CN215575406U - Bus fault detection circuit, on-vehicle OBD equipment and car - Google Patents
Bus fault detection circuit, on-vehicle OBD equipment and car Download PDFInfo
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- CN215575406U CN215575406U CN202121187183.4U CN202121187183U CN215575406U CN 215575406 U CN215575406 U CN 215575406U CN 202121187183 U CN202121187183 U CN 202121187183U CN 215575406 U CN215575406 U CN 215575406U
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Abstract
The application relates to a bus fault detection circuit, on-vehicle OBD equipment and car. The bus fault detection circuit comprises a comparison unit, wherein one input end of the comparison unit is used for accessing a reference level, and the other input end of the comparison unit is used for accessing the level of a data lead of the CAN bus; the comparison unit outputs a comparison signal through the output end under the condition that the level of the data lead is higher than the reference level; the input end of the display unit is connected with the output end of the comparison unit; the display unit is used for receiving the comparison signal, displaying an alarm and outputting a trigger signal through an output end; the control unit is connected in series with the data lead; the control end of the control unit is connected with the output end of the display unit; and the control unit disconnects the data lead under the condition of receiving the trigger signal so as to shut off the CAN bus. The application can improve the detection efficiency and reduce the cost.
Description
Technical Field
The application relates to the technical field of automobiles, in particular to a bus fault detection circuit, an on-board OBD device and an automobile.
Background
With the continuous development of the car networking technology, the popularization and application of intelligent transportation become one of the important development trends at present, and the car networking relies on the collection and transmission of vehicle data. One important system for collecting vehicle data is OBD (On Board Diagnostics), which is a detection system extended for vehicle fault diagnosis. The OBD can detect the running state of the automobile in the running process of the automobile, can monitor whether the power system and the control system are abnormal or not and the working states of other parts, and can judge specific fault conditions and send fault alarms to personnel on the automobile when the automobile breaks down.
In the application of the field of OBD products, the conventional method for detecting a bus fault of a Controller Area Network (CAN) of an automobile mainly includes the following 3 methods: (1) measuring the level and waveform of the CAN bus by using a tool (a universal meter, an oscilloscope and the like) and judging the communication state of the CAN bus; (2) reading the level of the CAN bus and the bus data through an MCU (micro controller Unit), and judging the communication state of the CAN bus; (3) and judging the communication state of the CAN bus by sending the test frame. In the implementation process, at least the following problems are found in the conventional technology: the traditional detection mode has the problems of low detection efficiency, high cost and the like.
SUMMERY OF THE UTILITY MODEL
In view of the above, it is desirable to provide a bus fault detection circuit, an on-board OBD device, and an automobile that can improve detection efficiency and reduce cost.
In order to achieve the above object, in one aspect, an embodiment of the present application provides a bus fault detection circuit, including:
one input end of the comparison unit is used for accessing a reference level, and the other input end of the comparison unit is used for accessing the level of a data lead of the CAN bus; the comparison unit outputs a comparison signal through the output end under the condition that the level of the data lead is higher than the reference level;
the input end of the display unit is connected with the output end of the comparison unit; the display unit is used for receiving the comparison signal, displaying an alarm and outputting a trigger signal through an output end;
the control unit is connected in series with the data lead; the control end of the control unit is connected with the output end of the display unit; and the control unit disconnects the data lead under the condition of receiving the trigger signal so as to shut off the CAN bus.
In one embodiment, the comparison unit comprises a first comparison module and a second comparison module; the display unit comprises a first display module and a second display module; the control unit comprises a first switch and a second switch;
the first input end of the first comparison module is used for connecting a reference power supply, the second input end of the first comparison module is used for connecting a CANH lead of a CAN bus, and the output end of the first comparison module is connected with the input end of the first display module; the output end of the first display module is connected with the control end of the first switch; the first switch is connected in series with the CANH lead;
the first input end of the second comparison module is used for connecting a reference power supply, the second input end of the second comparison module is used for connecting a CANL lead of a CAN bus, and the output end of the second comparison module is connected with the input end of the second display module; the output end of the second display module is connected with the control end of the second switch; the second switch is used for being connected in series with the CANL lead.
