CN216848543U - Diagnostic device with digital-to-analog conversion function - Google Patents

Abstract

The present invention relates to a diagnostic apparatus having a digital-to-analog conversion function. The diagnostic device with digital-to-analog conversion function of the utility model comprises: an OBD interface comprising at least two ports; the digital-to-analog conversion module is electrically connected with the port and is used for converting a digital signal into an analog signal; the first switch module is connected between the port and the digital-to-analog conversion module and is used for controlling the connection and disconnection between the port and the digital-to-analog conversion module; and the control module is electrically connected with the digital-to-analog conversion module and the first switch module respectively. The diagnostic device with the digital-to-analog conversion function can realize digital-to-analog conversion so as to output analog voltage to the OBD pin.

Description

Diagnostic device with digital-to-analog conversion function

Technical Field

The present invention relates to a vehicle diagnostic system, and more particularly, to a diagnostic device having a digital-to-analog conversion function.

Background

OBD is an abbreviation for On-Board Diagnostic in English, the "On-Board Diagnostic System". The system can monitor the running state of the engine and the working state of the exhaust aftertreatment system at any time, and can immediately send out a warning once the condition that the emission possibly exceeds the standard is found. When the system has a fault, a fault lamp (MIL) or a Check Engine (Check Engine) warning lamp is turned on, meanwhile, the OBD system stores fault information into a memory, and relevant information can be read in the form of fault codes through an external diagnostic device and a diagnostic interface (OBD I, OBDII). According to the prompt of the fault code, the maintenance personnel can check relevant parts, components and circuits in a targeted manner, and the nature and the part of the fault can be determined quickly and accurately.

At present, when a vehicle OBD is turned on and an OBD information diagnosis is performed on the vehicle by a vehicle diagnostic apparatus, the protocol type of a specific Electronic Control Unit (ECU) system on the vehicle is usually determined by sequentially scanning various vehicle communication protocols, for example, scanning is performed according to the sequence of a Controller Area Network (CAN) protocol, a Pulse Width Modulation (PWM) protocol, a Variable Pulse Width Modulation (VPW) protocol, a KWP protocol, and an ISO9141 protocol, if an ECU system using the KWP protocol as a communication protocol and an ECU system using the ISO9141 protocol as a communication protocol are provided on the vehicle, the KWP protocol and the ISO protocol are scanned after all the scan of the CAN protocol, the PWM protocol, and the VPW protocol is completed, and it is determined that an ECU system using the KWP protocol as a communication protocol and a system using the ISO9141 protocol as a communication protocol are provided on the vehicle, and then, the KWP protocol and the ISO9141 protocol are respectively used for communicating with the corresponding ECU system, so that the diagnosis of the OBD information of the vehicle is realized.

At present, a vehicle diagnostic apparatus needs to output an analog voltage to an OBD pin, and in order to solve the technical problem, the applicant designs a diagnostic apparatus having a digital-to-analog conversion function to achieve the purpose of outputting an analog voltage to the OBD pin.

SUMMERY OF THE UTILITY MODEL

In view of the above, an object of the present invention is to provide a diagnostic apparatus having a digital-to-analog conversion function, which can perform digital-to-analog conversion to output an analog voltage to an OBD pin.

A diagnostic device having digital-to-analog conversion functionality, the diagnostic device comprising: an OBD interface comprising at least two ports; the digital-to-analog conversion module is electrically connected with the port and is used for converting a digital signal into an analog signal; the first switch module is connected between the port and the digital-to-analog conversion module and is used for controlling the connection and disconnection between the port and the digital-to-analog conversion module; and the control module is electrically connected with the digital-to-analog conversion module and the first switch module respectively.

Furthermore, the first switch module includes a first controlled switch and a second controlled switch, a controlled end of the first controlled switch is electrically connected to the control module, an output end or an input end of the first controlled switch is electrically connected to a controlled end of the second controlled switch, an input end of the second controlled switch is electrically connected to the digital-to-analog conversion module, and an output end of the second controlled switch is electrically connected to the port.

Further, the first controlled switch is a triode, and the second controlled switch is a triode.

