CN115514060A - Lithium battery pack discharge overheat protection circuit, power supply device and electric equipment - Google Patents

Abstract

The invention discloses a lithium battery pack discharge overheat protection circuit, a power supply device and electric equipment, wherein the circuit comprises a series voltage division network, a comparison circuit and a switch circuit; the series voltage division network is formed by connecting a first resistor and a thermistor in series, the other end of the first resistor is connected with the anode of the lithium battery pack, the other end of the thermistor is connected with the cathode of the lithium battery pack, and the thermistor is used for detecting the temperature of the lithium battery pack; the comparison circuit is connected between the series voltage division network connection and the switch circuit and is used for outputting a control signal for controlling the switch state of the switch circuit according to the voltage division value of the thermistor; the switch circuit is used for controlling the on-off of a discharging loop between the lithium battery pack and a load to be powered, the discharging loop is closed when the switch circuit is switched on, and the discharging loop is disconnected when the switch circuit is switched off. The invention can effectively improve the use safety of the lithium battery pack and the service life of the lithium battery.

Description

Lithium battery discharge overheating protection circuit and power supply device, electrical equipment

technical field

The invention relates to the technical field of battery protection circuits, in particular to a discharge overheat protection circuit for a lithium battery pack, a power supply device, and electrical equipment.

Background technique

At present, lithium batteries have been widely used in various electronic products. The rationality and safety of the charging and discharging performance of lithium batteries are very important and have an important impact on the quality of electronic products. Lithium batteries are not suitable for discharge at high or low temperature, and need to be protected by high temperature and low temperature charging. If the lithium battery continues to heat up during use, it will cause a significant drop in the performance and capacity of the lithium battery, and even cause explosion and fire hazards. In order to prevent damage to the battery caused by excessive battery temperature, it is necessary to protect the lithium battery from high temperature throughout the discharge process.

Therefore, how to realize the full overheating protection of the lithium battery pack during the discharge process is of great significance to ensure the safety of electronic products and prolong the service life of lithium batteries.

Contents of the invention

The invention provides a lithium battery pack discharge overheat protection circuit, power supply device, and electrical equipment to solve the problems in the prior art that the lithium battery continues to heat up during use and cause damage to the battery and affect the service life of the battery. .

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

The invention proposes a lithium battery pack discharge overheating protection circuit, including a series voltage divider network, a comparison circuit and a switch circuit;

The series voltage divider network is composed of a first resistor and a thermistor connected in series, the other end of the first resistor is connected to the positive pole of the lithium battery pack, the other end of the thermistor is connected to the negative pole of the lithium battery pack, and the thermistor is used to detect The temperature of the lithium battery pack;

The comparison circuit is connected between the series voltage divider network connection and the switch circuit, and is used to output a control signal for controlling the switch state of the switch circuit according to the voltage divider value of the thermistor;

The switch circuit is used to control the on-off of the discharge circuit between the lithium battery pack and the load to be powered. When the switch circuit is turned on, the discharge circuit is closed, and when the switch circuit is turned off, the discharge circuit is disconnected.

Furthermore, the thermistor is pasted on the surface of the lithium battery pack.

Further, the switch circuit includes a first MOS transistor, the gate of the first MOS transistor is connected to the output terminal of the comparison circuit, and the drain of the first MOS transistor is connected to the positive electrode of the lithium battery pack, so The source of the first MOS transistor is used to connect the load.

Further, the comparison circuit includes a voltage comparator, the output terminal of the voltage comparator is connected to the control terminal of the switch circuit, and the positive input terminal of the voltage comparator is connected to the connection between the first resistor and the thermistor. connection node, the negative input terminal of the voltage comparator is connected to the electrical signal output module, when the divided voltage value of the thermistor is less than the first voltage value of the output signal of the electrical signal output module, the control signal output by the comparison circuit is low level, the switch circuit disconnects the discharge circuit between the lithium battery pack and the load to be powered, wherein the first voltage value is the voltage across the thermistor when the upper threshold temperature of the lithium battery pack is monitored. Voltage.

Further, the voltage comparator is a hysteresis comparator;

The electrical signal output module includes a signal source, a stable voltage source and a second MOS tube, the signal source is connected in series with the stable voltage source and connected to the negative input terminal of the voltage comparator, and the second MOS The drain of the transistor is connected to the output terminal of the signal source, the source of the second MOS transistor is connected to the negative input terminal of the voltage comparator, and the gate of the second MOS transistor is connected to the voltage comparator output connection;

When the divided voltage value of the thermistor is greater than the second voltage value of the output signal of the electrical signal output module, the control signal output by the voltage comparator is at a high level, and the switch circuit closes the connection between the lithium battery pack and the load to be powered. The discharge circuit, wherein the second voltage value is the voltage across the thermistor when the lower limit threshold temperature of the lithium battery pack is monitored.

