Lithium battery low-voltage detection alarm circuit and method

Abstract

The invention relates to the technical field of lithium battery low-voltage detection, and discloses a lithium battery low-voltage detection alarm circuit and method, and the circuit comprises a battery voltage detection circuit, a reference voltage generation circuit, an operational amplifier N1 and an alarm circuit. In actual use, the low-voltage detection alarm circuit generates the corresponding reference voltage according to the current temperature through the reference voltage generation circuit, so that different reference voltages can be provided according to different temperatures; therefore, the operational amplifier N1 can carry out voltage comparison according to the corresponding reference voltage in different temperature environments, and the accuracy of the low-voltage detection result of the lithium battery is ensured. In addition, when low-voltage detection alarm is carried out on the lithium battery, comparison detection is carried out through an operational amplifier N1, prompting is carried out through a warning circuit, the whole circuit does not need a single-chip microcomputer and other processing chips to participate, and therefore the size, cost and power consumption of the product can be further reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery low voltage detection, and in particular to a lithium battery low voltage detection alarm circuit and method. Background Art

[0002] Night vision instruments, equipment and some devices are mostly powered by batteries, and many of them use 18650 secondary lithium batteries as power sources. In order to let users know the current status of the product's battery, when the battery voltage is low, it is necessary to remind users to replace the battery in time, that is, to issue a low voltage alarm when the battery voltage is low, so as to avoid the battery running out and causing the product to shut down unexpectedly.

[0003] Night vision products often work in complex temperature environments such as high temperature, normal temperature and low temperature, and the discharge curve of the battery in different environments will change. However, most common low voltage alarm circuits have fixed voltage alarm thresholds, such as using a voltage divider circuit formed by multiple resistors to perform voltage detection. For example, the low-power consumption, small-area temperature compensation low voltage detection circuit disclosed in the patent document with the authorization publication number CN110806777A uses the first voltage divider resistor, the second voltage divider resistor, the third voltage divider resistor, the fourth voltage divider resistor and the fifth voltage divider resistor for detection;

[0004] For this low battery voltage detection circuit with a fixed voltage alarm threshold, the following problems exist when it is applied in a complex temperature environment:

[0005] The discharge curve of lithium batteries will change at different temperatures, so changes in temperature will cause corresponding changes in the voltage of lithium batteries. However, a fixed voltage alarm threshold will cause inaccurate low-voltage detection results when the temperature changes, which may easily lead to false alarms.

[0006] In addition, most of the existing low-voltage alarm circuits use a single-chip microcomputer to process the voltage and detect the voltage. For example, a low-voltage alarm circuit disclosed in the patent application publication number CN106569133A uses a single-chip microcomputer for temperature compensation detection, which will lead to complex circuits, increase the size and power consumption of products such as night vision instruments, and reduce the single-use time of lithium batteries. Summary of the invention

[0007] In view of the shortcomings of the background technology, the present invention provides a lithium battery low voltage detection alarm circuit and method. The technical problem to be solved is that the existing lithium battery low voltage detection alarm circuit has inaccurate detection results due to temperature influence during use, and is prone to false alarms. In addition, the use of a single-chip microcomputer for low voltage detection will result in high product cost and high power consumption.

[0008] To solve the above technical problems, in a first aspect, the present invention provides the following technical solutions: a lithium battery low voltage detection alarm circuit, comprising a battery voltage detection circuit, a reference voltage generation circuit, an operational amplifier N1 and a warning circuit;

[0009] The battery voltage detection circuit is used to detect the voltage of the battery connection terminal BAT and input the battery detection voltage to the inverting input terminal of the operational amplifier N1;

[0010] The reference voltage generating circuit is used to input a reference voltage to the non-inverting input terminal of the operational amplifier N1 according to the current temperature;

[0011] The operational amplifier N1 compares the battery detection voltage with the reference voltage and outputs a comparison signal;

[0012] The warning circuit is electrically connected to the output terminal of the operational amplifier N1 and generates a warning light based on the comparison signal.

