Lithium battery low-power protection circuit and device

Abstract

The utility model provides a lithium battery low electric quantity protection circuit and a lithium battery low electric quantity protection device, which relate to the technical field of battery safety detection and comprise a voltage comparator U2, a voltage division module, a first switch tube, a second switch tube, a resistor R1, a reference voltage module, a system power supply and a battery power supply, the battery power supply is connected with a first input end of the voltage comparator U2 through the voltage dividing module, a second input end of the voltage comparator U2 is connected with the reference voltage module, an output end of the voltage comparator U2 is connected with a control end of the second switch tube, and a first pin end of the second switch tube is grounded; the battery power supply is respectively connected with the second pin end of the second switch tube and the control end of the first switch tube through a resistor R1, and the battery power supply is also connected with the system power supply through the first pin end of the first switch tube and the second pin end of the first switch tube in sequence. According to the utility model, the problem of high cost of the protection circuit for the low electric quantity of the lithium battery in the prior art is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of battery safety detection, in particular to a low-power protection circuit and device for a lithium battery. Background Technique

[0002] For most rechargeable electronic products on the market, lithium batteries are used. Given the limitations of lithium battery materials, both too high and too low voltages of lithium batteries will cause permanent damage. Therefore, when charging a lithium battery, the voltage should not exceed 4.2V. To meet this requirement, a charging management chip needs to be added to the product, and the charging management chip will automatically cut off the charging at 4.2V. When discharging, that is, when the product is in normal use, the voltage of the lithium battery should not be allowed to be lower than 2.7V. Therefore, generally when the power of the lithium battery is lower than a certain threshold, it is necessary to alarm or cut off the power for the user in a certain way, and do not continue to use the product, and the lithium battery of the product needs to be charged.

[0003] Most of the low-power protection circuits on the market are as Figure 1 shown:

[0004] The voltage of the lithium battery is divided by resistors R1 and R2, and then the voltage value after voltage division is sampled by the microcontroller U1 through AD. Then, the sampled voltage value is compared with the designed low-power threshold. If the sampled voltage value is less than the designed low-power threshold, the microcontroller is used to cut off the power supply of the lithium battery.

[0005] The disadvantage of this solution is that in order to implement the function, a microcontroller and a corresponding software engineer are required to write code for power detection. Even in order to provide a stable AD reference voltage for the microcontroller, an LDO chip needs to be added to provide a stable power supply VCC for the microcontroller. For some low-cost application scenarios that do not require a microcontroller, the function of protecting the lithium battery from low power cannot be achieved through this solution. Content of the Utility Model

[0006] Aiming at the deficiencies in the prior art, the utility model provides a low-power protection circuit and device for a lithium battery, which solves the problem of high cost of the protection circuit for low power of the lithium battery in the prior art.

[0007] At least one embodiment of the utility model provides a low-power protection circuit for a lithium battery, including:

[0008] A voltage comparator U2, a voltage division module, a first switching tube, a second switching tube, a resistor R1, a reference voltage module, a system power supply, and a battery power supply, wherein,

[0009] The battery power source is connected to the first input terminal of the voltage comparator U2 through the voltage divider module, the second input terminal of the voltage comparator U2 is connected to the reference voltage module, the output terminal of the voltage comparator U2 is connected to the control terminal of the second switch tube, and the first pin terminal of the second switch tube is grounded;

[0010] The battery power supply is connected to the second pin end of the second switch tube and the control end of the first switch tube through the resistor R1 respectively, and the battery power supply is also connected to the system power supply through the first pin end of the first switch tube and the second pin end of the first switch tube in sequence.

[0011] The above solution has at least the following beneficial effects:

[0012] The reference voltage module can be used to configure the standard for low battery of lithium battery. After the battery passes through the voltage divider module, it is input into the voltage comparator U2 together with the reference voltage output by the reference voltage module. At this time, the voltage comparator U2 can output a corresponding high level or low level according to the remaining power in the battery power, thereby controlling the conduction of the second switch tube; when the battery power provided by the lithium battery is high, the voltage comparator U2 outputs a high level, and the second switch tube is turned on. At this time, the control end of the first switch tube is low, so that the battery power supplies the system power. If the battery power is low, the second switch tube is disconnected, so that the battery power is connected to the control end of the first switch tube through the resistor R1, and then the first switch tube is switched, so that the battery power is disconnected from the system power, thereby cutting off the power supply to the system power.

