A circuit for protecting a car battery from low voltage and its control method

Abstract

This invention discloses a vehicle battery depletion protection circuit and its control method, comprising: a battery; an ignition switch, one end of which is connected to the battery and the other end to an overload disconnect circuit; and an overload disconnect circuit for preventing battery depletion due to excessive load, comprising a Zener diode D1, at least two transistors Q1 and Q2, and voltage divider resistors R2 and R3. The protection circuit provided by this invention has low modification costs, requiring only a simple circuit added between the battery and the vehicle load. This circuit only requires two transistors and three resistors, without the need for additional control modules. The protection circuit and control method constantly monitor the vehicle battery, ensuring that the battery charge remains within a reasonable range to prevent shortened battery life due to excessive discharge, significantly reducing the probability of engine failure due to battery depletion.

Description

Technical Field

[0001] This invention relates to the fields of in-vehicle intelligent cockpit and vehicle networking technology, and in particular to a battery depletion protection circuit and its control method for automobiles. Background Technology

[0002] With the development of automotive electronics technology, there are more and more electronic devices in cars. Although there is no risk of battery depletion when the car is running, using electronic devices when the vehicle is not running, or even keeping the hazard lights on for an extended period, can easily cause the battery voltage to drop too low, leading to ignition failure and the vehicle failing to start. In cold winters, the battery's power supply capacity also weakens, causing the vehicle to fail to start. Because the battery is located in the engine compartment, the size and weight of the vehicle limit the ability to solve the problem of battery depletion by simply increasing its capacity. Summary of the Invention

[0003] In view of the above problems, the present invention provides a car battery depletion protection circuit to prevent the engine from failing to start due to excessive power consumption.

[0004] According to one aspect of the present invention, a vehicle battery depletion protection circuit is provided, comprising:

[0005] A storage battery is used to provide electrical power to onboard loads.

[0006] The ignition switch has one end connected to the battery and the other end connected to the overload power-off circuit.

[0007] An overload power-off circuit is used to prevent battery depletion due to excessive load. It includes a Zener diode D1, at least two transistors Q1 and Q2, and voltage divider resistors R2 and R3. The negative terminal of Zener diode D1 is connected to the base of transistor Q2, and its positive terminal is connected to the positive terminal of the battery through voltage divider resistors R2 and R3. The base of transistor Q2 receives the signal from Zener diode D1 through the voltage divider resistors, its collector is connected to the base of transistor Q1, and its emitter is grounded. The base of transistor Q1 is controlled by transistor Q2, and its collector and emitter are connected to the positive terminal of the battery and the vehicle load, respectively. Voltage divider resistors R2 and R3 are connected in parallel, with one end connected to the positive terminal of Zener diode D1 and the other end grounded.

[0008] In one alternative approach, the Zener diode D1 and the voltage divider resistor R3 together set the over-discharge protection voltage. When the battery voltage drops below the over-discharge protection voltage, the power supply to the load is automatically cut off to preserve the power supply to the ignition function and ensure that the engine can start normally.

[0009] In an alternative embodiment, the circuit further includes capacitors C1 and C2; wherein one end of capacitor C1 is connected to voltage divider resistor R3 and the other end is connected to Zener diode D1; one end of capacitor C2 is connected to the load and the other end is connected to voltage divider resistor R3.

[0010] In an alternative embodiment, the circuit further includes a warning light for indicating whether the circuit is in a protected state. One end of the warning light is connected to the collector of transistor Q2 or the output of a logic gate controlled by the state of transistor Q2, and the other end is grounded or connected to the negative power supply.

[0011] In one alternative embodiment, an adjustment unit is also included, which adapts to different specifications of automotive batteries by changing the voltage regulation value of the Zener diode D1 and the resistance values ​​of the voltage divider resistors R2 and R3.

[0012] In an alternative embodiment, a voltage detection unit is also included, which is connected to the positive terminal of the battery to monitor the battery voltage in real time and send a control signal to the overload power-off circuit and provide early warning when the voltage approaches the over-discharge protection threshold.