[0013] In a certain implementation of the first aspect, the reference voltage output by the reference voltage generating circuit matches a discharge curve of the lithium battery.

[0014] In a certain embodiment of the first aspect, the reference voltage generating circuit includes a first resistance branch and a second resistance branch, the input end of the first resistance branch is used to connect to the power supply VCC, the output end of the first resistance branch is used to be grounded, the input end and the output end of the second resistance branch are connected to two intermediate nodes of the first resistance branch, and the second resistance branch includes a thermistor RT1, and one end of the thermistor RT1 is electrically connected to the in-phase input end of the operational amplifier N1.

[0015] In a certain implementation manner of the first aspect, the first resistance branch includes a resistor R1, a resistor R2, and a resistor R4 connected in series in sequence, one end of the resistor R1 is an input end of the first resistance branch, and is used to be electrically connected to the power supply VCC, and one end of the resistor R4 is an output end of the first resistance branch, and is grounded;

[0016] The second resistance branch further includes a resistor R3, one end of which is electrically connected to the non-inverting input end of the operational amplifier N1, the other end of which is electrically connected to the other end of the resistor R4, and the other end of the temperature-sensitive resistor RT1 is electrically connected to the other end of the resistor R1.

[0017] In a certain implementation of the first aspect, the battery voltage detection circuit includes a resistor R7 and a resistor R8, one end of the resistor R7 is electrically connected to the battery connection terminal BAT, and the other end of the resistor R7 is grounded through the resistor R8, for outputting the battery detection voltage.

[0018] In a certain embodiment of the first aspect, the warning circuit includes a positive wave generator and a light emitting lamp LED, and the positive wave generator inputs a pulse signal to the light emitting lamp LED based on the comparison signal.

[0019] In certain implementations of the first aspect, the positive wave generator includes a diode D1, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a capacitor C1, and an operational amplifier N2;

[0020] The cathode of the diode D1 is electrically connected to the output terminal of the operational amplifier N1; the anode of the diode D1 is electrically connected to one end of the resistor R9, the other end of the resistor R9 is electrically connected to one end of the resistor R10, one end of the resistor R11 and the non-inverting input terminal of the operational amplifier N2, the other end of the resistor R11 is grounded, the other end of the resistor R10 is electrically connected to the output terminal of the operational amplifier N2, one end of the resistor R13 and one end of the resistor R12, the other end of the resistor R12 is grounded through the capacitor C1 and is electrically connected to the inverting input terminal of the operational amplifier N1, and the other end of the resistor R13 is electrically connected to the light emitting lamp LED.

[0021] In a certain embodiment of the first aspect, the battery voltage detection circuit is electrically connected to the battery connection terminal BAT through an anti-reverse circuit, and the anti-reverse circuit is used to input the battery voltage to the battery voltage detection circuit when the battery connection terminal BAT is electrically connected to the positive electrode of the lithium battery, and to disconnect the battery connection terminal BAT from the battery voltage detection circuit when the battery connection terminal BAT is electrically connected to the negative electrode of the lithium battery.

[0022] In a certain embodiment of the first aspect, the anti-reverse circuit includes a transistor Q1, a transistor Q2, a MOS transistor N1, a resistor R5 and a resistor R6; the drain of the MOS transistor N1 is electrically connected to the battery connection terminal BAT and the emitter of the transistor Q1, respectively, the source of the MOS transistor N1 is electrically connected to the emitter of the transistor Q2 and the battery voltage detection circuit, the base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q1 and one end of the resistor R5, the gate of the MOS transistor N1 is electrically connected to the collector of the transistor Q2 and one end of the resistor R6, respectively, and the other end of the resistor R5 and the other end of the resistor R6 are both grounded.