Further, the comparison circuit further includes a third resistor, one end of the third resistor is connected to the output end of the voltage comparator, and the other end of the third resistor is connected to the gate of the second MOS transistor.

Further, the thermistor is a negative temperature coefficient thermistor.

Further, the first MOS transistor is an N-type MOS transistor.

In addition, the present invention also provides a power supply device, including a lithium battery pack and the lithium battery pack discharge overheat protection circuit as described above.

In addition, the present invention also provides an electric device, including the above-mentioned power supply device.

Compared with the prior art, the main advantages of the technical solution of the present invention are as follows:

The invention adopts pure hardware means to realize the whole-process overheating protection of the lithium battery pack discharge process, the detection method is simple, the operation is safe and reliable, there is no lossy device, the cost is saved, the action time can be effectively shortened, no software judgment is required, the result is accurate, and the interference is anti-interference Strong ability, effectively improving the safety of lithium battery packs and the service life of lithium batteries.

The above description is only an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, it can be implemented according to the contents of the description, and in order to make the above and other purposes, features and advantages of the present invention more obvious and understandable , the specific embodiments of the present invention are enumerated below.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention. Also throughout the drawings, the same reference numerals are used to designate the same parts. In the attached picture:

FIG. 1 is a schematic structural diagram of a lithium battery pack discharge overheating protection circuit provided by an embodiment of the present invention;

FIG. 2 is a schematic circuit diagram of a lithium battery pack discharge overheat protection circuit provided by an embodiment of the present invention.

detailed description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided for more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

Those skilled in the art can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which this invention belongs. It should also be understood that terms, such as those defined in commonly used dictionaries, should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be used in an idealized or overly formal sense unless specifically defined to explain.

FIG. 1 is a schematic structural diagram of a lithium battery pack discharge overheat protection circuit provided by an embodiment of the present invention. As shown in Figure 1, the lithium battery pack discharge overheating protection circuit provided by this embodiment includes a series voltage divider network 10, a comparison circuit 20 and a switch circuit 30, wherein:

The series voltage divider network 10 is composed of a first resistor R1 and a thermistor R2 connected in series, the other end of the first resistor R1 is connected to the positive pole of the lithium battery pack, and the other end of the thermistor R2 is connected to the negative pole of the lithium battery pack. The sensitive resistor R2 is used to detect the temperature of the lithium battery pack;

The comparison circuit 20 is connected between the series voltage divider network 10 and the switch circuit 30, and is used to output a control signal for controlling the switch state of the switch circuit 30 according to the voltage divider value of the thermistor R2;

The switch circuit 30 is used to control the on-off of the discharge circuit between the lithium battery pack and the load to be powered. When the switch circuit 30 is turned on, the discharge circuit is closed, and when the switch circuit 30 is turned off, the discharge circuit is disconnected.

The lithium battery pack discharge overheating protection circuit of the present invention adopts pure hardware means to realize the whole process of overheating protection for the lithium battery pack discharge process, the detection method is simple, the operation is safe and reliable, there is no loss device, the cost is saved, and the safety of the lithium battery pack is effectively improved. performance and lithium battery life.

In the embodiment of the present invention, the thermistor R2 is pasted on the surface of the lithium battery pack. Specifically, it is closely attached to the surface of the lithium battery and used as a temperature sensing package. The thermistor R2 is a negative temperature coefficient thermistor NTC, which is a kind of sensor resistance whose resistance value decreases with the increase of temperature.

In one embodiment of the present invention, as shown in FIG. 2, the switch circuit 30 includes a first MOS transistor Q1, the gate of the first MOS transistor Q1 is connected to the output end of the comparison circuit 20, and the The drain of the first MOS transistor Q1 is connected to the positive electrode of the lithium battery pack, and the source of the first MOS transistor Q1 is used to connect to a load.

In the specific example shown in FIG. 2, the comparison circuit 20 includes a voltage comparator U1, the output terminal of the voltage comparator U1 is connected to the control terminal of the switch circuit 30, that is, to the gate of the first MOS transistor Q1 connected, the positive input end of the voltage comparator U1 is connected to the connection node between the first resistor R1 and the thermistor R2, the negative input end of the voltage comparator U1 is connected to the electrical signal output module, when the thermistor When the divided voltage value of the resistor R2 is less than the first voltage value of the output signal of the electrical signal output module, the control signal output by the voltage comparator U1 is at a low level, and the switch circuit, that is, the first MOS transistor Q1 disconnects the lithium battery pack and A discharge circuit between loads to be powered, wherein the first voltage value is the voltage across the thermistor R2 when the upper threshold temperature of the thermistor R2 is monitored.

