Lithium battery ultralow-temperature full-power working protection circuit

Abstract

The utility model relates to the technical field of lithium battery protection, in particular to an ultralow-temperature full-power working protection circuit for a lithium battery, which comprises at least one group of battery protection control units, more than two groups of battery protection control units are connected in series, and each group of battery protection control units consists of a battery module and a protection control circuit, the protection control circuit comprises a voltage sampling module and a driving control module; the driving control module comprises optical couplers U2 and U3, current-limiting resistors R17 and R18 and a battery protection chip U1; the voltage sampling module is composed of a sampling resistor and a filter capacitor, and the main control circuit comprises a charging control circuit and a discharging control circuit; the temperature compensation module comprises a negative temperature coefficient thermistor HT2 and a divider resistor R23 which are connected in series. The lithium battery protection circuit has the characteristics of high reliability, low-temperature adaptability and light weight, and an efficient and economical lithium battery protection solution is provided for an ultralow-temperature high-power application scene.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery protection technology, and in particular to a lithium battery ultra-low temperature full power operation protection circuit. Background Technology

[0002] In fields such as aircraft and robotics, where battery performance requirements are stringent, lithium-ion battery packs must continuously output high currents in ultra-low temperature environments (such as -40°C) to meet high power demands. However, existing technologies suffer from the following problems:

[0003] Traditional lithium battery packs have limited rated voltages due to restrictions on the number of batteries connected in series. According to the formula P=UI, high voltage requires high current to achieve high power output, but this high current rapidly increases battery temperature, triggering over-temperature protection and forcing the system to shut down. In ultra-low temperature environments, the battery's internal resistance increases dramatically, causing a significant voltage drop during high-current discharge, easily triggering undervoltage protection and resulting in power outages. Existing protection circuits lack effective low-temperature compensation mechanisms and cannot maintain continuous discharge under extreme temperatures. Connecting multiple battery packs in series requires multiple independent protection circuits, increasing system size and weight, making it difficult to meet the lightweight requirements of aerospace equipment. Utility Model Content

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution.

[0005] Design a lithium battery ultra-low temperature full-power operation protection circuit, including at least one set of battery protection control units. When there are two or more sets of battery protection control units, the two or more sets of battery protection control units are connected in series. Each set consists of a battery module composed of multiple battery packs connected in series and a corresponding protection control circuit. The protection control circuit includes a voltage sampling module and a drive control module. The drive control module includes optocouplers U2 and U3, current-limiting resistors R17 and R18, and a battery protection chip U1. The optocoupler U3 is connected to the charging control terminal COUT of the battery protection chip U1 through the current-limiting resistor R18, and the optocoupler U2 is connected to the discharging control terminal DOUT of the battery protection chip U1 through the current-limiting resistor R17, so as to realize the signal isolation control of charging and discharging on and off.

[0006] The voltage sampling module consists of multiple sampling resistors and multiple filter capacitors connected in series with each of them. One end of each sampling resistor is connected to the positive terminal of the corresponding battery pack, and the other end is input to the sampling terminal of the battery protection chip U1. Each filter capacitor is connected in parallel to the two ends of the corresponding battery pack, and the filtered battery voltage is input to the sampling terminal of the battery protection chip U1.

[0007] It also includes a master control circuit for receiving battery module protection signals, which includes a charging control circuit connected between the battery module and the charger and a discharging control circuit connected between the battery module and the load.

[0008] A temperature compensation module is connected to the discharge control signal terminal of the discharge control circuit. The temperature compensation module includes a negative temperature coefficient thermistor HT2 and a voltage divider resistor R23 connected in series.

[0009] Preferably, the output terminal of the optocoupler U3 of the first group of battery protection control units is directly connected to the charging control circuit, the output terminal of the optocoupler U2 is directly connected to the discharging control circuit, a terminal J5 is connected to the output terminal of the protection control circuit, and multiple terminals J3 are connected to the input terminal of the main control circuit. Each subsequent group of battery protection control units is connected to the input terminal J3 through the output terminal J5.

[0010] Preferably, each battery module consists of 3-16 battery packs, and each battery pack consists of multiple individual cells connected in parallel.

[0011] Preferably, the sampling terminals V1 to V15 of the battery protection chip U1 are connected to the positive terminals of each battery pack BT1 to BT15 respectively through resistors R1 to R15, and the sampling terminal V16 is shorted to the sampling terminal V15.

