A charging and discharging protection circuit of a slow voltage-dividing switch and a lithium battery pack

Abstract

The present invention relates to the field of lithium battery control technology, and in particular to a charging and discharging protection circuit of a slow voltage-dividing switch and a lithium battery pack, which are applied to a lithium battery protection board for an automobile. A protection module is provided on the protection board, and the protection module is provided with a discharge MOS tube Q2 connected to the negative electrode of the lithium battery, and is also connected in sequence to a charging MOS tube Q1, a farad capacitor C100 and a MOS tube Q3. The gate of the charging MOS tube Q1 is connected to the capacitor C1. The protection module also includes a slow charging circuit of C1, a slow discharging circuit of C1, a lithium battery discharge detection circuit, a C1 fast charging circuit, a positive feedback circuit, a C100 voltage limiting switch circuit, and a lithium battery voltage limiting charging switch circuit. The present application can solve the problem of interference with automobile electrical system caused by voltage fluctuation during the charging process of the lithium battery pack by the generator, avoid the occurrence of the event of damaging the farad capacitor due to excessive pressure difference between the lithium battery and the charging device, and ensure the stable operation of the lithium battery and the automobile electrical system under various working conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery control, and in particular to a charge and discharge protection circuit of a slow-type voltage divider switch and a lithium battery pack. Background Art

[0002] When a lithium-ion battery is fully charged, typical charging control circuits typically disable the charging MOSFET Q1 to prevent overcharging. However, in this case, the freewheeling current generated by the generator's inductive energy storage can cause the generator's output voltage to be significantly higher than the lithium-ion battery's voltage, resulting in a voltage difference between the generator and the battery. Because the generator is suspended outside the lithium-ion battery and lacks a stable load to absorb power, this voltage difference can cause significant voltage fluctuations.

[0003] The rapid shutdown of the charging MOS tube Q1 is the main factor causing the surge voltage generated by the generator. As mentioned above, the surge voltage is absorbed by C100. However, due to the internal resistance of C100, the transition cannot be smooth, and some voltage fluctuations may occur, which may also affect the normal operation of some automotive electrical appliances.

[0004] When the charging MOS tube Q1 is suddenly turned on for charging from the off state, the rated voltage of the generator will suddenly drop to the voltage of the lithium battery pack. The sudden voltage change will cause some cars to generate fault alarms.

[0005] After the lithium battery pack is fully charged, the charging MOS transistor Q1 is turned off. When the car engine is turned off, the car generator stops generating power, and the lithium battery pack immediately supplies power to the car's electrical appliances. Conventional lithium battery protection boards immediately turn on the charging MOS transistor Q1 upon detecting a large discharge current. The present invention uses a method of slowly turning on the charging MOS transistor Q1 to reduce voltage fluctuations. When the engine is just turned off, only the diode D1 in the charging MOS transistor Q1 is turned on, resulting in a tube voltage drop of approximately 0.7V. At this time, when the car motor is started, the large current will not be able to turn on the MOS transistor Q1 immediately, causing the diode to heat up and be damaged.

[0006] Take a four-string lithium iron battery pack as an example. The rated voltage is 12.8V. When the voltage of the lithium battery pack drops below 12V, high temperature or other factors cause the lithium battery protection board chip to shut down the charging MOS tube Q1. Since the voltage of the car generator is around 15V, the voltage on the farad capacitor will exceed 3V, and the farad capacitor will be damaged due to overvoltage. If the lithium battery pack is charged with an external charger with a no-load voltage greater than 17.5V, the voltage on the farad capacitor will also exceed 3V after the battery is fully charged and charging stops, causing damage.

[0007] In a high temperature environment, the lithium battery protection board will usually protect the charging to prevent high temperature charging from damaging the lithium battery. Under long-term high temperature and repeated starting and stopping of the engine, the lithium battery will be continuously discharged and cannot be charged and the power will be exhausted, and the car will not be able to start after parking.

