A lithium battery over-discharge voltage detection circuit

Abstract

The utility model discloses a kind of lithium battery overdischarge voltage detection circuit, it is related to voltage detection field, the lithium battery overdischarge voltage detection circuit includes: circuit starting module, for whether switch control circuit loop is conducted by switch;Signal switch module, for when lithium battery voltage is higher than first threshold value, output drive signal;Power switch module, for after receiving drive signal, load power on work;Voltage comparison module, for monitoring lithium battery voltage, when lithium battery voltage is lower than second threshold value, control signal switch module stops output drive signal, compared with prior art, the beneficial effects of the utility model are: the utility model can effectively and reliably realize the overdischarge protection of multiple lithium batteries, peripheral circuit is very simple, and scalability is relatively strong, and different string number lithium battery detection can be realized by changing voltage dividing resistor, and there is very big cost advantage compared with the cost of special battery voltage acquisition chip on market, at least can reduce more than 1 times cost.

Description

Technical Field

[0001] This utility model relates to the field of voltage detection, specifically a lithium battery over-discharge voltage detection circuit. Background Technology

[0002] Lithium-ion batteries are widely used in mobile phones, laptops, power banks, home appliances, electric vehicles, and energy storage due to their advantages such as high energy density, long cycle life, and no memory effect. Unlike nickel-cadmium and nickel-metal hydride batteries, lithium batteries must be designed with safety in mind during charging and discharging to prevent performance degradation.

[0003] The core hazards of lithium battery over-discharge:

[0004] 1. Long-term capacity degradation: When the discharge voltage of a lithium battery falls below the cutoff voltage (typically 2.5V-3.0V, depending on the material type), the graphite layer structure of the negative electrode collapses due to excessive lithium ion insertion and extraction, leading to a reversible capacity decrease. Experimental data shows that a single over-discharge to 1.5V can cause a 5%-15% loss in battery capacity.

[0005] 2. Internal chemical side reactions intensify. During over-discharge, the electrolyte decomposes at low voltage to generate gases (such as hydrogen and methane), causing the battery to bulge. Copper current collectors may also dissolve and deposit on the separator, triggering micro-short circuits.

[0006] 3. Increased safety risks: Deep over-discharge (e.g., voltage <1.0V) may cause separator perforation, leading to a direct short circuit during charging and discharging. Laboratory tests show that batteries that have undergone over-discharge have a 3-fold increased probability of catching fire during recharging.

[0007] In summary, it is necessary to detect over-discharge of lithium batteries to prevent them from being over-discharged. Utility Model Content

[0008] The purpose of this invention is to provide a lithium battery over-discharge voltage detection circuit to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, this utility model provides the following technical solution:

[0010] A lithium battery over-discharge voltage detection circuit includes:

[0011] The circuit start-up module is used to control whether the circuit loop is connected via a switch.

[0012] The signal switch module is used to output a drive signal when the lithium battery voltage is higher than a first threshold.

[0013] The power switch module is used to power the load after receiving a drive signal;

[0014] The voltage comparison module is used to monitor the lithium battery voltage. When the lithium battery voltage is lower than the second threshold, the control signal switch module stops outputting the drive signal. When the lithium battery voltage is higher than the second threshold, the control signal switch module maintains the output of the drive signal.

[0015] The output of the circuit startup module is connected to the first input of the signal switch module and the first input of the power switch module. The output of the signal switch module is connected to the second input of the power switch module and the input of the voltage comparison module. The output of the voltage comparison module is connected to the second input of the power switch module.

[0016] As a further embodiment of this utility model: the circuit start-up module includes a switch S1, one end of which is connected to the positive terminal PACK+ of the lithium battery (or the positive terminal of the lithium battery pack if it is a lithium battery pack), and the other end of which is connected to the first input terminal of the signal switch module and the first input terminal of the power switch module.