[0012] Preferably, the power supply terminal VDD of the battery protection chip U1 is connected to the positive terminal of the battery pack BT15 through a current-limiting resistor R19 and a filter capacitor C16, and the other end of C16 is connected to the negative terminal of the battery pack BAT1 together with the ground connection terminal VSS of the battery protection chip U1.

[0013] Preferably, the charging control circuit includes a charging MOSFET Q3, a Zener diode ZD2, and resistors R20 and R22. One end of resistor R20 is connected to the positive terminal of the battery module, and the other end is connected to the cathode of Zener diode ZD2. The anode of Zener diode ZD2 is connected to the charging negative terminal of the corresponding battery module. The discharging control circuit includes discharging MOSFETs Q7 to Q10, voltage divider resistors R24 to R27, and a Zener diode ZD1. The gates of discharging MOSFETs Q7 to Q10 are connected to Zener diode ZD1 through the corresponding voltage divider resistors R24 to R27. The sources are all connected to the negative terminal of the battery module, and the drains are all connected to the discharging negative terminal output by the battery module.

[0014] Preferably, the gate of the charging MOS transistor Q3 is connected to the cathode of the Zener diode ZD2 through resistor R22, the source is connected to the negative terminal of the battery module, and the drain is connected to the negative terminal of the battery module.

[0015] Preferably, the negative temperature coefficient thermistor HT2 and the voltage divider resistor R23 are connected in series and then connected in parallel with the Zener diode ZD1.

[0016] The beneficial effects of this utility model are as follows:

[0017] 1. This invention increases the rated voltage of the battery pack by increasing the number of batteries connected in series. When the battery pack operates at high power, the output current decreases, and the internal temperature of the battery itself decreases, ensuring normal operation of the battery pack. Furthermore, the high-voltage design reduces the current demand during high-power output, reduces battery temperature rise, avoids false triggering of over-temperature protection, and improves energy transfer efficiency.

[0018] 2. In ultra-low temperature (-40℃) environments, the resistance of the negative temperature coefficient thermistor HT2 increases significantly. When connected in series with the voltage divider resistor R23, it raises the drive voltage of the MOSFET, maintaining the discharge circuit's continuity and preventing undervoltage protection malfunctions due to increased battery internal resistance. As the cell temperature rises during discharge, the resistance of HT2 decreases rapidly, automatically restoring the undervoltage protection function and ensuring system safety.

[0019] 3. This circuit uses a single master control circuit to coordinate multiple battery protection modules, reducing redundant circuit components and lowering system weight and complexity.

[0020] 4. This utility model supports triple protection against overvoltage, undervoltage, and overtemperature. It quickly cuts off the charging and discharging circuit through optocouplers and MOSFETs, ensuring battery safety while also achieving full-power discharge within a temperature range of -40℃ to room temperature, meeting the stable power supply needs of aircraft and other equipment in extreme environments. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the overall circuit connection structure of this utility model;

[0022] Figure 2 This is a circuit connection diagram of the battery protection control unit of this utility model;

[0023] Figure 3 This is the overall control circuit connection diagram of this utility model; Detailed Implementation

[0024] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0025] Example 1

[0026] A lithium battery ultra-low temperature full-power operation protection circuit, such as Figures 1 to 3As shown, it includes a battery protection control unit, which consists of a battery module composed of 15 battery packs connected in series and a protection control circuit. Each battery pack consists of multiple parallel individual cells. A set of battery modules can provide an output voltage of 54V. The output terminals of the battery protection control unit are directly connected to the charging control circuit and the discharging control circuit, respectively. Specifically, the collector of the phototransistor of optocoupler U3 is directly connected to the cathode of Zener diode ZD2, and the emitter is directly connected to the anode of Zener diode ZD2. The collector of the phototransistor of optocoupler U2 is directly connected to the temperature compensation module, and the emitter is directly connected to the negative terminal of the battery module. Figure 1 Simply short-circuit pins 1 and 2 of the middle terminal J4.

[0027] The protection control circuit includes a voltage sampling module and a drive control module. The drive control module includes optocouplers U2 and U3, current-limiting resistors R17 and R18, and a battery protection chip U1. Optocoupler U3 is connected to the charging control terminal COUT of the battery protection chip U1 through the current-limiting resistor R18, and optocoupler U2 is connected to the discharging control terminal DOUT of the battery protection chip U1 through the current-limiting resistor R17, so as to realize the signal isolation control of charging and discharging on and off.

