An automotive battery low-voltage cut-off circuit with a self-locking judgment mechanism
By using a combination of NPN transistor and N-MOS tube in the low-voltage shutdown circuit of the automobile battery, the automobile battery voltage is directly judged and different thresholds are set, which solves the problem that the existing technology cannot effectively prevent excessive discharge under low-voltage conditions, and achieves simple and reliable battery management.
Patent Information
- Application Number
- CN201911388509.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2019-12-30
- Publication Date
- 2025-06-13
- Estimated Expiration
- 2039-12-30
AI Technical Summary
The existing low-voltage shutdown circuit of the car battery cannot effectively prevent excessive discharge in the low-voltage state, resulting in the car being unable to ignite and start, and the equipment cannot reset itself after it is turned off, which requires external conditions to trigger or backup battery wake-up.
A low-voltage shutdown circuit for automobile batteries with self-locking judgment mechanism was designed. Through the combination of NPN transistor and N-MOS tube, the car battery voltage is directly judged, different thresholds are set, and the battery type is locked to avoid the device reset and restart.
It effectively prevents excessive discharge of the car battery in a low-voltage state and avoids the device reset and restart. It is simple and reliable, and does not require the participation of the internal MCU.
Smart Images
Figure CN113060083B_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to an automotive battery, and more particularly to a low-voltage cut-off circuit for an automotive battery with a self-locking judgment mechanism. Background Art
[0002] Currently, the rated voltages of commonly used automotive batteries are 12V and 24V, and the required voltage levels for battery discharge are different for the two types of automotive batteries. With the improvement of the integration level of in-vehicle terminals and the increase in the withstand voltage of chips, a terminal can often adopt a wide-voltage design and can adapt to multiple automotive batteries. Therefore, in order to prevent the automotive battery from being over-discharged in a low-voltage state, resulting in the inability of the vehicle to start by ignition, and at the same time to prevent the service life of the automotive battery from being reduced due to over-discharge, generally, there are requirements for the sleep power consumption and static power consumption of each electronic component on the vehicle. At the same time, it is required that when the voltage of the automotive battery is lower than a certain value, the in-vehicle terminal should turn off the external power supply to prevent the terminal from continuously drawing power from the automotive battery, resulting in battery discharge. Currently, most of the in-vehicle terminals in use adopt an MCU to control the enable pin of the DC-DC chip to set the low-voltage cut-off voltage under different battery voltages. This solution can flexibly configure the low-voltage cut-off value of the device, but this solution can only be carried out when the MCU is guaranteed to be working. Once the low-voltage cut-off occurs, even if the battery charging voltage recovers, it cannot be woken up again, and an external condition trigger or an internal backup battery and other power sources are required to provide a wake-up signal. At the same time, it is necessary to ensure that there is a stable internal power source (backup battery) to meet the requirements, otherwise, the phenomenon of repeated start-up and cut-off will occur. Summary of the Invention
[0003] The present invention aims to provide a low-voltage cut-off circuit for an automotive battery with a self-locking judgment mechanism to solve the above problems. To this end, the specific technical solution adopted by the present invention is as follows:
[0004] According to an embodiment of the present invention, a low-voltage cut-off circuit for an automotive battery with a self-locking judgment mechanism is provided. The low-voltage cut-off circuit for the automotive battery includes resistors R1, R3, R4, R5, R6, R7, R8, R9, R10, diodes D1, D2, D3, an NPN transistor Q1, and an N-MOS transistor Q2. Among them, the base of the NPN transistor Q1 is connected in series with resistors R7 and R3 to the automotive battery voltage V_BAT after front-end EMC processing, the collector is connected in series with resistor R8 and diode D1 to the enable trigger pin DC_EN of the power conversion chip, the emitter is grounded, the gate of the N-MOS transistor Q2 is connected in series with resistor R1 to V_BAT and in series with R6 to the collector of the NPN transistor Q1, the drain is connected in series with resistors R5 and R4 to ground, the source is grounded, diode D3 is connected between the gate and the source of the N-MOS transistor Q2, resistors R4 and R5 are connected between resistors R3 and R7, resistors R9, diode D2, and resistor R10 are connected in series between V_BAT and ground, and DC_EN is connected between diode D2 and resistor R10.
[0005] Further, the low-voltage cut-off circuit for the automotive battery may further include a resistor R2 and a capacitor C1. The resistor R2 is connected between resistor R3 and V_BAT, one end of the capacitor C1 is connected between resistor R4 and ground, and the other end is connected between resistors R2 and R3.
[0006] Furthermore, the capacitor C1 is an electrolytic capacitor, its positive electrode is connected between resistors R2 and R3, and its negative electrode is connected between resistor R4 and ground.
[0007] Further, the low-voltage cut-off circuit for the automotive battery may further include capacitors C2 and C3. One end of the capacitor C2 is connected between the emitter of the NPN transistor Q1 and ground, and one end is connected between resistors R7 and R3, and one end of the capacitor C3 is connected between R10 and ground, and the other end is connected to DC_EN.