[0023] In a second aspect, the present invention provides a lithium battery low voltage detection alarm method, which is implemented by the above-mentioned lithium battery low voltage detection alarm circuit, and is specifically as follows:

[0024] The discharge curve of the lithium battery is obtained, and the resistance values ​​of the resistors R1, R2, R3 and R4 are adjusted according to the discharge curve of the lithium battery, so that the reference voltage output by the reference voltage generating circuit matches the discharge curve of the lithium battery.

[0025] Compared with the prior art, the present invention has the following beneficial effects: the low voltage detection alarm circuit of the present invention generates a corresponding reference voltage according to the current temperature through a reference voltage generating circuit, so that reference voltages of different magnitudes can be provided according to different temperatures, so that the operational amplifier N1 can perform voltage comparison according to the corresponding reference voltage in different temperature environments, thereby ensuring the accuracy of the low voltage detection result of the lithium battery;

[0026] In addition, when the lithium battery is low-voltage detected and warned, comparative detection is performed through operational amplifier N1, and a prompt is given through the warning circuit. The entire circuit does not require the participation of processing chips such as microcontrollers, thereby further reducing product size, cost and power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the first structure of the present invention in Embodiment 1;

[0028] Figure 2 It is a second structural schematic diagram of the present invention in Embodiment 2;

[0029] Figure 3 This is an implementation circuit diagram of the present invention in Example 3. DETAILED DESCRIPTION

[0030] The present invention will now be described in further detail with reference to the accompanying drawings. These drawings are simplified schematic diagrams, which only illustrate the basic structure of the present invention in a schematic manner, and therefore only show the components related to the present invention.

[0031] Embodiment 1

[0032] In order to accurately detect the voltage of lithium batteries in complex temperature environments, so that when the voltage of the lithium battery is too low, an alarm will be issued in time without affecting the normal use of products equipped with lithium batteries. Figure 1 As shown, this embodiment provides a lithium battery low voltage detection alarm circuit, including a battery voltage detection circuit 1, a reference voltage generation circuit 2, an operational amplifier N1 and a warning circuit 3;

[0033] The battery voltage detection circuit 1 is used to detect the voltage of the battery connection terminal BAT and input the battery detection voltage to the inverting input terminal of the operational amplifier N1;

[0034] The reference voltage generating circuit 2 is used to input a reference voltage to the non-inverting input terminal of the operational amplifier N1 according to the current temperature;

[0035] Operational amplifier N1 compares the battery detection voltage with the reference voltage and outputs a comparison signal;

[0036] The warning circuit 3 is electrically connected to the output terminal of the operational amplifier N1 and generates a warning light based on the comparison signal.

[0037] In actual use, the low voltage detection alarm circuit of the present invention generates a corresponding reference voltage according to the current temperature through the reference voltage generating circuit 2, so that different reference voltages can be provided according to different temperatures, so that the operational amplifier N1 can perform voltage comparison according to the corresponding reference voltage in different temperature environments, thereby ensuring the accuracy of the low voltage detection result of the lithium battery;

[0038] In addition, when the lithium battery is low-voltage detected and warned, comparative detection is performed through the operational amplifier N1, and a prompt is given through the warning circuit 4. The entire circuit does not require the participation of processing chips such as microcontrollers, thereby further reducing product size, cost and power consumption.

[0039] In some implementations, a warning sound may be generated based on the comparison signal to provide a low voltage warning for the lithium battery. For example, the power on and off of the buzzer may be controlled by the comparison signal to provide a warning.

[0040] For lithium batteries, when they are in different temperature environments, their discharge curves will also change accordingly, and the changes in the discharge curve will cause different low-voltage judgment values ​​of the lithium battery. In order to better match the changes in the discharge curve of the lithium battery caused by temperature, in this embodiment, the reference voltage output by the reference voltage generating circuit 2 matches the discharge curve of the lithium battery, so that different reference voltages can be provided in different temperature environments, thereby accurately detecting the low voltage of the lithium battery.