In one embodiment, the first comparing module is a first voltage comparator; the comparison unit further comprises a first resistor, a second resistor and a third resistor;
the positive phase input end of the first voltage comparator is used for being connected with a CANH _ A of a CANH lead and is connected with one end of a third resistor, the negative phase input end of the first voltage comparator is connected between the first resistor and the second resistor, the output end of the first voltage comparator is connected with the input end of the display unit, one power supply pin is used for being connected with a reference power supply, and the other power supply pin is grounded;
one end of the first resistor is connected with a reference power supply, and the other end of the first resistor is grounded through the second resistor; the other end of the third resistor is used for grounding.
In one embodiment, the second comparing module is a second voltage comparator; the comparison unit further comprises a fourth resistor, a fifth resistor and a sixth resistor;
the positive phase input end of the second voltage comparator is used for being connected with the CANL _ A of the CANL lead wire and one end of the sixth resistor, the negative phase input end of the second voltage comparator is connected between the fourth resistor and the fifth resistor, the output end of the second voltage comparator is connected with the input end of the display unit, one power supply pin is used for being connected with a reference power supply, and the other power supply pin is used for being grounded;
one end of the fourth resistor is connected with the reference power supply, and the other end of the fourth resistor is grounded through the fifth resistor; the other end of the sixth resistor is used for grounding.
In one embodiment, the first display module comprises a first light emitting diode, a first triode and a first current limiting resistor; the second display module comprises a second light emitting diode, a second triode and a second current limiting resistor;
the base electrode of the first triode is connected with the output end of the first comparison module, the collector electrode of the first triode is connected with the negative electrode of the first light-emitting diode, the emitter electrode of the first triode is connected with the control end of the first switch, and the emitter electrode of the first triode is used for grounding; the anode of the first light emitting diode is connected with one end of the first current limiting resistor; the other end of the first current-limiting resistor is used for being connected with a reference power supply;
the base electrode of the second triode is connected with the output end of the second comparison module, the collector electrode of the second triode is connected with the negative electrode of the second light-emitting diode, the emitter electrode of the second triode is connected with the control end of the second switch, and the emitter electrode of the second triode is used for grounding; the anode of the second light-emitting diode is connected with one end of a second current-limiting resistor; the other end of the second current limiting resistor is used for being connected with a reference power supply.
In one embodiment, the first display module further comprises a third transistor; the second display module further comprises a fourth triode;
the base electrode of the third triode is connected between the output end of the first comparison module and the base electrode of the first triode, the collector electrode of the third triode is connected between the emitter electrode of the first triode and the control end of the first switch, and the emitter electrode of the third triode is used for grounding;
the base electrode of the fourth triode is connected between the output end of the second comparison module and the base electrode of the second triode, the collector electrode of the fourth triode is connected between the emitter electrode of the second triode and the control end of the second switch, and the emitter electrode of the fourth triode is used for being grounded.
In one embodiment, the first switch is a first relay; the second switch is a second relay;
one end of a coil of the first relay is connected with the output end of the first display module, and the other end of the coil of the first relay is used for being connected with a reference power supply; one contact of the first relay is used for connecting CANH _ A of a CANH lead, and the other contact of the first relay is used for connecting CANH _ B of the CANH lead;
one end of a coil of the second relay is connected with the output end of the second display module, and the other end of the coil of the second relay is used for being connected with a reference power supply; one contact of the second relay is used for connecting the CANL _ a of the CANL lead and the other contact is used for connecting the CANL _ B of the CANL lead.
In one embodiment, the control unit further comprises a first diode and a second diode;
the anode of the first diode is connected between the output end of the first display module and one end of the coil of the first relay, and the cathode of the first diode is used for connecting a reference power supply; the anode of the second diode is connected between the output end of the second display module and one end of the coil of the second relay, and the cathode of the second diode is used for being connected with a reference power supply.
A vehicle-mounted OBD device comprises a CAN bus and the bus fault detection circuit connected with the CAN bus.
An automobile comprises the vehicle-mounted OBD device.