[0008] Furthermore, the capacitors C2 and C3 are non-polar capacitors.
[0009] Further, the diodes D2 and D3 are voltage-regulating diodes.
[0010] Further, the model of the power conversion chip is TI LMR16030.
[0011] The present invention adopts the above technical solutions and has the following beneficial effects: The present invention is designed with discrete components. Through the combination of the front-end triode and MOS transistor, different threshold settings can be made by directly judging the automotive battery voltage, and at the same time, the type of the currently used automotive battery can be locked, so that the phenomenon of reset and restart after the device is turned off will not occur, and there is no need for the internal MCU to participate, which is more concise and reliable. Description of the Drawings
[0012] To further illustrate the embodiments, the present invention provides accompanying drawings. These drawings are part of the disclosure of the present invention, mainly used to illustrate the embodiments, and can be combined with the relevant descriptions in the specification to explain the operating principle of the embodiments. With reference to these contents, those of ordinary skill in the art should be able to understand other possible implementation manners and the advantages of the present invention. The components in the drawings are not drawn to scale, and similar component symbols are usually used to represent similar components.
[0013] Figure 1 is the circuit schematic diagram of the present invention. Detailed implementation manners
[0014] The present invention will be further described below in conjunction with the accompanying drawings and detailed implementation manners.
[0015] As Figure 1 shown, an automotive battery low-voltage cut-off circuit with a self-locking judgment mechanism may include resistors R1, R3, R4, R5, R6, R7, R8, R9, R10, diodes D1, D2, D3, an NPN transistor Q1, and an N-MOS transistor Q2. Among them, the base of the NPN transistor Q1 is connected in series with resistors R7 and R3 to the automotive battery voltage V_BAT after front-end EMC processing, the collector is connected in series with resistor R8 and diode D1 to the enable trigger pin DC_EN of the power conversion chip, the emitter is grounded, the gate of the N-MOS transistor Q2 is connected in series with resistor R1 to V_BAT and in series with R6 to the collector of the NPN transistor Q1, the drain is connected in series with resistors R5 and R4 to ground, the source is grounded, diode D3 is connected between the gate and source of the N-MOS transistor Q2, resistors R4 and R5 are connected between resistors R3 and R7, resistors R9, diode D2, and resistor R10 are connected in series between V_BAT and ground, and DC_EN is connected between diode D2 and resistor R10.
[0016] In addition, the automotive battery low-voltage cut-off circuit may further include resistor R2 and capacitor C1. Resistor R2 is connected between resistor R3 and V_BAT, one end of capacitor C1 is connected between resistor R4 and ground, and the other end is connected between resistors R2 and R3. C1 and R2 form a delay circuit to prevent system misjudgment caused by the conduction delay of Q2, and also prevent device reset caused by the sudden drop of the automotive battery voltage resulting in enable failure. Preferably, capacitor C1 is an electrolytic capacitor, with its positive pole connected between resistors R2 and R3 and its negative pole connected between resistor R4 and ground.
[0017] In addition, the automotive battery low-voltage cut-off circuit may further include capacitors C2 and C3. One end of capacitor C2 is connected between the emitter of the NPN transistor Q1 and ground, and one end is connected between resistors R7 and R3, and one end of capacitor C3 is connected between R10 and ground, and the other end is connected to DC_EN. Capacitors C2 and C3 can prevent the impact of surges on the circuit. Preferably, capacitors C2 and C3 are non-polar capacitors.
[0018] In the illustrated embodiment, diodes D2 and D3 are voltage-regulator diodes, and their model is ZMM55C5V6. The NPN transistor Q1 has a model of BC817-25, and the N-MOS transistor Q2 has a model of P7502CMG.
[0019] In a specific embodiment, for example, when the model of the power conversion chip is TI LMR16030, V_24V is set to 17V, V cut_12V is set to 8V, and V cut_24V is set to 17V; at this time, the resistance values of the respective voltage-dividing resistors are as Figure 1 shown.
[0020] The working principle of the low-voltage cut-off circuit for automotive batteries of the present invention is described below:
[0021] When the in-vehicle terminal is connected to the automotive battery, the V GS> V GS(th) of Q2, Q2 conducts, and the automotive battery type determination threshold V_24V is determined by the voltage division of resistors R2, R3, R4, and R5. That is, by adjusting the resistance values of R2, R3, R4, and R5, the value of V_24V can be adjusted;
[0022] When the voltage of the automotive battery is less than V_24V, the voltage division of R2, R3, R4, and R5 is less than the turn-on voltage of Q1, and Q1 is cut off. The system is a 12V voltage system. At this time, the low-voltage threshold value V cut_12V of the vehicle is determined by the voltage division of R9, R10, and D2. That is, by adjusting the resistance values of R9 and R10, the value of V cut_12V can be adjusted; when the voltage of the automotive battery is lower than V cut_12V , the power supply is turned off to prevent the automotive battery from being over-discharged. When the system resumes at V cut_12V , the system resumes power supply;
[0023] When the voltage of the automotive battery is higher than V_24V, Q1 conducts, and the system is a 24V voltage system. At this time, the low-voltage threshold value V cut_24V of the vehicle is determined by the voltage division of R8, R9, R10, and D2. That is, by adjusting the resistance values of R8, R9, and R10, the value of V cut_24V can be adjusted; when the automotive battery is lower than V cut_24V , the power supply is turned off to prevent the automotive battery from being over-discharged. When the system resumes at V cut_24V , the system resumes power supply; at the same time, V GS <V GS(th) , Q2 is cut off. At this time, the turn-on voltage of Q1 is determined by the voltage division of R2, R3, and R4. The turn-on voltage of Q1 is set to be less than the cut-off voltage of the 12V voltage system to prevent the system from misjudging and restarting due to excessive discharge of the automotive battery for other reasons.
