A multi-protection circuit for lithium battery charge and discharge management

Abstract

The utility model discloses a kind of multi-protection circuit of lithium battery charge-discharge management, including lithium battery, and charging anti-reverse connection unit, power-on anti-reverse connection unit and overvoltage protection unit;Charging anti-reverse connection unit includes triode Q1, MOS tube Q2 and charging IC;When lithium battery is normally charged, Q1 and Q2 are used to form charging loop;When lithium battery is reversed, Q2 cuts off charging loop;Power-on anti-reverse connection unit includes MOS tube Q3;Q3 is used to form power supply loop and cut off power supply loop;Overvoltage protection unit includes triode Q4, MOS tube Q5 and drive IC;When drive IC voltage is normal, Q4 and Q5 are used to form discharge loop;When drive IC is overvoltage, Q4 cuts off drive voltage, Q5 is cut off, and discharge loop is cut off.The technical scheme provided by the utility model accurately covers the key risk scene of user misuse battery, forms complete protection chain, and improves the safety and reliability of lithium battery charge-discharge system.

Description

Technical Field

[0001] This utility model relates to the field of lithium battery charge and discharge management and protection technology, and in particular to a multi-protection circuit for lithium battery charge and discharge management. Background Technology

[0002] With the continuous iteration of battery technology and integrated circuits, lithium battery electronic products have been widely integrated into daily life. In products with replaceable lithium batteries, ordinary users, lacking knowledge of circuits and batteries, often mistakenly use batteries with incorrect parameters, which can lead to minor damage to equipment or even explosions, posing significant safety risks. Currently available products have obvious limitations in their protective measures: structural reverse connection protection alone cannot handle overvoltage batteries, easily causing the driver IC to burn out; they only have reverse connection protection upon power-on and lack protection during charging, making comprehensive protection difficult to achieve.

[0003] To address the aforementioned pain points, the circuit design proposed in this paper focuses on three core functions: overvoltage protection, reverse connection protection upon power-on, and reverse connection protection during charging. These functions precisely cover key risk scenarios where users misuse batteries, forming a complete protection chain. Utility Model Content

[0004] To overcome the shortcomings of existing technologies, this utility model provides a multi-protection circuit for lithium battery charging and discharging management, which can realize three major functions: overvoltage protection, reverse connection protection upon power-on, and reverse connection protection during charging. It accurately covers key risk scenarios of user misuse of batteries, forms a complete protection chain, and improves the safety and reliability of lithium battery charging and discharging systems.

[0005] A multi-protection circuit for lithium battery charge and discharge management includes a lithium battery, and a charging reverse connection protection unit, a power-on reverse connection protection unit, and an overvoltage protection unit that form a charge and discharge circuit with the lithium battery; wherein,

[0006] The reverse connection protection unit includes a first transistor Q1, a second MOSFET Q2, and a charging IC. When the lithium battery is charging normally, the first transistor Q1 provides the main path for the charging current from the charging IC to the lithium battery, while the second MOSFET Q2 is turned on to form a charging circuit. When the lithium battery is reverse connected, the second MOSFET Q2 cuts off the charging circuit.

[0007] The reverse connection protection unit includes a third MOSFET Q3; when the lithium battery is powered on normally, the third MOSFET Q3 is turned on and provides a power supply path for the subsequent circuit, forming a power supply loop; when the lithium battery is powered on in reverse, the third MOSFET Q3 is turned off, cutting off the power supply loop.

[0008] The overvoltage protection unit includes a fourth transistor Q4, a fifth MOSFET Q5, and a driver IC. When the voltage of the driver IC is normal, the fourth transistor Q4 and the fifth MOSFET Q5 are turned on, forming a discharge circuit. At the same time, the fourth transistor Q4 provides a driving voltage for the fifth MOSFET Q5. When the driver IC is overvoltaged, the fourth transistor Q4 cuts off the driving voltage, and the fifth MOSFET Q5 is turned off, thus cutting off the discharge circuit.

[0009] Optionally, the charging reverse connection protection unit further includes: a first voltage divider resistor R1, a second voltage divider resistor R2, a third voltage divider resistor R3, a fourth voltage divider resistor R4, and a fifth voltage divider resistor R5;

[0010] The emitter of the first transistor Q1 is connected to the BAT+ terminal of the charging IC, and the collector of the first transistor Q1 is connected to one end of the fifth voltage divider resistor R5; the base of the first transistor Q1 is connected to the BAT+ terminal of the charging IC through the first voltage divider resistor R1, and simultaneously connected to the source of the second MOSFET Q2 through the second voltage divider resistor R2; the drain of the second MOSFET Q2 is connected to the GND terminal of the charging IC, and the source of the second MOSFET is connected to the negative terminal path of the lithium battery through the fourth voltage divider resistor R4; the gate of the second MOSFET Q2 is connected to the connection point between the second voltage divider resistor R2 and the source of the second MOSFET Q2 through the third voltage divider resistor R3.