[0041] Embodiment 2

[0042] like Figure 2 As shown, this embodiment also provides another structure of a lithium battery low voltage detection alarm circuit. Figure 1 The difference is, Figure 2 The battery voltage detection circuit 1 of the circuit is electrically connected to the battery connection terminal BAT through the anti-reverse circuit 4. The anti-reverse circuit 4 is used to input the battery voltage to the battery voltage detection circuit 1 when the battery connection terminal BAT is electrically connected to the positive electrode of the lithium battery, and disconnect the battery connection terminal BAT from the battery voltage detection circuit 1 when the battery connection terminal BAT is electrically connected to the negative electrode of the lithium battery.

[0043] In actual use, the anti-reverse circuit 4 can avoid circuit failures caused by wiring errors, thereby improving circuit reliability.

[0044] Embodiment 3

[0045] like Figure 3 As shown, this embodiment provides a specific circuit of a lithium battery low voltage detection alarm circuit. Figure 3In the figure, the reference voltage generating circuit 2 includes a first resistor branch 20 and a second resistor branch 21, the input end of the first resistor branch 20 is used to connect to the power supply VCC, the output end of the first resistor branch 20 is used to be grounded, the input end and the output end of the second resistor branch 21 are connected to two intermediate nodes of the first resistor branch 20, and the second resistor branch includes a thermistor RT1, one end of the thermistor RT1 is electrically connected to the in-phase input end of the operational amplifier N1.

[0046] More specifically, the first resistance branch 20 includes a resistor R1, a resistor R2 and a resistor R4 connected in series in sequence, one end of the resistor R1 is an input end of the first resistance branch, which is used to be electrically connected to the power supply VCC, and one end of the resistor R4 is an output end of the first resistance branch, which is grounded;

[0047] The second resistor branch 21 further includes a resistor R3 , one end of which is electrically connected to the non-inverting input end of the operational amplifier N1 , the other end of which is electrically connected to the other end of the resistor R4 , and the other end of the temperature-sensitive resistor RT1 is electrically connected to the other end of the resistor R1 .

[0048] right Figure 3 The reference voltage generating circuit 2 in is analyzed as follows:

[0049] First, the calculation formula of the resistance of thermistor RT1 is as follows:

[0050]

[0051] Where R0 is the nominal resistance of the NTC resistor at T0, B is the B value parameter of the NTC resistor, T is the ambient temperature, R T is the resistance value of thermistor RT1 at temperature T, where the temperature is expressed in absolute temperature;

[0052] According to the series-parallel relationship of resistors R1, R2, R3, R4 and thermistor RT1, the reference voltage V can be obtained. t The expression is as follows:

[0053]

[0054] According to the reference voltage V t By combining the temperature-resistance curve of thermistor RT1 and the discharge curve of the lithium battery at different temperatures, the reference voltage can be made consistent with the battery low-voltage warning voltage at different temperatures by setting the resistance values ​​of resistors R1, R2, R3 and R4, thereby achieving self-regulation of the reference voltage following the temperature and ensuring the accuracy of the lithium battery low-voltage detection result.

[0055] Specifically, in this embodiment, the battery voltage detection circuit 1 includes a resistor R7 and a resistor R8, one end of the resistor R7 is electrically connected to the battery connection terminal BAT, and the other end of the resistor R7 is grounded through the resistor R8 for outputting the battery detection voltage.

[0056] Resistors R7 and R8 form a voltage dividing branch. In actual use, the number of resistors in the voltage dividing branch can be increased according to actual needs, so as to obtain more battery voltage dividing ratios.

[0057] Specifically, in this embodiment, Figure 3 As shown, the warning circuit 3 includes a positive wave generator 30 and a light-emitting lamp LED. The positive wave generator 30 inputs a pulse signal to the light-emitting lamp LED based on the comparison signal, and the pulse signal is used to drive the light-emitting lamp LED to flash for prompting.

