Battery protection circuit

Abstract

The utility model relates to the technical field of battery circuit protection, and discloses a battery protection circuit, which comprises a control unit, a first switching circuit and a second switching circuit, the output end of the control unit is connected with the control end of the first switching circuit and the control end of the second switching circuit; the first end of the first switching circuit is connected with the first end of the second switching circuit, and the second end of the first switching circuit is connected with the second end of the load; and the second end of the second switching circuit is connected with the negative electrode of the battery. The size of the battery protection circuit can be reduced, the circuit cost is reduced, and the battery protection circuit is suitable for protection of batteries with higher power.

Description

Technical Field

[0001] This utility model relates to the field of battery circuit protection technology, specifically to a battery protection circuit. Background Technology

[0002] The secondary protection circuit is an important component of the mobile phone battery circuit protection system. Its main function is to provide additional protection when the battery experiences abnormal conditions such as overcharging, over-discharging, or short circuits. By monitoring key parameters such as battery voltage and current, the secondary protection circuit can quickly take measures, such as cutting off the charging and discharging circuit, to prevent battery damage when abnormal conditions are detected.

[0003] Traditional battery protection circuits, when their internal switches malfunction and the discharge voltage is too low or the discharge current is too high, cannot promptly cut off the battery's output. This forces the battery to operate under extreme voltage and current conditions, reducing cell lifespan and damaging downstream circuits such as loads. Furthermore, the thermistors (Positive Temperature Coefficients) in traditional battery protection circuits have relatively low power ratings. As power increases, larger and more expensive PTCs or switches are required, resulting in higher circuit costs and a wider battery protection board. Utility Model Content

[0004] In view of this, the present invention provides a battery protection circuit to solve the problem of low reliability of battery protection circuits.

[0005] This utility model provides a battery protection circuit, including: a control unit, a first switching circuit, and a second switching circuit. The input terminal of the control unit is connected to the positive terminal of the battery and a first terminal of the load. The output terminal of the control unit is connected to the control terminals of the first and second switching circuits. The control unit is used to output a fault signal when the battery fails. The first terminal of the first switching circuit is connected to the first terminal of the second switching circuit, and the second terminal of the first switching circuit is connected to the second terminal of the load. The first switching circuit is used to shut down based on the fault signal. The second terminal of the second switching circuit is connected to the negative terminal of the battery. When there is a fault signal and the first switching circuit fails, the second switching circuit is used to reduce the current flowing through the load based on the fault signal.

[0006] The battery protection circuit provided by this utility model has a first switch circuit and a second switch circuit that are redundant with each other. When the battery fails, the control unit prioritizes controlling the first switch circuit to turn off, cutting off the battery output and achieving the purpose of limiting the battery output to protect the load. When the first switch circuit fails and cannot be turned off, the control unit controls the second switch circuit to switch its state, thereby increasing the internal resistance of the second switch circuit and reducing the current flowing through the second switch circuit, which in turn reduces the current flowing through the load, achieving the purpose of limiting the battery output to protect the load.

[0007] In one optional embodiment, the control unit includes: a control chip, a first current limiting unit, and a first filtering unit, wherein a first terminal of the control chip is connected to a first terminal of the first current limiting unit and a first terminal of the first filtering unit, a second terminal of the control chip is connected to a second terminal of the first filtering unit and a first terminal of the first switching circuit, a third terminal of the control chip is connected to a third terminal of the first filtering unit, and an output terminal of the control chip is connected to a control terminal of the first switching circuit and a control terminal of the second switching circuit; the second terminal of the first current limiting unit is connected to the positive terminal of the battery.

[0008] In one optional embodiment, the first filtering unit includes a first capacitor and a second capacitor, wherein a first terminal of the first capacitor is connected to a first terminal of the control chip, a second terminal of the first capacitor is connected to the first terminal of the second capacitor and a second terminal of the control chip, and a second terminal of the second capacitor is connected to a third terminal of the control chip.