One of the above technical solutions has the following advantages and beneficial effects:
the CAN bus fault detection method is rapid and simple in detection and flexible in circuit design, and CAN bus fault detection is achieved through devices such as the comparison unit, the display unit and the control unit; specifically, after power-on, this application CAN report to the police and show based on the display element when detecting that CAN line level appears unusually to pull up, and then whether the rapid judgement breaks down to CAN meet an emergency according to the detection demand, through the data lead wire of control unit disconnection, with shutoff CAN bus. The application has low cost and multiple choices, and does not have cost pressure. Corresponding protection measures can be implemented for fault conditions based on the application; the CAN bus circuit CAN detect the CAN bus fault of the automobile end, and CAN effectively protect the CAN bus circuit inside the vehicle-mounted OBD equipment when the CAN bus has a short-circuit fault.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments or the conventional technologies of the present application, the drawings used in the descriptions of the embodiments or the conventional technologies will be briefly introduced below, it is obvious that the drawings in the following descriptions are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a diagram of an exemplary implementation of a bus fault detection circuit;
FIG. 2 is a schematic diagram of a bus fault detection circuit according to an embodiment;
FIG. 3 is a schematic diagram of another embodiment of a bus fault detection circuit;
fig. 4 is a schematic diagram of a specific structure of the bus fault detection circuit in one embodiment.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Embodiments of the present application are set forth in the accompanying drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
It will be understood that, as used herein, the terms "first," "second," and the like may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish one element from another.
Spatial relational terms, such as "under," "below," "under," "over," and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements or features described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary terms "under" and "under" can encompass both an orientation of above and below. In addition, the device may also include additional orientations (e.g., rotated 90 degrees or other orientations) and the spatial descriptors used herein interpreted accordingly.
It will be understood that when an element is referred to as being "connected" to another element, it can be directly connected to the other element or be connected to the other element through intervening elements. Further, "connection" in the following embodiments is understood to mean "electrical connection", "communication connection", or the like, if there is a transfer of electrical signals or data between the connected objects.
As used herein, the singular forms "a", "an" and "the" may include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises/comprising," "includes" or "including," etc., specify the presence of stated features, integers, steps, operations, components, parts, or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, as used in this specification, the term "and/or" includes any and all combinations of the associated listed items.
The traditional technology only supports detection aiming at the CAN bus fault of the automobile end and does not contain protection of the vehicle-mounted OBD product. In addition, the fault detection speed of the traditional detection mode is low, and the risk that the CAN chip is damaged in the fault detection process exists; the detection cost is high, and part of tools (oscilloscopes and the like) are expensive; furthermore, the traditional scheme can only complete the detection function and does not have a corresponding protection mechanism; conventional hardware circuits do not support the above functionality due to objective condition limitations.
This application CAN be applied to current on-vehicle OBD product, specifically, this application circuit CAN detect the CAN bus trouble of car end to when CAN bus short circuit fault appears, CAN protect the inside CAN bus circuit of on-vehicle OBD product effectively. The application is suitable for the field of bus fault detection and car networking products. In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further 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 application and are not intended to limit the present application.
The bus fault detection circuit provided by the application can be applied to the application environment shown in fig. 1. The CAN bus network is mainly hung on CAN _ H and CAN _ L, and each node realizes serial differential transmission of signals through the two lines; in practical application, there are two CAN data buses, one is CAN _ High and the other is CAN _ Low. CANH in the present application may refer to a high-level CAN bus, CANL may refer to a low-level CAN bus, and in some embodiments, CANH and CANL are referred to herein using data leads of the CAN bus.
In addition, as shown in fig. 1, the bus fault detection circuit CAN be applied to vehicle-mounted OBD equipment, CAN detect the CAN bus fault of the automobile end, and CAN effectively protect the CAN bus circuit inside the vehicle-mounted OBD equipment when the CAN bus has a short-circuit fault.
In one embodiment, as shown in fig. 2, a bus fault detection circuit is provided, which is described by taking an example of the application of the bus fault detection circuit to the vehicle OBD device in fig. 1, and includes:
one input end of the comparison unit 110 is used for accessing a reference level, and the other input end of the comparison unit 110 is used for accessing the level of a data lead of the CAN bus; the comparison unit 110 outputs a comparison signal through an output terminal in a case where the level of the data pin is higher than a reference level;
the input end of the display unit 120 is connected with the output end of the comparison unit 110; the display unit 120 is used for receiving the comparison signal, displaying an alarm and outputting a trigger signal through an output end;
a control unit 130 for connecting in series to the data lead; the control end of the control unit 130 is connected with the output end of the display unit 120; the control unit 130 disconnects the data lead to turn off the CAN bus in case of receiving the trigger signal.