[0013] Through the above solution, it is possible to automatically cut off the connection between the battery power supply and the system power supply when the battery power supply is low without using a single-chip microcomputer, thereby achieving the purpose of protecting the battery power supply and lowering the cost.

[0014] In one embodiment provided by the present utility model, the voltage divider module includes: a resistor R5 and a resistor R6, wherein:

[0015] The battery power source is grounded via the resistor R5 and the resistor R6 in sequence, and the first input terminal of the voltage comparator U2 is connected between the resistor R5 and the resistor R6.

[0016] The above solution has at least the following beneficial effects:

[0017] Resistors R5 and R6 can be used to divide the voltage of the battery power supply to avoid excessive voltage.

[0018] In one embodiment provided by the present utility model, the reference voltage module includes: a resistor R2 and a voltage reference chip U1, wherein:

[0019] The battery power supply is respectively connected to the output pin and the power supply pin of the voltage reference chip U1 through the resistor R2. The ground pin of the voltage reference chip U1 is grounded, and the output pin of the voltage reference chip U1 is connected to the second input terminal of the voltage comparator U2.

[0020] After adopting the above solution, at least the following beneficial effects are achieved:

[0021] Through the voltage reference chip, a stable reference voltage can be provided for the voltage comparator U2, and this reference voltage is used as the judgment standard for the low battery power of the battery power supply.

[0022] In one embodiment provided by the present invention, the power supply terminal of the voltage comparator U2 is connected to the battery power supply, and this power supply terminal is also grounded through the capacitor C1.

[0023] After adopting the above solution, at least the following beneficial effects are achieved:

[0024] Through the setting of the capacitor C1, filtering can be performed to isolate external interference.

[0025] In one embodiment provided by the present invention, both the first switching tube and the second switching tube are MOS tubes.

[0026] In one embodiment provided by the present invention, the second switching tube is an N-channel MOS tube Q2. The gate of the MOS tube Q2 is the control end of the second switching tube, the source of the MOS tube Q2 is the first pin end of the second switching tube, and the drain of the MOS tube Q2 is the second pin end of the second switching tube.

[0027] In one embodiment provided by the present invention, it further includes: a resistor R3. The output terminal of the voltage comparator U2 is connected to the gate of the MOS tube Q2 through the resistor R3.

[0028] After adopting the above solution, at least the following beneficial effects are achieved:

[0029] Through the resistor R3, the switching speed of the MOS tube Q2 can be slowed down to protect the MOS tube Q2.

[0030] In one embodiment provided by the present invention, it further includes: a resistor R4. The gate of the MOS tube Q2 is connected to the source of the MOS tube Q2 through the resistor R4.

[0031] After adopting the above solution, at least the following beneficial effects are achieved:

[0032] The resistor R4 can be used as a discharge resistor to release the static electricity between the source and the gate of the MOS tube Q2, prevent the MOS tube Q2 from malfunctioning, and at the same time provide a bias voltage for the MOS tube Q2.

[0033] In one embodiment provided by the present utility model, the first switching tube is a P-channel MOS transistor Q1. The gate of the MOS transistor Q1 is the control end of the first switching tube, the source of the MOS transistor Q1 is the first pin end of the first switching tube, and the drain of the MOS transistor Q1 is the second pin end of the first switching tube.

[0034] The present utility model also provides a lithium battery low-power protection device, including a lithium battery low-power protection circuit as described above. Description of the Drawings

[0035] Figure 1 It is a circuit diagram for the prior art to protect a lithium battery with low power;

[0036] Figure 2 It is a control schematic diagram of a lithium battery low-power protection circuit according to the present utility model;

[0037] Figure 3 It is a circuit diagram of a lithium battery low-power protection circuit according to the present utility model. Detailed Embodiments

[0038] The principles and features of the present utility model will be described below with reference to the accompanying drawings. The examples given are only used to explain the present utility model and are not intended to limit the scope of the present utility model.

[0039] The present utility model provides a lithium battery low-power protection circuit. Please refer here Figure 2 as shown, including:

[0040] A voltage comparator U2, a voltage dividing module, a first switching tube, a second switching tube, a resistor R1, a reference voltage module, a system power supply, and a battery power supply. Among them,

[0041] The battery power supply is connected to the first input end of the voltage comparator U2 through the voltage dividing module. The second input end of the voltage comparator U2 is connected to the reference voltage module. The output end of the voltage comparator U2 is connected to the control end of the second switching tube. The first pin end of the second switching tube is grounded;

[0042] The battery power supply is respectively connected to the second pin end of the second switching tube and the control end of the first switching tube through the resistor R1. The battery power supply also sequentially passes through the first pin end and the second pin end of the first switching tube and is connected to the system power supply.