[0011] Optionally, the power-on reverse connection protection unit further includes a pull-down resistor R6;

[0012] The drain of the third MOSFET Q3 is connected to the positive terminal path of the lithium battery, and the source of the third MOSFET Q3 is connected to the negative terminal path of the lithium battery; the gate of the third MOSFET Q3 is connected to the negative terminal path of the lithium battery through the pull-down resistor R6.

[0013] Optionally, the overvoltage protection unit further includes a seventh voltage divider detection resistor R7, an eighth voltage divider detection resistor R8, and a ninth gate drive resistor R9;

[0014] One end of the seventh voltage divider detection resistor R7 is connected to the positive terminal path of the lithium battery, and the other end is connected to one end of the eighth voltage divider detection resistor R8 and the base of the fourth transistor Q4; the other end of the eighth voltage divider detection resistor R8 is connected to the negative terminal path of the lithium battery; the emitter of the fourth transistor Q4 is connected to the negative terminal path of the lithium battery, and the collector of the fourth transistor Q4 is connected to the gate of the fifth MOSFET Q5 through the ninth gate drive resistor R9; the drain of the fifth MOSFET Q5 is connected to the BAT+ terminal of the driver IC, and the source of the fifth MOSFET Q5 is connected to the GND terminal of the driver IC.

[0015] Optionally, the first transistor Q1 is a PNP transistor, and the fourth transistor Q4 is an NPN transistor; the second MOSFET Q2, the third MOSFET Q3, and the fifth MOSFET Q5 are all N-channel MOSFETs.

[0016] The multi-protection circuit for lithium battery charging and discharging management provided by this utility model improves the safety and reliability of the lithium battery charging and discharging management system and reduces circuit maintenance costs through the coordinated action of three unit modules: charging reverse connection protection unit, power-on reverse connection protection unit, and overvoltage protection unit.

[0017] Compared with the prior art, the technical solution provided by this utility model has the following beneficial effects:

[0018] 1) Reverse Connection Protection for Charging: Covers charging scenarios that are easily overlooked. If a user mistakenly judges that "the device cannot be used because the battery is dead" after reversing the battery and then attempts to charge it, this function can promptly block the reverse charging current, preventing the charging IC from burning out and making up for the loophole of traditional protection that only covers power-on and lacks charging protection.

[0019] 2) Reverse connection protection function: Focuses on the risks during battery installation. When a user accidentally installs the battery in reverse and powers on the device, the circuit will quickly cut off the dangerous circuit, preventing the current from flowing backward and preventing damage to circuit components due to reverse polarity from the source, thus strengthening safety protection in the initial stage of power-on.

[0020] 3) Overvoltage protection function: Specifically designed to solve the problem of "battery output voltage exceeding product operating voltage". When the user mistakenly uses an overvoltage battery, the circuit can monitor the voltage in real time. Once the safety threshold is exceeded, protection is immediately activated to prevent the driver IC from being burned out due to overvoltage, filling the gap in the traditional reverse connection protection structure that cannot cope with the risk of overvoltage;

[0021] Furthermore, this circuit design boasts advantages such as low cost, small footprint, and flexible protection voltage settings: its low cost and small size adapt to the design needs of various small and medium-sized electronic products, while the adjustable protection voltage ensures compatibility with lithium batteries of different specifications. In summary, this integrated circuit design, encompassing overvoltage protection, reverse connection protection upon power-on, and reverse connection protection during charging, not only comprehensively addresses the shortcomings of existing protection systems but also enhances product quality, serving as a crucial last line of defense to remind users to operate correctly and safeguard equipment and user safety.

[0022] In summary, the integrated design of the three unit modules fully realizes multi-dimensional protection during the charging and discharging process of lithium batteries, which has significant practical value and promotion potential. Attached Figure Description

[0023] Figure 1 This is a circuit diagram of the multi-protection circuit for lithium battery charge and discharge management in an embodiment of this utility model. Detailed Implementation

[0024] To make the technical problems, technical solutions, and beneficial effects of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present utility model and are not intended to limit the present utility model.

