Charging and discharging protection circuit of slow voltage dividing switch and lithium battery pack

Abstract

The invention relates to the technical field of lithium battery control, in particular to a charging and discharging protection circuit of a slow voltage dividing switch and a lithium battery pack, the charging and discharging protection circuit is applied to an automobile lithium battery protection board, a protection module is arranged on the protection board, the protection module is provided with a discharging MOS tube Q2 connected with the negative electrode of a lithium battery, and the protection module is further connected with a charging MOS tube Q1, a farad capacitor C100 and an MOS tube Q3 in sequence. The grid electrode of the charging MOS tube Q1 is connected with the capacitor C1, and the protection module further comprises a slow charging circuit of the C1, a slow discharging circuit of the C1, a lithium battery discharging detection circuit, a fast charging circuit of the C1, a positive feedback circuit, a C100 voltage limiting switch circuit and a lithium battery voltage limiting charging switch circuit. The phenomenon that voltage fluctuation interferes with automobile electricity is avoided, the phenomenon that a farad capacitor is damaged due to the fact that the voltage difference between the lithium battery and charging equipment is too large is avoided, and stable operation of the lithium battery and an automobile electrical system under various working conditions is guaranteed.

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 voltage divider switch and a lithium battery pack. Background Art

[0002] After the lithium battery is fully charged, the general charging control circuit usually turns off the charging MOS tube Q1 to prevent overcharging. However, in this case, the freewheeling generated by the generator inductive energy storage will make the generator output voltage significantly higher than the lithium battery voltage, resulting in a voltage difference between the generator and the lithium battery. Since the generator is suspended outside the lithium battery and there is no stable load to absorb electrical energy, this voltage difference will cause significant voltage fluctuations.

[0003] The rapid shutdown of the charging MOS tube Q1 is the main factor that causes the generator to generate impulse voltage. As mentioned above, the impulse 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 may cause a fault alarm in some cars.

[0005] After the lithium battery pack is fully charged, the charging MOS tube Q1 is turned off. When the car engine is turned off, the car generator stops generating electricity, and the lithium battery pack immediately supplies power to the car electrical appliances. A common lithium battery protection board will immediately turn on the charging MOS tube Q1 after detecting a large current discharge. The present invention adopts a method of slowly turning on the charging MOS tube Q1 to reduce voltage fluctuations. When the engine is just turned off, only the diode D1 in the charging MOS tube Q1 is turned on, generating a tube voltage drop of about 0.7V. At this time, when the car motor is started, the large current will cause the diode of the MOS tube Q1 to heat up and be damaged because the MOS tube Q1 cannot be turned on immediately.

[0006] Take a four-string lithium iron battery pack as an example, with a rated voltage of 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, after the charging is fully charged and stopped, the voltage on the farad capacitor will also exceed 3V and be damaged.

[0007] In a high temperature environment, the lithium battery protection board usually protects the charging to prevent high temperature charging from damaging the lithium battery. Long-term high temperature and repeated starting and stopping of the engine will cause the lithium battery to be continuously discharged and exhausted due to lack of charging, and the car cannot be started after parking.

[0008] Although some existing solutions can alleviate the problem of voltage fluctuation and high temperature charging protection to a certain extent, they do not have completely reasonable control logic and the effect is not ideal, which will still have adverse effects on the vehicle's lights and electronic equipment, and even affect the vehicle's driving. Therefore, it is urgent to develop a technical means of slow switching charging and stabilizing voltage to prevent voltage fluctuations caused by the start and stop of charging of lithium batteries, and a reasonable high temperature charging protection method. 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, and provides a technical means to slowly start charging and slowly shut down charging to stabilize the voltage, thereby preventing voltage fluctuations caused by 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 of a slow voltage divider switch is applied to a protection board of a lithium battery of an automobile. A protection module is arranged on the protection board. 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. 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 charge MOS tube Q1. The gate and source of the charge MOS tube Q1 are connected to a gate capacitor C1. The gate capacitor C1 is connected to a charging resistor R4 and a discharge triode Q4. The gate capacitor C1 is also connected to a diode D2 for fast charging the gate capacitor C1 and a diode D3 for charging the gate capacitor C1 by a voltage detection circuit of the lithium battery. The gate of the MOS tube Q3 is connected to a MOS tube Q7 and a bias resistor R9.