Further, the digital-to-analog conversion module includes: the output end of the linear voltage stabilizer is electrically connected with the port; the voltage output end of the DC-DC converter is electrically connected with the voltage input end of the linear voltage stabilizer; the input end of the digital potentiometer is electrically connected with the control module, and the output end of the digital potentiometer is electrically connected with the resistance adjusting end of the linear voltage stabilizer.

Further, the linear voltage regulator is a low-voltage linear voltage regulator.

Further, the DC-DC converter is used for boosting the system voltage to be more than 20V.

Furthermore, the diagnostic apparatus further includes a second switch module and an internal DC power supply, an input terminal of the second switch module is electrically connected to the internal DC power supply, an output terminal of the second switch module is electrically connected to an input terminal of the DC-DC converter, and a controlled terminal of the second switch module is electrically connected to the control module.

Further, the second switch module includes a third controlled switch and a fourth controlled switch, a controlled end of the third controlled switch is electrically connected to the control module, an output end or an input end of the third controlled switch is electrically connected to a controlled end of the fourth controlled switch, an input end of the fourth controlled switch is electrically connected to the internal DC power supply, and an output end of the fourth controlled switch is electrically connected to an input end of the DC-DC converter.

Further, the third controlled switch is a triode, and the fourth controlled switch is a triode.