[0008] While existing solutions can alleviate voltage fluctuations and high-temperature charging protection issues to a certain extent, they lack fully rational control logic and are suboptimal, potentially adversely affecting vehicle lighting and electronic equipment, and even hindering vehicle operation. Therefore, developing a slow-charging and voltage-stabilizing technology to prevent voltage fluctuations caused by the on-off charging of lithium batteries and a reasonable high-temperature charging protection method is a pressing issue. Summary of the Invention

[0009] In order to overcome the above technical problems, the present invention provides a charge and discharge protection circuit and a lithium battery pack with a slow voltage divider switch, providing a technical means to stabilize the voltage by slowly starting charging and slowly shutting down charging, thereby preventing voltage fluctuations caused by the sudden shutdown of lithium battery charging due to external reasons or stopping charging after being fully charged.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A charge and discharge protection circuit for a slow-type voltage divider switch is applied to a protection board for an automotive lithium battery. The protection board is provided with a protection module, which includes a discharge MOS transistor Q2 connected to the lithium battery, a charge MOS transistor Q1, a farad capacitor C100, and a MOS transistor Q3 for protecting the farad capacitor C100. The source of the discharge MOS transistor Q2 is connected to the negative electrode of the lithium battery. The farad capacitor C100 is connected in series with the MOS transistor Q3 and then in parallel with the charge MOS transistor Q1. The gate and source of the charge MOS transistor Q1 are connected to a gate capacitor C1. The gate capacitor C1 is connected to a charging resistor R4 and a discharge transistor Q4. The gate capacitor C1 is also connected to a diode D2 for fast charging, a lithium battery voltage detection circuit, and a diode D3 for charging the gate capacitor C1. The gate of the MOS transistor Q3 is connected to a MOS transistor Q7 and a bias resistor R9.

[0012] Furthermore, a capacitor C2 is connected in parallel to the drain and source of the charging MOS tube Q1. The source of the charging MOS tube Q1 and the positive electrode of the lithium battery are connected to the capacitor C3. When the discharging MOS tube Q2 is turned on and the charging MOS tube Q1 is turned off, the capacitor C2 is connected in series with the lithium battery and then in parallel with the capacitor C3. When the MOS tube Q3 is turned on, the farad capacitor C100 is connected in parallel with the capacitor C2 and then in series with the lithium battery.

[0013] The present invention uses a method of slowly shutting down a charging MOS tube to reduce the surge voltage generated by the generator, slowly transitioning the voltage of the lithium battery pack to the rated voltage of the generator. Without connecting the farad capacitor C100, capacitors C2 and C3 can filter the higher-frequency voltage of the generator without affecting the vehicle's driving. However, the low-frequency fluctuation of the generator voltage at idle speed can cause the lights to flicker and feel uncomfortable. The main function of the farad capacitor C100 is transformed from peak voltage absorption to low-frequency voltage filtering, which reduces the burden on the farad capacitor and reduces its usage. The organic combination of the farad capacitor C100 with capacitors C2 and C3 and their joint participation in the generator voltage filtering can achieve a better filtering effect.

[0014] Furthermore, the protection module also includes a slow charging circuit for charging the MOS tube Q1. The slow charging circuit includes a gate capacitor C1 and a resistor R4. The gate capacitor C1 and the resistor R4 are connected in series. The other end of the resistor R4 is connected to the chip CO output circuit and the resistor R1.

[0015] The present invention adopts a method of slowly starting the charging MOS to slowly transition from the rated voltage of the generator to the voltage of the lithium battery pack, thereby avoiding automobile fault alarms caused by sudden voltage changes caused by suddenly starting to charge the lithium battery pack.

[0016] Furthermore, the gate capacitor C1 of the charging MOS tube Q1 is further provided with a slow discharge circuit, which includes resistors R1, R2, R3 and transistor Q4, forming a PNP transistor emitter follower circuit.

[0017] The present invention adopts a method of slowly shutting down the charging MOS, so that the power supply voltage of the vehicle electrical system slowly transitions from the voltage of the lithium battery pack to the rated voltage of the generator, avoiding the vehicle fault alarm caused by a sudden increase in the generator voltage due to the sudden shutdown of the generator charging the lithium battery pack.