[0013] In an alternative embodiment, a voltage comparator is also included. One input of the voltage comparator is connected to the junction of voltage divider resistors R2 and R3, and the other input is set to a reference voltage. When the detected battery voltage is lower than the reference voltage, the output signal of the voltage comparator controls transistor Q2 to turn off.

[0014] In one alternative embodiment, a third capacitor C3 and a control logic circuit are also included. One end of the third capacitor C3 is connected to the positive terminal of the battery, and the other end is connected to the input terminal of the control logic circuit. The control logic circuit is a comparator, with its positive power supply pin connected to the positive terminal of the battery and its ground pin connected to the negative terminal of the battery.

[0015] According to another aspect of the present invention, a control method for a vehicle battery undervoltage protection circuit is provided, comprising:

[0016] Step S1: Start the system by switching on the ignition switch;

[0017] Step S2: When the battery voltage is higher than the preset limit value, the voltage is allowed to supply the vehicle load normally; otherwise, if the voltage drops below the preset limit voltage, the power supply to the load is immediately cut off to ensure that the battery energy is used only to maintain the power demand of the ignition function.

[0018] In an alternative approach, the method further includes:

[0019] In step S2, the on or off status of the warning light indicates whether the circuit is open or closed.

[0020] According to the solution provided by the present invention, the device includes: a storage battery for providing electrical energy to a vehicle load; an ignition switch, one end of which is connected to the storage battery and the other end of which is connected to a protection circuit; and a protection circuit for preventing the storage battery from being depleted due to excessive load power consumption, comprising a Zener diode D1, at least two transistors Q1 and Q2, and voltage divider resistors R2 and R3; wherein the negative terminal of the Zener diode D1 is connected to the base of transistor Q2, and the positive terminal is connected to the positive terminal of the storage battery through voltage divider resistors R2 and R3; the base of transistor Q2 receives the signal from the Zener diode D1 through the voltage divider resistors, the collector is connected to the base of transistor Q1, and the emitter is grounded; the base of transistor Q1 is controlled by transistor Q2, and its collector and emitter are respectively connected to the positive terminal of the storage battery and the vehicle load; and voltage divider resistors R2 and R3 are connected in parallel, one end of which is connected to the positive terminal of the Zener diode D1, and the other end is grounded. The protection circuit provided by this invention has low modification costs. It only requires adding a simple circuit between the battery and the vehicle load. The cost of this circuit is only two transistors and three resistors. No additional control module is needed. It can be widely used in many cars. This protection circuit and control method constantly monitor the car battery to keep the battery charge within a reasonable range, so as to ensure that the battery life is not shortened due to excessive discharge. It also greatly reduces the probability of the engine failing to start due to battery depletion. In addition, it can reduce the probability of the vehicle failing to start due to excessive power consumption of electrical circuits when the vehicle is not used for a long time.

[0021] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0022] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 A schematic diagram of a vehicle battery depletion protection circuit according to an embodiment of the present invention is shown.

[0024] Figure 2 A flowchart illustrating the control method of the automotive battery depletion protection circuit according to an embodiment of the present invention is shown. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0026] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0027] Figure 1 A schematic diagram of a vehicle battery depletion protection circuit according to an embodiment of the present invention is shown, including:

[0028] A storage battery is used to provide electrical power to onboard loads.

[0029] The ignition switch has one end connected to the battery and the other end connected to the protection circuit.

[0030] A protection circuit is used to prevent battery depletion due to excessive load. It includes a Zener diode D1, at least two transistors Q1 and Q2, and voltage divider resistors R2 and R3. The negative terminal of Zener diode D1 is connected to the base of transistor Q2, and its positive terminal is connected to the positive terminal of the battery through voltage divider resistors R2 and R3. The base of transistor Q2 receives the signal from Zener diode D1 through the voltage divider resistors, its collector is connected to the base of transistor Q1, and its emitter is grounded. The base of transistor Q1 is controlled by transistor Q2, and its collector and emitter are connected to the positive terminal of the battery and the vehicle load, respectively. Voltage divider resistors R2 and R3 are connected in parallel, with one end connected to the positive terminal of Zener diode D1 and the other end grounded.

