branch. The gate of power MOSFET Q2 is connected to the discharge drive voltage through resistors R15 and R11. Resistors R15 and R11 are connected in series. The connection point of resistors R15 and R11 is defined as point A. The source of power MOSFET Q2 is connected to the positive terminal of the battery. The turn-off delay branch includes MOSFET Q3, current-limiting resistor R20, MOSFET Q5, resistor R21, transistor Q4, diode D3, capacitor C10, and resistor R23. The drain of MOSFET Q3 is connected to the drain of power MOSFET Q2 and one end of current-limiting resistor R20. The source of MOSFET Q3 is connected to the negative terminal of the battery. The drain of MOSFET Q5 is connected to the other end of current-limiting resistor R20, and its source is connected to the base of transistor Q4 through resistor R21. The collector of transistor Q4 is connected to point A. The anode of diode D3 is connected to point A, and its cathode is connected to the gate of MOSFET Q5, one end of capacitor C10, and one end of resistor R23. The other ends of capacitor C10 and resistor R23 are both grounded.

2. The high-current short-circuit protection circuit for lithium battery packs according to claim 1, characterized in that, It also includes diode D4, MOSFET Q6, capacitor C11, resistor R24 ​​and resistor R25. The positive terminal of diode D4 is connected to point A, the negative terminal of diode D4 is connected to the gate of MOSFET Q6, one end of capacitor C11 and one end of resistor R24, the drain of MOSFET Q6 is connected to the battery status lock signal, the source is connected to one end of resistor R25, and the other ends of capacitor C11, resistor R24 ​​and resistor R25 are all grounded.

3. The high-current short-circuit protection circuit for lithium battery packs according to claim 1 or 2, characterized in that, It also includes capacitor C9 and resistor R22. Capacitor C9 and resistor R22 are connected in parallel. One end of capacitor C9 is connected to the base of transistor Q4, and the other end is grounded along with the emitter of transistor Q4.

4. The high-current short-circuit protection circuit for lithium battery packs according to claim 1 or 2, characterized in that, The capacitance of capacitor C10 is adjustable, and the resistance of resistor R23 is adjustable.

5. The high-current short-circuit protection circuit for lithium battery packs according to claim 2, characterized in that, The capacitance of capacitor C11 is adjustable, and the resistance of resistor R24 ​​is adjustable.

6. The high-current short-circuit protection circuit for a lithium battery pack according to claim 1 or 2, characterized in that, It also includes a freewheeling diode ZD1 and a resistor R16. The positive terminal of the freewheeling diode ZD1 is connected to the source of the MOSFET Q3 and the negative terminal of the battery, and the negative terminal of the freewheeling diode ZD1 is connected to the gate of the MOSFET Q3. The resistor R16 is connected in parallel with the freewheeling diode, and the gate of the MOSFET Q3 is connected to the charging drive voltage.

7. The high-current short-circuit protection circuit for a lithium battery pack according to claim 1 or 2, characterized in that, The discharge driving voltage is provided by the lithium battery protection chip.

8. The high-current short-circuit protection circuit for lithium battery packs according to claim 7, characterized in that, The lithium battery protection chip used is CW1053.