Battery pack overcurrent protection circuit with floating threshold

Abstract

The utility model relates to a battery pack overcurrent protection circuit with a floating threshold, which is characterized in that a battery pack is connected to an in-phase input end of a comparator, and the voltage of the battery pack is utilized to compensate a large-current protection threshold of the comparator, so that the large-current protection threshold of the comparator floats along with the voltage change of the battery pack. When the voltage of the battery pack is high, the large-current protection threshold value of the comparator is also increased, otherwise, the large-current protection threshold value is decreased, and the technical problems that the large-current protection threshold value of a traditional battery pack over-current protection circuit is single, and different requirements of the battery pack for large-current protection in the high-voltage state and the low-voltage state cannot be met are effectively solved.

Description

Technical Field

[0001] This utility model belongs to the field of current detection technology, specifically relating to a battery pack overcurrent protection circuit with a floating threshold. Background Technology

[0002] Handheld power tools are currently selling very well in the market and are widely used in construction, woodworking, metal processing, and other fields. The current "short circuit" high current protection of power tools on the market is achieved by setting a fixed current protection point using a comparator. When the current exceeds this protection point, the controller executes the protection action. This method is not well-suited for the different current levels generated by the battery pack under low and high voltage conditions. Because the overcurrent protection point is the same, to ensure the effectiveness of "short circuit" high current protection at low voltage, the protection point is typically set based on the large current generated at low voltage. However, this makes it easy to trigger the high current protection at high voltage, thus affecting work efficiency. Utility Model Content

[0003] The technical problem to be solved by this utility model is to provide a battery pack overcurrent protection circuit with a floating threshold, which solves the problem that the traditional battery pack overcurrent protection circuit has a single high current protection threshold and cannot meet the different needs of the battery pack for high current protection under high and low voltage conditions.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a battery pack overcurrent protection circuit with a floating threshold, including a comparator. The non-inverting input of the comparator is connected to a power supply module, which outputs a constant reference voltage. The inverting input of the comparator is connected to the battery pack power supply circuit through a current sampling circuit. The positive terminal of the comparator is connected to the power supply, and the negative terminal is grounded. The output of the comparator is connected to a controller, which controls the on / off state of the battery pack power supply circuit. The positive terminal of the battery pack is connected to the non-inverting input of the comparator through a third voltage divider resistor. The power supply module is grounded through a first voltage divider resistor and a second voltage divider resistor connected in series. One end of the third voltage divider resistor is connected between the second voltage divider resistor and the first voltage divider resistor, and the other end is connected to the positive terminal of the battery pack. The non-inverting input of the comparator is connected between the second voltage divider resistor and the first voltage divider resistor.

[0005] As a preferred embodiment, a first filter circuit is connected in series between the current sampling circuit and the inverting input of the comparator.

[0006] As a preferred embodiment, the non-inverting input terminal is also connected to a first filter capacitor. The positive terminal of the first filter capacitor is connected between the second voltage divider resistor and the first voltage divider resistor, and the negative terminal of the first filter capacitor is grounded.

[0007] As a preferred option, the output of the comparator is also connected in parallel with a pull-up resistor and a second filter capacitor. The other end of the pull-up resistor is connected to the power supply module, and the other end of the second filter capacitor is grounded.

[0008] As a preferred embodiment, the positive terminal of the comparator is connected to a third filter capacitor, the other end of which is grounded.

[0009] The beneficial effects of this utility model are as follows: By connecting a battery pack to the non-inverting input terminal of the comparator, the voltage of the battery pack is used to compensate for the high current protection threshold of the comparator. This allows the high current protection threshold of the comparator to fluctuate with the voltage change of the battery pack. When the battery pack voltage is high, the high current protection threshold of the comparator also increases, and vice versa. This effectively solves the technical problem that the high current protection threshold of the traditional battery pack overcurrent protection circuit is singular and cannot meet the different needs of the battery pack for high current protection under high and low voltage conditions. Attached Figure Description

[0010] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings, wherein:

[0011] Figure 1 This is the circuit diagram of this utility model;

[0012] Figure 1 In the circuit: 1. Comparator; 2. Power supply module; 3. Current sampling circuit; 4. Controller; 5. Third voltage divider resistor; 6. First voltage divider resistor; 7. Second voltage divider resistor; 8. Filter circuit; 9. First filter capacitor; 10. Pull-up resistor; 11. Second filter capacitor; 12. Third filter capacitor. Detailed Implementation

[0013] The specific implementation scheme of this utility model will now be described in detail with reference to the accompanying drawings.

[0014] like Figure 1The battery pack overcurrent protection circuit with a floating threshold shown includes a comparator 1. The non-inverting input (a) of comparator 1 is connected to a power module 2, which outputs a constant reference voltage to comparator 1. The inverting input (b) of comparator 1 is connected to the battery pack power supply circuit via a current sampling circuit 3. The positive terminal of comparator 1 is connected to the power supply VCC, and the negative terminal is grounded. The output (co) of comparator 1 is connected to a controller 4, which controls the on / off state of the battery pack power supply circuit. The controller 4 is an MCU or microcontroller. The positive terminal (B+) of the battery pack is connected to the non-inverting input (a) of comparator 1 via a third voltage divider resistor 5. The power module 2 is grounded via a first voltage divider resistor 6 and a second voltage divider resistor 7 connected in series. One end of the third voltage divider resistor 5 is connected between the second voltage divider resistor 7 and the first voltage divider resistor 6, and the other end is connected to the positive terminal of the battery pack. The non-inverting input of comparator 1 is connected between the second voltage divider resistor 7 and the first voltage divider resistor 6.