[0031] The working principle of the protection circuit provided in this embodiment is as follows: After the switch S1 is closed, since the battery is initially fully charged, the battery voltage causes the Zener diode D1 to conduct in reverse, resulting in a bias voltage at the base of transistor Q2, causing Q2 to saturate and conduct. The conduction of Q2 will also cause a corresponding current to flow through the base of Q1, causing Q1 to also saturate and conduct. In this way, the battery supplies power to the load through the switching transistor Q1. In the circuit, Q1 is used as a switching transistor, and the current flowing through it will be relatively large. In actual construction, it is advisable to select a transistor with slightly higher power rating.

[0032] As the battery slowly discharges, the battery voltage begins to decrease. When it drops below the over-discharge protection voltage (below the voltage that would cause D1 to reverse conduct), Q2 turns off, and Q1 will also turn off. This cutoff of the switching transistor Q1 disconnects the circuit between the battery and the load, protecting the battery. Adjusting the voltage regulation value of the Zener diode and the resistance values ​​of the voltage divider resistors R2 and R3 allows you to test batteries with different voltages.

[0033] The advantage of this embodiment is that the modification cost of the protection circuit is low. It only requires adding a simple circuit between the battery and the vehicle load. The cost of this circuit is only 2 transistors and 3 resistors. No additional control module is required. It can be widely used in many cars. This protection circuit and control method constantly monitor the car battery to keep the battery charge within a reasonable range, so as to ensure that the battery life is not shortened due to excessive discharge. It also greatly reduces the probability of the engine failing to start due to battery depletion. In addition, it can reduce the probability of the vehicle failing to start due to excessive power consumption of electrical circuits when the vehicle is not used for a long time.

[0034] In one alternative approach, the Zener diode D1 and the voltage divider resistor R3 together set the over-discharge protection voltage. When the battery voltage drops below the over-discharge protection voltage, the power supply to the load is automatically cut off to preserve the power supply to the ignition function and ensure that the engine can start normally.

[0035] In this embodiment, Zener diode D1 acts as a voltage reference, only turning on when the voltage across it exceeds its stable voltage. Therefore, the stable voltage of Zener diode D1 plus the voltage drop across the voltage divider resistor R3 together determine the over-discharge protection threshold of the circuit. The voltage divider resistor R3, connected in series with Zener diode D1, works with R2 to regulate the voltage reaching the base of transistor Q2 through the principle of resistor voltage division. When the battery voltage drops to a certain level, the voltage drop across R3 decreases, causing the voltage applied to the base of Q2 to fall below its conduction threshold, thereby controlling the operation of subsequent circuits. When the battery voltage gradually decreases due to discharge, reaching the over-discharge protection voltage jointly set by Zener diode D1 and R3, Zener diode D1 stops conducting or its conduction weakens, causing the bias voltage at the base of transistor Q2 to decrease, and transistor Q2 to turn off. The turn-off of transistor Q2 causes transistor Q1 to lose its bias current and also turn off, thus cutting off the power supply from the battery to the vehicle load. Therefore, even though the load is no longer powered, it is possible to ensure that there is at least enough electrical energy to supply the ignition system and guarantee the normal starting of the engine.

[0036] In an alternative embodiment, the circuit further includes capacitors C1 and C2; wherein one end of capacitor C1 is connected to voltage divider resistor R3 and the other end is connected to Zener diode D1; one end of capacitor C2 is connected to the load and the other end is connected to voltage divider resistor R3.

[0037] In this embodiment, when the load is suddenly disconnected or the power supply is briefly interrupted, capacitor C2 can release the previously stored energy to provide temporary power support for the load, thus avoiding circuit malfunction or restart caused by a sudden voltage drop.

[0038] In an alternative embodiment, the circuit further includes a warning light for indicating whether the circuit is in a protected state. One end of the warning light is connected to the collector of transistor Q2 or the output of a logic gate controlled by the state of transistor Q2, and the other end is grounded or connected to the negative power supply.