[0043] In this embodiment, the first input end of the voltage comparator U2 is its non-inverting input end, and the second input end of the voltage comparator U2 is its inverting input end.

[0044] Using a reference voltage module, the standard for low battery power of a lithium battery can be configured. After the battery passes through a voltage division module, it is input into a voltage comparator U2 together with the reference voltage output by the reference voltage module. At this time, the voltage comparator U2 can output a corresponding high level or low level according to the remaining power in the battery power supply, thereby controlling the conduction of the second switching tube. When the battery power supply provided by the lithium battery is at a high level, the voltage comparator U2 outputs a high level and the second switching tube conducts. At this time, the control terminal of the first switching tube is at a low level, enabling the battery power supply to supply power to the system power supply. If the battery power supply is at a low level, the second switching tube disconnects, causing the battery power supply to be connected to the control terminal of the first switching tube through a resistor R1, thereby switching the first switching tube and disconnecting the battery power supply from the system power supply to cut off the power supply to the system power supply.

[0045] Through the above solution, it is possible to control and realize the automatic disconnection of the connection between the battery power supply and the system power supply when the battery power supply is at a low level without using a single-chip microcomputer, thereby achieving the purpose of protecting the battery power supply and having a lower cost.

[0046] Specifically, please refer to Figure 3 and Figure 2 as shown. Among them, Battry represents a lithium battery, which is used to provide a battery power supply of VBAT, and VCC is a system power supply used to supply power to the system. The voltage division module includes: resistor R5 and resistor R6, where

[0047] The battery power supply is grounded through the resistor R5 and the resistor R6 in sequence, and the first input terminal of the voltage comparator U2 is connected between the resistor R5 and the resistor R6.

[0048] Using resistor R5 and resistor R6, the voltage division of the battery power supply can be realized to avoid excessive voltage.

[0049] Specifically, the reference voltage module includes: resistor R2 and a voltage reference chip U1, where

[0050] The battery power supply is connected to the output pin and the power supply pin of the voltage reference chip U1 through the resistor R2 respectively. The ground pin of the voltage reference chip U1 is grounded, and the output pin of the voltage reference chip U1 is connected to the second input terminal of the voltage comparator U2.

[0051] Through the voltage reference chip, a stable reference voltage can be provided for the voltage comparator U2 and used as the judgment standard for low battery power of the battery power supply.

[0052] Specifically, the power supply terminal of the voltage comparator U2 is connected to the battery power supply, and this power supply terminal is also grounded through a capacitor C1.

[0053] By setting the capacitor C1, filtering can be performed to isolate external interference.

[0054] Specifically, both the first switching transistor and the second switching transistor are MOS transistors. Of course, if necessary, the first switching transistor and the second switching transistor can also be bipolar transistors.

[0055] The second switching transistor is an N-channel MOS transistor Q2. The gate of the MOS transistor Q2 is the control end of the second switching transistor, the source of the MOS transistor Q2 is the first pin end of the second switching transistor, and the drain of the MOS transistor Q2 is the second pin end of the second switching transistor.

[0056] The first switching transistor is a P-channel MOS transistor Q1. The gate of the MOS transistor Q1 is the control end of the first switching transistor, the source of the MOS transistor Q1 is the first pin end of the first switching transistor, and the drain of the MOS transistor Q1 is the second pin end of the first switching transistor.

[0057] Specifically, this circuit further includes: a resistor R3. The output end of the voltage comparator U2 is connected to the gate of the MOS transistor Q2 through the resistor R3.

[0058] The switching speed of the MOS transistor Q2 can be slowed down through the resistor R3 to protect the MOS transistor Q2.

[0059] Specifically, this circuit further includes: a resistor R4. The gate of the MOS transistor Q2 is connected to the source of the MOS transistor Q2 through the resistor R4.

[0060] The resistor R4 can be used as a discharge resistor to release the static electricity between the source and the gate of the MOS transistor Q2, prevent the MOS transistor Q2 from malfunctioning, and at the same time provide a bias voltage for the MOS transistor Q2.

