Lithium battery low voltage drop current limiting circuit and corresponding lithium battery charging protection system

Abstract

The present invention provides a lithium battery low voltage difference current limiting circuit and a corresponding lithium battery charging protection system, which include a reference voltage module, a power supply module, a detection module, and a driving module. The reference voltage module can output a reference voltage, the charger outputs a collection voltage, and the lithium battery outputs a sampling voltage. The first voltage regulating unit generates a first comparison voltage based on the sampling voltage and the reference voltage. The second voltage regulating unit generates a second comparison voltage based on the reference voltage and the collection voltage. When the voltage value of the sampling voltage is 0.14V-0.16V, the second comparison voltage is greater than the first comparison voltage, and the detection signal generating unit of the detection module outputs a detection signal to the driving module. The detection signal can drive the driving module to start working, and the driving module outputs a driving signal. The driving signal drives the MOS tube group of the power supply module, and the charger outputs a charging voltage through the power supply module, and the charging voltage can perform current limiting charging on the lithium battery.

Description

Technical Field

[0001] The present invention relates to the field of circuits, and in particular to a lithium battery low voltage difference current limiting circuit and a corresponding lithium battery charging protection system. Background Art

[0002] In modern society, lithium batteries are widely used in daily life. After the power of lithium batteries is consumed, lithium batteries need to be charged by a charger. However, in the existing lithium battery charging system, a large voltage difference between the charger and the lithium battery is required for the charger to charge the lithium battery. As a result, the existing lithium battery charging system will cause the battery to not be fully charged, resulting in false labeling of the lithium battery capacity, making the after-sales cost of the lithium battery high. The existing lithium battery charging system has the technical problem of not being able to fully charge the lithium battery.

[0003] Therefore, it is necessary to provide a lithium battery low voltage difference current limiting circuit and a corresponding lithium battery charging protection system to solve the above technical problems. Summary of the invention

[0004] The present invention provides a lithium battery low voltage difference current limiting circuit and a corresponding lithium battery charging protection system, which effectively solves the technical problem that the existing lithium battery charging system cannot fully charge the lithium battery.

[0005] The present invention provides a lithium battery low voltage difference current limiting circuit, which comprises:

[0006] A reference voltage module, used for outputting a reference voltage;

[0007] A charger, used for outputting the collected voltage;

[0008] Lithium battery, used to output sampling voltage;

[0009] A power supply module, one end of which is connected to the charger, and the other end of which is connected to the lithium battery;

[0010] A detection module, comprising a first voltage regulating unit, a second voltage regulating unit and a detection signal generating unit, wherein the first voltage regulating unit generates a first comparison voltage based on the sampled voltage and the reference voltage, and the second voltage regulating unit generates a second comparison voltage based on the reference voltage and the acquisition voltage, and the detection signal generating unit is used to compare the first comparison voltage with the second comparison voltage, and when the voltage value of the sampled voltage is 0.14V-0.16V, the second comparison voltage is greater than the first comparison voltage, and the detection signal generating unit outputs a detection signal;

[0011] A driving module receives the detection signal, wherein the detection signal drives the driving module to start working, and the driving module outputs a driving signal;

[0012] Among them, the power supply module includes a MOS tube group, the driving signal is used to drive the MOS tube group, the charger outputs a charging voltage through the power supply module, and the charging voltage is used to limit the current charging of the lithium battery. When the voltage difference between the charger and the lithium battery is 0.15V, the lithium battery is current-limited to ensure that the battery can be fully charged.

[0013] In the lithium battery low voltage difference current limiting circuit described in the present invention, the detection signal generating unit includes a comparator, the comparator includes a positive input terminal, a negative input terminal and a comparator output terminal, the first voltage regulating unit includes a first resistor, a second resistor and a third resistor, one end of the first resistor is grounded, and the other end of the first resistor is connected to the negative input terminal; one end of the second resistor is connected to the output terminal of the reference voltage module, and the other end of the second resistor is connected to the negative input terminal; one end of the third resistor is connected to the negative input terminal, and the other end of the third resistor is connected to the comparator output terminal.

[0014] In the lithium battery low voltage difference current limiting circuit described in the present invention, the second voltage regulating unit also includes a fourth voltage and a fifth resistor, one end of the fourth resistor is connected to the positive input end, and the other end of the fourth resistor is connected to the output end of the reference voltage module; one end of the fifth resistor is connected to the negative electrode of the lithium battery, and the other end of the fifth resistor is connected to the positive input end.

[0015] In the lithium battery low voltage difference current limiting circuit described in the present invention, the voltage value of the reference voltage is 5.75V-6.95V, the resistance value of the first resistor is 4.6KΩ-5.6KΩ, the resistance value of the second resistor is 4.6KΩ-5.6KΩ, the resistance value of the third resistor is 0.9MΩ-1.1MΩ, the resistance value of the fourth resistor is 4.5KΩ-5.3KΩ, and the resistance value of the fifth resistor is 4.3KΩ-5.1KΩ.

[0016] In the lithium battery low voltage difference current limiting circuit described in the present invention, the detection signal generating unit includes an optocoupler, and the optocoupler includes a first end, a second end, a third end, and a fourth end. The first end is connected to the output end of the reference voltage module, the second end is respectively connected to the output end of the reference voltage module and the comparator output end, the third end is grounded, and the fourth end is used to output the detection signal.

[0017] In the lithium battery low voltage difference current limiting circuit described in the present invention, the MOS tube group includes a charging MOS tube and a discharging MOS tube, the drain of the charging MOS tube is connected to the drain of the discharging MOS tube, the source of the charging MOS tube is connected to the negative electrode of the charger, and the source of the discharging MOS tube is connected to the negative electrode of the lithium battery.