[0039] In this embodiment, under normal circumstances, i.e., when the battery voltage is sufficient and transistor Q2 is conducting, the circuit allows current to flow to the vehicle load, and the warning light does not illuminate, indicating that the circuit is not in a protected state. However, once the battery voltage drops below the set protection level, transistor Q2 is cut off, and the circuit cuts off the power supply to the load. At this time, a current path is established through the warning light, and the warning light illuminates, indicating to the driver or maintenance personnel that the circuit is in a protected state, i.e., the battery is being protected against over-discharge.

[0040] In one alternative embodiment, an adjustment unit is also included, which adapts to different specifications of automotive batteries by changing the voltage regulation value of the Zener diode D1 and the resistance values ​​of the voltage divider resistors R2 and R3.

[0041] In this embodiment, the adjustment unit fine-tunes the protection circuit according to different automotive battery types and capacities. Specifically, the adjustment unit sets the over-discharge protection trigger point by replacing Zener diodes with different voltage regulation values, and finds the most suitable protection voltage threshold through adjustment. The adjustment unit fine-tunes the voltage division ratio by replacing resistors with different resistance values ​​or using variable resistors to adapt to the sensitivity requirements of the protection circuit under different voltage levels. Even under extreme temperature conditions (such as battery performance degradation caused by severe cold), the response of the protection circuit can be guaranteed by adjusting the resistance value of the voltage divider resistor.

[0042] In an alternative embodiment, a voltage detection unit is also included, which is connected to the positive terminal of the battery to monitor the battery voltage in real time and send a control signal to the protection circuit and issue an early warning when the voltage approaches the over-discharge protection threshold.

[0043] In this embodiment, the voltage detection unit continuously monitors the battery voltage level, achieving continuous, real-time voltage sampling. When the detected voltage value approaches but has not yet reached the over-discharge protection threshold, the comparator output changes, generating a warning signal. The warning signal is sent to the protection circuit to notify the driver or vehicle management system that the battery charge is about to reach a critical point and measures need to be taken, such as reducing the use of unnecessary electronic devices or starting the vehicle to charge it as soon as possible.

[0044] In an alternative embodiment, a voltage comparator is also included. One input of the voltage comparator is connected to the junction of voltage divider resistors R2 and R3, and the other input is set to a reference voltage. When the detected battery voltage is lower than the reference voltage, the output signal of the voltage comparator controls transistor Q2 to turn off.

[0045] In this embodiment, when the battery voltage is higher than the set reference voltage, the voltage comparator output is low, keeping transistor Q2 on and allowing transistor Q1 to also conduct, thus enabling the battery to supply power to the vehicle load normally. Once the detected battery voltage drops due to discharge, reaching or falling below the preset reference voltage, the voltage comparator output switches to high. This causes the base of transistor Q2 to lose its bias voltage, thus turning it off. The turn-off of transistor Q2 then triggers transistor Q1 to also enter the turn-off state, effectively cutting off the power circuit between the battery and the vehicle load, preventing deep battery depletion caused by continued power consumption from the load.

[0046] In one alternative embodiment, a third capacitor C3 and a control logic circuit are also included. One end of the third capacitor C3 is connected to the positive terminal of the battery, and the other end is connected to the input terminal of the control logic circuit. The control logic circuit is a comparator, with its positive power supply pin connected to the positive terminal of the battery and its ground pin connected to the negative terminal of the battery.

[0047] In this embodiment, one end of the third capacitor C3 is directly connected to the positive terminal of the battery, and the other end is connected to the input terminal of the control logic circuit (not shown in the figure). When the vehicle starts, the third capacitor C3 begins to charge. Since capacitor charging takes a certain amount of time, this charging process can be used as a natural delay mechanism. Before the capacitor is fully charged, the control logic circuit does not issue a command to turn on the transistor Q1, thereby temporarily preventing current from flowing to the vehicle load. The third capacitor C3 can also smooth out the current surge at the moment of startup to a certain extent, avoiding excessive stress on the battery and circuit, which is beneficial to protecting the long-term health of the battery and circuit components. The control logic circuit receives charging dynamic information from C3 and determines when to release the restriction on the power supply to the load based on a preset delay time or voltage threshold. When C3 is charged to a predetermined level, that is, when the set delay time or voltage threshold is reached, the control logic circuit outputs a signal to turn on the transistor Q1, thereby allowing current to flow to the vehicle load. The control logic circuit can be a simple comparator or logic gate circuit. When the control logic circuit is a comparator (not shown in the figure), the positive power supply pin of the comparator is connected to the positive terminal of the battery through a Zener diode (not shown in the figure) to ensure that the comparator obtains a stable operating voltage, and the ground pin is directly connected to the negative terminal of the battery.