[0015] In this embodiment, power module 2 provides a 5V voltage. The first voltage divider resistor 6 has a resistance of 51kΩ, the second voltage divider resistor 7 has a resistance of 2.7kΩ, and the third voltage divider resistor 5 has a resistance of 360kΩ. The voltage of power module 2 and the voltage of the battery pack are divided and applied to the non-inverting input terminal a of comparator 1 as the high current protection threshold. When the battery pack voltage decreases, the voltage divided to the non-inverting input terminal a also decreases, thereby lowering the high current protection threshold. When the battery pack voltage increases, the voltage divided to the non-inverting input terminal a also increases, thereby raising the high current protection threshold. Through this setting, the high current protection threshold for overcurrent protection can fluctuate with the battery pack voltage to adapt to the different requirements of the high current protection threshold under high and low voltage conditions of the battery pack.

[0016] In this embodiment, the current sampling circuit 3 is a sampling resistor R connected in series between the load M and the negative terminal, and the inverting input terminal b of the comparator 1 is connected to the positive terminal of the sampling resistor R.

[0017] In this embodiment, a first filter circuit 8 is connected in series between the current sampling circuit 3 and the inverting input terminal b of the comparator 1 to improve the stability of the operating current received at the inverting input terminal b, eliminate noise, and improve the accuracy of the overcurrent protection current. The first filter circuit 8 is a conventional circuit and will not be described in this embodiment.

[0018] In this embodiment, the non-inverting input terminal a is also connected to a first filter capacitor 9. The positive terminal of the first filter capacitor 9 is connected between the second voltage divider resistor 7 and the first voltage divider resistor 6, and the negative terminal of the first filter capacitor 9 is grounded.

[0019] The output terminal co of comparator 1 is also connected in parallel with a pull-up resistor 10 and a second filter capacitor 11. The other end of the pull-up resistor 10 is connected to the power supply module 2, and the other end of the second filter capacitor 11 is grounded. Setting the pull-up resistor 10 makes comparator 1 output a stable high level when it is not in the high current protection state, while when comparator 1 enters the high current protection state, the high level is pulled down, and the controller 4 can effectively detect the low level.

[0020] In this embodiment, a third filter capacitor 12 is connected to the positive terminal of comparator 1, and the other end of the third filter capacitor 12 is grounded. The third filter capacitor 12 protects the comparator 1 for safe operation.

[0021] The working process of this utility model is as follows: Figure 1 As shown, the power module 2 and the positive terminal B+ of the battery pack jointly input the high current protection threshold voltage to the input terminal a of the comparator 1. The voltage at the inverting input terminal b of the comparator is the voltage of the current sampling circuit 3. This voltage can reflect the current magnitude of the battery pack power supply circuit. When the input voltage at the inverting input terminal b of the comparator is greater than the high current protection threshold voltage at the non-inverting input terminal a of the comparator, the output terminal of the comparator 1 outputs a low level to the controller 4. When the controller 4 receives this low level, it disconnects the battery pack power supply circuit through a switch such as a MOSFET or a transistor to protect the circuit safety.

[0022] When the input voltage at the inverting input terminal b of the comparator is less than the high current protection threshold voltage at the non-inverting input terminal a of the comparator, the output terminal of comparator 1 outputs a high level to controller 4, and controller 4 does not react.

[0023] When the battery pack voltage drops, the voltage across the non-inverting input terminal a also drops, causing the high current protection threshold to decrease. Conversely, when the battery pack voltage increases, the voltage across the non-inverting input terminal a also increases, causing the high current protection threshold to increase.

[0024] The above embodiments are merely illustrative of the principles and effects of the present invention, as well as some examples of its application, and are not intended to limit the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention.

Claims

1. A battery pack overcurrent protection circuit with a floating threshold, comprising a comparator (1), the non-inverting input of which is connected to a power supply module (2), the power supply module (2) outputting a constant reference voltage, the inverting input of which is connected to the battery pack power supply circuit via a current sampling circuit (3), the positive terminal of which is connected to the power supply and the negative terminal to ground, and the output of which is connected to a controller (4), the controller (4) being used to control the on / off state of the battery pack power supply circuit, characterized in that, The positive terminal of the battery pack is connected to the non-inverting input of the comparator (1) through a third voltage divider resistor (5). The power module (2) is grounded through a first voltage divider resistor (6) and a second voltage divider resistor (7) connected in series. One end of the third voltage divider resistor (5) is connected between the second voltage divider resistor (7) and the first voltage divider resistor (6), and the other end is connected to the positive terminal of the battery pack. The non-inverting input of the comparator (1) is connected between the second voltage divider resistor (7) and the first voltage divider resistor (6).

2. The battery pack overcurrent protection circuit with a floating threshold according to claim 1, characterized in that, A first filter circuit (8) is connected in series between the current sampling circuit (3) and the inverting input terminal of the comparator (1).

3. The battery pack overcurrent protection circuit with a floating threshold according to claim 1, characterized in that, The non-inverting input terminal is also connected to a first filter capacitor (9). The positive terminal of the first filter capacitor (9) is connected between the second voltage divider resistor (7) and the first voltage divider resistor (6), and the negative terminal of the first filter capacitor (9) is grounded.

4. The battery pack overcurrent protection circuit with a floating threshold according to claim 1, characterized in that, The output of the comparator (1) is also connected in parallel with a pull-up resistor (10) and a second filter capacitor (11). The other end of the pull-up resistor (10) is connected to the power supply module (2), and the other end of the second filter capacitor (11) is grounded.

5. The battery pack overcurrent protection circuit with a floating threshold according to claim 1, characterized in that, The positive terminal of the comparator (1) is connected to a third filter capacitor (12), and the other end of the third filter capacitor (12) is grounded.

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