[0018] In the lithium battery low voltage difference current limiting circuit described in the present invention, the driving module includes a driving chip, and the driving chip also includes a power supply pin, an enable pin, and an output pin. The power supply pin is connected to the power supply, the enable pin is connected to the fourth end, the enable pin is used to output the detection signal, the output pin is connected to the gate of the charging MOS tube, and the output pin is used to output the driving signal.

[0019] In the lithium battery low voltage difference current limiting circuit described in the present invention, the power supply module includes a power resistor, and the driving chip also includes an input pin. One end of the power resistor is connected to the negative pole of the charger, and the other end of the power resistor is connected to the input pin. Based on the voltage of the power resistor, the driving module adjusts the switching frequency of the MOS tube group through the driving signal.

[0020] In the lithium battery low voltage difference current limiting circuit of the present invention, when the discharge MOS tube is turned off, the driving chip recognizes that the charger is in working state based on the voltage received from the power resistor.

[0021] A lithium battery charging protection system comprises any of the above-mentioned lithium battery low voltage difference current limiting circuits.

[0022] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a low-voltage difference current limiting circuit for lithium batteries, which is provided with a reference voltage module, a power supply module, a detection module, and a driving module. The detection module includes a first voltage regulating unit, a second voltage regulating unit, and a detection signal generating unit. The first voltage regulating unit can generate a first comparison voltage based on the sampling voltage output by the lithium battery and the reference voltage output by the reference voltage module. The second voltage regulating unit generates a second comparison voltage based on the reference voltage output by the reference voltage module and the acquisition voltage output by the charger. The detection signal generating unit can compare the magnitude of the first comparison voltage with the second comparison voltage. When the voltage value of the sampling voltage is 0.14V-0.16V, the second comparison voltage is greater than the first comparison voltage, so that the detection signal generating unit outputs a detection signal. The detection signal can drive the driving module to start working, so that the driving module outputs a driving signal. The driving signal can be used to drive the MOS tube group of the power supply module. The charger outputs a charging voltage through the power supply module, and the charging voltage can limit the current charging of the lithium battery. Therefore, when the voltage difference between the charger and the battery reaches 0.14-0.16V, the charger can perform current-limited charging on the lithium battery. Compared with the existing chargers that need to reach a larger voltage difference to charge the lithium battery, the circuit of the present invention can achieve current-limited charging of the lithium battery by the charger when the voltage difference between the charger and the lithium battery is very small. Therefore, the lithium battery low-voltage difference current-limiting circuit can ensure that the lithium battery is fully charged, so that the capacity of the lithium battery can reach the nominal value. It effectively solves the technical problem that the existing lithium battery charging system cannot fully charge the lithium battery. In addition, the lithium battery low-voltage difference current-limiting circuit can effectively solve the problem that the after-sales battery cannot be fully charged, thereby reducing the after-sales cost of the lithium battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The block diagram of the lithium battery low voltage difference current limiting circuit of the present invention is shown in FIG.

[0024] Figure 2 The circuit diagram is a reference voltage module of the lithium battery low voltage difference current limiting circuit of the present invention.

[0025] Figure 3 This is a circuit diagram of a power supply module of a lithium battery low voltage difference current limiting circuit of the present invention.

[0026] Figure 4 The circuit diagram of the detection module of the lithium battery low voltage difference current limiting circuit of the present invention.

[0027] Figure 5 The circuit diagram of the driving module of the lithium battery low voltage difference current limiting circuit of the present invention is shown.

[0028] In the figure, 10, lithium battery low voltage difference current limiting circuit; 11, reference voltage module; 12, power supply module; 121, MOS tube group; 13, detection module; 131, first voltage regulating unit; 132, second voltage regulating unit; 133, detection signal generating unit; 14, driving module; 15, charger; 16, lithium battery. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0030] The directional terms mentioned in the present invention, such as "up", "down", "front", "back", "left", "right", "inside", "outside", "side", "top" and "bottom", are only for reference to the orientation of the drawings. The directional terms used are used to illustrate and understand the present invention, but not to limit the present invention.

[0031] The terms "first", "second", etc. in the present invention are used for descriptive purposes only and should not be understood as indicating or implying relative importance, and should not be used as a limitation on the order of precedence.

[0032] In the figures, structurally similar elements are denoted by the same reference numerals.

[0033] Please refer to Figure 1 The present invention provides a lithium battery low voltage difference current limiting circuit 10. The lithium battery low voltage difference current limiting circuit 10 is applied to a lithium battery charging protection system, and the lithium battery low voltage difference current limiting circuit 10 includes a reference voltage module 11, a power supply module 12, and a detection module 13.

[0034] Please refer to Figure 1 and Figure 2The reference voltage module 11 is used to output the reference voltage. The reference voltage module 11 includes a first diode D3 and a first MOS tube Q3. The positive electrode of the first diode D3 is connected to the power supply DC, which can be a 13V DC power supply. The negative electrode of the first diode D3 is connected to the drain of the first MOS tube Q3, and the source of the first MOS tube Q3 is connected to the output terminal VCC393 of the reference voltage module 11. The reference voltage module 11 includes a sixth resistor R9, a seventh resistor R10 and an eighth resistor R11. One end of the sixth resistor R9 is connected to the negative electrode of the first diode D3, and the other end of the sixth resistor R9 is connected to the gate of the first MOS tube Q3. One end of the seventh resistor R10 is connected to the negative electrode of the first diode D3, and the other end of the seventh resistor R10 is connected to the drain of the first MOS tube Q3. One end of the eighth resistor R11 is connected to the negative electrode of the first diode D3, and the other end of the eighth resistor R11 is connected to the drain of the first MOS tube Q3.