[0048] Figure 2 A flowchart illustrating a control method for a vehicle battery depletion protection circuit according to an embodiment of the present invention is shown, including the following steps:

[0049] Step S1: Start the system by switching on the ignition switch;

[0050] Step S2: When the battery voltage is higher than the preset limit value, the voltage is allowed to supply the vehicle load normally; otherwise, if the voltage drops below the preset limit voltage, the power supply to the load is immediately cut off to ensure that the battery energy is used only to maintain the power demand of the ignition function.

[0051] For example, when the driver operates the ignition switch, the electrical system is activated. The ignition switch, acting as the main switch, establishes a current path from the car battery to the entire electrical system upon closing. If the detected battery voltage is higher than a preset safety lower limit, it indicates that the battery has sufficient charge to support the normal operation of the vehicle's electronic devices. The circuit remains unobstructed, allowing the battery's power to be smoothly transmitted to various vehicle loads, such as lights, audio, and infotainment systems, ensuring that all functions of the vehicle are powered during operation. When the battery voltage drops below a preset low-voltage threshold, it is usually due to prolonged inactivity, excessive use of vehicle equipment, or battery aging. In this case, the protection mechanism immediately activates, quickly cutting off power to non-critical vehicle loads. This ensures that the vehicle's entertainment system and other non-essential equipment lose power, but the most critical ignition system still receives enough power to ensure the engine can start successfully. The purpose is to prioritize preserving battery power for ignition, avoiding the predicament of being unable to start the vehicle due to excessive battery discharge. This protection circuit effectively balances the usage requirements of in-vehicle electronic devices with the ability to ensure vehicle starting capability. It satisfies the convenience of daily driving while ensuring that the vehicle can start smoothly in emergency situations, greatly improving the reliability of vehicle use and user experience.

[0052] In an alternative approach, the method further includes:

[0053] In step S2, the on or off status of the warning light indicates whether the circuit is open or closed.

[0054] For example, when the car battery voltage is higher than a preset limit voltage, the circuit maintains normal operation, allowing the battery to supply power to the vehicle's loads. At this time, the warning light is off, and the protection mechanism is not activated. Once the battery voltage is detected to drop below the preset limit voltage, the circuit's protection mechanism responds immediately, automatically cutting off power to the vehicle's loads. This ensures that the remaining electrical energy is primarily used for the ignition function, preventing the engine from failing to start due to low battery. The warning light illuminates, alerting the driver or vehicle maintenance personnel that the circuit has entered protection mode, and some or all non-critical electronic devices are restricted from use due to insufficient power.

[0055] According to the solution provided by the present invention, the device includes: a storage battery for providing electrical energy to a vehicle load; an ignition switch, one end of which is connected to the storage battery and the other end of which is connected to a protection circuit; and a protection circuit for preventing the storage battery from being depleted due to excessive load power consumption, comprising a Zener diode D1, at least two transistors Q1 and Q2, and voltage divider resistors R2 and R3; wherein the negative terminal of the Zener diode D1 is connected to the base of transistor Q2, and the positive terminal is connected to the positive terminal of the storage battery through voltage divider resistors R2 and R3; the base of transistor Q2 receives the signal from the Zener diode D1 through the voltage divider resistors, the collector is connected to the base of transistor Q1, and the emitter is grounded; the base of transistor Q1 is controlled by transistor Q2, and its collector and emitter are respectively connected to the positive terminal of the storage battery and the vehicle load; and voltage divider resistors R2 and R3 are connected in parallel, one end of which is connected to the positive terminal of the Zener diode D1, and the other end is grounded. The protection circuit provided by this invention has low modification costs. It only requires adding a simple circuit between the battery and the vehicle load. The cost of this circuit is only two transistors and three resistors. No additional control module is needed. It can be widely used in many cars. This protection circuit and control method constantly monitor the car battery to keep the battery charge within a reasonable range, so as to ensure that the battery life is not shortened due to excessive discharge. It also greatly reduces the probability of the engine failing to start due to battery depletion. In addition, it can reduce the probability of the vehicle failing to start due to excessive power consumption of electrical circuits when the vehicle is not used for a long time.