[0009] In one optional embodiment, the output terminal of the control unit includes a first output terminal and a second output terminal. The first switching circuit includes a first switching unit and a second filtering unit, wherein a first terminal of the first switching unit is connected to a first terminal of the second switching circuit and a first terminal of the second filtering unit, a second terminal of the first switching unit is connected to a second terminal of the load, and a first control terminal and a second control terminal of the first switching unit are respectively connected to the first output terminal and the second output terminal of the control unit. When a battery discharge fault occurs, the first output terminal of the control unit is used to output a fault signal. When a battery charging fault occurs, the second output terminal of the control unit is used to output a fault signal. The first switching unit is used to turn off based on the fault signal.

[0010] In one alternative implementation, the second filtering unit includes a plurality of third capacitors connected in series.

[0011] In one optional embodiment, the second switching circuit includes a second switching unit and a second current limiting unit, wherein a first terminal of the second switching unit is connected to a first terminal of the second current limiting unit and the negative terminal of the battery, a second terminal of the second switching unit is connected to a second terminal of the second current limiting unit and a first terminal of the first switching circuit, and a control terminal of the second switching unit is connected to the output terminal of the control unit; when there is a fault signal and the first switching circuit fails, the second switching unit is used to reduce the current flowing through the load based on the fault signal.

[0012] In one optional embodiment, the second current limiting unit includes a thermistor, wherein a first end of the thermistor is connected to a first end of the second switching unit, a second end of the thermistor is connected to a second end of the second switching unit, and the resistance of the thermistor is proportional to the temperature.

[0013] The battery protection circuit provided by this utility model, when the first switching circuit fails and cannot be turned off, the second switching unit turns off based on the fault signal. The current in the battery protection circuit flows through the thermistor, causing the thermistor's temperature to rise rapidly and its resistance to increase rapidly, thereby reducing the current in the battery protection circuit and achieving the purpose of limiting the battery output to protect the load. Furthermore, when the battery protection circuit does not trigger overcurrent protection, and both the second switching unit and the first switching circuit are on, the first switching unit is connected in parallel with the thermistor to shunt the current to the thermistor. This allows the small-sized thermistor to be used in high-power circuits without damage. Simultaneously, the small size of the thermistor reduces the size and cost of the battery protection circuit.

[0014] In one optional embodiment, the battery protection circuit further includes a support circuit, wherein a first end of the support circuit is connected to the input end of the control unit, and a second end of the support circuit is connected to the second end of the first switching circuit, and the support circuit is used to stabilize the voltage across the load.

[0015] The battery protection circuit provided by this utility model can smooth the output voltage of the battery, stabilize the voltage at both ends of the load, prevent voltage overshoot and instantaneous overvoltage from damaging the load, and ensure the reliability and stability of battery power supply.

[0016] In one alternative implementation, the support circuit includes a plurality of fourth capacitors connected in series.

[0017] In one optional embodiment, the battery protection circuit further includes a third current limiting unit, wherein the third current limiting unit is connected in series between the first switching circuit and the second switching circuit, and the third current limiting unit is used for current limiting. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of this utility model or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a battery protection circuit according to an embodiment of the present invention;

[0020] Figure 2 This is a component diagram of a control unit according to an embodiment of the present utility model;

[0021] Figure 3 This is a specific circuit structure diagram of the first filtering unit according to an embodiment of the present utility model;

[0022] Figure 4 This is a schematic diagram of a first switching circuit according to an embodiment of the present invention;

[0023] Figure 5 This is a schematic diagram of a second switching circuit according to an embodiment of the present invention;

[0024] Figure 6 This is another component diagram of the battery protection circuit according to an embodiment of the present utility model;

[0025] Figure 7 This is a specific circuit structure diagram of the battery protection circuit according to an embodiment of the present utility model;

[0026] Explanation of reference numerals in the attached figures:

[0027] 1: Control unit; 2: First switching circuit; 3: Second switching circuit; 4: Support circuit; 5: Third current limiting unit;

[0028] 11: Control chip; 12: First current limiting unit; 13: First filtering unit;

[0029] 21: First switching unit; 22: Second filtering unit;

[0030] 31: Second switching unit; 32: Second current limiting unit. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0032] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0033] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can also refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0034] Furthermore, the technical features involved in the different embodiments of this utility model described below can be combined with each other as long as they do not conflict with each other.