[0035] Please refer to Figure 1 and Figure 2 The reference voltage module 11 includes a second diode D2, a voltage stabilizing diode Z1, a first capacitor C6, a second capacitor C7, and a third capacitor C8. The anode of the second diode D2 is connected, and the cathode of the second diode D2 is connected. The anode of the voltage stabilizing diode Z1 is connected, and the cathode of the voltage stabilizing diode Z1 is connected. One end of the first capacitor C6 is connected to the output terminal VCC393 of the reference voltage module 11, and the other end of the first capacitor C6 is grounded. One end of the second capacitor C7 is connected to the output terminal VCC393 of the reference voltage module 11, and the other end of the second capacitor C7 is grounded. One end of the third capacitor C8 is connected to the drain of the first MOS tube Q3, and the other end of the third capacitor C8 is grounded.

[0036] Please refer to Figure 1 and Figure 3, the charger 15 is used to output the collected voltage, and the lithium battery 16 is used to output the sampled voltage. One end of the power supply module 12 is connected to the charger 15, and the other end of the power supply module 12 is connected to the lithium battery 16 to collect the voltage. The power supply module 12 includes a MOS tube group 121, and the MOS tube group 121 includes a charging MOS tube Q1 and a discharging MOS tube Q2. The drain of the charging MOS tube Q1 is connected to the drain of the discharging MOS tube Q2, the source of the charging MOS tube Q1 is connected to the negative electrode of the charger 15, and the source of the discharging MOS tube Q2 is connected to the negative electrode of the lithium battery 16. The lithium battery low voltage difference current limiting circuit 10 also includes a control module, which is connected to the gate AFE_DEF of the discharging MOS tube Q2. The control module can output a control signal, and the control signal can control the discharging MOS tube Q2 to be turned on or off. The power supply module 12 also includes a fourth capacitor C2, a fifth capacitor C1, and a three-terminal voltage regulator diode D1. One end of the fourth capacitor C2 is connected to the positive electrode BAT+ of the charger 15, and the other end of the fourth capacitor C2 is connected to the negative electrode P- of the charger. The negative electrode P- of the charger is used to output the collected voltage, and the negative electrode P- of the charger can be grounded. One end of the fifth capacitor C1 is connected to the positive electrode BAT+ of the charger 15, and the other end of the fifth capacitor C1 is connected to the negative electrode P- of the charger. The common port of the three-terminal voltage-stabilizing diode D1 is connected to the positive electrode BAT+ of the charger 15, and the other two ports of the three-terminal voltage-stabilizing diode are connected to the drain of the charging MOS tube Q1.

[0037] Please refer to Figure 1 and Figure 3 , the power supply module 12 also includes a sixth capacitor C4, a seventh capacitor C5 and an inductor L1. The positive electrode BAT1+ of the lithium battery 16 is connected to the positive electrode BAT+ of the charger 15, and the negative electrode VBAT- of the lithium battery 16 can output a sampling voltage. One end of the inductor L1 is connected to the drain of the charging MOS tube Q1, and the other end of the inductor L1 is connected to the drain of the discharging MOS tube Q2. One end of the sixth capacitor C4 is connected to the positive electrode BAT1+ of the lithium battery 16, and the other end of the sixth capacitor C4 is connected to the negative electrode VBAT- of the lithium battery. One end of the seventh capacitor C5 is connected to the positive electrode BAT1+ of the lithium battery 16, and the other end of the seventh capacitor C5 is connected to the negative electrode VBAT- of the lithium battery.

[0038] Please refer to Figure 1 and Figure 3, the power supply module 12 includes a power resistor R5, and the driving chip also includes an input pin +IN_1. One end of the power resistor R5 is connected to the negative electrode of the charger 15, and the other end of the power resistor R5 is connected to the input pin +IN_1. Based on the voltage of the power resistor R5, the driving module 14 adjusts the switching frequency of the MOS tube group 121 through a driving signal. The voltage of the power resistor R5 is output by the power resistor voltage output terminal I+, and the power resistor voltage output terminal I+ is connected to the input pin +IN_1. In the prior art, since there is no external detection charger 15 online circuit, the lithium battery charging system needs to turn on the charging MOS tube first, and then directly charge the lithium battery through the loop of the charging MOS tube. When the lithium battery charging system detects that the charging current is greater than the current limit value, the lithium battery charging system first turns off the charging MOS tube, and then turns on the current limit for charging. Subsequently, after the charging system detects that there is no current, it turns on the charging MOS tube. However, because the power resistor R5 is connected between the charger 15 and the input pin +IN_1, the driving module 14 compares the charging current with the current limit value based on the voltage of the power resistor R5. Furthermore, the driving module 14 adjusts the switching frequency of the MOS tube group 121 through the driving signal, so that the charger 15 performs current limiting charging on the lithium battery 16. Therefore, when the user uses this circuit, the steps of switching the charging MOS tube and comparing the charging current with the current limiting value can be omitted, and it is more convenient for the user to use the low voltage difference current limiting circuit 10 of the lithium battery 16. In addition, the low voltage difference current limiting circuit 10 of the lithium battery can avoid directly turning on the charging MOS tube, causing a large current impact on the lithium battery 16. Therefore, the user uses the low voltage difference current limiting circuit 10 of the lithium battery to charge the lithium battery, which can effectively extend the service life of the battery. In addition, the low voltage difference current limiting circuit 10 of the lithium battery can avoid frequent switching of the charging MOS tube, resulting in excessive stress on the charging MOS tube, causing the battery to overcharge and catch fire. Moreover, since one end of the power resistor R5 is connected to the negative pole of the charger 15, the low voltage difference current limiting circuit 10 of the lithium battery detects that the charger 15 is online. Subsequently, the low voltage difference current limiting circuit 10 of the lithium battery turns on the current limiting and charges the lithium battery 16.