[0056] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

[0057] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0058] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0059] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0060] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A circuit for protecting an automotive battery from low discharge, characterized in that, include: A storage battery is used to provide electrical power to onboard loads. The ignition switch has one end connected to the battery and the other end connected to the overload power-off circuit. An overload power-off circuit is used to prevent battery depletion due to excessive load. It includes a Zener diode D1, at least two transistors Q1 and Q2, and voltage divider resistors R2 and R3. The negative terminal of Zener diode D1 is connected to the emitter of transistor Q1, and its positive terminal is connected to the negative terminal of the battery through voltage divider resistors R2 and R3. The base of transistor Q2 receives the signal from Zener diode D1 through voltage divider resistor R2, its collector is connected to the base of transistor Q1, and its emitter is grounded. The base of transistor Q1 is controlled by transistor Q2, and its collector and emitter are connected to the positive terminal of the battery and the vehicle load, respectively. Voltage divider resistors R2 and R3 are connected in series, with one end connected to the positive terminal of Zener diode D1 and the other end grounded.

2. The automotive battery undervoltage protection circuit according to claim 1, characterized in that, The Zener diode D1 and the voltage divider resistor R3 together set the over-discharge protection voltage. When the battery voltage drops below the over-discharge protection voltage value, the power supply to the load is automatically cut off to preserve the power supply to the ignition function and ensure that the engine can start normally.

3. The automotive battery depletion protection circuit according to claim 1 or 2, characterized in that, The circuit also includes capacitors C1 and C2; one end of capacitor C1 is connected to voltage divider resistor R3 and the other end is connected to Zener diode D1; one end of capacitor C2 is connected to the load and the other end is connected to voltage divider resistor R3.

4. The automotive battery undercurrent protection circuit according to claim 1, characterized in that, The circuit also includes a warning light for indicating whether the circuit is in a protected state. One end of the warning light is connected to the collector of transistor Q2 or the output of a logic gate circuit controlled by the state of transistor Q2, and the other end is grounded or connected to the negative power supply.

5. The automotive battery undercurrent protection circuit according to claim 1, characterized in that, It also includes an adjustment unit, which adjusts the voltage regulation value of Zener diode D1 and the resistance values ​​of voltage divider resistors R2 and R3 to adapt to different specifications of automotive batteries.

6. The automotive battery undercurrent protection circuit according to claim 1, characterized in that, It also includes a voltage detection unit, which is connected to the positive terminal of the battery and is used to monitor the battery voltage in real time. When the voltage approaches the over-discharge protection threshold, it sends a control signal to the overload power-off circuit and provides an early warning.

7. The automotive battery undercurrent protection circuit according to claim 1, characterized in that, It also includes a voltage comparator, one input of which is connected to the connection point of voltage divider resistors R2 and R3, and the other input is set to a reference voltage. When the detected battery voltage is lower than the reference voltage, the output signal of the voltage comparator controls the transistor Q2 to be turned off.

8. The automotive battery undercurrent protection circuit according to claim 1, characterized in that, It also includes a third capacitor C3 and a control logic circuit. One end of the third capacitor C3 is connected to the positive terminal of the battery, and the other end is connected to the input terminal of the control logic circuit. The control logic circuit is a comparator, and the positive power supply pin of the comparator is connected to the positive terminal of the battery, and the ground pin is connected to the negative terminal of the battery.

9. A control method for a vehicle battery discharge protection circuit, based on the vehicle battery discharge protection circuit of claim 1, characterized in that, include: Step S1: Start the system by switching on the ignition switch; Step S2: When the battery voltage is higher than the preset limit value, the voltage is allowed to supply the vehicle load normally; otherwise, if the voltage drops below the preset limit voltage, the power supply to the load is immediately cut off to ensure that the battery energy is used only to maintain the power demand of the ignition function.

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