[0035] Lithium-ion batteries are widely used in electronic products due to their high energy density, lightweight design, and long lifespan, which has led to widespread attention and application. However, lithium-ion batteries pose certain safety hazards during charging and discharging. Without proper protection measures, problems such as overcharging, over-discharging, and short circuits may occur, potentially even causing fires or explosions. The design of a lithium-ion battery protection board is crucial for ensuring battery safety. Within this board, the secondary protection circuit is a critical design element. It primarily monitors parameters such as battery voltage, temperature, and current, and promptly cuts off the battery's output to protect it in case of any abnormalities.

[0036] However, traditional battery protection circuits cannot promptly cut off the battery's output when the internal switch fails and the discharge voltage is too low or the discharge current is too high. This causes the battery to operate under extreme voltage and current conditions, reducing cell life and damaging downstream circuits such as loads. Furthermore, the PTCs used in traditional battery protection circuits have relatively low power ratings. As power increases, larger and more expensive PTCs or switches are required, resulting in higher circuit costs and a wider battery protection board.

[0037] Therefore, this utility model provides a battery protection circuit, such as Figure 1 As shown, it includes: a control unit 1, a first switching circuit 2, and a second switching circuit 3. The input terminal of the control unit 1 is connected to the positive terminal of the battery and the first terminal of the load. The output terminal of the control unit 1 is connected to the control terminal of the first switching circuit 2 and the control terminal of the second switching circuit 3. The first terminal of the first switching circuit 2 is connected to the first terminal of the second switching circuit 3. The second terminal of the first switching circuit 2 is connected to the second terminal of the load. The second terminal of the second switching circuit 3 is connected to the negative terminal of the battery.

[0038] Specifically, Figure 1In this circuit, control unit 1 is used to identify whether the battery has faults such as excessively low or high discharge voltage, excessively low or high charging voltage, or excessive discharge or charging current. When control unit 1 detects such faults, it outputs a fault signal and controls the first switching circuit 2 to shut down, directly cutting off the battery's output. When the first switching circuit 2 cannot be shut down based on the fault signal, control unit 1 can control the second switching circuit 3 to switch its state, increasing the resistance inside the second switching circuit 3, limiting the battery's output current, and thus reducing the current flowing through the load.

[0039] Optionally, Figure 1 In this circuit, the battery protection circuit can consist of a battery, a control unit 1, a first switching circuit 2, and a load. When the control unit 1 detects the aforementioned battery fault, it outputs a fault signal and controls the first switching circuit 2 to shut off, directly cutting off the battery's output. Alternatively, the battery protection circuit can consist of a battery, a control unit 1, a second switching circuit 3, and a load. When the control unit 1 detects the aforementioned battery fault, it controls the second switching circuit 3 to switch its state, increasing the internal resistance of the second switching circuit 3 and limiting the battery's output current, thereby reducing the current flowing through the load. Those skilled in the art can flexibly set the number and type of switching circuits according to actual circuit cost and requirements.

[0040] Optionally, the second switching circuit 3 may include multiple resistors. When the second switching circuit 3 switches the switching state, the connection relationship of the internal resistors of the second switching circuit 3 changes, causing the overall resistance of the second switching circuit 3 to increase. When the overcurrent of the battery flows through the second switching circuit 3, the magnitude of the current is limited, thereby achieving the purpose of limiting the battery output and protecting the load.