[0024] The present invention is designed with discrete components. Through the combination of the front-end triode Q1 and MOS transistor Q2, different threshold settings can be made by directly judging the voltage of the automotive battery, and at the same time, the type of automotive battery currently in use can be locked, so as to avoid the phenomenon of reset and restart after the device is turned off, and there is no need for the internal MCU to participate, which is more concise and reliable.
[0025] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, those skilled in the art should understand that various changes can be made to the present invention in terms of form and details without departing from the spirit and scope of the present invention defined by the appended claims, and all of them are within the protection scope of the present invention.
Claims
1. An automotive battery low-voltage cut-off circuit with a self-locking judgment mechanism, characterized in that, the automotive battery low-voltage cut-off circuit includes resistors R1, R3, R4, R5, R6, R7, R8, R9, R10, diodes D1, D2, D3, an NPN transistor Q1 and an N-MOS transistor Q2. Among them, the base of the NPN transistor Q1 is connected in series with resistors R7 and R3 to the automotive battery voltage V_BAT after front-end EMC processing, the collector is connected in series with resistor R8 and diode D1 to the enable trigger pin DC_EN of the power conversion chip, the emitter is grounded, the gate of the N-MOS transistor Q2 is connected in series with resistor R1 to V_BAT and in series with R6 to the collector of the NPN transistor Q1, the drain is connected in series with resistors R5 and R4 to ground, the source is grounded, diode D3 is connected between the gate and the source of the N-MOS transistor Q2, resistors R4 and R5 are connected between resistors R3 and R7, resistors R9, diode D2 and resistor R10 are connected in series between V_BAT and ground, and DC_EN is connected between diode D2 and resistor R10; where: When the automotive battery is connected, Q2 conducts, and the automotive battery category judgment threshold V_24V is determined by the voltage division of resistors R2, R3, R4, and R5; When the voltage of the automotive battery is less than V_24V, the voltage division of R2, R3, R4, and R5 is less than the turn-on voltage of Q1, and Q1 is turned off. The automotive battery is a 12V voltage system. At this time, the low-voltage threshold V of the vehicle cut_12V is determined by the voltage division of R9, R10, and D2; when the voltage of the automotive battery is lower than V cut_12V , the power supply is turned off. When the voltage of the automotive battery returns to V cut_12V , the power supply is restored; among them, the turn-on voltage of Q1 is less than V cut_12V ; When the voltage of the automotive battery is higher than V_24V, Q1 conducts, and the automotive battery powers the 24V voltage system. At this time, the low-voltage threshold V of the vehicle cut_24V is determined by the voltage division of R8, R9, R10, and D2; when the automotive battery voltage is lower than V cut_24V , the power supply is turned off. When the voltage of the automotive battery resumes to V cut_24V , the power supply is restored; when Q1 conducts, Q2 cuts off, and the turn-on voltage of Q1 is determined by the voltage division of R2, R3, and R4.
2. The automotive battery low-voltage cut-off circuit according to claim 1, characterized in that, it further includes a resistor R2 and a capacitor C1. The resistor R2 is connected between resistor R3 and V_BAT, one end of the capacitor C1 is connected between resistor R4 and ground, and the other end is connected between resistors R2 and R3.
3. The automotive battery low-voltage cut-off circuit according to claim 2, characterized in that, the capacitor C1 is an electrolytic capacitor, its positive electrode is connected between resistors R2 and R3, and its negative electrode is connected between resistor R4 and ground.
4. The automotive battery low-voltage cut-off circuit according to claim 1, characterized in that, it further includes capacitors C2 and C3. One end of the capacitor C2 is connected between the emitter of the NPN transistor Q1 and ground, and one end is connected between resistors R7 and R3, and one end of the capacitor C3 is connected between R10 and ground, and the other end is connected to DC_EN.
5. The automotive battery low-voltage cut-off circuit according to claim 4, characterized in that, the capacitors C2 and C3 are non-polar capacitors.
6. The automotive battery low-voltage cut-off circuit according to claim 1, characterized in that, the diodes D2 and D3 are zener diodes.
7. The automotive battery low-voltage cut-off circuit according to claim 1, characterized in that, the model of the power conversion chip is TILMR16030.
Citation Information
Patent Citations
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