[0028] The voltage sampling module consists of sampling resistors R1 to R15 and filter capacitors C1 to C15. One end of the sampling resistors R1 to R15 is connected to the positive terminal of battery packs BT1 to BT15 respectively, and the other end is input to the sampling terminal of battery protection chip U1. The filter capacitors C1 to C15 are connected in parallel to the two ends of battery packs BT1 to BT15 respectively, and the filtered battery voltage is input to the sampling terminal of battery protection chip U1.

[0029] The sampling terminals V1 to V15 of the battery protection chip U1 are connected to the positive terminals of each cell BT1 to BT15 respectively through resistors R1 to R15. The sampling terminal V16 is shorted to the sampling terminal V15. The power supply terminal VDD of the battery protection chip U1 is connected to the positive terminal of the battery pack BT15 through the current limiting resistor R19 and the filter capacitor C16. The other end of C16 is connected to the negative terminal of the battery pack BAT1 together with the ground connection terminal VSS of the battery protection chip U1.

[0030] It also includes a master control circuit for receiving battery pack protection signals, which is used to cut off the charging circuit when there is overvoltage, cut off the discharging circuit when there is undervoltage, and cut off the charging and discharging circuits simultaneously when there is overtemperature; it includes a charging control circuit connected between the battery module and the charger and a discharging control circuit connected between the battery module and the load.

[0031] The charging control circuit includes a charging MOSFET Q3, a Zener diode ZD2, and resistors R20 and R22. One end of resistor R20 is connected to the positive terminal of the corresponding battery module, and the other end is connected to the cathode of Zener diode ZD2. The anode of Zener diode ZD2 is connected to the negative terminal of the corresponding battery module. The gate of charging MOSFET Q3 is connected to the cathode of Zener diode ZD2 through resistor R22, the source is connected to the negative terminal of the battery module, and the drain is connected to the negative terminal of the battery module.

[0032] The discharge control circuit includes discharge MOSFETs Q7 to Q10, voltage divider resistors R24 to R27, and Zener diode ZD1. The gates of discharge MOSFETs Q7 to Q10 are connected to Zener diode ZD1 through the corresponding voltage divider resistors R24 to R27. The sources are connected to the negative terminal of the battery module, and the drains are connected to the negative terminal of the battery module output discharge.

[0033] A temperature compensation module is connected to the discharge control signal terminal of the discharge control circuit. The temperature compensation module includes a negative temperature coefficient thermistor HT2 and a voltage divider resistor R23, which are connected in series and then in parallel with the Zener diode ZD1. The negative temperature coefficient thermistor HT2 is installed close to the battery cell to sense the temperature in real time. The negative temperature coefficient thermistor HT2 has a resistance greater than 70kΩ at -40℃ and is used to compensate for the voltage drop caused by the increased internal resistance of the battery in ultra-low temperature environments.

[0034] Among them, the temperature compensation module and the drive control module work together to maintain the discharge MOSFET on in ultra-low temperature environment through the high resistance of the negative temperature coefficient thermistor HT2, and restore the undervoltage protection function after the battery temperature rises.

[0035] Zener diodes ZD2 and ZD1 are used to limit the driving voltage of charging MOSFET Q3 and discharging MOSFETs Q7 to Q10, respectively.

[0036] Example 2

[0037] A lithium battery ultra-low temperature full-power operation protection circuit differs from Embodiment 1 in that it includes two or more sets of battery protection control units connected in series. Each set consists of a battery module composed of 15 battery packs connected in series and a protection control circuit. The two sets of battery modules connected in series are used to provide a high voltage output with a rated voltage of 108V or higher. Terminal J5 is connected to the output terminal of the protection control circuit, and multiple terminals J3 are connected to the input terminal of the main control circuit. Each set of battery protection control units after the second set is connected to the input terminal J3 through the output terminal J5, and the output terminal... The J5 outputs a protection signal for the battery module, and after logical judgment, performs global control of the battery pack's charging and discharging. Specifically, the collector of the phototransistor of optocoupler U3 is connected to pin 1 of terminal J5, and the emitter is connected to pin 2 of terminal J5. The collector of the phototransistor of optocoupler U2 is connected to pin 3 of terminal J5, and the emitter is connected to pin 4 of terminal J5. The cathode and anode of Zener diode ZD2 are connected to pins 1 and 2 of terminal J3 respectively. The temperature compensation module is connected to pin 3 of J3, and the negative terminal of the battery module is connected to pin 4 of J3. Figure 2 The middle terminal J7 is short-circuited between pins 1 and 2, and the terminal J6 is short-circuited with... Figure 1 Connect the corresponding pin J4 in the circuit, and so on, to connect multiple battery protection control units in series.