[0017] As a further embodiment of this utility model: the signal switch module includes resistors R1, R2, R4, and R8, transistor Q1, capacitor C2, capacitor C1, transistor Q3, transistor Q4, and voltage regulator Z2. One end of resistor R1 is connected to the emitter of transistor Q1 and the output terminal of the circuit startup module, and the other end of resistor R1 is connected to the base of transistor Q1 and one end of resistor R2. The collector of transistor Q1 is connected to the second input terminal of the power switch module and the input terminal of the voltage comparator module. The other end of 2 is connected to the collector of transistor Q3, one end of resistor R4, and the output of the voltage comparator module. The other end of resistor R4 is connected to the negative terminal of Zener diode Z2, the base of transistor Q4, one end of resistor R8, and one end of capacitor C2. The other end of resistor R8 is grounded, the other end of capacitor C2 is grounded, the collector of transistor Q4 is grounded, the emitter of transistor Q4 is connected to one end of capacitor C1 and the emitter of transistor Q3, the base of transistor Q3 is connected to the positive terminal of Zener diode Z2, and the other end of capacitor C1 is grounded.

[0018] As a further embodiment of this utility model: the power switch module includes a diode D1, a MOSFET Q2, a resistor R3, a Zener diode Z1, and a resistor R6. The negative terminal of the diode D1 is connected to the positive terminal LOAD+ of the load and the output terminal of the circuit startup module. The positive terminal of the diode D1 is connected to the negative terminal LOAD- of the load and the drain terminal of the MOSFET Q2. The source terminal of the MOSFET Q2 is grounded. The gate terminal of the MOSFET Q2 is connected to one end of the resistor R3, the negative terminal of the Zener diode Z1, and one end of the resistor R6. The other end of the resistor R6 is grounded. The positive terminal of the Zener diode Z1 is grounded. The other end of the resistor R3 is connected to the output terminal of the signal switch module.

[0019] As a further embodiment of this utility model: the voltage comparison module includes resistor R5, resistor R7, and chip IC1. The chip IC1 is a TL431. One end of resistor R5 is connected to the output terminal of the signal switch module, and the other end of resistor R5 is connected to one end of resistor R7 and the first terminal of chip IC1. The other end of resistor R7 is grounded, the second terminal of chip IC1 is grounded, and the third terminal of chip IC1 is connected to the second input terminal of the power switch module.

[0020] Compared with the prior art, the beneficial effects of this utility model are: this utility model can effectively and reliably realize over-discharge protection of multi-string lithium batteries, the peripheral circuit is very simple, and the scalability is strong. By changing the voltage divider resistor, lithium battery detection with different numbers of strings can be realized. Compared with the cost of dedicated battery voltage acquisition chips on the market, it has a very large cost advantage, and can reduce the cost by at least 100%. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of a lithium battery over-discharge voltage detection circuit. Detailed Implementation

[0022] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0023] Please see Figure 1 A lithium battery over-discharge voltage detection circuit, comprising:

[0024] The circuit start-up module is used to control whether the circuit loop is connected via a switch.

[0025] The signal switch module is used to output a drive signal when the lithium battery voltage is higher than a first threshold.

[0026] The power switch module is used to power the load after receiving a drive signal;

[0027] The voltage comparison module is used to monitor the lithium battery voltage. When the lithium battery voltage is lower than the second threshold, the control signal switch module stops outputting the drive signal. When the lithium battery voltage is higher than the second threshold, the control signal switch module maintains the output of the drive signal.

[0028] The output of the circuit startup module is connected to the first input of the signal switch module and the first input of the power switch module. The output of the signal switch module is connected to the second input of the power switch module and the input of the voltage comparison module. The output of the voltage comparison module is connected to the second input of the power switch module.

[0029] In this embodiment: Please refer to Figure 1 The circuit startup module includes a switch S1. One end of the switch S1 is connected to the positive terminal PACK+ of the lithium battery (or the positive terminal of the lithium battery pack if it is a lithium battery pack). The other end of the switch S1 is connected to the first input terminal of the signal switch module and the first input terminal of the power switch module.

[0030] After switch S1 is closed, the circuit forms a loop and the circuit begins to work.