[0025] A multi-protection circuit for lithium battery charge and discharge management, such as Figure 1 As shown, it includes a lithium battery, and a charging reverse connection protection unit 1, a power-on reverse connection protection unit 2, and an overvoltage protection unit 3 that form a charging and discharging circuit with the lithium battery.

[0026] The reverse connection protection unit includes a first transistor Q1, a second MOSFET Q2, and a charging IC. Q1 serves as the main switch of the charging circuit, while Q2 acts as the core switch for reverse connection protection. During normal charging of the lithium battery, the first transistor Q1 provides the main path for the charging current from the charging IC to the lithium battery, while the second MOSFET Q2 is turned on, forming a charging circuit. When the lithium battery is reverse connected, the second MOSFET Q2 cuts off the charging circuit.

[0027] The reverse connection protection unit includes a third MOSFET Q3, which acts as the main switch for the power-on circuit. When the lithium battery is powered on normally, the third MOSFET Q3 is turned on and provides a power supply path for the subsequent circuits, forming a power supply circuit; when the lithium battery is powered on in reverse, the third MOSFET Q3 is turned off, cutting off the power supply circuit.

[0028] The overvoltage protection unit includes a fourth transistor Q4, a fifth MOSFET Q5, and a driver IC. Q4 acts as the drive switch for overvoltage protection, and Q5 acts as the protection switch for the discharge circuit. When the driver IC voltage is normal, both the fourth transistor Q4 and the fifth MOSFET Q5 are turned on, forming a discharge circuit. Simultaneously, the fourth transistor Q4 provides the drive voltage for the fifth MOSFET Q5. When the driver IC experiences an overvoltage, the fourth transistor Q4 cuts off the drive voltage, and the fifth MOSFET Q5 is turned off, thus disconnecting the discharge circuit.

[0029] Through the synergistic effect of the above three unit modules, the following was achieved:

[0030] 1) Reverse polarity protection during charging: Prevents damage to the charging IC and battery caused by reverse polarity during lithium battery charging;

[0031] 2) Reverse polarity protection upon power-on: Prevents damage to downstream circuit components caused by reverse polarity of the lithium battery.

[0032] 3) Overvoltage protection: Prevents the driver IC from being damaged due to overvoltage.

[0033] More specifically, within the framework of the aforementioned multi-protection circuit, each unit module can be implemented in the following manner:

[0034] 1) Reverse connection protection unit for charging

[0035] Components: PNP transistor Q1, resistors R1, R2, R3, R4, R5, and N-channel MOSFET Q2.

[0036] Connections: The emitter of Q1 is connected to the BAT+ terminal of the charging IC, and the collector is connected to one end of R5; the base of Q1 is connected to the BAT+ terminal of the charging IC through R1, and also to the source of Q2 through R2. The drain of Q2 is connected to the GND terminal of the charging IC, and the source is connected to the negative terminal of the lithium battery through R4; the gate of Q2 is connected to the connection point between R2 and the source of Q2 through R3.

[0037] Working principle: When the lithium battery is in the correct polarity, the gate voltage of Q2 is higher than the source voltage, and the N-channel MOSFET Q2 is turned on; at the same time, the emitter voltage of Q1 is higher than the base voltage, and the PNP transistor Q1 is turned on, so the charging circuit is unobstructed; when the lithium battery is reverse-connected, the source voltage of Q2 is higher than the gate voltage, Q2 is turned off, cutting off the charging circuit and preventing reverse current from damaging the charging IC and other components.

[0038] Function of components:

[0039] Q1 is a PNP transistor, which is the "main switch" of the charging circuit: it is turned on during normal charging, providing the main path for the charging current from the charging IC to the lithium battery; when reverse connected, it is turned off with Q2 and there is no current, preventing reverse conduction.

[0040] R1, together with R2, provides a bias voltage to the base of Q1: by dividing the voltage, the voltage at the emitter of Q1 (connected to the BAT+ terminal of the charging IC) is higher than the base voltage, ensuring that Q1 conducts stably during normal charging.

[0041] R2 is a voltage divider resistor with a dual function: 1. It forms a voltage divider network with R1 to set the base bias of Q1; 2. It forms a gate voltage divider network with R3 and R4 to provide the gate potential for Q2 to conduct.

[0042] R3 is a voltage divider resistor that can adjust the gate potential of Q2: together with R2 and R4, it ensures that the gate voltage of Q2 is higher than the source voltage when the lithium battery is in normal polarity, so that Q2 is turned on; when reversed, it does not affect the cutoff state of Q2.