[0038] The working process of this utility model:

[0039] (1) Voltage sampling and protection triggering

[0040] Battery protection chip U1 monitors the voltage of each cell in real time through resistors R1 to R15. If overvoltage or undervoltage is detected, the corresponding MOSFET performs the following actions:

[0041] Overvoltage protection: When the battery charging voltage reaches the overvoltage protection value, the overvoltage trigger COUT terminal of U1 outputs a high level, driving the optocoupler U3 to conduct. Then, the Zener diode ZD2 is reverse-broken and conducts. At this time, the voltage across R22 drops to 0V due to the clamping effect of ZD2, and the gate voltage of the N-channel charging MOSFET Q3 is pulled low, causing the MOSFET Q3 to be turned off and stopping charging.

[0042] During normal charging, in this embodiment, an 18V voltage is applied to resistor R22. The battery protection chip U1 detects that the cell voltage is normal, and its COUT terminal outputs a low level. The optocoupler U3 is cut off, and the charging MOSFET Q3 is turned on for charging.

[0043] Undervoltage protection: When the battery discharge voltage is less than or equal to the undervoltage protection value, the undervoltage trigger DOUT terminal of U1 outputs a high level, which drives the optocoupler U2 to conduct through the current limiting resistor R17, pulling down the drive voltage VGS of the discharge MOSFETs Q7 to Q10. When the drive voltage VGS is lower than its conduction voltage, the discharge MOSFETs Q7 to Q10 are turned off, and the discharge stops.

[0044] During normal discharge, the battery protection chip U1 detects that the output voltage is normal, and its undervoltage trigger DOUT terminal outputs a low level. The optocoupler U2 is cut off, and the driving voltage of the discharge MOSFETs Q7 to Q10 is 18V, which causes the MOSFETs Q7 to Q10 to conduct and discharge.

[0045] (2) Temperature-compensated continuous discharge under ultra-low temperature environment

[0046] In an ultra-low temperature environment of -40℃, the battery's internal resistance increases, and the output voltage decreases during high-current, high-rate discharge, resulting in an undervoltage state. The actual battery capacity is relatively high, and due to the high-rate, high-current discharge, the battery's internal resistance is relatively large, so the temperature rises relatively quickly, and the battery's temperature itself can easily rise.

[0047] The resistance of the negative temperature coefficient thermistor HT2 is very high in an ultra-low temperature environment of -40°C. As the battery temperature gradually rises, the resistance of the negative temperature coefficient thermistor HT2 will decrease rapidly.

[0048] In this embodiment, the negative temperature coefficient thermistor with a resistance of 2KΩ at 25℃ can reach a resistance of 70KΩ at -40℃.

[0049] Phase 1: In an ultra-low temperature environment of -40°C, the battery module will enter an undervoltage protection state when discharging at a high current and high rate. At this time, the transistor of optocoupler U2 will be turned on. After being turned on, it will pull the driving voltage of the driving discharge MOSFETs Q7 to Q10 to the negative terminal of the battery module through the negative temperature coefficient thermistor HT2. Since the resistance of the negative temperature coefficient thermistor HT2 will be very large in an ultra-low temperature environment of -40°C, the voltage on HT2 will also be high, and the voltage drop on HT2 will also be relatively large. Therefore, the driving voltage applied to MOSFETs Q7 to Q10 (across ZD1) will be raised to drive the discharge MOSFETs Q7 to Q10 to be turned on, so that the battery module can discharge at full power.

[0050] The second stage (temperature recovery): As the battery discharges at a high current and high rate, the battery temperature rises. The resistance of the negative temperature coefficient thermistor HT2, which is close to the battery module, will also rise with the cell temperature. At this time, the resistance of the negative temperature coefficient thermistor HT2 will decrease rapidly. At the same time, the voltage drop across the thermistor HT2 will also decrease as the resistance decreases. The series voltage division effect between the thermistor HT2 and the voltage divider resistor R23 will weaken. As a result, the driving voltage (across ZD1) applied to MOSFETs Q7 to Q10 will decrease. Then, the discharge MOSFETs Q7 to Q10 will be cut off, and the undervoltage protection function of the circuit will be restored again.

[0051] Before the undervoltage protection function is restored, as the battery temperature gradually reaches normal, the battery's internal resistance decreases, and the output voltage increases. Therefore, there is no undervoltage, and the transistor in optocoupler U2 is cut off. At this point, the battery pack no longer needs undervoltage protection, and MOSFETs Q7 to Q10 remain on, allowing the battery pack to continue discharging at full power. This effectively avoids the undervoltage protection caused by increased battery internal resistance due to low temperatures, allowing the battery to continue high-rate, high-current discharge in ultra-low temperature environments down to -40°C.