[0012] Furthermore, a capacitor C2 is connected in parallel with the drain and source of the charging MOS tube Q1, and 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 adopts a method of slowly shutting down a charging MOS tube to reduce the impact voltage generated by the generator, and slowly transitions from the voltage of the lithium battery pack to the rated voltage of the generator. In the case where the farad capacitor C100 is not connected, C2 and C3 can filter the higher-frequency voltage of the generator, and will not affect the driving of the car. However, the low-frequency fluctuation of the generator voltage at the idle speed of the car will make the light flicker and feel uncomfortable. The main function of the farad capacitor C100 is converted from the original peak voltage absorption to the low-frequency voltage filtering function, which reduces the burden of the farad capacitor and reduces the usage. The farad capacitor C100 is organically combined with C2 and C3 and participates in the generator voltage filtering together to make the filtering effect better.

[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 is connected in series with the resistor R4, and 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 also 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 automobile electrical system slowly transitions from the voltage of the lithium battery pack to the rated voltage of the generator, thereby avoiding automobile fault alarm caused by a sudden increase in the generator voltage due to sudden shutdown of the charging of the lithium battery pack by the generator.

[0018] Furthermore, 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.

[0019] Furthermore, 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.

[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, and a positive feedback circuit is provided to extend the time for the transistor Q6 to charge the gate capacitor C1.

[0021] Furthermore, the MOS tube Q3 is provided with a bias resistor R9, and the protection module also includes a voltage limiting switch circuit of the 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 resistors R10 and R11 connected in series 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+.

[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 the voltage across the MOS tube Q1 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-limited charging switch circuit for a lithium battery. The voltage-limited charging switch circuit includes a voltage stabilizing chip IC2, a resistor R13, a resistor R14, a resistor R15, and 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.

[0024] The present invention adopts that 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 forced to be turned on by the low-voltage charging start circuit, which is not affected by the ambient temperature. Because the single cell voltage is below 3.25V, charging of lithium iron phosphate at about 80°C has little effect on the lithium battery pack. After exceeding 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 of a slow voltage divider switch and a lithium battery pack. The setting of the protection module can effectively absorb and stabilize the voltage fluctuation of the generator when the charging MOS tube Q1 is turned off or on, reduce the phenomenon of vehicle light flickering and fault alarm, protect other sensitive electronic components in automotive electrical appliances from damage by overvoltage, and extend the service life.

[0028] After the lithium battery is fully charged, when the car engine is turned off and the car motor is quickly started, the 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. The MOS tube Q3 is connected in series with the farad capacitor C100 and then connected in parallel to the MOS tube Q1. The lithium battery operates in an abnormal environment without the participation of the farad capacitor, avoiding operating risks and ensuring the reliable operation of the lithium battery 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 The 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 of 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 is 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 is 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, on which a protection module is provided. 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 to 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 thereof, and is also connected to a diode D3 for charging the gate capacitor C1 by a voltage detection circuit of the lithium battery. 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 with 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.

[0038] like Figure 2 As shown in the figure, there is a surge voltage of about 10V when C100 stops charging. Figure 3 As shown in the figure, the voltage waveform after adding C100 on the market currently has 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 main factor for the generator to generate impulse voltage. As mentioned above, the impulse voltage is absorbed by C100. Due to the internal resistance of C100, it cannot transition smoothly, and there are some voltage fluctuations, which will also affect the normal operation of some vehicles. The present invention adopts the method of slowly shutting down the charging MOS tube to reduce the impulse voltage generated by the generator, and the voltage of the lithium battery pack slowly transitions to the rated voltage of the generator. The main function of the farad capacitor C100 is converted from the original peak voltage absorption to the low-frequency voltage filtering function, which reduces the burden of the farad capacitor and reduces the usage. The farad capacitor C100 is connected in parallel with C2 and then in series with the lithium battery pack to form a new battery pack that runs 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 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.

[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. The voltage mutation may cause a fault alarm in some cars. The present invention adopts a method of slowly turning on the charging MOS to slowly 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 voltage mutation 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 slow voltage division shutdown process time 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 shows the charging current curve in the middle and the voltage curve above. The voltage slowly transitions after the charging MOS is slowly turned on. The process time can be set to 1-3 seconds. Figure 5 As shown, when the charging voltage is turned on, it drops rapidly and the fluctuation 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 a transistor Q4, forming a PNP transistor emitter follower circuit.

[0044] like Figure 1 As shown, resistors R1, R2, R3 and transistor Q4 form a slow discharge circuit for charging the gate capacitor C1 of the MOS tube Q1. First, resistors R1 and R4 are connected in series to discharge the capacitor C1. Then, the capacitor C1 is discharged through the emitter and base of the transistor Q4 and resistors R2 and R1. The capacitor C1 is discharged with a larger current to the PNP transistor emitter follower circuit centered on the transistor Q4. 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 slow voltage division shutdown process time 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 voltage divided gradually increases. Figure 4 In the left half of the curve shown, there is no sudden surge voltage, but 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 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.