[0031] In this embodiment: Please refer to Figure 1 The signal switch module includes resistors R1, R2, R4, and R8, transistor Q1, capacitor C2, capacitor C1, transistor Q3, transistor Q4, and voltage regulator Z2. One end of resistor R1 is connected to the emitter of transistor Q1 and the output terminal of the circuit startup module, while the other end of resistor R1 is connected to the base of transistor Q1. One end of resistor R2 is connected to the collector of transistor Q1, which is connected to the second input terminal of the power switch module and the input terminal of the voltage comparator module. The other end of resistor R2 is connected to... The collector of transistor Q3, one end of resistor R4, and the output of the voltage comparator module are connected. The other end of resistor R4 is connected to the negative terminal of Zener diode Z2, the base of transistor Q4, one end of resistor R8, and one end of capacitor C2. The other end of resistor R8 and capacitor C2 are grounded. The collector of transistor Q4 is grounded. The emitter of transistor Q4 is connected to one end of capacitor C1 and the emitter of transistor Q3. The base of transistor Q3 is connected to the positive terminal of Zener diode Z2. The other end of capacitor C1 is grounded.

[0032] The negative terminal PACK- of the lithium battery is directly grounded. When the voltage of the connected lithium battery (the voltage difference between PACK+ and PACK-) is greater than 18V + 0.7V, the positive terminal PACK+ of the lithium battery, resistors R1, R2, R4, and R8, and the negative terminal PACK- of the lithium battery form a circuit. The voltage across resistor R8 is sufficient to turn on the Zener diode Z2, providing current to the base of transistor Q3, causing transistor Q3 to conduct. Capacitor C1 charges, and during the charging process of capacitor C1, the voltage at the common point A decreases, causing transistor Q1 to conduct. Transistor Q1 outputs a high level, triggering the power switch module to work, and the load starts working, completing the startup process.

[0033] In this embodiment: Please refer to Figure 1The power switch module includes diode D1, MOSFET Q2, resistor R3, Zener diode Z1, and resistor R6. The negative terminal of diode D1 is connected to the positive terminal LOAD+ of the load and the output terminal of the circuit startup module. The positive terminal of diode D1 is connected to the negative terminal LOAD- of the load and the drain terminal of MOSFET Q2. The source terminal of MOSFET Q2 is grounded. The gate terminal of MOSFET Q2 is connected to one end of resistor R3, the negative terminal of Zener diode Z1, and one end of resistor R6. The other end of resistor R6 is grounded. The positive terminal of Zener diode Z1 is grounded. The other end of resistor R3 is connected to the output terminal of the signal switch module.

[0034] Transistor Q1 outputs a high level, which is clamped by Zener diode Z1, triggering MOSFET Q2 to conduct. This causes PACK+, switch S1, the positive terminal LOAD+ of the load, the negative terminal LOAD- of the load, MOSFET Q2, and PACK- to form a circuit, and the load is powered on and starts working.

[0035] In this embodiment: Please refer to Figure 1 The voltage comparison module includes resistors R5 and R7, and chip IC1. The model of chip IC1 is TL431. One end of resistor R5 is connected to the output terminal of the signal switch module, and the other end of resistor R5 is connected to one end of resistor R7 and the first terminal of chip IC1. The other end of resistor R7 is grounded, the second terminal of chip IC1 is grounded, and the third terminal of chip IC1 is connected to the second input terminal of the power switch module.

[0036] Chip IC1, resistors R5 and R7 form a battery voltage comparison mechanism. When the voltage at common point B (reflecting the lithium battery voltage) is greater than the TL431's reference voltage of 2.5V, chip IC1 conducts, maintaining the voltage at common point A at a low potential, thus keeping transistor Q1 conducting. After chip IC1 conducts, the base voltage of transistor Q4 is 0V, satisfying the conduction condition of transistor Q4, which in turn discharges capacitor C1. After capacitor C1 discharges, the start-up circuit resets. During the discharge process, when the lithium battery voltage drops below 15V (2.5V / cell), and the voltage at common point B drops below the TL431's reference voltage of 2.5V, chip IC1 cuts off, causing transistors Q1 and Q2 to exit the conducting state, disconnecting the load and achieving over-discharge protection for the battery pack.