In this embodiment, in order to prevent frequent switchover of the power switching point, the voltage comparator U1 may be a hysteresis comparator.

Further, the electrical signal output module includes a signal source vin, a stable voltage source vs and a second MOS transistor Q2, the signal source vin is connected in series with the stable voltage source vs and connected to the negative input of the voltage comparator U1 terminal, the drain of the second MOS transistor Q2 is connected to the output terminal of the signal source vs, the source of the second MOS transistor Q2 is connected to the negative input terminal of the voltage comparator U1, and the first The gate of the second MOS transistor Q2 is connected to the output terminal of the voltage comparator U1;

When the divided voltage value of the thermistor R2 is greater than the second voltage value of the output signal of the electrical signal output module, the control signal output by the voltage comparator U1 is at a high level, and the switch circuit 30 closes the lithium battery pack and the load to be powered The discharge circuit between them, wherein the second voltage value is the voltage across the thermistor R2 when the lower threshold temperature of the thermistor R2 is monitored.

Among them, T1 and T2 are taken as the two temperature thresholds of the lithium battery pack, and T1<T2, it is considered that when the temperature exceeds (T1+T2)/2, the discharge of the lithium battery pack is no longer safe.

Vs is a stable voltage source, Vs+Vin- corresponds to the voltage across R2 at T1 temperature, which is the first voltage value; Vin- is a fixed input voltage, corresponding to the voltage across R2 at T2 temperature, which is the second voltage value.

The hysteresis comparator has two threshold voltages, and when the input changes in one direction, the output only jumps once. Therefore, when the input changes from large to small, it corresponds to a small threshold voltage; when the input changes from small to large, it corresponds to a large threshold voltage. When the temperature rises, the corresponding threshold voltage Vin-; when the temperature drops, the corresponding threshold voltage Vs+Vin-. When the temperature is changed in the range of T2-T1, frequent switching of the switching tube will not be caused, and the anti-interference ability is enhanced.

Further, the comparison circuit further includes a third resistor R3, one end of the third resistor R3 is connected to the output end of the voltage comparator, and the other end of the third resistor R3 is connected to the gate of the second MOS transistor connect. The third resistor R3 is a feedback resistor of U1.

Further, both the first MOS transistor Q1 and the first MOS transistor Q2 are N-type MOS transistors.

The lithium battery pack discharge overheating protection circuit provided by the embodiment of the present invention uses an NTC temperature sensor R2 close to the battery surface and a first resistor R1 to form a series voltage divider network, and selects a suitable resistor according to the impedance temperature characteristic table of the NTC resistor R2 R1. R3 is the feedback resistor of the comparator U1. When the comparator outputs a high level, both Q1 and Q2 are turned on, and the discharge circuit of the lithium battery pack is closed.

It is set that the lithium battery pack has two temperature thresholds from low to high, namely T1 and T2. When the temperature rises, the resistance value of R2 decreases, the resistance value of R1 remains unchanged, the current IAC, that is, the current of the series voltage divider network increases, R1 and R2 are connected in series to divide the voltage, the voltage UBC across R2 decreases, and the voltage across R1 UAB Increase.

Specifically, when the temperature rises, when the temperature T<T1, UBC>Vs+Vin-, the switch tube Q1 is turned on, the threshold is Vin-, the lithium battery pack is closed in the charging and discharging circuit, and the normal discharge is performed; when the temperature T1<T< At T2, Vin-<UBC<Vs+Vin-, U1 outputs a high level, and the lithium battery pack is still closed and keeps working in the discharge circuit; when the temperature T>T2, UBC<Vin-, U1 outputs a low level, Q1, Q2 is off and the threshold is Vs+Vin-.

When the temperature decreases from high, when the temperature T1<T<T2, UBC increases, Vin-<UBC<Vs+Vin-, U1 output is low, and the discharge circuit is still disconnected; when the temperature T<T1, UBC increases, UBC>Vs+Vin-, U1 output is high level, Q1 and Q2 are closed, the threshold is Vin-, and the discharge circuit is closed.

The above logic is expressed in Table 1 as follows:

Further, the MOS tube can also be replaced with a suitable triode or optocoupler device to realize the isolation of the discharge circuit, which is not specifically limited in the present invention.