[0043] R4 and R5 are voltage divider resistors that can stabilize the gate-source potential difference of Q2: together with R3, they limit the gate potential of Q2 to prevent the gate voltage from being too high and damaging Q2, while ensuring that the source voltage of Q2 is higher than the gate voltage when reverse connected, thus maintaining cutoff.

[0044] Q2 is an N-channel MOSFET, which is the "core switch" for reverse connection protection during charging: it conducts when the polarity is normal, forming a charging circuit; when the lithium battery is reverse connected, it cuts off the charging circuit directly, preventing reverse current from flowing into the charging IC and front-end components.

[0045] 2) Power-on reverse connection protection unit

[0046] Components: N-channel MOSFET Q3, resistor R6.

[0047] Connection relationship: The drain of Q3 is connected to the positive electrode path of the lithium battery, and the source is connected to the negative electrode path of the lithium battery; the gate of Q3 is connected to the negative electrode path of the lithium battery through R6.

[0048] Working principle: When the polarity of the lithium battery is normal, the gate of Q3 is properly biased through R6, the N-channel MOSFET Q3 is turned on, and the battery supplies power normally; when the lithium battery is reverse-connected, the gate potential of Q3 cannot meet the conduction condition, Q3 is turned off, cutting off the power supply circuit and avoiding reverse current damage to the subsequent circuit.

[0049] Function of components:

[0050] Q3 is an N-channel MOSFET that acts as the "main switch" of the power-on circuit: it conducts when the lithium battery is powered on normally, providing a power supply path for subsequent circuits (such as module ③ and driver IC); it is cut off when the power is reversed, cutting off the power supply circuit.

[0051] R6 is a gate pull-down resistor that can stabilize the gate potential of Q3: During normal power-up, the gate of Q3 is properly biased by pulling it down (ensuring that the gate voltage is higher than the source voltage and Q3 is turned on); when reversed, it prevents the gate from being floating and maintains the off state of Q3.

[0052] 3) Overvoltage protection unit

[0053] Components: Resistors R7, R8, R9, NPN transistor Q4, N-channel MOSFET Q5.

[0054] Function of components:

[0055] One end of R7 is connected to the positive electrode path of the lithium battery, and the other end is connected to one end of R8 and the base of Q4; the other end of R8 is connected to the negative electrode path of the lithium battery; the emitter of Q4 is connected to the negative electrode path of the lithium battery, and the collector is connected to the gate of Q5 through R9. The drain of Q5 is connected to the BAT+ terminal of the driver IC, and the source is connected to the GND terminal of the driver IC.

[0056] Working principle: When the voltage at the driver IC terminal is normal, the voltage divider of R7 and R8 makes the base voltage of Q4 higher than the emitter voltage, turning on the NPN transistor Q4. The gate of Q5 receives the driving voltage, turning on the N-channel MOSFET Q5, and the discharge circuit is unobstructed. When an overvoltage occurs at the driver IC terminal, the voltage divider of R7 and R8 lowers the base voltage of Q4, turning off Q4. The gate of Q5 loses the driving voltage and turns off, cutting off the discharge circuit and preventing the overvoltage from damaging the driver IC.

[0057] Function of components:

[0058] R7 is a voltage divider detection resistor, which together with R8 forms an "overvoltage detection network": the voltage divider collects the voltage signal at the driver IC terminal, and when the voltage is over-voltage, it triggers subsequent protection actions by changing the voltage divider ratio.

[0059] R8 is a voltage divider detection resistor that works with R7 to set the overvoltage threshold: by adjusting the resistance ratio of R7 and R8, the "overvoltage trigger point" of the driver IC is determined (such as triggering protection when it exceeds 5V), ensuring accurate detection when overvoltage occurs.

[0060] R9 is the gate drive resistor that provides current limiting for the gate of Q5: when Q4 is turned on, R9 limits the current flowing into the gate of Q5 to prevent excessive gate current from damaging Q5, and at the same time stabilizes the on / off switching of Q5.

[0061] Q4 is an NPN transistor that acts as an overvoltage protection "drive switch": it is turned on under normal voltage to provide drive voltage to the gate of Q5; it is turned off under overvoltage to cut off the gate drive signal of Q5, thus turning Q5 off.

[0062] Q5 is an N-channel MOSFET that acts as a "protective switch" for the discharge circuit: it conducts under normal voltage to ensure unobstructed discharge from the lithium battery to the driver IC; it cuts off under overvoltage to prevent damage to the driver IC.