[0058] More specifically, the positive wave generator 30 includes a diode D1, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a capacitor C1 and an operational amplifier N2;

[0059] The cathode of the diode D1 is electrically connected to the output terminal of the operational amplifier N1; the anode of the diode D1 is electrically connected to one end of the resistor R9, the other end of the resistor R9 is electrically connected to one end of the resistor R10, one end of the resistor R11 and the non-inverting input terminal of the operational amplifier N2, the other end of the resistor R11 is grounded, the other end of the resistor R10 is electrically connected to the output terminal of the operational amplifier N2, one end of the resistor R13 and one end of the resistor R12, the other end of the resistor R12 is grounded through the capacitor C1 and is electrically connected to the inverting input terminal of the operational amplifier N1, and the other end of the resistor R13 is electrically connected to the light emitting lamp LED.

[0060] In actual use, when the comparison signal is at a low level, the positive wave generator 30 does not work; when the comparison signal is at a high level, the positive wave generator 30 enters the working mode and outputs a square wave. When the square wave is at a high level, the light-emitting lamp LED is turned on, and when the square wave is at a low level, the light-emitting lamp LED is turned off. This cycle repeats itself, causing the light-emitting lamp LED to flash and start the lithium battery low voltage alarm.

[0061] Specifically, in this embodiment, Figure 3 As shown, the anti-reverse circuit 4 includes a transistor Q1, a transistor Q2, a MOS transistor N1, a resistor R5 and a resistor R6; the drain of the MOS transistor N1 is electrically connected to the battery connection terminal BAT and the emitter of the transistor Q1 respectively, the source of the MOS transistor N1 is electrically connected to the emitter of the transistor Q2 and the battery voltage detection circuit respectively, the base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q1 and one end of the resistor R5 respectively, the gate of the MOS transistor N1 is electrically connected to the collector of the transistor Q2 and one end of the resistor R6 respectively, and the other end of the resistor R5 and the other end of the resistor R6 are both grounded.

[0062] Embodiment 4

[0063] This embodiment provides a lithium battery low voltage detection alarm method, which is implemented by the lithium battery low voltage detection alarm circuit in the third embodiment, as follows:

[0064] The discharge curve of the lithium battery is obtained, and the resistance values ​​of the resistors R1, R2, R3 and R4 are adjusted according to the discharge curve of the lithium battery, so that the reference voltage output by the reference voltage generating circuit matches the discharge curve of the lithium battery.

[0065] The above is based on the present invention as an inspiration. Through the above description, relevant staff can make various changes and modifications without departing from the technical idea of ​​this invention. The technical scope of this invention is not limited to the content in the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A lithium battery low voltage detection alarm circuit, characterized in that: It includes a battery voltage detection circuit, a reference voltage generation circuit, an operational amplifier N1 and a warning circuit; The battery voltage detection circuit is used to detect the voltage of the battery connection terminal BAT and input the battery detection voltage to the inverting input terminal of the operational amplifier N1; The reference voltage generating circuit is used to input a reference voltage to the non-inverting input terminal of the operational amplifier N1 according to the current temperature; The operational amplifier N1 compares the battery detection voltage with the reference voltage and outputs a comparison signal; The warning circuit is electrically connected to the output terminal of the operational amplifier N1 and generates a warning light based on the comparison signal.

2. A lithium battery low voltage detection alarm circuit according to claim 1, characterized in that: The reference voltage output by the reference voltage generating circuit matches the discharge curve of the lithium battery.

3. A lithium battery low voltage detection alarm circuit according to claim 2, characterized in that: The reference voltage generating circuit includes a first resistance branch and a second resistance branch, the input end of the first resistance branch is used to connect to the power supply VCC, the output end of the first resistance branch is used to be grounded, the input end and the output end of the second resistance branch are connected to two intermediate nodes of the first resistance branch, the second resistance branch includes a thermistor RT1, and one end of the thermistor RT1 is electrically connected to the non-inverting input end of the operational amplifier N1.