Specifically, based on the comparison unit 110, the present application CAN detect whether the data lead level of the CAN bus is abnormally pulled up; the comparing unit 110 may compare the data lead level (e.g., CANH level, CANL level) with the reference level, and when the data lead level is higher than the reference level, it is determined that the CAN bus level is abnormally pulled up, and then the comparing unit 110 may output a comparison signal. In some embodiments, the function of the comparison unit 110 in the present application may be implemented by using a comparator or a corresponding comparator circuit, and the comparison signal may be high level.
The comparator circuit may have a function of comparing the voltages of the non-inverting input terminal Vin (+) and the inverting input terminal Vin (-). In a specific example, when the voltage of the non-inverting input terminal Vin (+) is greater than the voltage of the inverting input terminal Vin (-), the output terminal Vout outputs a high level. When the voltage of the inverting input terminal Vin (-) is greater than the voltage of the non-inverting input terminal Vin (+), the output terminal Vout outputs a low level.
It should be noted that, the reference level in the present application may be provided by a reference power supply; for example, a 12V reference supply. The comparing unit 110 may compare the data pin level with the reference level after voltage division, and then determine whether the CAN bus level is abnormally pulled up.
When receiving the comparison signal output by the comparison unit 110 (for example, the high level output by the comparison unit 110), the display unit 120 confirms that the CAN bus level is abnormally pulled high, and the display unit 120 CAN perform alarm display, thereby quickly determining whether a fault occurs. In some embodiments, the display unit 120 in the present application may be implemented by an indicator light unit; the indicator light unit may include a plurality of indicator lights, mainly for alarming. In other embodiments, the related functions of the display unit 120 can also be implemented by using corresponding light emitting diodes and supporting transistors. When the level of the data lead is higher than the reference level, the triode can be conducted, so that the light emitting diode is lightened, and meanwhile, the triode can output a corresponding trigger signal.
Further, the display unit 120 may output a trigger signal to trigger the control unit 130 to act when receiving the comparison signal; the control unit 130 may be connected in series to the data lead of the CAN bus, and a control terminal of the control unit 130 is connected to the output terminal of the display unit 120. Taking the data lead as a CANH lead as an example, one contact of the control unit 130 may be connected to CANH _ a of the CANH lead, and the other contact may be connected to CANH _ B of the CANH lead.
This application CAN be met an emergency according to the measuring demand, and control unit 130 is under the condition that receives trigger signal, disconnection data lead wire to turn off the CAN bus, and then realize the setting of opening a circuit of the data lead wire (CANH, CANL) of CAN bus. That is, the control unit 130 in the present application is used for CAN bus turn-off control, and when the comparison unit 110 outputs a high-level comparison signal, the control unit 130 turns off the CAN line to protect the CAN line.
In some embodiments, the related functions of the control unit 130 may be implemented using switches, switching circuits, and/or corresponding relays. The relay comprises an electromagnetic system and a contact system, wherein the electromagnetic system is composed of a coil, a fixed iron core and a movable armature, and the contact system is composed of a movable contact and a static contact. When the input quantity of a coil of the relay electromagnetic system reaches a threshold value, the iron core generates magnetic force under the electromagnetic action to attract the armature, and the armature drives the movable contact of the contact system to act, so that the contact is closed or opened, and the on-off of a circuit connected with the contact system is changed. According to the input quantity change of the electromagnetic system coil, the on-off of the contacts is controlled, when the input quantity of the coil reaches a threshold value, the normally open contacts are closed, and the normally closed contacts are opened, so that the working state of a circuit connected with the contacts is changed.