[0063] The above is a description of the present utility model to help understand it; however, the implementation of the present utility model is not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the principle of the present utility model shall be considered equivalent substitutions and shall be included within the protection scope of the present utility model.

Claims

1. A multi-protection circuit for lithium battery charge and discharge management, characterized in that, It includes a lithium battery, and a charging reverse connection protection unit, a power-on reverse connection protection unit, and an overvoltage protection unit that form a charging and discharging circuit with the lithium battery; wherein, The reverse connection protection unit includes a first transistor Q1, a second MOSFET Q2, and a charging IC. When the lithium battery is charging normally, the first transistor Q1 provides the main path for the charging current from the charging IC to the lithium battery, while the second MOSFET Q2 is turned on to form a charging circuit. When the lithium battery is reverse connected, the second MOSFET Q2 cuts off the charging circuit. The reverse connection protection unit includes a third MOSFET Q3; when the lithium battery is powered on normally, the third MOSFET Q3 is turned on and provides a power supply path for the subsequent circuit, forming a power supply loop; when the lithium battery is powered on in reverse, the third MOSFET Q3 is turned off, cutting off the power supply loop. The overvoltage protection unit includes a fourth transistor Q4, a fifth MOSFET Q5, and a driver IC. When the voltage of the driver IC is normal, the fourth transistor Q4 and the fifth MOSFET Q5 are turned on, forming a discharge circuit. At the same time, the fourth transistor Q4 provides a driving voltage for the fifth MOSFET Q5. When the driver IC is overvoltaged, the fourth transistor Q4 cuts off the driving voltage, and the fifth MOSFET Q5 is turned off, thus cutting off the discharge circuit.

2. The multi-protection circuit for lithium battery charge and discharge management as described in claim 1, characterized in that, The reverse connection protection unit for charging further includes: a first voltage divider resistor R1, a second voltage divider resistor R2, a third voltage divider resistor R3, a fourth voltage divider resistor R4, and a fifth voltage divider resistor R5; The emitter of the first transistor Q1 is connected to the BAT+ terminal of the charging IC, and the collector of the first transistor Q1 is connected to one end of the fifth voltage divider resistor R5; the base of the first transistor Q1 is connected to the BAT+ terminal of the charging IC through the first voltage divider resistor R1, and simultaneously connected to the source of the second MOSFET Q2 through the second voltage divider resistor R2; the drain of the second MOSFET Q2 is connected to the GND terminal of the charging IC, and the source of the second MOSFET is connected to the negative terminal path of the lithium battery through the fourth voltage divider resistor R4; the gate of the second MOSFET Q2 is connected to the connection point between the second voltage divider resistor R2 and the source of the second MOSFET Q2 through the third voltage divider resistor R3.

3. The multi-protection circuit for lithium battery charge and discharge management as described in claim 1, characterized in that, The power-on reverse connection protection unit also includes a pull-down resistor R6; The drain of the third MOSFET Q3 is connected to the positive terminal path of the lithium battery, and the source of the third MOSFET Q3 is connected to the negative terminal path of the lithium battery; the gate of the third MOSFET Q3 is connected to the negative terminal path of the lithium battery through the pull-down resistor R6.

4. The multi-protection circuit for lithium battery charge and discharge management as described in claim 1, characterized in that, The overvoltage protection unit also includes a seventh voltage divider detection resistor R7, an eighth voltage divider detection resistor R8, and a ninth gate drive resistor R9. One end of the seventh voltage divider detection resistor R7 is connected to the positive terminal path of the lithium battery, and the other end is connected to one end of the eighth voltage divider detection resistor R8 and the base of the fourth transistor Q4; the other end of the eighth voltage divider detection resistor R8 is connected to the negative terminal path of the lithium battery; the emitter of the fourth transistor Q4 is connected to the negative terminal path of the lithium battery, and the collector of the fourth transistor Q4 is connected to the gate of the fifth MOSFET Q5 through the ninth gate drive resistor R9; the drain of the fifth MOSFET Q5 is connected to the BAT+ terminal of the driver IC, and the source of the fifth MOSFET Q5 is connected to the GND terminal of the driver IC.

5. The multi-protection circuit for lithium battery charge and discharge management as described in any one of claims 1 to 4, characterized in that, The first transistor Q1 is a PNP transistor, and the fourth transistor Q4 is an NPN transistor; the second MOSFET Q2, the third MOSFET Q3, and the fifth MOSFET Q5 are all N-channel MOSFETs.

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