[0052] Finally, it should be noted that the above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Although the present utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A lithium battery ultra-low temperature full-power operation protection circuit, characterized in that, It includes at least one set of battery protection control units. When there are two or more sets of battery protection control units, the two or more sets of battery protection control units are connected in series. Each set consists of a battery module composed of multiple battery packs connected in series and a corresponding protection control circuit. The protection control circuit includes a voltage sampling module and a drive control module. The drive control module includes optocouplers U2 and U3, current-limiting resistors R17 and R18, and a battery protection chip U1. The optocoupler U3 is connected to the charging control terminal COUT of the battery protection chip U1 through the current-limiting resistor R18, and the optocoupler U2 is connected to the discharging control terminal DOUT of the battery protection chip U1 through the current-limiting resistor R17, so as to realize the signal isolation control of charging and discharging on and off. The voltage sampling module consists of multiple sampling resistors and multiple filter capacitors connected in series with each of them. One end of each sampling resistor is connected to the positive terminal of the corresponding battery pack, and the other end is input to the sampling terminal of the battery protection chip U1. Each filter capacitor is connected in parallel to the two ends of the corresponding battery pack, and the filtered battery voltage is input to the sampling terminal of the battery protection chip U1. It also includes a master control circuit for receiving battery module protection signals, which includes a charging control circuit connected between the battery module and the charger and a discharging control circuit connected between the battery module and the load. A temperature compensation module is connected to the discharge control signal terminal of the discharge control circuit. The temperature compensation module includes a negative temperature coefficient thermistor HT2 and a voltage divider resistor R23 connected in series.

2. The lithium battery ultra-low temperature full-power operation protection circuit as described in claim 1, characterized in that: The output of the first group of battery protection control units is directly connected to the charging control circuit via the optocoupler U3, and the output of the optocoupler U2 is directly connected to the discharging control circuit. Terminal J5 is connected to the output of the protection control circuit, and multiple terminals J3 are connected to the input of the main control circuit. Each subsequent group of battery protection control units is connected to the input terminal J3 via the output terminal J5.

3. The lithium battery ultra-low temperature full-power operation protection circuit as described in claim 1, characterized in that: Each battery module consists of 3-16 battery packs, and each battery pack consists of multiple individual cells connected in parallel.

4. The lithium battery ultra-low temperature full-power operation protection circuit as described in claim 3, characterized in that: The sampling terminals V1 to V15 of the battery protection chip U1 are connected to the positive terminals of each battery pack BT1 to BT15 respectively through resistors R1 to R15, and the sampling terminal V16 is shorted to the sampling terminal V15.

5. The lithium battery ultra-low temperature full-power operation protection circuit as described in claim 3, characterized in that: The power supply terminal VDD of the battery protection chip U1 is connected to the positive terminal of the battery pack BT15 through the current limiting resistor R19 and the filter capacitor C16. The other end of C16 is connected to the negative terminal of the battery pack BAT1 together with the ground connection terminal VSS of the battery protection chip U1.

6. The lithium battery ultra-low temperature full-power operation protection circuit as described in claim 1, characterized in that: The charging control circuit includes a charging MOSFET Q3, a Zener diode ZD2, and resistors R20 and R22. One end of resistor R20 is connected to the positive terminal of the battery module, and the other end is connected to the cathode of Zener diode ZD2. The anode of Zener diode ZD2 is connected to the charging negative terminal of the corresponding battery module. The discharging control circuit includes discharging MOSFETs Q7 to Q10, voltage divider resistors R24 to R27, and a Zener diode ZD1. The gates of discharging MOSFETs Q7 to Q10 are connected to Zener diode ZD1 through the corresponding voltage divider resistors R24 to R27. Their sources are all connected to the negative terminal of the battery module, and their drains are all connected to the discharging negative terminal output by the battery module.

7. The lithium battery ultra-low temperature full-power operation protection circuit as described in claim 6, characterized in that: The gate of the charging MOSFET Q3 is connected to the cathode of the Zener diode ZD2 through resistor R22, the source is connected to the negative terminal of the battery module, and the drain is connected to the negative terminal of the battery module.

8. The lithium battery ultra-low temperature full-power operation protection circuit as described in claim 6, characterized in that: The negative temperature coefficient thermistor HT2 and the voltage divider resistor R23 are connected in series and then connected in parallel with the Zener diode ZD1.

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