[0046] After the lithium battery pack is fully charged, the charging MOS tube Q1 is turned off. When the car engine is turned off, the car generator stops generating electricity, and the lithium battery pack immediately supplies power to the car electrical appliances. A common lithium battery protection board will immediately turn on the charging MOS tube Q1 after detecting a large current discharge. The present invention adopts a method of slowly turning on the charging MOS tube Q1 to reduce voltage fluctuations. When the engine is just turned off, only the diode D1 in the charging MOS tube Q1 is turned on, generating a tube voltage drop of about 0.7V. At this time, when the car motor is started, the large current will cause the diode of the MOS tube Q1 to heat up and be damaged because the MOS tube Q1 cannot be turned on immediately.

[0047] The present invention adopts a discharge detection circuit. Once the lithium battery is detected to be discharged, 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, the resistor R5 and the 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 the resistor R6 and the resistor 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] The MOS tube Q3 is provided with a bias resistor R9, and the protection module also 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 resistors R10 and R11 connected in series 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+.

[0050] 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 about 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 connected 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 being fully charged is above 13V, the generator charging voltage is below 15V, and the farad capacitor's operating 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 there is no need for the farad capacitor to participate in the operation, and there is an operational risk. Figure 1 As shown, resistor R9 is the bias resistor of MOS tube Q3, voltage regulator chip IC1, resistor R10 and resistor R11 are voltage regulator power supplies, and the voltage regulation value is about 2V. The 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 worse. When the voltage of the farad capacitor exceeds 2.5V, the voltage across resistor R12 will exceed 0.5V, turn on MOS tube Q7, turn off MOS tube Q3, and the large voltage across the farad capacitor will no longer increase and will not participate in the circuit operation; overvoltage charging caused by other reasons, such as damage to the generator voltage regulator, generator overvoltage (greater than 18V), or the lithium battery pack is charged with an external charger, and the charger no-load voltage exceeds 18V. This circuit can also ensure that the farad capacitor is not damaged.

[0051] The present invention can also be used for eight strings of 25.6V parking lithium battery packs, with two farad capacitors connected in series, and the voltage stabilization value of the voltage stabilization power supply or the voltage stabilizing diode being about 5V, and other relevant data can be deduced accordingly.

[0052] The protection module also includes a voltage-limited charging switch circuit for a lithium battery. The voltage-limited charging switch circuit includes a voltage stabilizing chip IC2, a resistor R13, a resistor R14, a resistor R15, and 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.

[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, which 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 forced to be turned on by the low-voltage charging start circuit, which is not affected by the ambient temperature. Because the single cell voltage is below 3.25V, charging of lithium iron phosphate at about 80°C has little effect on the lithium battery pack. After exceeding 13V, the charging start function of the low-voltage charging start circuit is released, such as Figure 1 As shown, R12 and R13 form a voltage detection circuit, IC2 voltage regulator chip and R14 form a voltage regulator switch circuit, when the voltage of the lithium battery pack is higher than 13V, IC2 outputs a low level, and when it is lower than 13V, the output voltage is a high level, and the charging MOS tube Q1 is turned on through D2; it mainly solves the problem that after the lithium battery pack is charged under high temperature environment for a long time in the engine compartment of the automobile, after the engine is started and stopped many times, the lithium battery is continuously discharged and cannot be charged and the power is exhausted, and the vehicle cannot be started after parking; the present invention not only maintains the original high temperature charging protection, but also can be charged moderately at high temperature, so it has both safety guarantee and reliable operation.

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

[0055] The above are only preferred specific implementation modes of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope 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 to 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 the resistor R4, the gate capacitor C1 is also connected to a diode D2 for fast charging, and is also connected to a diode D3 for charging the gate capacitor C1 by the voltage detection circuit of the lithium battery, the gate of the MOS tube Q3 is connected to a MOS tube Q7, and is also connected to a bias resistor R9.

2. The charge and discharge protection circuit according to claim 1, characterized in that: The drain and source of the charging MOS tube Q1 are connected in parallel with a capacitor C2, and the source of the charging MOS tube Q1 and the positive electrode of the lithium battery are connected to a 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.

3. 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.

4. 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.

5. 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.

6. The charge and discharge protection circuit according to claim 5, 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.

7. 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+.

8. 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 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.

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

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