The bus fault detection circuit has the advantages of quick and simple detection and flexible circuit design; according to the CAN bus fault detection method, the CAN bus fault detection is realized through devices such as the comparison unit 110, the display unit 120 and the control unit 130; specifically, after the power is turned on, when the CAN line level is detected to be abnormally pulled up, the alarm display CAN be carried out based on the display unit 120, so that whether the CAN line level is in fault or not CAN be rapidly judged, and the strain CAN be carried out according to the detection requirement, and the data lead is disconnected through the control unit 130 so as to turn off the CAN bus. The application has low cost and multiple choices, and does not have cost pressure. Corresponding protection measures can be implemented for fault conditions based on the application; the CAN bus circuit CAN detect the CAN bus fault of the automobile end, and CAN effectively protect the CAN bus circuit inside the vehicle-mounted OBD equipment when the CAN bus has a short-circuit fault.
In one embodiment, as shown in fig. 3, a bus fault detection circuit is provided, which is described by taking an example of the application of the bus fault detection circuit to the vehicle OBD device in fig. 1, and includes:
one input end of the comparison unit 110 is used for accessing a reference level, and the other input end of the comparison unit 110 is used for accessing the level of a data lead of the CAN bus; the comparison unit 110 outputs a comparison signal through an output terminal in a case where the level of the data pin is higher than a reference level; the comparing unit 110 includes a first comparing module 112 and a second comparing module 114;
the input end of the display unit 120 is connected with the output end of the comparison unit 110; the display unit 120 is used for receiving the comparison signal, displaying an alarm and outputting a trigger signal through an output end; wherein the display unit 120 includes a first display module 122 and a second display module 124;
a control unit 130 for connecting in series to the data lead; the control end of the control unit 130 is connected with the output end of the display unit 120; the control unit 130 disconnects the data lead to turn off the CAN bus under the condition of receiving the trigger signal; wherein the control unit 130 includes a first switch 132 and a second switch 134;
further, a first input end of the first comparing module 112 is used for connecting a reference power supply, a second input end is used for connecting a CANH lead of the CAN bus, and an output end is connected to an input end of the first display module 122; the output end of the first display module 122 is connected to the control end of the first switch 132; the first switch 132 is connected in series to the CANH lead;
a first input end of the second comparing module 114 is used for connecting a reference power supply, a second input end is used for connecting a CANL lead of the CAN bus, and an output end is connected with an input end of the second display module 124; the output end of the second display module 124 is connected to the control end of the second switch 134; the second switch 134 is arranged to be connected in series to the CANL lead.
Specifically, as shown in fig. 3, the comparing unit 110 may implement the related functions by using a first comparing module 112 and a second comparing module 114. The first comparing module 112 may compare the CANH level with the reference level, and when the CANH level is higher than the reference level, it is determined that the CAN bus level is abnormally pulled up, and then a high level may be output. The second comparing module 112 may compare the CANL level with the reference level, and when the CANL level is higher than the reference level, it is determined that the CAN bus level is abnormally pulled up, and then a high level may be output.
In one embodiment, as shown in fig. 4, the first comparing module may be a first voltage comparator U1; the comparison unit further comprises a first resistor R1, a second resistor R2 and a third resistor R3;
the positive phase input end of the first voltage comparator U1 is used for connecting a CANH _ A of a CANH lead and connecting one end of a third resistor R3, the negative phase input end is connected between the first resistor R1 and the second resistor R2, the output end is connected with the input end of the display unit, one power supply pin is used for being connected with a reference power supply, and the other power supply pin is grounded;
one end of the first resistor R1 is connected with a reference power supply, and the other end is grounded through the second resistor R2; the other end of the third resistor R3 is used for ground.
In one embodiment, as shown in fig. 4, the second comparing module may be a second voltage comparator U2; the comparison unit further comprises a third resistor R3, a fifth resistor R5 and a sixth resistor R6;
a positive phase input end of the second voltage comparator U2 is used for connecting CANL _ a of the CANL lead and connecting one end of a sixth resistor R6, a negative phase input end is connected between the third resistor R3 and the fifth resistor R5, an output end is connected with an input end of the display unit, one power supply pin is used for connecting with a reference power supply, and the other power supply pin is used for grounding;
one end of the third resistor R3 is connected with a reference power supply, and the other end is grounded through a fifth resistor R5; the other end of the sixth resistor R6 is used for ground.
In the above, the comparison unit in the present application can be implemented by using a voltage comparator. When CANH and CANL levels are compared with the reference level after voltage division, and the CAN line level is abnormally pulled high, the comparator outputs a high level.