[0041] Optionally, the second switching circuit 3 may include a temperature-sensitive element. When the battery experiences an overcurrent fault and the first switching circuit 2 fails to shut off, the second switching circuit 3 switches the switching state based on the fault signal, switching the overcurrent path of the battery. This causes the overcurrent to flow through the temperature-sensitive element, raising its temperature and causing its resistance to increase rapidly. The temperature-sensitive element then limits the overcurrent, thereby limiting the battery output and protecting the load.

[0042] The battery protection circuit provided in this embodiment has a first switch circuit and a second switch circuit that are redundant with each other. When the battery fails, the control unit prioritizes controlling the first switch circuit to turn off, cutting off the battery output and achieving the purpose of limiting the battery output to protect the load. When the first switch circuit fails and cannot be turned off, the control unit controls the second switch circuit to switch its state, thereby increasing the internal resistance of the second switch circuit and reducing the current flowing through the second switch circuit, which in turn reduces the current flowing through the load, thus achieving the purpose of limiting the battery output to protect the load.

[0043] In some alternative implementations, such as Figure 2 As shown, the control unit 1 includes: a control chip 11, a first current limiting unit 12, and a first filtering unit 13. The first terminal of the control chip 11 is connected to the first terminal of the first current limiting unit 12 and the first terminal of the first filtering unit 13. The second terminal of the control chip 11 is connected to the second terminal of the first filtering unit 13 and the first terminal of the first switching circuit 2. The third terminal of the control chip 11 is connected to the third terminal of the first filtering unit 13. The output terminal of the control chip 11 is connected to the control terminal of the first switching circuit 2 and the control terminal of the second switching circuit 3. The second terminal of the first current limiting unit 12 is connected to the positive terminal of the battery.

[0044] Specifically, after the control chip 11 collects the battery voltage and current through the first current limiting unit 12, it identifies the battery's operating state based on a pre-set, relatively mature battery operating state judgment program, including whether parameters such as the battery's charging current, charging voltage, discharging current, and discharging voltage are within a preset range. The first filtering unit 13 is used to filter out interference signals from the control chip 11, improving the accuracy of the control chip 11.

[0045] In some alternative implementations, such as Figure 3 As shown, the first filter unit 13 includes a first capacitor C1 and a second capacitor C2, wherein the first end of the first capacitor C1 is connected to the first end of the control chip 11, the second end of the first capacitor C1 is connected to the first end of the second capacitor C2 and the second end of the control chip 11, and the second end of the second capacitor C2 is connected to the third end of the control chip 11.

[0046] Optionally, the first filtering unit 13 can also be an RC filter circuit or other structures.

[0047] In some alternative implementations, such as Figure 4 As shown, the output terminals of the control unit 1 include a first output terminal DOUT and a second output terminal COUT. The first switching circuit 2 includes a first switching unit 21 and a second filtering unit 22. The first terminal of the first switching unit 21 is connected to the first terminal of the second switching circuit 3 and the first terminal of the second filtering unit 22. The second terminal of the first switching unit 21 is connected to the second terminal of the load. The first control terminal and the second control terminal of the first switching unit 21 are respectively connected to the first output terminal DOUT and the second output terminal COUT of the control unit 1.

[0048] Specifically, Figure 4In this system, when a battery discharges, such as when the discharge voltage is too low or the discharge current is too high, the first output terminal DOUT of the control unit 1 outputs a fault signal; when a battery charges, such as when the charging voltage is too high or the charging current is too high, the second output terminal COUT of the control unit 1 outputs a fault signal. The first switching unit 21 is capable of shutting off based on the fault signal, thereby cutting off the battery's input or output, thus protecting the battery and the load.

[0049] Optionally, the second filter unit 22 includes: multiple third capacitors connected in series, or it can be a pure capacitor structure with RC circuit or other connection methods.