[0039] In the prior art, the lithium battery charging system first charges through the charging MOS tube, but if the internal resistance of the lithium battery 16 is very low, the lithium battery charging system will perform overcurrent protection, and the lithium battery charging system will try to turn on the charging MOS tube to charge the battery. In a certain period, the charging MOS tube will be in an oscillation mode, the battery is not cumulatively charged, and the battery pack is prone to overcharging and causing fire. The existing lithium battery charging system frequently switches the charging MOS tube, and the existing lithium battery 16 charging system frequently switches between the direct charging mode and the current limiting mode. During long-term use, the fatigue resistance of the charging MOS tube increases, and the probability of failure of the charging MOS tube increases. When the charging MOS tube fails, the lithium battery will easily overcharge and cause a fire. Moreover, the charger is frequently turned on and off with a large current, and the charger is also prone to failure. Therefore, the existing lithium battery 16 charging system has high requirements for the charger, and the cost of the charger will also increase.

[0040] However, because the power resistor R5 is connected between the charger 15 and the input pin +IN_1, the driving module 14 compares the charging current with the current limiting value based on the voltage of the power resistor R5. Furthermore, the driving module 14 adjusts the switching frequency of the MOS tube group 121 through the driving signal, so that the charger 15 performs current limiting charging on the lithium battery 16. Therefore, the lithium battery low voltage difference current limiting circuit 10 can directly turn on the current limiting at the end of the lithium battery, so that the lithium battery low voltage difference current limiting circuit 10 can generate a small current to limit the current charging of the lithium battery, avoiding the large current impact directly triggering the overvoltage protection. In this way, the voltage difference between the battery pack monomers is greatly reduced, and the battery life is also greatly extended, which is more conducive to the long-term use of the lithium battery. When the internal resistance of the battery increases, if the charging system frequently switches between high current charging and low current limiting charging, the battery will be overcharged. Moreover, if the MOS tube is frequently switched on and off, the fatigue resistance of the MOS tube will be reduced, and the MOS tube is also easily damaged. Then the battery pack is also prone to overcharging and catching fire, causing safety accidents. The driving module 14 first compares the charging current with the current limiting value according to the voltage of the power resistor R5, and then adjusts the switching frequency of the MOS tube group 121, so that the charger 15 performs current limiting charging on the lithium battery 16. Thus, the lithium battery low voltage difference current limiting circuit 10 can avoid frequent switching between high current charging and current limiting charging. The lithium battery low voltage difference current limiting circuit 10 can stably perform current limiting charging on the lithium battery, so that the lithium battery does not overcharge. Therefore, it is safer for users to use this circuit to charge lithium batteries, and it can also effectively extend the service life of the battery and the charging MOS tube. Since it is always in a low current limiting charging state, the lithium battery low voltage difference current limiting circuit 10 has relatively low requirements for chargers on the market. It effectively reduces the procurement cost of the charger, and the use of the charger is also safer.

[0041] When the discharge MOS tube is turned off, based on the voltage received from the power resistor R5, the driver chip can identify that the charger 15 is in working state. In the existing lithium battery charging system, both the charging MOS tube and the discharge MOS tube are controlled by the negative terminal. When the discharge MOS tube is disconnected, the ground wire will be disconnected, generating two GNDs. Due to the lack of common ground, the charging signal cannot be directly collected online for collecting the circuit signal behind the discharge MOS tube. Since the circuit connects the charger 15 and the driver chip U3 through the power resistor R5, even if the discharge MOS tube Q2 is disconnected, the driver chip U3 can also collect the signal sent by the charger 15. Therefore, the driver chip U3 can identify whether the charger 15 is in normal working state through the signal. Thus, when the lithium battery cannot receive the charging voltage, the driver chip U3 determines whether the lithium battery low voltage difference current limiting circuit 10 has a circuit fault or the charger 15 has a fault. Furthermore, it is more convenient for users to detect the lithium battery low voltage difference current limiting circuit 10. When the circuit fails, the user has a higher efficiency in detecting the lithium battery low voltage difference current limiting circuit 10. The charging MOS tube and the discharging MOS tube of the circuit are both controlled by the negative terminal. When the discharging MOS tube is disconnected, even if different GNDs are generated, the lithium battery low voltage difference current limiting circuit 10 can still collect the charger 15 online.

[0042] Please refer to Figure 1 and Figure 4 The detection module 13 includes a first voltage regulating unit 131, a second voltage regulating unit 132 and a detection signal generating unit 133. Based on the sampling voltage and the reference voltage, the first voltage regulating unit 131 can generate a first comparison voltage. Based on the reference voltage and the acquisition voltage, the second voltage regulating unit 132 generates a second comparison voltage. The detection signal generating unit 133 is used to compare the first comparison voltage with the second comparison voltage. When the voltage value of the sampling voltage is 0.14V-0.16V, the second comparison voltage is greater than the first comparison voltage, and the detection signal generating unit 133 outputs a detection signal.