The display unit 120 in the present application may be implemented by a first display module 122 and a second display module 124; the first display module 122 and the second display module 124 display an alarm when receiving the high level output by the corresponding comparison module, and output corresponding trigger signals to the control unit 130. Specifically, the first display module 122 outputs a trigger signal to the first switch 132, and the second display module 124 outputs a trigger signal to the second switch 134.
In one embodiment, as shown in fig. 4, the first display module may include a first light emitting diode (i.e., a red light in fig. 4), a first transistor Q9, and a first current limiting resistor R13; the second display module may include a second light emitting diode (i.e., a yellow lamp in fig. 4), a second transistor Q10, and a second current limiting resistor R14;
a base electrode of the first triode Q9 is connected with an output end of the first comparison module (i.e., the output end of the U1), a collector electrode of the first triode Q9 is connected with a negative electrode of the first light emitting diode, an emitter electrode of the first triode Q9 is connected with a control end of the first switch, and the emitter electrode of the first triode Q9 is used for grounding; the anode of the first light-emitting diode is connected with one end of a first current-limiting resistor R13; the other end of the first current limiting resistor R13 is used for being connected with a reference power supply;
a base electrode of the second triode Q10 is connected with an output end (namely, an output end of the U2) of the second comparing module, a collector electrode of the second triode Q10 is connected with a negative electrode of the second light emitting diode, an emitter electrode of the second triode Q10 is connected with a control end of the second switch, and the emitter electrode of the second triode Q10 is used for grounding; the anode of the second light-emitting diode is connected with one end of a second current-limiting resistor R14; the other end of the second current limiting resistor R14 is used for being connected with a reference power supply.
In one embodiment, as shown in fig. 4, the first display module may further include a third transistor Q11; the second display module may further include a fourth transistor Q13;
the base electrode of the third triode Q11 is connected between the output end of the first comparison module and the base electrode of the first triode Q9, the collector electrode of the third triode Q11 is connected between the emitter electrode of the first triode Q9 and the control end of the first switch, and the emitter electrode of the third triode Q11 is grounded;
the base electrode of the fourth triode Q13 is connected between the output end of the second comparison module and the base electrode of the second triode Q10, the collector electrode is connected between the emitter electrode of the second triode Q10 and the control end of the second switch, and the emitter electrode is used for grounding.
In the above, the display unit in the present application may be implemented by using corresponding indicator lights, for example, 2 indicator lights. When the CANH _ A, CANL _ a level is higher than the reference level, the transistors Q9 and Q10 are both turned on, and the indicator light is turned on. It should be noted that the red light and the yellow light in fig. 4 of the present application are only exemplary, and in practical applications, the corresponding light group may be selected according to requirements for alarm display. The display unit obviously improves the monitoring efficiency, the detection method is quick and simple, and whether faults occur or not can be quickly judged through the indicator lamp after the power is on.
The control unit 130 in the present application may be implemented by a first switch 132 and a second switch 134. The first switch 132 is used for the CANH line turn-off control, and when the first comparing module 112 outputs a high level, the first switch 132 turns off the CANH line, thereby playing a role in protecting the CAN line. The second switch 134 is used for controlling the CANL line to be turned off, and when the second comparing module 114 outputs a high level, the second switch 134 turns off the CANL line, thereby protecting the CAN line.
In one embodiment, as shown in fig. 4, the first switch may be a first relay K1; the second switch may be a second relay K2;
one end of the coil of the first relay K1 is connected to the output end of the first display module (i.e. the emitter of Q9), and the other end is used for connecting to a reference power supply; one contact of the first relay K1 is used for connecting CANH _ A of a CANH lead, and the other contact is used for connecting CANH _ B of the CANH lead;
one end of a coil of the second relay K2 is connected to the output end (i.e. the emitter of Q10) of the second display module, and the other end is used for connecting to a reference power supply; one contact of the second relay K2 is used to connect CANL _ a of the CANL lead and the other contact is used to connect CANL _ B of the CANL lead.
In one embodiment, as shown in fig. 4, the control unit may further include a first diode D6 and a second diode D8;
the anode of the first diode D6 is connected between the output terminal of the first display module (i.e., the emitter of Q9) and one end of the coil of the first relay K1, and the cathode is used for connecting a reference power supply; the anode of the second diode D8 is connected between the output terminal of the second display module (i.e., the emitter of Q10) and one end of the coil of the second relay K2, and the cathode is used for connecting a reference power source.