[0050] In some alternative implementations, such as Figure 5 As shown, the second switching circuit 3 includes a second switching unit 31 and a second current limiting unit 32. The first end of the second switching unit 31 is connected to the first end of the second current limiting unit 32 and the negative terminal of the battery. The second end of the second switching unit 31 is connected to the second end of the second current limiting unit 32 and the first end of the first switching circuit 2. The control end of the second switching unit 31 is connected to the output end of the control unit 1.

[0051] Optionally, Figure 5 In this circuit, the second current-limiting unit 32 includes a thermistor. The first terminal of the thermistor is connected to the first terminal of the second switching unit, and the second terminal of the thermistor is connected to the second terminal of the second switching unit. The resistance of the thermistor is proportional to temperature. When the battery malfunctions and the first switching circuit 2 fails to shut off and maintain its conducting state, the second switching unit 31 shuts off based on the fault signal from the control unit 1, allowing current between the battery and the load to flow through the thermistor. Since the resistance of the thermistor increases with temperature, when the current flowing through the thermistor is high, the temperature of the thermistor rises rapidly, increasing its resistance and limiting the current in the circuit, thereby reducing the current in the circuit and protecting the load and battery.

[0052] Optionally, the second current limiting unit 32 can be composed of multiple resistors connected in series, parallel, or series-parallel. When the second switch unit 31 is turned off and the first switch circuit 2 is fault-connected, the current between the battery and the load flows through the second current limiting unit 32. The resistors in the second current limiting unit 32 change their connection relationship due to the second switch unit 31 being turned off, thereby changing their voltage division capability. When the second switch unit 31 is turned off, the overall resistance of the second current limiting unit 32 increases, thus limiting the current in the circuit.

[0053] Optionally, both the first switching unit 21 and the second switching unit 31 include MOSFETs.

[0054] It should be noted that the structure cost of PTC (Potentially Tolerant Circuit) is lower than that of other battery protection circuits of the same specification. However, the PTC currently used in lithium battery protection circuits is only suitable for circuits with a maximum power of 50W, that is, it is only suitable for a continuous current of 10A. This application divides the current flowing through the PTC by connecting a second switching unit 31 in parallel across the PTC, so that the small-sized PTC can be used in high-power circuits, which improves the applicability of the PTC. Moreover, high-power circuits no longer need to use large-sized PTCs, reducing the size of the battery protection circuit and lowering the circuit cost.

[0055] The battery protection circuit provided in this embodiment, when the first switching circuit fails to turn off, the second switching unit turns off based on the fault signal. The current in the battery protection circuit flows through the thermistor, causing its temperature to rise and its resistance to increase rapidly, thereby reducing the current in the battery protection circuit and achieving the purpose of limiting the battery output to protect the load. Furthermore, when the battery protection circuit does not trigger overcurrent protection, and both the second switching unit and the first switching circuit are on, the first switching unit is connected in parallel with the thermistor to shunt the current to the thermistor. This allows the small-sized thermistor to be used in high-power circuits without damage. Simultaneously, the small size of the thermistor reduces the size and cost of the battery protection circuit.

[0056] In some alternative implementations, such as Figure 6 As shown, the battery protection circuit also includes a support circuit 4, wherein the first end of the support circuit 4 is connected to the input end of the control unit 1, and the second end of the support circuit 4 is connected to the second end of the first switching circuit 2. The support circuit 4 is used to stabilize the voltage across the load.

[0057] Optionally, the support circuit includes: a plurality of fourth capacitors connected in series.

[0058] Optionally, Figure 6 The battery protection circuit also includes a third current limiting unit 5, which is connected in series between the first switching circuit 2 and the second switching circuit 3 to limit the current in the circuit.

[0059] For example, Figure 7 This is a specific circuit diagram of a battery protection circuit. J1 is the terminal block of the battery protection circuit, which can be connected to devices such as loads or charging devices. The working principle of the battery protection circuit is the same as that in this embodiment and any of its optional embodiments, and will not be repeated here.