Further, the diagnostic device further comprises a first power supply module, wherein the first power supply module is used for supplying power to the control module or the digital potentiometer; the first power supply module comprises a first switch circuit and a voltage reduction circuit, wherein a controlled end of the first switch circuit is electrically connected with the control module, an output end of the first switch circuit is electrically connected with an input end of the voltage reduction circuit, and an output end of the voltage reduction circuit is electrically connected with the control module or the digital potentiometer; the first switch circuit comprises a fifth controlled switch and a sixth controlled switch, wherein a controlled end of the fifth controlled switch is electrically connected with the control module, an output end or an input end of the fifth controlled switch is electrically connected with a controlled end of the sixth controlled switch, and an output end of the sixth controlled switch is electrically connected with an input end of the voltage reduction circuit; the fifth controlled switch is a triode, and the sixth controlled switch is an MOS (metal oxide semiconductor) tube; the voltage reduction circuit comprises a first voltage reduction unit, a first filtering unit, a second filtering unit, a third filtering unit and a fourth filtering unit, the output end of the first switch circuit sequentially passes through the first filtering unit and the second filtering unit and then is electrically connected with the input end of the first voltage reduction unit, and the output end of the first voltage reduction unit sequentially passes through the third filtering unit and the fourth filtering unit and then is electrically connected with the control module or the digital potentiometer; the first filtering unit comprises a first common mode choke coil, the input end of the first common mode choke coil is electrically connected with the output end of the first switching circuit, and the output end of the first common mode choke coil is electrically connected with the input end of the second filtering unit; the second filtering unit comprises a first capacitor and a second capacitor, the first capacitor and the second capacitor are sequentially connected between the output end of the first filtering unit and the input end of the first voltage reduction unit, and two ends of the first capacitor and two ends of the second capacitor are both connected between the output end of the first filtering unit and a ground end in parallel; the third filtering unit comprises a third capacitor, a fourth capacitor and a fifth capacitor, the third capacitor, the fourth capacitor and the fifth capacitor are sequentially connected between the output end of the first voltage reduction unit and the input end of the fourth filtering unit, and two ends of the third capacitor, the fourth capacitor and the fifth capacitor are all connected between the output end of the first voltage reduction unit and a ground end in parallel; the fourth filtering unit comprises a second common mode choke coil, the input end of the second common mode choke coil is electrically connected with the output end of the third filtering unit, and the output end of the second common mode choke coil is electrically connected with the control module or the digital potentiometer; the diagnosis device further comprises a second power supply module, wherein the second power supply module is used for supplying power to the first power supply module; a power supply pin is arranged on the OBD interface; the second power supply module comprises a second voltage reduction unit, a fifth filtering unit, a sixth filtering unit, a seventh filtering unit and an eighth filtering unit, the power supply pin sequentially passes through the fifth filtering unit and the sixth filtering unit and then is electrically connected with the input end of the second voltage reduction unit, and the output end of the second voltage reduction unit sequentially passes through the seventh filtering unit and the eighth filtering unit and then is electrically connected with the input end of the first switch circuit; the fifth filtering unit comprises a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor and a tenth capacitor, the sixth capacitor, the seventh capacitor, the eighth capacitor, the ninth capacitor and the tenth capacitor are sequentially connected between the power supply pin and the input end of the sixth filtering unit, and two ends of the sixth capacitor, the seventh capacitor, the eighth capacitor, the ninth capacitor and the tenth capacitor are all bridged between the anode and the cathode of the OBD interface; the sixth filtering unit comprises a third common mode choke, an input end of the third common mode choke is electrically connected with an output end of the fifth filtering unit, and an output end of the third common mode choke is electrically connected with an input end of the second voltage reducing unit; the seventh filtering unit comprises a fourth common mode choke, an input end of the fourth common mode choke is electrically connected with an output end of the second voltage reduction unit, and an output end of the fourth common mode choke is electrically connected with an input end of the eighth filtering unit; the eighth filtering unit comprises an eleventh capacitor, a twelfth capacitor, a thirteenth capacitor, a fourteenth capacitor, a fifteenth capacitor and a sixteenth capacitor, the eleventh capacitor, the twelfth capacitor, the thirteenth capacitor, the fourteenth capacitor, the fifteenth capacitor and the sixteenth capacitor are all connected between the output end of the seventh filtering unit and the input end of the first switch circuit, and two ends of the eleventh capacitor, the twelfth capacitor, the thirteenth capacitor, the fourteenth capacitor, the fifteenth capacitor and the sixteenth capacitor are all connected in parallel between the output end of the seventh filtering unit and the ground end; the second power supply module further comprises a ninth filtering unit, the ninth filtering unit is arranged between the sixth filtering unit and the second voltage reduction unit, and the ninth filtering unit is arranged between the internal direct current power supply and the second voltage reduction unit; the ninth filtering unit comprises a seventeenth capacitor, an eighteenth capacitor, a nineteenth capacitor, a twentieth capacitor and a twenty-first capacitor, wherein the seventeenth capacitor, the eighteenth capacitor, the nineteenth capacitor, the twentieth capacitor and the twenty-first capacitor are connected between the internal direct-current power supply and the second voltage reduction unit, the seventeenth capacitor, the eighteenth capacitor, the nineteenth capacitor, the twentieth capacitor and the twenty-first capacitor are connected between the sixth filtering unit and the second voltage reduction unit, and the seventeenth capacitor, the eighteenth capacitor, the nineteenth capacitor, the twentieth capacitor and the twenty-first capacitor are connected between the input end and the grounding end of the second voltage reduction unit in parallel.

For a better understanding and practice, the present invention is described in detail below with reference to the accompanying drawings.

Drawings

FIG. 1 is a schematic view of a diagnostic device according to an embodiment;

FIG. 2 is a circuit diagram of a first switch module according to an embodiment;

fig. 3 is a circuit schematic diagram of a digital-to-analog conversion module and a second switch module according to an embodiment;

FIG. 4 is a schematic circuit diagram of a first power module according to an embodiment;

FIG. 5 is a schematic circuit diagram of a second power module according to an embodiment;

reference numerals:

1. an OBD interface; 11. a port; 12. a power supply pin; 2. a first switch module; q11, a first controlled switch; q10, a second controlled switch; 3. a digital-to-analog conversion module; u13, linear regulator; u14, DC-DC converter; u15, digital potentiometer; 4. a control module; 5. a second switch module; q8, a third controlled switch; q7, a fourth controlled switch; 6. a first power supply module; 61. a first switching circuit; q3, a fifth controlled switch; q2, a sixth controlled switch; 62. a voltage reduction circuit; u11, a first voltage reduction unit; l7, a first common mode choke; c49, a first capacitance; c51, a second capacitor; c50, a third capacitance; c52, a fourth capacitance; c53, a fifth capacitance; l8, a second common mode choke; 7. a second power supply module; u1, a second voltage reduction unit; c2, a sixth capacitor; c3, a seventh capacitance; c6, an eighth capacitor; c7, ninth capacitance; c8, tenth capacitance; l2, a third common mode choke; l1, a fourth common mode choke; c12, an eleventh capacitor; c13, twelfth capacitor; c14, a thirteenth capacitor; c15, fourteenth capacitance; c16, fifteenth capacitance; c17, sixteenth capacitance; c4, seventeenth capacitance; c5, eighteenth capacitor; c9, nineteenth capacitance; c10, twentieth capacitance; c11, twenty-first capacitance; 8. an internal DC power supply.

Detailed Description

A diagnostic apparatus with digital-to-analog conversion function, see fig. 1 to 3, includes an OBD interface 1, a first switch module 2, a digital-to-analog conversion module 3, and a control module 4. The OBD interface 1 is used for being connected to an automobile fault diagnosis seat located on an automobile, and the OBD interface 1 is provided with a plurality of ports 11. Digital-to-analog conversion module 3 is through first switch module 2 with 11 electric connection of port with OBD interface 1, digital-to-analog conversion module 3 is used for converting digital signal into analog signal, first switch module 2 is used for controlling digital-to-analog conversion module 3 and the break-make of OBD interface 1's port 11. The control module 4 is electrically connected to the first switch module 2 and the digital-to-analog conversion module 3, and the control module 4 is configured to control the first switch module 2 and input digital signals to the digital-to-analog conversion module 3.

The using process comprises the following steps: firstly, a user sets the control module 4 to control the conduction of the first switch module 2 according to requirements, so that the output end of a digital-to-analog conversion signal is communicated with a certain port 11 of the OBD interface 1; then, the control module 4 sends a digital signal to the digital-to-analog conversion module 3; finally, the digital-to-analog conversion signal converts the digital signal into an analog signal, and transmits the analog signal to the port 11 of the OBD interface 1 through the first switch module 2.

Specifically, the first switch module 2 includes at least one controlled switch, which may be an optocoupler, a triode, a MOS transistor, or the like. More specifically, the first switch module 2 includes a first controlled switch Q11 and a second controlled switch Q10, a controlled terminal of the first controlled switch Q11 is electrically connected to the control module 4, an output terminal or an input terminal of the first controlled switch Q11 is electrically connected to a controlled terminal of the second controlled switch Q10, an input terminal of the second controlled switch Q10 is electrically connected to an output terminal of the digital-to-analog conversion module 3, and an output terminal of the second controlled switch Q10 is electrically connected to the port 11 of the OBD interface 1; the first controlled switch Q11 is a transistor, and the second controlled switch Q10 is a transistor.

Specifically, referring to fig. 3, the digital-to-analog conversion module 3 includes a linear voltage regulator U14, a DC-DC converter U13, and a digital potentiometer U15. The output end of the DC-DC converter U13 is electrically connected with the voltage input end of the linear voltage regulator U14, and the DC-DC converter U13 is used for boosting the system voltage to be more than 20V. The input end of the digital potentiometer U15 is electrically connected with the control module 4, the output end of the digital potentiometer U15 is electrically connected with the voltage regulation end of the linear voltage regulator U14, the digital potentiometer U15 is used as the voltage regulation end resistor of the linear voltage regulator U14, and the control module 4 is used for setting the resistance value of the voltage regulation end resistor of the linear voltage regulator U14, so that the purpose of controlling the output analog voltage of the linear voltage regulator U14 is achieved. In this embodiment, the linear regulator U14 is a low voltage linear regulator U14, which can effectively reduce the heat generated by the linear regulator U14, and the low voltage linear regulator U14 may adopt LP2952, LP2953, etc.; the DC-DC converter U13 may adopt LT3580EMS8E, etc.; the digital potentiometer U15 may be an AD5231BRU10 or the like.

Specifically, the control module 4 includes, but is not limited to, one or a combination of any of an MCU, an MPU, a DPU, a CPU, an ASIC, and the like.