[0043] Please refer to Figure 1 and Figure 4, the detection signal generating unit 133 includes a comparator, the model of the comparator is LM393, and the comparator includes a positive input terminal, a negative input terminal and a comparator output terminal. The first voltage regulating unit 131 includes a first resistor R1, a second resistor R2 and a third resistor R6, one end of the first resistor R1 is grounded, and the other end of the first resistor R1 is connected to the negative input terminal. Since the negative electrode P- of the charger is grounded, the first resistor R1 is also connected to the negative electrode P- of the charger. One end of the second resistor R2 is connected to the output terminal of the reference voltage module 11, and the other end of the second resistor R2 is connected to the negative input terminal. One end of the third resistor R6 is connected to the negative input terminal, and the other end of the third resistor R6 is connected to the comparator output terminal. The second voltage regulating unit 132 also includes a fourth resistor R3 and a fifth resistor R4. One end of the fourth resistor R3 is connected to the positive input terminal, and the other end of the fourth resistor R3 is connected to the output terminal of the reference voltage module 11. One end of the fifth resistor R4 is connected to the negative electrode of the lithium battery 16, and the other end of the fifth resistor R4 is connected to the positive input terminal.

[0044] Please refer to Figure 1 and Figure 4 , the voltage value of the reference voltage can be 5.75V-6.95V, the resistance value of the first resistor R1 can be 4.6KΩ-5.6KΩ, and the resistance value of the second resistor R2 can be 4.6KΩ-5.6KΩ. The resistance value of the third resistor R6 can be 0.9MΩ-1.1MΩ, the resistance value of the fourth resistor R3 can be 4.5KΩ-5.3KΩ, and the resistance value of the fifth resistor R4 can be 4.3KΩ-5.1KΩ. In this embodiment, the reference voltage output by the output terminal VCC393 of the reference voltage module 11 is 6.35V, the resistance value of the first resistor R1 is 5.1KΩ, the resistance value of the second resistor R2 is 5.1KΩ, the resistance value of the third resistor R6 is 1MΩ, the resistance value of the fourth resistor R3 is 4.9KΩ, and the resistance value of the fifth resistor R4 is 4.7KΩ. V1 is the voltage input to the positive input terminal of the comparator U1, and the input source is used as the reference source. V2 is the negative input terminal of the comparator U1, and V3 is the voltage output by the comparator output terminal. When the voltage of V1 is greater than the voltage of V2, V3 outputs a high level, and the optocoupler U2 is not turned on. When the voltage of V1 is less than the voltage of V2, V3 outputs a low level, and the optocoupler U2 is turned on. Since the positive electrode BAT1+ of the lithium battery 16 is connected to the positive electrode BAT+ of the charger 15, the charger 15 and the lithium battery 16 are a common positive electrode, so the negative electrode VBAT- of the lithium battery is not at the same voltage potential as the negative electrode P- of the charger. According to the virtual short circuit V1=V2, to know the VBAT- voltage, you need to know the V1 voltage. The V1 voltage is:

[0045]

[0046] Among them, VP is the voltage value of the collected voltage, VCC393 is the voltage value of the first reference power supply, VCC393=6.35V, R1=R2=5.1KΩ, R6=1MΩ, V3=VCC393=6.35V.

[0047] V1=3.183V, according to virtual short, V2=V1=3.183V.

[0048] According to the superposition principle:

[0049]

[0050] Among them, VCC393=6.35V, R3=4.9KΩ, R4=4.7KΩ.

[0051] VBAT=0.145V, where VBAT is the voltage value of the sampling voltage.

[0052] After the above calculation, when VBAT is greater than 0.145V, the comparator output of the comparator U1 will change from a high level to a low level, and the optocoupler U2 will be turned on. Therefore, when the voltage of the charger 15 is higher than the voltage of the lithium battery 16 by 0.145V, the charger 15 can output a charging voltage through the power supply module 12, and the charging voltage can limit the current charging of the lithium battery 16. Therefore, even if the voltage difference between the charger 15 and the lithium battery 16 is very small, the charger 15 can limit the current charging of the lithium battery 16. The lithium battery low voltage difference current limiting circuit 10 can ensure that the charger 15 fully charges the lithium battery 16 in the current limiting mode.

[0053] Please refer to Figure 1 and Figure 4 , the detection signal generating unit 131 includes an optical coupler U2, and the optical coupler U2 includes a first end, a second end, a third end, and a fourth end. The first end is connected to the output end of the reference voltage module 11, and the second end is respectively connected to the output end of the reference voltage module 11 and the comparator output end. The third end is grounded, and the fourth end is used to output the detection signal. The detection module 13 includes a ninth resistor R8, a tenth resistor R7, and an eighth capacitor C3. The ninth resistor R8 is connected between the output end of the reference voltage module 11 and the first end, and the tenth resistor R7 is connected between the output end of the reference voltage module 11 and the second end. One end of the eighth capacitor C3 is connected to the third end, and the other end of the eighth capacitor C3 is connected to the fourth end. The capacitive reactance of the eighth capacitor C3 is 0.1μF, and the withstand voltage value of the eighth capacitor is 50V.

[0054] Please refer to Figure 1 and Figure 4, the driving module 14 includes a detection signal input terminal POW_LT, and the driving module 14 can receive a detection signal. The detection signal drives the driving module 14 to start working, and the driving module 14 can output a driving signal. The driving module 14 includes a driving chip U3, the model of the driving chip U3 is TL494, and the driving chip U3 includes a power supply pin VCC, an enable pin D-T_CON, and an output pin E1. The power supply pin is connected to the power supply DC, and the power supply pin VCC can receive the voltage output by the power supply DC. The enable pin D-T_CON is connected to the fourth end, and the enable pin D-T_CON is used to output a detection signal. The output pin E1 is connected to the gate of the charging MOS tube, and the output pin E1 is used to output a driving signal, and the driving signal is used to drive the MOS tube group 121.