In the above, in the present application, the voltage comparator U1 and the voltage comparator U2 respectively compare the two line levels of CANH _ A, CANL _ a with the corresponding reference levels, when the level of CANH _ A, CANL _ a is higher than the reference level, the transistors Q9 and Q10 are both turned on, the indicator light is turned on, the coils of the relays K1 and K2 are turned on, and the circuit of CANH _ A, CANL _ a is turned off, so as to protect the CAN line.
The circuit is flexible in design, only uses devices such as transistors, operational amplifiers and resistance-capacitance devices, and can be strained according to detection requirements. The scheme of the application has low cost, the transistor and the operational amplifier have low cost, and the transistor and the operational amplifier have multiple choices and do not have cost pressure. The detection method is quick and simple, and whether the fault occurs can be quickly judged through the indicator lamp after the power is on. Moreover, the method and the device have corresponding protection measures aiming at the fault condition. The bus fault detection circuit CAN detect the CAN bus fault of the automobile end, and CAN effectively protect the CAN bus circuit inside the vehicle-mounted OBD product when the CAN bus has a short-circuit fault.
In one embodiment, an on-board OBD device is provided that includes a CAN bus, and a bus fault detection circuit as described above connected to the CAN bus.
In one embodiment, an automobile is provided, comprising the on-board OBD device described above.
It will be understood by those skilled in the art that the configurations shown in fig. 1-4 are only block diagrams of some configurations relevant to the present disclosure, and do not constitute a limitation on the components and/or devices to which the present disclosure may be applied, and that a particular component and/or device may include more or less components than those shown in the figures, or may combine certain components, or have a different arrangement of components.
In the description herein, references to the description of "some embodiments," "other embodiments," "desired embodiments," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, a schematic description of the above terminology may not necessarily refer to the same embodiment or example.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the utility model. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (10)
1. A bus fault detection circuit, comprising:
one input end of the comparison unit is used for accessing a reference level, and the other input end of the comparison unit is used for accessing the level of a data lead of a CAN bus; the comparison unit outputs a comparison signal through an output end under the condition that the level of the data lead is higher than the reference level;
the input end of the display unit is connected with the output end of the comparison unit; the display unit is used for receiving the comparison signal, displaying an alarm and outputting a trigger signal through an output end;
the control unit is connected in series on the data lead; the control end of the control unit is connected with the output end of the display unit; and the control unit disconnects the data lead under the condition of receiving the trigger signal so as to turn off the CAN bus.
2. The bus fault detection circuit of claim 1, wherein the comparison unit comprises a first comparison module and a second comparison module; the display unit comprises a first display module and a second display module; the control unit comprises a first switch and a second switch;
the first input end of the first comparison module is used for being connected with a reference power supply, the second input end of the first comparison module is used for being connected with a CANH lead of the CAN bus, and the output end of the first comparison module is connected with the input end of the first display module; the output end of the first display module is connected with the control end of the first switch; the first switch is used for being connected to the CANH lead in series;
the first input end of the second comparison module is used for connecting a reference power supply, the second input end of the second comparison module is used for connecting a CANL lead of the CAN bus, and the output end of the second comparison module is connected with the input end of the second display module; the output end of the second display module is connected with the control end of the second switch; the second switch is configured to be connected in series to the CANL lead.
3. The bus fault detection circuit of claim 2, wherein the first comparison module is a first voltage comparator; the comparison unit further comprises a first resistor, a second resistor and a third resistor;
the positive phase input end of the first voltage comparator is used for being connected with a CANH _ A of the CANH lead and one end of the third resistor, the negative phase input end of the first voltage comparator is connected between the first resistor and the second resistor, the output end of the first voltage comparator is connected with the input end of the display unit, one power supply pin is used for being connected with the reference power supply, and the other power supply pin is grounded;
one end of the first resistor is connected with the reference power supply, and the other end of the first resistor is grounded through the second resistor; the other end of the third resistor is used for grounding.