[0018] Furthermore, the protection module also includes a discharge detection circuit, which includes a resistor R5, a transistor Q5 and a charging MOS transistor Q1. One end of the resistor R5 is connected to the source of the charging MOS transistor Q1 and the lithium battery P- through the base of the transistor Q5. The emitter of the transistor Q5 is connected to the drain of the charging MOS transistor Q1. The collector of the transistor Q5 is connected to the base and emitter of the transistor Q6 through the resistor R6 and the resistor R7 respectively. The emitter of the transistor Q6 is connected to the lithium battery B+. The collector of the transistor Q6 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the gate capacitor C1 of Q1.

[0019] Furthermore, the discharge detection circuit is provided with a positive feedback circuit, which includes a capacitor C4 and a resistor R8, wherein the capacitor C4 and the resistor R8 are connected in series, the collector of the transistor Q6 is connected to the capacitor C4, and the resistor R8 is connected to the base of the transistor Q5.

[0020] The present invention adopts a discharge detection circuit. Once the lithium battery discharge is detected, the charging MOS tube Q1 is immediately turned on. A positive feedback circuit is also provided to extend the time for the transistor Q6 to charge the gate capacitor C1.

[0021] Furthermore, the MOS transistor Q3 is provided with a bias resistor R9, and the protection module also includes a voltage-limiting switch circuit for the farad capacitor C100. The voltage-limiting switch circuit includes a voltage regulator chip IC1, resistors R10, R11, and R12, and a MOS transistor Q7. The midpoint of the series connection of resistors R10 and R11 is connected to the reference terminal of the voltage regulator chip IC1, the other end of the resistor R10 is connected to the cathode of the voltage regulator chip IC1 and the positive electrode of the farad capacitor C100, the other end of the resistor R11 is connected to the anode of the voltage regulator chip IC1, the gate of the MOS transistor Q7, and the resistor R12, the drain of the MOS transistor Q3 is connected to the negative electrode of the farad capacitor C100, the source of the MOS transistor Q7 is connected to the source of the MOS transistor Q3 and the resistor R12, the gate of the MOS transistor Q3 is connected to the drain of the MOS transistor Q7 and the bias resistor R9, and the other end of the resistor R9 is connected to the lithium battery B+.

[0022] The present invention adopts a MOS tube Q3 and a farad capacitor C100 connected in series and then connected in parallel to the MOS tube. When the voltage across the MOS tube Q1 is lower than about 2.5V, the MOS tube Q3 is turned on and the farad capacitor C100 operates normally. When it is higher than 2.5V, Q3 is turned off and the farad capacitor C100 stops operating.

[0023] Furthermore, the protection module also includes a voltage-limiting charging switch circuit for the lithium battery. The voltage-limiting charging switch circuit includes a voltage regulator chip IC2, a resistor R13, a resistor R14, a resistor R15, and a diode D3. The midpoint of the resistor R13 and the resistor R14 connected in series is connected to the reference end of the voltage regulator chip IC2, the other end of the resistor R13 is connected to the anode of the voltage regulator chip IC2 and the lithium battery B-, the other end of the resistor R14 is connected to the resistor R15 and the lithium battery B+, the other end of the resistor R15 is connected to the cathode of the voltage regulator chip IC2 and the anode of the diode D3, and the cathode of the diode D3 is connected to the charging MOS tube gate capacitor C1.

[0024] In the present invention, when the total voltage of the lithium battery pack is above 13V, the charging high-temperature protection is set by the BMS chip, and the protection temperature is about 80°C. When the total voltage of the lithium battery pack is below 13V, the charging MOS tube Q1 is forcibly turned on by the low-voltage charging start circuit, which is not affected by the ambient temperature. Because the cell voltage is below 3.25V, charging of lithium iron phosphate at about 80°C has little effect on the lithium battery pack. When the voltage exceeds 13V, the charging start function of the low-voltage charging start circuit is released.