[0055] Please refer to Figure 1 and Figure 4 , the driving module 14 also includes a second MOS tube Q4, a first transistor Q5, and a third diode D4. The cathode of the third diode D4 is connected to the fourth end of the optical coupler U2, and the anode of the third diode D4 is connected to the base of the first transistor Q5. The emitter of the first transistor Q5 is connected to the power supply DC, and the collector of the first transistor Q5 is connected to the gate of the second MOS tube Q4. The drain of the second MOS tube Q4 is connected to the enable pin D-T_CON, and the source of the second MOS tube Q4 is grounded. The driving module 14 also includes an eleventh resistor R13, a twelfth resistor R15, a thirteenth resistor R16, a fourteenth resistor R14, and a fifteenth resistor R20. One end of the eleventh resistor is connected to the anode of the third diode D4, and the other end of the eleventh resistor is connected to the base of the first transistor Q5. One end of the twelfth resistor is connected to the base of the first transistor Q5, and the other end of the twelfth resistor is connected to the emitter of the first transistor Q5. One end of the thirteenth resistor is connected to the collector of the first transistor Q5, and the other end of the thirteenth resistor is connected to the gate of the second MOS transistor Q4. One end of the fourteenth resistor is connected to the gate of the second MOS transistor Q4, and the other end of the fourteenth resistor is grounded. One end of the fifteenth resistor is connected to the second MOS transistor Q4, and the other end of the fifteenth resistor is connected to the enable pin D-T_CON.

[0056] Please refer to Figure 1 and Figure 4, the driving module 14 also includes a ninth capacitor C15, a tenth capacitor C9, an eleventh capacitor C10, a twelfth capacitor C14, a sixteenth resistor R23, a seventeenth resistor R22, an eighteenth resistor R19, a nineteenth resistor R17, and a twentieth resistor R18, and the driving chip U3 includes a REF_OUT pin, a +IN_2 pin, a -_IN_2 pin, and an FB pin. One end of the ninth capacitor C15 is connected, and the other end of the ninth capacitor C15 is connected. The driving module 14 also includes a voltage point V5, which is connected to the REF_OUT pin. One end of the ninth capacitor C15 is connected to the voltage point V5, and the other end of the ninth capacitor C15 is connected to the enable pin D-T_CON. One end of the tenth capacitor C9 is connected to the -_IN_2 pin, and the other end of the tenth capacitor C9 is grounded. One end of the eleventh capacitor C10 is connected to the +IN_2 pin, and the other end of the eleventh capacitor C10 is grounded. One end of the twelfth capacitor C14 is connected to the -_I N_2 pin, and the other end of the twelfth capacitor C14 is connected to the FB pin.

[0057] Please refer to Figure 1 and Figure 4 , one end of the sixteenth resistor R23 is connected to the -_IN_2 pin, and the other end of the sixteenth resistor R23 is connected to the voltage point V5. One end of the seventeenth resistor R22 is connected to the enable pin D-T_CO, and the other end of the seventeenth resistor R22 is connected to the voltage point V5. One end of the eighteenth resistor R19 is connected to the -_IN_2 pin, and the other end of the eighteenth resistor R19 is grounded. One end of the nineteenth resistor R17 is connected to the +IN_2 pin, and the other end of the nineteenth resistor R17 is grounded. One end of the twentieth resistor R18 is connected to the twelfth capacitor C14, and the other end of the twentieth resistor R18 is connected to the FB pin.

[0058] Please refer to Figure 1 and Figure 4, the driving module 14 also includes a thirteenth capacitor C11, a fourteenth capacitor C13, a fifteenth capacitor C12, a twenty-first resistor R21, a twenty-second resistor R24, and a twenty-third resistor R12, and the driving chip U3 includes input pins +IN_1 and -IN_1 pins. One end of the thirteenth capacitor C11 is connected to the -IN_1 pin, and the other end of the thirteenth capacitor C11 is connected to the FB pin. One end of the fourteenth capacitor C13 is connected to the -IN_1 pin, and one end of the fourteenth capacitor C13 is grounded. One end of the fifteenth capacitor C12 is connected to the input pin +IN_1, and the other end of the fifteenth capacitor C12 is grounded. One end of the twenty-first resistor R21 is connected to the -IN_1 pin, and the other end of the twenty-first resistor R21 is grounded. One end of the twenty-second resistor R24 ​​is connected to the voltage point V5, and the other end of the twenty-second resistor R24 ​​is connected to the -IN_1 pin. One end of the twenty-third resistor R12 is connected to the input pin +IN_1, and one end of the twenty-third resistor R12 is connected to the power resistor R5R5.