4. A lithium battery low voltage detection alarm circuit according to claim 3, characterized in that: The first resistance branch includes a resistor R1, a resistor R2 and a resistor R4 connected in series in sequence, one end of the resistor R1 is an input end of the first resistance branch, and is used to be electrically connected to the power supply VCC, and one end of the resistor R4 is an output end of the first resistance branch, and is grounded; The second resistance branch further includes a resistor R3, one end of which is electrically connected to the non-inverting input end of the operational amplifier N1, the other end of which is electrically connected to the other end of the resistor R4, and the other end of the temperature-sensitive resistor RT1 is electrically connected to the other end of the resistor R1.

5. A lithium battery low voltage detection alarm circuit according to claim 1, characterized in that: The battery voltage detection circuit includes a resistor R7 and a resistor R8. One end of the resistor R7 is electrically connected to the battery connection terminal BAT, and the other end of the resistor R7 is grounded through the resistor R8 for outputting the battery detection voltage.

6. A lithium battery low voltage detection alarm circuit according to claim 1, characterized in that: The warning circuit includes a positive wave generator and a light emitting lamp (LED), and the positive wave generator inputs a pulse signal to the light emitting lamp (LED) based on the comparison signal.

7. A lithium battery low voltage detection alarm circuit according to claim 6, characterized in that: The positive wave generator includes a diode D1, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a capacitor C1 and an operational amplifier N2; The cathode of the diode D1 is electrically connected to the output terminal of the operational amplifier N1; the anode of the diode D1 is electrically connected to one end of the resistor R9, the other end of the resistor R9 is electrically connected to one end of the resistor R10, one end of the resistor R11 and the non-inverting input terminal of the operational amplifier N2, the other end of the resistor R11 is grounded, the other end of the resistor R10 is electrically connected to the output terminal of the operational amplifier N2, one end of the resistor R13 and one end of the resistor R12, the other end of the resistor R12 is grounded through the capacitor C1 and is electrically connected to the inverting input terminal of the operational amplifier N1, and the other end of the resistor R13 is electrically connected to the light emitting lamp LED.

8. A lithium battery low voltage detection alarm circuit according to claim 1, characterized in that: The battery voltage detection circuit is electrically connected to the battery connection terminal BAT through an anti-reverse circuit. The anti-reverse circuit is used to input the battery voltage to the battery voltage detection circuit when the battery connection terminal BAT is electrically connected to the positive electrode of the lithium battery, and to disconnect the battery connection terminal BAT from the battery voltage detection circuit when the battery connection terminal BAT is electrically connected to the negative electrode of the lithium battery.

9. A lithium battery low voltage detection alarm circuit according to claim 8, characterized in that: The anti-reverse circuit includes a transistor Q1, a transistor Q2, a MOS transistor N1, a resistor R5 and a resistor R6; the drain of the MOS transistor N1 is electrically connected to the battery connection terminal BAT and the emitter of the transistor Q1 respectively, the source of the MOS transistor N1 is electrically connected to the emitter of the transistor Q2 and the battery voltage detection circuit respectively, the base of the transistor Q1 is electrically connected to the base of the transistor Q2, the collector of the transistor Q1 and one end of the resistor R5 respectively, the gate of the MOS transistor N1 is electrically connected to the collector of the transistor Q2 and one end of the resistor R6 respectively, and the other end of the resistor R5 and the other end of the resistor R6 are both grounded.

10. A lithium battery low voltage detection and alarm method, characterized in that: It is realized by the lithium battery low voltage detection alarm circuit as described in claim 4, specifically as follows: The discharge curve of the lithium battery is obtained, and the resistance values ​​of the resistors R1, R2, R3 and R4 are adjusted according to the discharge curve of the lithium battery, so that the reference voltage output by the reference voltage generating circuit matches the discharge curve of the lithium battery.

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