[0025] Furthermore, the present invention provides a lithium battery pack including the above charge and discharge protection circuit, and the present invention can also be applied to a parking lithium battery with a rated voltage of 25.6V.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a charge and discharge protection circuit for a slow-type voltage divider switch and a lithium battery pack. The protection module enables the charging MOS tube Q1 to effectively absorb and stabilize the voltage fluctuation of the generator when it is turned off or on, thereby reducing the flashing of vehicle lights and fault alarms, protecting other sensitive electronic components in automotive electrical appliances from damage due to overvoltage, and extending their service life.

[0028] After the lithium battery is fully charged, when the car engine is turned off and the car motor is quickly started, a discharge detection circuit is used to immediately turn on the charging MOS tube Q1 to prevent the MOS tube Q1 from being damaged due to failure to turn on immediately. MOS tube Q3 is connected in series with a farad capacitor C100 and then connected in parallel to the MOS tube Q1. When the lithium battery operates in an abnormal environment, there is no need for the farad capacitor to participate in the operation, which avoids operational risks and ensures that the lithium battery can operate reliably in a high-temperature environment. The circuit structure designed in this application is simple, fully functional, and has low manufacturing and maintenance costs. At the same time, it improves the voltage stability of the automotive lithium battery pack and ensures the stable operation of the automotive electrical system under various working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a circuit diagram of the lithium battery protection board of the present invention;

[0030] Figure 2 This is the voltage waveform when the charging MOS tube Q1 is turned off without the protection module C100;

[0031] Figure 3 This is the voltage waveform when the charging MOS tube Q1 is turned off in the protection module with C100;

[0032] Figure 4 The left half of the curve shows the voltage waveform when the charging MOS tube Q1 is slowly turned off with the protection module of the slow discharge circuit added. The right half of the curve shows the voltage waveform when the charging MOS tube Q1 is slowly turned on with the protection module of the slow charging circuit added.

[0033] Figure 5 This is the fluctuation of the charging voltage drop when only farad capacitor is used. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] like Figure 1 As shown, the present application provides a charge and discharge protection circuit of a slow voltage divider switch and a lithium battery pack, providing a technical means for slow charging and discharging and voltage stabilization to prevent the lithium battery from suddenly shutting down or starting up and voltage fluctuations caused by full charge.

[0036] Specifically, the present application is applied to a lithium battery protection board for an automobile. A protection module is provided on the protection board. The protection module is provided with a discharge MOS tube Q2, a charging MOS tube Q1, a farad capacitor C100 and a MOS tube Q3 for protecting the farad capacitor C100 connected to the lithium battery. The source of the discharge MOS tube Q2 is connected to the negative electrode of the lithium battery. The farad capacitor C100 is connected in series with the MOS tube Q3 and then connected in parallel with the charging MOS tube Q1. The gate and source of the charging MOS tube Q1 are connected to the gate capacitor C1. The gate capacitor C1 is connected to a resistor R4. The gate capacitor C1 is also connected to a diode D2 for fast charging it, and is also connected to a voltage detection circuit of the lithium battery and a diode D3 for charging the gate capacitor C1. The gate of the MOS tube Q3 is connected to a MOS tube Q7 and is also connected to a bias resistor R9.

[0037] A capacitor C2 is connected in parallel to the drain and source of the charging MOS tube Q1. The source of the charging MOS tube Q1 and the positive electrode of the lithium battery are connected to capacitor C3. When the discharging MOS tube Q2 is turned on and the charging MOS tube Q1 is turned off, capacitor C2 is connected in series with the lithium battery and then in parallel with capacitor C3. When the MOS tube Q3 is turned on, the farad capacitor C100 is connected in parallel with capacitor C2 and then in series with the lithium battery.

[0038] like Figure 2 As shown in the figure, there is a surge voltage of about 10V when C100 stops charging. Figure 3 The voltage waveform after adding C100 on the market is shown. There is an impact voltage of about 2V. The lower one is the charging current curve and the upper one is the voltage curve.