[0059] Please refer to Figure 1 and Figure 4 , the driving module 14 also includes a thirteenth capacitor C16, a fourteenth capacitor C17, and a fifteenth capacitor C18, and the driving chip U3 includes a C1 pin and a C2 pin. The C1 pin and the C2 pin are both connected to the power supply DC, one end of the thirteenth capacitor C16 is connected to the REF_OUT pin, and the other end of the thirteenth capacitor C16 is grounded. One end of the fourteenth capacitor C17 is connected to the C1 pin, the other end of the fourteenth capacitor C17 is grounded, and the fifteenth capacitor C18 is connected in parallel with the fourteenth capacitor C17. The driving chip U3 includes an E2 pin, a CT pin, and an RT pin, and the driving module 14 also includes a fifteenth capacitor C19 and a twenty-fourth resistor R26. The E2 pin is connected to the output pin E1, one end of the fifteenth capacitor C19 is connected to the CT pin, and the other end of the fifteenth capacitor C19 is grounded. One end of the twenty-fourth resistor R26 is connected to the RT pin, and one end of the twenty-fourth resistor R26 is grounded.

[0060] Please refer to Figure 1 and Figure 4, the driving module 14 also includes a second transistor Q6, a fourth diode D6, a fifth diode D5, a twenty-fifth resistor R25, a twenty-sixth resistor R27, and a sixteenth capacitor C20. The base of the second transistor Q6 is connected to the E2 pin and the E1 pin, the positive electrode of the fourth diode D6 is connected to the base of the second transistor Q6, the negative electrode of the fourth diode D6 is connected to the emitter of the second transistor Q6, and the collector of the second transistor Q6 is grounded. One end of the twenty-fifth resistor R25 is connected to the base of the second transistor Q6, and the other end of the twenty-fifth resistor R25 is grounded. The positive electrode of the twenty-sixth resistor R27 is connected to the emitter of the second transistor Q6, and the negative electrode of the twenty-sixth resistor R27 is connected to the gate MOS_DRV of the charging MOS tube. The positive electrode of the fifth diode D5 is connected to the emitter of the second transistor Q6, and the negative electrode of the fifth diode D5 is connected to the gate MOS_DRV of the charging MOS tube. One end of the sixteenth capacitor C20 is connected to the negative electrode of the fifth diode D5, and the other end of the sixteenth capacitor C20 is grounded.

[0061] Please refer to Figure 1 and Figure 3 , when the MOS tube group 121 is driven, the charger 15 can output a charging voltage through the power supply module 12, and the charging voltage is used to limit the current charging of the lithium battery 16. When the voltage value of the sampling voltage is 0.14V-0.16V, the second comparison voltage is greater than the first comparison voltage, and the detection signal generation unit 133 outputs a detection signal. Since the driving module 14 can output a driving signal based on the detection signal, when the voltage difference between the charger 15 and the lithium battery 16 is 0.15V, the driving MOS tube group 121 is driven. The charger 15 performs current limiting charging on the lithium battery 16, and the low voltage difference current limiting circuit 10 of the lithium battery 16 can ensure that the battery can be fully charged. When the voltage difference between the charger 15 and the lithium battery 16 is low, the charger 15 performs current limiting charging on the lithium battery 16, which can effectively reduce the after-sales maintenance of the lithium battery 16, and the service life of the lithium battery 16 can also be effectively increased, and the use of the lithium battery 16 is also safer and more reliable.

[0062] The working principle of the present invention is as follows: when the lithium battery low voltage difference current limiting circuit 10 is working, the reference voltage module 11 outputs a reference voltage, and the lithium battery 16 outputs a sampling voltage and a collection voltage output by the charger 15. Based on the sampling voltage and the reference voltage, the first voltage regulating unit 131 generates a first comparison voltage. Based on the reference voltage and the collection voltage, the second voltage regulating unit 132 generates a second comparison voltage. The comparator U1 of the detection signal generating unit 133 can compare the magnitude of the first comparison voltage and the second comparison voltage. When the voltage value of the sampling voltage is 0.14V-0.16V, the second comparison voltage is greater than the first comparison voltage. Thus, the comparator U1 outputs a low-level signal. Furthermore, the optical coupler U2 is turned on, and the detection signal generating unit 133 outputs a low-level detection signal. Then, the detection signal input terminal POW_LT is input with a low-level enable signal. Subsequently, the first transistor Q5 and the second MOS tube Q4 are both turned on, and the DT_CON pin of the driver chip U3 inputs a low-level signal, and the driver chip U3 starts to work. Then, the driving module 14 outputs a driving signal to the gate of the charging MOS tube, so that the MOS tube group 121 is turned on. In addition, the driving chip U3 can adjust the duty cycle of the driving signal based on the voltage of the power resistor R5R5. Since one end of the power supply module is connected to the charger and the other end of the power supply module is connected to the lithium battery, the charger 15 outputs a charging voltage through the power supply module 12, and the charging voltage can limit the current charging of the lithium battery 16. The present invention also provides a lithium battery charging protection system, and the working principle of the lithium battery charging protection system is the same as the working principle of the lithium battery low voltage difference current limiting circuit 10.

[0063] The present invention provides a lithium battery low voltage difference current limiting circuit, which is provided with a reference voltage module, a power supply module, a detection module, and a driving module. The detection module includes a first voltage regulating unit, a second voltage regulating unit, and a detection signal generating unit. The first voltage regulating unit can generate a first comparison voltage based on the sampled voltage output by the lithium battery and the reference voltage output by the charger. The second voltage regulating unit generates a second comparison voltage based on the reference voltage output by the reference voltage module and the sampled voltage output by the charger, and the detection signal generating unit can compare the magnitude of the first comparison voltage with the second comparison voltage. When the voltage value of the sampled voltage is 0.14V-0.16V, the second comparison voltage is greater than the first comparison voltage, so that the detection signal generating unit outputs a detection signal. The detection signal can drive the driving module to start working, so that the driving module outputs a driving signal. The driving signal can be used to drive the MOS tube group of the power supply module, and the charger outputs a charging voltage through the power supply module, and the charging voltage can limit the current charging of the lithium battery. Therefore, when the voltage difference between the charger and the battery reaches 0.14-0.16V, the charger can limit the current charging of the lithium battery. Compared with the existing chargers that need to achieve a large voltage difference to charge lithium batteries, the circuit of the present invention can achieve current limiting charging of lithium batteries by the charger when the voltage difference between the charger and the lithium battery is very small. Therefore, the lithium battery low voltage difference current limiting circuit can ensure that the lithium battery is fully charged, so that the capacity of the lithium battery can reach the nominal value. It effectively solves the technical problem that the existing lithium battery charging system cannot fully charge the lithium battery. In addition, the lithium battery low voltage difference current limiting circuit can effectively solve the problem that the after-sales battery cannot be fully charged, so that the cost of the after-sales lithium battery is reduced.