Referring to fig. 1 and 3, the diagnostic apparatus further comprises a second switch module 5. The second switch module 5 is used for controlling the on-off of the system power supply and the DC-DC converter U13. The input end of the second switch module 5 is used for accessing a system power supply, the output end of the second switch module 5 is electrically connected with the input end of the DC-DC converter U13, and the controlled end of the second switch module 5 is electrically connected with the control module 4. After the control module 4 sends a control signal to the second switch module 5, the second switch module 5 is turned on, and the system power supplies power to the DC-DC converter U13. The second switch module 5 includes at least one controlled switch, which may be an optocoupler, a triode, a MOS transistor, or the like. More specifically, the second switch module 5 includes a third controlled switch Q8 and a fourth controlled switch Q7, the controlled terminal of the third controlled switch Q8 is electrically connected to the control module 4, the output terminal or the input terminal of the third controlled switch Q8 is electrically connected to the controlled terminal of the fourth controlled switch Q7, the input terminal of the fourth controlled switch Q7 is electrically connected to the system power supply, and the output terminal of the fourth controlled switch Q7 is electrically connected to the input terminal of the DC-DC converter U13; the third controlled switch Q8 is a transistor, and the fourth controlled switch Q7 is a transistor.

Referring to fig. 1 and 4, the diagnostic apparatus further includes a first power supply module 6, where the first power supply module 6 is configured to supply power to the control module 4 and the digital potentiometer U15. The first power supply module 6 includes a first switch circuit 61 and a voltage dropping circuit 62, a controlled end of the first switch circuit 61 is electrically connected to the control module 4, an input end of the first switch circuit 61 is used for accessing an external dc power supply, an output end of the first switch circuit 61 is electrically connected to an input end of the voltage dropping circuit 62, and an output end of the voltage dropping circuit 62 is electrically connected to the control module 4 and the digital potentiometer U15 respectively. When the control module 4 sends a control signal to the first switch circuit 61, the first switch circuit 61 is turned on, and the external dc power supply is stepped down by the step-down circuit 62 to supply power to the control module 4 and the digital potentiometer U15.

Specifically, the first switch circuit 61 includes at least one controlled switch, which may be an optocoupler, a triode, a MOS transistor, or the like. More specifically, the first switch circuit 61 includes a fifth controlled switch Q3 and a sixth controlled switch Q2, a controlled terminal of the fifth controlled switch Q3 is electrically connected to the control module 4, an output terminal or an input terminal of the fifth controlled switch Q3 is electrically connected to a controlled terminal of the sixth controlled switch Q2, an input terminal of the sixth controlled switch Q2 is used for accessing an external dc power supply, and an output terminal of the sixth controlled switch Q2 is electrically connected to an input terminal of the step-down circuit 62; the fifth controlled switch Q3 is a triode, and the sixth controlled switch Q2 is a MOS transistor.

Specifically, the voltage dropping circuit 62 is configured to drop the voltage of the external dc power supply to a voltage suitable for the control module 4 and the digital potentiometer U15 to operate, and in this embodiment, the voltage dropping circuit 62 drops the voltage of 5V of the external dc power supply to a voltage of 3.3V. The voltage reducing circuit 62 includes a first voltage reducing unit U11, a first filtering unit, a second filtering unit, a third filtering unit, and a fourth filtering unit. The output end of the first switch circuit 61 sequentially passes through the first filtering unit and the second filtering unit and then is electrically connected to the input end of the first voltage reduction unit U11, and the output end of the first voltage reduction unit U11 sequentially passes through the third filtering unit and the fourth filtering unit and then is electrically connected to the control module 4 and the digital potentiometer U15.

More specifically, the first voltage reduction unit U11 may employ a voltage reduction chip such as AMS 1117.