[0039] The rapid shutdown of the charging MOS tube Q1 is the primary factor in the surge voltage generated by the generator. As previously described, the surge voltage is absorbed by C100. However, due to the internal resistance of C100, a smooth transition is not possible, resulting in some voltage fluctuations and affecting the normal operation of some vehicles. The present invention uses a method of slowly shutting down the charging MOS tube to reduce the surge voltage generated by the generator, slowly transitioning the voltage of the lithium battery pack to the rated voltage of the generator. The main function of the farad capacitor C100 is transformed from peak voltage absorption to low-frequency voltage filtering, reducing the burden on the farad capacitor and reducing its usage. Farad capacitor C100 is connected in parallel with C2 and then in series with the lithium battery pack to form a new battery pack, which operates in parallel with the generator and C3 to better stabilize the generator voltage.

[0040] The protection module also includes a slow charging circuit for charging the MOS tube Q1. The slow charging circuit includes a gate capacitor C1 and a resistor R4. The gate capacitor C1 and the resistor R4 are connected in series. The other end of the resistor R4 is connected to the chip CO output circuit and the resistor R1.

[0041] When the charging MOS tube Q1 is suddenly turned on for charging from the off state, the rated voltage of the generator will suddenly drop to the voltage of the lithium battery pack. This sudden voltage change may cause a fault alarm in some cars. The present invention adopts a method of slowly turning on the charging MOS tube to gradually transition from the rated voltage of the generator to the voltage of the lithium battery pack, thereby avoiding the car fault alarm caused by the sudden voltage change caused by suddenly starting to charge the lithium battery pack.

[0042] like Figure 1 As shown in the figure, the gate voltage of the charging MOS tube Q1 composed of R4 and C1 rises slowly. The time of the slow voltage division shutdown process of the MOS tube Q1 is mainly determined by the values ​​of C1 and R4, so that the impedance of the MOS tube Q1 slowly decreases from the blocking state until it is fully turned on. In the process of impedance reduction, the voltage divided by it gradually decreases. Figure 4 The right half of the curve is shown, the middle is the charging current curve, the upper part is the voltage curve, the voltage slowly transition waveform after the charging MOS is slowly turned on, the process time can be set to 1-3 seconds, such as Figure 5 As shown in the figure, when the charging voltage is turned on, the fluctuation range is about 2V, which significantly reduces the interference to the car's electrical appliances.

[0043] The gate capacitor C1 of the charging MOS tube Q1 is also provided with a slow discharge circuit, which includes resistors R1, R2, R3 and transistor Q4, forming a PNP transistor emitter follower circuit.

[0044] like Figure 1As shown, resistors R1, R2, R3, and transistor Q4 form a slow discharge circuit for charging the gate capacitance C1 of the MOS tube Q1. First, resistors R1 and R4 are connected in series to discharge the capacitance C1. Then, the capacitance C1 is discharged through the emitter and base of the transistor Q4 and resistors R2 and R1. The capacitance C1 is discharged with a larger current to the PNP transistor emitter follower circuit centered on the transistor Q4. The magnitude of the discharge current is determined by the resistor R3. The discharge time is mainly determined by the values ​​of the capacitors C1 and R3. The time of the slow voltage division shutdown process of the MOS tube Q1 is mainly determined by the values ​​of C1 and R3. During the slow voltage division shutdown process of the MOS tube Q1, the impedance of the on-state slowly increases until it is completely blocked, and the divided voltage gradually increases. Figure 4 In the left half of the curve shown, there is no sudden surge voltage and a corresponding process time, which can generally be set at 1-3 seconds.

[0045] The protection module also includes a discharge detection circuit, which includes a resistor R5, a transistor Q5 and a charging MOS transistor Q1. One end of the resistor R5 is connected to the source of the charging MOS transistor Q1 and the lithium battery P- through the base of the transistor Q5. The emitter of the transistor Q5 is connected to the drain of the charging MOS transistor Q1. The collector of the transistor Q5 is connected to the base and emitter of the transistor Q6 through the resistor R6 and the resistor R7 respectively. The emitter of the transistor Q6 is connected to the lithium battery B+. The collector of the transistor Q6 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the gate capacitor C1 of Q1.