[0060] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery protection circuit, characterized in that, include: The control unit, the first switching circuit, and the second switching circuit, wherein, The input terminal of the control unit is connected to the positive terminal of the battery and the first terminal of the load, and the output terminal of the control unit is connected to the control terminal of the first switching circuit and the control terminal of the second switching circuit. The control unit is used to output a fault signal when the battery fails. The first terminal of the first switching circuit is connected to the first terminal of the second switching circuit, and the second terminal of the first switching circuit is connected to the second terminal of the load. The first switching circuit is used to turn off based on the fault signal. The second terminal of the second switching circuit is connected to the negative terminal of the battery. When there is a fault signal and the first switching circuit fails, the second switching circuit is used to reduce the current flowing through the load based on the fault signal.

2. The battery protection circuit according to claim 1, characterized in that, The control unit includes: a control chip, a first current limiting unit, and a first filtering unit, wherein... The first terminal of the control chip is connected to the first terminal of the first current limiting unit and the first terminal of the first filtering unit; the second terminal of the control chip is connected to the second terminal of the first filtering unit and the first terminal of the first switching circuit; the third terminal of the control chip is connected to the third terminal of the first filtering unit; and the output terminal of the control chip is connected to the control terminal of the first switching circuit and the control terminal of the second switching circuit. The second end of the first current limiting unit is connected to the positive terminal of the battery.

3. The battery protection circuit according to claim 2, characterized in that, The first filtering unit includes: a first capacitor and a second capacitor, wherein, The first terminal of the first capacitor is connected to the first terminal of the control chip, and the second terminal of the first capacitor is connected to the first terminal of the second capacitor and the second terminal of the control chip. The second terminal of the second capacitor is connected to the third terminal of the control chip.

4. The battery protection circuit according to claim 1, characterized in that, The output terminals of the control unit include a first output terminal and a second output terminal, and the first switching circuit includes a first switching unit and a second filtering unit, wherein... The first terminal of the first switching unit is connected to the first terminal of the second switching circuit and the first terminal of the second filtering unit, the second terminal of the first switching unit is connected to the second terminal of the load, and the first control terminal and the second control terminal of the first switching unit are respectively connected to the first output terminal and the second output terminal of the control unit. When the battery experiences a discharge fault, the first output terminal of the control unit is used to output a fault signal; When the battery experiences a charging failure, the second output terminal of the control unit is used to output a fault signal; The first switching unit is used to turn off based on the fault signal.

5. The battery protection circuit according to claim 4, characterized in that, The second filtering unit includes: Multiple third capacitors connected in series.

6. The battery protection circuit according to claim 1, characterized in that, The second switching circuit includes: a second switching unit and a second current limiting unit, wherein, The first terminal of the second switching unit is connected to the first terminal of the second current limiting unit and the negative terminal of the battery; the second terminal of the second switching unit is connected to the second terminal of the second current limiting unit and the first terminal of the first switching circuit; and the control terminal of the second switching unit is connected to the output terminal of the control unit. When a fault signal is received and the first switching circuit fails, the second switching unit is used to reduce the current flowing through the load based on the fault signal.

7. The battery protection circuit according to claim 6, characterized in that, The second current limiting unit includes: a thermistor, wherein, The first end of the temperature-sensitive resistor is connected to the first end of the second switching unit, and the second end of the temperature-sensitive resistor is connected to the second end of the second switching unit. The resistance of the temperature-sensitive resistor is proportional to the temperature.

8. The battery protection circuit according to claim 1, characterized in that, Also includes: Supporting circuit, in which, The first end of the support circuit is connected to the input end of the control unit, and the second end of the support circuit is connected to the second end of the first switching circuit. The support circuit is used to stabilize the voltage across the load.

9. The battery protection circuit according to claim 8, characterized in that, The support circuit includes: Multiple fourth capacitors connected in series.

10. The battery protection circuit according to claim 1, characterized in that, Also includes: The third current limiting unit, in which... The third current limiting unit is connected in series between the first switching circuit and the second switching circuit, and the third current limiting unit is used for current limiting.

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