In addition, an embodiment of the present invention also provides a power supply device, including a lithium battery pack and the lithium battery pack discharge overheat protection circuit as described in the above embodiment.

In addition, an embodiment of the present invention also provides an electric device, including the above-mentioned power supply device. The power supply device includes a lithium battery pack and the lithium battery pack discharge overheat protection circuit as described in the above embodiment.

Compared with the prior art, the main advantages of the technical solution of the present invention are as follows:

The invention adopts pure hardware means to realize the whole-process overheating protection of the lithium battery pack discharge process, the detection method is simple, the operation is safe and reliable, there are no lossy devices, the cost is saved, the action time can be shortened, no software judgment is required, the result is accurate, and the anti-interference ability Strong, prevent frequent switching of the power switch point, effectively improve the safety of the lithium battery pack and the service life of the lithium battery.

Those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are meant to be within the scope of the invention and form different examples. For example, in the following claims, any of the claimed embodiments may be used in any combination.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: it can still be Modifications are made to the technical solutions described in the foregoing embodiments, or equivalent replacements are made to some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims (10)

1. A lithium battery pack discharge overheat protection circuit is characterized by comprising a series voltage division network, a comparison circuit and a switch circuit;

the series voltage division network is formed by connecting a first resistor and a thermistor in series, the other end of the first resistor is connected with the anode of the lithium battery pack, the other end of the thermistor is connected with the cathode of the lithium battery pack, and the thermistor is used for detecting the temperature of the lithium battery pack;

the comparison circuit is connected between the series voltage division network connection and the switch circuit and is used for outputting a control signal for controlling the switch state of the switch circuit according to the voltage division value of the thermistor;

the switch circuit is used for controlling the on-off of a discharging loop between the lithium battery pack and a load to be powered, the discharging loop is closed when the switch circuit is switched on, and the discharging loop is disconnected when the switch circuit is switched off.

2. The lithium battery pack discharge overheat protection circuit according to claim 1, wherein the thermistor is attached to a surface of the lithium battery pack.

3. The lithium battery pack discharge overheating protection circuit according to claim 1, wherein the switching circuit includes a first MOS transistor, a gate of the first MOS transistor is connected to the output terminal of the comparison circuit, a drain of the first MOS transistor is connected to the positive electrode of the lithium battery pack, and a source of the first MOS transistor is used for connecting a load.

4. The lithium battery pack discharge overheating protection circuit according to claim 1, wherein the comparison circuit includes a voltage comparator, an output terminal of the voltage comparator is connected to a control terminal of the switch circuit, a positive input terminal of the voltage comparator is connected to a connection node between the first resistor and the thermistor, a negative input terminal of the voltage comparator is connected to the electrical signal output module, when a voltage division value of the thermistor is smaller than a first voltage value of an output signal of the electrical signal output module, a control signal output by the comparison circuit is a low level, and the switch circuit disconnects a discharge loop between the lithium battery pack and a load to be powered, wherein the first voltage value is a voltage across the thermistor when an upper threshold temperature of the lithium battery pack is monitored.

5. The lithium battery pack discharge overheating protection circuit of claim 4, wherein the voltage comparator is a hysteresis comparator;

the electric signal output module comprises a signal source, a stable voltage source and a second MOS tube, the signal source is connected with the stable voltage source in series and then is connected to the negative input end of the voltage comparator, the drain electrode of the second MOS tube is connected with the output end of the signal source, the source electrode of the second MOS tube is connected to the negative input end of the voltage comparator, and the grid electrode of the second MOS tube is connected with the output end of the voltage comparator;

when the voltage division value of the thermistor is greater than a second voltage value of the output signal of the electric signal output module, the control signal output by the voltage comparator is a high level, the switching circuit closes a discharge loop between the lithium battery pack and a load to be powered, wherein the second voltage value is the voltage at two ends of the thermistor when the lower limit threshold temperature of the lithium battery pack is monitored.

6. The lithium battery pack discharge overheating protection circuit according to claim 5, wherein the comparison circuit further includes a third resistor, one end of the third resistor is connected to the output terminal of the voltage comparator, and the other end of the third resistor is connected to the gate of the second MOS transistor.

7. The lithium battery discharge overheat protection circuit according to any one of claims 1 to 6, wherein said thermistor is a negative temperature coefficient thermistor.

8. The lithium battery pack discharge overheat protection circuit according to claim 3, wherein the first MOS transistor is an N-type MOS transistor.

9. A power supply device comprising a lithium battery pack and a lithium battery pack discharge overheat protection circuit as claimed in any one of claims 1 to 8.

10. An electric consumer, characterized in that it comprises a power supply device according to claim 9.

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