[0061] The working process of this circuit is as follows:

[0062] Through the above method, the battery power supply VBAT provided by the lithium battery Battery is used to provide a stable reference voltage Vref to the inverting input terminal of the voltage comparator U2. The resistors R5 and R6 provide a sampled voltage V1 after dividing the voltage of the battery to the non-inverting input terminal of the comparator U2. When V1 > Vref, the output end of the voltage comparator U2 outputs a high level, then the MOS transistor Q2 conducts. Since the MOS transistor Q2 conducts to the ground, the gate of the MOS transistor Q1 is grounded and is at a low level. At this time, the MOS transistor Q1 also conducts, and the battery power supply VBAT supplies power to the system power supply.

[0063] When V1 < Vref, the output terminal of the voltage comparator U2 outputs a low level, then the MOS transistor Q2 is not turned on, and the gate of the MOS transistor Q1 is connected to the electromagnetic power supply VBAT through the resistor R1, which is at a high level, so the MOS transistor Q1 is not turned on, and the battery power supply VBAT stops supplying power to the system power supply.

[0064] Through the above principle, by selecting the values of the resistor R5 and the resistor R6 and the type selection of the reference voltage chip U1, the power supply to the system power supply can be automatically cut off when the lithium battery voltage is lower than a certain threshold, which not only prompts the user that the low battery cannot be used but also avoids the use of the backend circuit and the battery under low voltage conditions, thereby protecting the lifespan of the backend circuit and the battery.

[0065] The present invention also provides a lithium battery low power protection device, including a lithium battery low power protection circuit as described above.

[0066] In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0067] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limitations on the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A low battery protection circuit for a lithium battery, characterized in that, Comprising: A voltage comparator U2, a voltage dividing module, a first switching transistor, a second switching transistor, a resistor R1, a reference voltage module, a system power supply, and a battery power supply, wherein, The battery power supply is connected to the first input terminal of the voltage comparator U2 through the voltage dividing module, the second input terminal of the voltage comparator U2 is connected to the reference voltage module, the output terminal of the voltage comparator U2 is connected to the control terminal of the second switching transistor, and the first pin terminal of the second switching transistor is grounded; The battery power supply is connected to the second pin terminal of the second switching transistor and the control terminal of the first switching transistor through the resistor R1, and the battery power supply is further connected to the system power supply through the first pin terminal and the second pin terminal of the first switching transistor in sequence.

2. The low-battery protection circuit of a lithium battery according to claim 1, wherein The voltage dividing module includes: a resistor R5 and a resistor R6, wherein, The battery power supply is grounded through the resistor R5 and the resistor R6 in sequence, and the first input terminal of the voltage comparator U2 is connected between the resistor R5 and the resistor R6.

3. The low battery protection circuit for a lithium battery according to claim 2, characterized in that The reference voltage module includes: a resistor R2 and a voltage reference chip U1, wherein, The battery power supply is connected to the output pin and the power supply pin of the voltage reference chip U1 through the resistor R2, the ground pin of the voltage reference chip U1 is grounded, and the output pin of the voltage reference chip U1 is connected to the second input terminal of the voltage comparator U2.

4. A low battery protection circuit for a lithium battery according to claim 1, characterized in that, The power supply terminal of the voltage comparator U2 is connected to the battery power supply, and this power supply terminal is also grounded through a capacitor C1.

5. A low battery protection circuit for a lithium battery according to claim 1, characterized in that, Both the first switching transistor and the second switching transistor are MOS transistors.

6. The low battery protection circuit for a lithium battery according to claim 5, characterized in that, The second switching transistor is an N-channel MOS transistor Q2. The gate of the MOS transistor Q2 is the control terminal of the second switching transistor, the source of the MOS transistor Q2 is the first pin terminal of the second switching transistor, and the drain of the MOS transistor Q2 is the second pin terminal of the second switching transistor.

7. The low - power protection circuit for a lithium battery according to claim 6, characterized in that, Further comprising: A resistor R3. The output terminal of the voltage comparator U2 is connected to the gate of the MOS transistor Q2 through the resistor R3.

8. The low battery protection circuit of a lithium battery according to claim 7, characterized in that, Further comprising: A resistor R4. The gate of the MOS transistor Q2 is connected to the source of the MOS transistor Q2 through the resistor R4.

9. The low battery protection circuit for a lithium battery according to claim 8, wherein The first switching transistor is a P-channel MOS transistor Q1. The gate of the MOS transistor Q1 is the control terminal of the first switching transistor, the source of the MOS transistor Q1 is the first pin terminal of the first switching transistor, and the drain of the MOS transistor Q1 is the second pin terminal of the first switching transistor.

10. A low battery protection device for a lithium battery, characterized in that, Including a lithium battery low power protection circuit according to any one of claims 1 to 9.

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