[0046] After the lithium battery pack is fully charged, the charging MOS transistor Q1 is turned off. When the car engine is turned off, the car generator stops generating power, and the lithium battery pack immediately supplies power to the car's electrical appliances. Conventional lithium battery protection boards immediately turn on the charging MOS transistor Q1 upon detecting a large discharge current. The present invention uses a method of slowly turning on the charging MOS transistor Q1 to reduce voltage fluctuations. When the engine is just turned off, only the diode D1 in the charging MOS transistor Q1 is turned on, resulting in a tube voltage drop of approximately 0.7V. At this time, when the car motor is started, the large current will not be able to turn on the MOS transistor Q1 immediately, causing the diode to heat up and be damaged.

[0047] The present invention adopts a discharge detection circuit. Once the lithium battery is detected to be discharging, the charging MOS tube Q1 is immediately turned on, and the tube voltage drop drops from 0.7V to approximately 0V, and the lithium battery enters normal discharge operation; Figure 1 As shown, resistor R5 and transistor Q5 form a lithium battery pack discharge detection circuit when the charging MOS tube is turned off. The diode in the charging MOS tube Q1 is turned on to generate a tube voltage drop of about 0.7V to turn on the transistor Q5, and the transistor Q6 is turned on through resistors R6 and R7. The capacitor C1 is quickly charged through the diode D2, and the MOS tube Q1 is quickly turned on.

[0048] The discharge detection circuit is provided with a positive feedback circuit, which includes a capacitor C4 and a resistor R8. The capacitor C4 and the resistor R8 are connected in series, the collector of the transistor Q6 is connected to the capacitor C4, and the resistor R8 is connected to the base of the transistor Q5. The capacitor C4 and the resistor R8 extend the time for Q6 to charge C1.

[0049] MOS transistor Q3 is provided with a bias resistor R9. The protection module also includes a voltage-limiting switch circuit for a farad capacitor C100. The voltage-limiting switch circuit includes a voltage-stabilizing chip IC1, resistors R10, R11, and R12, and a MOS transistor Q7. The midpoint of the series connection of resistors R10 and R11 is connected to the reference terminal of the voltage-stabilizing chip IC1. The other end of resistor R10 is connected to the cathode of the voltage-stabilizing chip IC1 and the positive electrode of the farad capacitor C100. The other end of resistor R11 is connected to the anode of the voltage-stabilizing chip IC1, the gate of the MOS transistor Q7, and the resistor R12. The drain of the MOS transistor Q3 is connected to the negative electrode of the farad capacitor C100. The source of the MOS transistor Q7 is connected to the source of the MOS transistor Q3 and the resistor R12. The gate of the MOS transistor Q3 is connected to the drain of the MOS transistor Q7 and the bias resistor R9. The other end of the resistor R9 is connected to the lithium battery B+.

[0050] Taking a four-string iron-lithium battery pack as an example, the rated voltage is 12.8V. When the voltage of the lithium battery pack drops below 12V, high temperature or other factors cause the lithium battery protection board chip to shut down the charging MOS tube Q1. Since the voltage of the car generator is around 15V, the voltage on the farad capacitor will exceed 3V, and the farad capacitor will be damaged due to overvoltage. The present invention uses a MOS tube Q3 in series with the farad capacitor and then connected in parallel to the MOS tube. When the voltage across Q1 is lower than about 2.5V, Q3 is turned on and the farad capacitor operates normally. When it is higher than 2.5V, Q3 is turned off and the farad capacitor stops running. Because under normal circumstances, the voltage of the car lithium battery pack after full charge is above 13V, the generator charging voltage is below 15V, and the farad capacitor working voltage is below 2V. If the voltage across the farad capacitor exceeds 2V, it proves that the lithium battery has been operating in an abnormal environment and does not require the participation of the farad capacitor in operation. There is an operational risk. Figure 1 As shown, resistor R9 is the bias resistor of MOS tube Q3, and voltage regulator chip IC1, resistor R10 and resistor R11 are the voltage regulator power supply with a regulated voltage value of about 2V. Voltage regulator chip IC1, resistor R10 and resistor R11 can also be replaced by a voltage regulator diode of about 2V, but the voltage regulation accuracy is slightly lower. When the voltage of the farad capacitor exceeds 2.5V, the voltage across resistor R12 will exceed 0.5V, turning on MOS tube Q7 and turning off MOS tube Q3. The maximum voltage across the farad capacitor no longer increases and does not participate in circuit operation. Overvoltage charging caused by other reasons, such as damage to the generator voltage regulator and generator overvoltage (greater than 18V), or charging the lithium battery pack with an external charger and the charger no-load voltage exceeding 18V, can also be prevented from being damaged by this circuit.