4. The bus fault detection circuit according to claim 2 or 3, wherein the second comparison module is a second voltage comparator; the comparison unit further comprises a fourth resistor, a fifth resistor and a sixth resistor;
a positive phase input end of the second voltage comparator is used for being connected with a CANL _ A of the CANL lead and one end of the sixth resistor, a negative phase input end of the second voltage comparator is connected between the fourth resistor and the fifth resistor, an output end of the second voltage comparator is connected with an input end of the display unit, one power supply pin is used for being connected with the reference power supply, and the other power supply pin is used for being grounded;
one end of the fourth resistor is connected with the reference power supply, and the other end of the fourth resistor is grounded through the fifth resistor; the other end of the sixth resistor is used for grounding.
5. The bus fault detection circuit of claim 2, wherein the first display module comprises a first light emitting diode, a first triode, and a first current limiting resistor; the second display module comprises a second light emitting diode, a second triode and a second current limiting resistor;
a base electrode of the first triode is connected with an output end of the first comparison module, a collector electrode of the first triode is connected with a negative electrode of the first light emitting diode, an emitter electrode of the first triode is connected with a control end of the first switch, and the emitter electrode is used for grounding; the anode of the first light emitting diode is connected with one end of the first current limiting resistor; the other end of the first current-limiting resistor is used for being connected with the reference power supply;
the base electrode of the second triode is connected with the output end of the second comparison module, the collector electrode of the second triode is connected with the negative electrode of the second light-emitting diode, the emitter electrode of the second triode is connected with the control end of the second switch, and the emitter electrode of the second triode is used for grounding; the anode of the second light emitting diode is connected with one end of the second current limiting resistor; and the other end of the second current-limiting resistor is used for being connected with the reference power supply.
6. The bus fault detection circuit of claim 5, wherein the first display module further comprises a third transistor; the second display module further comprises a fourth triode;
the base electrode of the third triode is connected between the output end of the first comparison module and the base electrode of the first triode, the collector electrode of the third triode is connected between the emitter electrode of the first triode and the control end of the first switch, and the emitter electrode of the third triode is grounded;
the base electrode of the fourth triode is connected between the output end of the second comparison module and the base electrode of the second triode, the collector electrode of the fourth triode is connected between the emitter electrode of the second triode and the control end of the second switch, and the emitter electrode of the fourth triode is used for being grounded.
7. The bus fault detection circuit of claim 2, wherein the first switch is a first relay; the second switch is a second relay;
one end of a coil of the first relay is connected with the output end of the first display module, and the other end of the coil of the first relay is used for being connected with the reference power supply; one contact of the first relay is used for connecting CANH _ A of the CANH lead, and the other contact of the first relay is used for connecting CANH _ B of the CANH lead;
one end of a coil of the second relay is connected with the output end of the second display module, and the other end of the coil of the second relay is used for being connected with the reference power supply; one contact of the second relay is used for connecting CANL _ A of the CANL lead wire, and the other contact is used for connecting CANL _ B of the CANL lead wire.
8. The bus fault detection circuit of claim 7, wherein the control unit further comprises a first diode and a second diode;
the anode of the first diode is connected between the output end of the first display module and one end of the coil of the first relay, and the cathode of the first diode is used for connecting the reference power supply; and the anode of the second diode is connected between the output end of the second display module and one end of the coil of the second relay, and the cathode of the second diode is used for being connected with the reference power supply.
9. An on-board OBD device comprising a CAN bus and the bus fault detection circuit of any of claims 1 to 8 connected to the CAN bus.
10. An automobile comprising the on-board OBD device of claim 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121187183.4U CN215575406U (en) | 2021-05-28 | 2021-05-28 | Bus fault detection circuit, on-vehicle OBD equipment and car |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202121187183.4U CN215575406U (en) | 2021-05-28 | 2021-05-28 | Bus fault detection circuit, on-vehicle OBD equipment and car |
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| Publication Number | Publication Date |
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| CN215575406U true CN215575406U (en) | 2022-01-18 |
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| CN202121187183.4U Active CN215575406U (en) | 2021-05-28 | 2021-05-28 | Bus fault detection circuit, on-vehicle OBD equipment and car |
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| Country | Link |
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| CN (1) | CN215575406U (en) |
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- 2021-05-28 CN CN202121187183.4U patent/CN215575406U/en active Active
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