[0037] The working principle of this utility model is as follows: the circuit start-up module is used to control whether the circuit loop is connected by a switch; the signal switch module is used to output a drive signal when the lithium battery voltage is higher than the first threshold; the power switch module is used to power the load after receiving the drive signal; the voltage comparison module is used to monitor the lithium battery voltage, and when the lithium battery voltage is lower than the second threshold, it controls the signal switch module to stop outputting the drive signal, and when the lithium battery voltage is higher than the second threshold, it controls the signal switch module to maintain the output of the drive signal.

[0038] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered exemplary and non-limiting in all respects.

[0039] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A lithium battery over-discharge voltage detection circuit, characterized in that, The lithium battery over-discharge voltage detection circuit includes: The circuit start-up module is used to control whether the circuit loop is connected via a switch. The signal switch module is used to output a drive signal when the lithium battery voltage is higher than a first threshold. The power switch module is used to power the load after receiving a drive signal; The voltage comparison module is used to monitor the lithium battery voltage. When the lithium battery voltage is lower than the second threshold, the control signal switch module stops outputting the drive signal. When the lithium battery voltage is higher than the second threshold, the control signal switch module maintains the output of the drive signal. The output of the circuit startup module is connected to the first input of the signal switch module and the first input of the power switch module. The output of the signal switch module is connected to the second input of the power switch module and the input of the voltage comparison module. The output of the voltage comparison module is connected to the second input of the power switch module.

2. The lithium battery over-discharge voltage detection circuit according to claim 1, characterized in that, The circuit startup module includes a switch S1. One end of the switch S1 is connected to the positive terminal PACK+ of the lithium battery, and the other end of the switch S1 is connected to the first input terminal of the signal switch module and the first input terminal of the power switch module.

3. The lithium battery over-discharge voltage detection circuit according to claim 1, characterized in that, The signal switch module includes resistors R1, R2, R4, and R8, transistor Q1, capacitor C2, capacitor C1, transistor Q3, transistor Q4, and voltage regulator Z2. One end of resistor R1 is connected to the emitter of transistor Q1 and the output terminal of the circuit startup module, while the other end of resistor R1 is connected to the base of transistor Q1. One end of resistor R2 and the collector of transistor Q1 are connected to the second input terminal of the power switch module and the input terminal of the voltage comparator module. The other end of resistor R2 is connected to the voltage regulator Z2. The collector of transistor Q3, one end of resistor R4, and the output of the voltage comparator module are connected. The other end of resistor R4 is connected to the negative terminal of Zener diode Z2, the base of transistor Q4, one end of resistor R8, and one end of capacitor C2. The other end of resistor R8 is grounded, the other end of capacitor C2 is grounded, the collector of transistor Q4 is grounded, the emitter of transistor Q4 is connected to one end of capacitor C1 and the emitter of transistor Q3, the base of transistor Q3 is connected to the positive terminal of Zener diode Z2, and the other end of capacitor C1 is grounded.

4. The lithium battery over-discharge voltage detection circuit according to claim 3, characterized in that, The power switch module includes diode D1, MOSFET Q2, resistor R3, Zener diode Z1, and resistor R6. The cathode of diode D1 is connected to the positive terminal LOAD+ of the load and the output terminal of the circuit startup module. The anode of diode D1 is connected to the negative terminal LOAD- of the load and the drain of MOSFET Q2. The source terminal of MOSFET Q2 is grounded. The gate terminal of MOSFET Q2 is connected to one end of resistor R3, the cathode of Zener diode Z1, and one end of resistor R6. The other end of resistor R6 is grounded. The anode of Zener diode Z1 is grounded. The other end of resistor R3 is connected to the output terminal of the signal switch module.

5. The lithium battery over-discharge voltage detection circuit according to claim 3, characterized in that, The voltage comparison module includes resistors R5 and R7, and chip IC1. The model of chip IC1 is TL431. One end of resistor R5 is connected to the output terminal of the signal switch module, and the other end of resistor R5 is connected to one end of resistor R7 and the first terminal of chip IC1. The other end of resistor R7 is grounded, the second terminal of chip IC1 is grounded, and the third terminal of chip IC1 is connected to the second input terminal of the power switch module.

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