[0051] The present invention can also be used for an eight-string 25.6V parking lithium battery pack, with two farad capacitors connected in series, a voltage regulator power supply voltage value or a voltage regulator diode selected to be around 5V, and other relevant data can be deduced accordingly.

[0052] The protection module also includes a voltage-limiting charging switch circuit for the lithium battery. The voltage-limiting charging switch circuit includes a voltage regulator chip IC2, a resistor R13, a resistor R14, a resistor R15, and a diode D3. The midpoint of the resistor R13 and the resistor R14 connected in series is connected to the reference end of the voltage regulator chip IC2, the other end of the resistor R13 is connected to the anode of the voltage regulator chip IC2 and the lithium battery B-, the other end of the resistor R14 is connected to the resistor R15 and the lithium battery B+, the other end of the resistor R15 is connected to the cathode of the voltage regulator chip IC2 and the anode of the diode D3, and the cathode of the diode D3 is connected to the charging MOS tube gate capacitor C1.

[0053] In order to operate reliably in a high temperature environment, the present invention adopts a charging high temperature protection when the total voltage of the lithium battery pack is above 13V. The BMS chip sets the protection temperature to about 80°C. When the total voltage of the lithium battery pack is below 13V, the low-voltage charging start circuit forces the charging MOS tube Q1 to be turned on. It is not affected by the ambient temperature. Because the single cell voltage is below 3.25V, charging lithium iron phosphate at about 80°C has little effect on the lithium battery pack. When the voltage exceeds 13V, the charging start function of the low-voltage charging start circuit is released. Figure 1 As shown, R12 and R13 form a voltage detection circuit, and IC2 and R14 form a voltage stabilizing switch circuit. When the voltage of the lithium battery pack is higher than 13V, IC2 outputs a low level. When it is lower than 13V, the output voltage is a high level, and the charging MOS tube Q1 is turned on through D2. The main problem is that after the lithium battery pack is charged in a high-temperature environment in the automobile engine compartment for a long time, after the thermal protection is applied, the lithium battery is continuously discharged and exhausted due to lack of charging after repeated engine starts and stops, and the vehicle cannot be started after parking. The present invention maintains the original high-temperature charging protection and can be charged moderately at high temperatures, thus ensuring safety and reliable operation.

[0054] The present invention provides a lithium battery pack including the above charge and discharge protection circuit.

[0055] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A charge and discharge protection circuit of a slow voltage divider switch, applied to a protection board for a car lithium battery, wherein a protection module is provided on the protection board, wherein the protection module is provided with a discharge MOS tube Q2 connected to the lithium battery, a charge MOS tube Q1, a farad capacitor C100 and a MOS tube Q3 for protecting the farad capacitor C100, characterized in that: The source of the discharging MOS tube Q2 is connected to the negative electrode of the lithium battery, the farad capacitor C100 is connected in series with the MOS tube Q3 and then connected in parallel with the charging MOS tube Q1, the gate and source of the charging MOS tube Q1 are connected to the gate capacitor C1, the gate capacitor C1 is connected to a resistor R4, the gate capacitor C1 is also connected to a diode D2 for fast charging, a voltage detection circuit of the lithium battery and a diode D3 for charging the gate capacitor C1, the gate of the MOS tube Q3 is connected to a MOS tube Q7, and is also connected to a bias resistor R9, the drain and source of the charging MOS tube Q1 are connected in parallel with a capacitor C2, the source of the charging MOS tube Q1 and the positive electrode of the lithium battery are connected to the capacitor C3, when the discharging MOS tube Q2 is turned on and the charging MOS tube Q1 is turned off, the capacitor C2 is connected in series with the lithium battery and then connected in parallel with the capacitor C3, when the MOS tube Q3 is turned on, the farad capacitor C100 is connected in parallel with the capacitor C2 and then connected in series with the lithium battery.