[0064] In summary, although the present invention has been disclosed as above in terms of preferred embodiments, the above preferred embodiments are not intended to limit the present invention. A person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be based on the scope defined in the claims.

Claims

1. A lithium battery low voltage drop current limiting circuit, characterized in that: It includes: A reference voltage module, used for outputting a reference voltage; A charger, used for outputting a collected voltage, wherein a negative electrode of the charger outputs the collected voltage, and a negative electrode P- of the charger is grounded; A lithium battery, used to output a sampling voltage, wherein the positive electrode of the lithium battery is connected to the positive electrode of the charger, and the negative electrode of the lithium battery outputs the sampling voltage; A power supply module, one end of which is connected to the charger, and the other end of which is connected to the lithium battery; A detection module, comprising a first voltage regulating unit, a second voltage regulating unit and a detection signal generating unit, wherein the first voltage regulating unit generates a first comparison voltage based on the sampled voltage and the reference voltage, and the second voltage regulating unit generates a second comparison voltage based on the reference voltage and the acquisition voltage, and the detection signal generating unit is used to compare the first comparison voltage with the second comparison voltage, and when the voltage value of the sampled voltage is 0.14V-0.16V, the second comparison voltage is greater than the first comparison voltage, and the detection signal generating unit outputs a detection signal; A driving module receives the detection signal, wherein the detection signal drives the driving module to start working, and the driving module outputs a driving signal; Wherein, the power supply module includes a MOS tube group, the driving signal is used to drive the MOS tube group, the charger outputs a charging voltage through the power supply module, and the charging voltage is used to perform current-limited charging on the lithium battery; The detection signal generating unit includes a comparator, the comparator includes a positive input terminal, a negative input terminal and a comparator output terminal, the first voltage regulating unit includes a first resistor, a second resistor and a third resistor, one end of the first resistor is grounded, and the other end of the first resistor is connected to the negative input terminal; one end of the second resistor is connected to the output terminal of the reference voltage module, and the other end of the second resistor is connected to the negative input terminal; one end of the third resistor is connected to the negative input terminal, and the other end of the third resistor is connected to the comparator output terminal; The second voltage regulating unit includes a fourth resistor and a fifth resistor, one end of the fourth resistor is connected to the positive input end, and the other end of the fourth resistor is connected to the output end of the reference voltage module; one end of the fifth resistor is connected to the negative electrode of the lithium battery, and the other end of the fifth resistor is connected to the positive input end; The voltage value of the reference voltage is 5.75V-6.95V, the resistance value of the first resistor is 4.6KΩ-5.6KΩ, the resistance value of the second resistor is 4.6KΩ-5.6KΩ, the resistance value of the third resistor is 0.9MΩ-1.1MΩ, the resistance value of the fourth resistor is 4.5KΩ-5.3KΩ, and the resistance value of the fifth resistor is 4.3KΩ-5.1KΩ.

2. The lithium battery low voltage drop current limiting circuit according to claim 1, characterized in that: The detection signal generating unit includes an optocoupler, which includes a first end, a second end, a third end, and a fourth end. The first end is connected to the output end of the reference voltage module, the second end is respectively connected to the output end of the reference voltage module and the comparator output end, the third end is grounded, and the fourth end is used to output the detection signal.

3. The lithium battery low voltage drop current limiting circuit according to claim 1, characterized in that: The MOS tube group includes a charging MOS tube and a discharging MOS tube, the drain of the charging MOS tube is connected to the drain of the discharging MOS tube, the source of the charging MOS tube is connected to the negative electrode of the charger, and the source of the discharging MOS tube is connected to the negative electrode of the lithium battery.

4. The lithium battery low voltage drop current limiting circuit according to claim 3, characterized in that: The driving module includes a driving chip, and the driving chip also includes a power supply pin, an enable pin, and an output pin. The power supply pin is connected to a power supply, the enable pin is connected to a fourth end, the enable pin is used to output the detection signal, the output pin is connected to a gate of the charging MOS tube, and the output pin is used to output a driving signal.

5. The lithium battery low voltage drop current limiting circuit according to claim 4, characterized in that: The power supply module includes a power resistor, and the driving chip also includes an input pin. One end of the power resistor is connected to the negative pole of the charger, and the other end of the power resistor R5 is connected to the input pin. Based on the voltage of the power resistor, the driving module adjusts the switching frequency of the MOS tube group through the driving signal.

6. The lithium battery low voltage drop current limiting circuit according to claim 5, characterized in that: When the discharge MOS tube is turned off, the driving chip recognizes that the charger is in a working state based on the voltage received from the power resistor.

7. A lithium battery charging protection system, characterized in that: It includes the lithium battery low voltage difference current limiting circuit as described in any one of claims 1-6.

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