2. The charge and discharge protection circuit according to claim 1, characterized in that: The protection module also includes a slow charging circuit for charging the MOS tube Q1. The slow charging circuit includes a gate capacitor C1 and a resistor R4. The gate capacitor C1 is connected in series with the resistor R4. The other end of the resistor R4 is connected to the chip CO output circuit and the resistor R1.

3. The charge and discharge protection circuit according to claim 1, characterized in that: The gate capacitor C1 of the charging MOS tube Q1 is also provided with a slow discharge circuit, which includes resistors R1, R2, R3 and a transistor Q4, forming a PNP transistor emitter follower circuit.

4. The charge and discharge protection circuit according to claim 1, characterized in that: The protection module also includes a discharge detection circuit, which includes a resistor R5, a transistor Q5 and a charging MOS tube Q1. One end of the resistor R5 is connected to the source of the charging MOS tube Q1 and the lithium battery P- through the base of the transistor Q5, the emitter of the transistor Q5 is connected to the drain of the charging MOS tube Q1, the collector of the transistor Q5 is connected to the base and emitter of the transistor Q6 through the resistor R6 and the resistor R7 respectively, the emitter of the transistor Q6 is connected to the lithium battery B+, the collector of the transistor Q6 is connected to the anode of the diode D2, and the cathode of the diode D2 is connected to the gate capacitor C1 of Q1.

5. The charge and discharge protection circuit according to claim 4, characterized in that: The discharge detection circuit is provided with a positive feedback circuit, which includes a capacitor C4 and a resistor R8. The capacitor C4 and the resistor R8 are connected in series, the collector of the transistor Q6 is connected to the capacitor C4, and the resistor R8 is connected to the base of the transistor Q5.

6. The charge and discharge protection circuit according to claim 1, characterized in that: The MOS tube Q3 is provided with a bias resistor R9, and the protection module further includes a voltage limiting switch circuit of a farad capacitor C100, the voltage limiting switch circuit includes a voltage stabilizing chip IC1, resistors R10, R11 and R12, and a MOS tube Q7, the midpoint of the series connection of the resistors R10 and R11 is connected to the reference end of the voltage stabilizing chip IC1, the other end of the resistor R10 is connected to the cathode of the voltage stabilizing chip IC1 and the positive electrode of the farad capacitor C100, the other end of the resistor R11 is connected to the anode of the voltage stabilizing chip IC1, the gate of the MOS tube Q7 and the resistor R12, the drain of the MOS tube Q3 is connected to the negative electrode of the farad capacitor C100, the source of the MOS tube Q7 is connected to the source of the MOS tube Q3 and the resistor R12, the gate of the MOS tube Q3 is connected to the drain of the MOS tube Q7 and the bias resistor R9, and the other end of the resistor R9 is connected to the lithium battery B+.

7. The charge and discharge protection circuit according to claim 1, characterized in that: The protection module also includes a voltage-limited charging switch circuit for a lithium battery, which includes a voltage-limited charging switch circuit including a voltage-stabilizing chip IC2, a resistor R13, a resistor R14, a resistor R15, and a diode D3. The midpoint of the resistor R13 and the resistor R14 connected in series is connected to the reference end of the voltage-stabilizing chip IC2, the other end of the resistor R13 is connected to the anode of the voltage-stabilizing chip IC2 and the lithium battery B-, the other end of the resistor R14 is connected to the resistor R15 and the lithium battery B+, the other end of the resistor R15 is connected to the cathode of the voltage-stabilizing chip IC2 and the anode of the diode D3, and the cathode of the diode D3 is connected to the charging MOS tube gate capacitor C1.

8. A lithium battery pack, characterized in that: It comprises the charge and discharge protection circuit as described in any one of claims 1 to 7.

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