More specifically, the first filtering unit suppresses high-frequency noise and spike interference on the signal line and the power line, and also has an effect of absorbing electrostatic pulses. The first filtering unit includes at least one common mode choke coil connected between the output terminal of the first switching circuit 61 and the input terminal of the first voltage dropping unit U11. In the embodiment, the first filtering unit includes a first common mode choke L7, an input terminal of the first common mode choke L7 is electrically connected to an output terminal of the first switch circuit 61, and an output terminal of the first common mode choke L7 is electrically connected to an input terminal of the second filtering unit. The first common mode choke L7 is composed of two identical coils wound in opposite directions on a core, and when a load current passes through the first common mode choke L7, magnetic lines generated by the coils connected in series on the positive line and the negative line are opposite in direction, and they cancel each other in the core. Therefore, even in the case of a large load current, the magnetic core is not saturated. For common-mode interference current, the magnetic fields generated by the two coils are in opposite directions, and larger inductance is presented, so that the common-mode interference signal is attenuated.

More specifically, the second filtering unit is configured to decouple and filter the output voltage of the first switch circuit 61, so as to stabilize the input voltage to the first voltage-reducing unit U11. The second filtering unit includes at least one capacitor, the capacitor is connected between the output terminal of the first switching circuit 61 and the input terminal of the first voltage dropping unit U11, and the capacitor is connected in parallel between the output terminal of the first switching circuit 61 and the ground terminal. In this embodiment, the second filtering unit includes a first capacitor C49 and a second capacitor C51, wherein the first capacitor C49 and the second capacitor C51 are sequentially connected between the output end of the first filtering unit and the output end of the first voltage-dropping unit U11, and both ends of the first capacitor C49 and the second capacitor C51 are connected in parallel between the output end of the first filtering unit and the ground end.

More specifically, the third filtering unit is used for decoupling and filtering the output voltage of the first voltage reducing unit U11 to be stably input to the control module 4 and the digital potentiometer U15. The third filtering unit includes at least one capacitor, the capacitor is connected between the output end of the first voltage-reducing unit U11 and the input end of the control module 4, the capacitor is connected between the output end of the first voltage-reducing unit U11 and the input end of the digital potentiometer U15, and the capacitor is connected in parallel between the output end of the first voltage-reducing unit U11 and the ground end. In this embodiment, the third filtering unit includes a third capacitor C50, a fourth capacitor C52, and a fifth capacitor C53, wherein the third capacitor C50, the fourth capacitor C52, and the fifth capacitor C53 are sequentially connected between the output end of the first voltage-reducing unit U11 and the output end of the fourth filtering unit, and both ends of the third capacitor C50, the fourth capacitor C52, and the fifth capacitor C53 are all connected in parallel between the output end of the first voltage-reducing unit U11 and the ground end.

More specifically, the fourth filtering unit is used for suppressing high-frequency noise and spike interference on the signal line and the power line and has the function of absorbing electrostatic pulses. The fourth filtering unit includes at least one common mode choke coil connected between the output terminal of the first voltage dropping unit U11 and the input terminal of the control module 4 or the digital potentiometer U15. In this embodiment, the fourth filtering unit includes a second common mode choke L8, an input terminal of the second common mode choke L8 is electrically connected to an output terminal of the third filtering unit, and an output terminal of the second common mode choke L8 is electrically connected to the control module 4 and an input terminal of the digital potentiometer U15, respectively. The second common mode choke L8 is composed of two identical coils wound in opposite directions around a core, and when a load current passes through the second common mode choke L8, the magnetic lines of force generated by the coils connected in series to the positive line and the magnetic lines of force generated by the coils connected in series to the negative line are opposite in direction, and they cancel each other in the core. Therefore, even in the case of a large load current, the magnetic core is not saturated. For common-mode interference current, the magnetic fields generated by the two coils are in opposite directions, and larger inductance is presented, so that the common-mode interference signal is attenuated.

Referring to fig. 1 and 5, the diagnostic apparatus further includes a second power supply module 7, where the second power supply module 7 is used to provide a dc power supply for the first power supply module 6. The OBD interface 1 is provided with a power supply pin 12. The second power supply module 7 includes a second voltage reduction unit U1, a fifth filtering unit, a sixth filtering unit, a seventh filtering unit, and an eighth filtering unit. The power pin 12 of the OBD interface 1 sequentially passes through the fifth filtering unit and the sixth filtering unit to be electrically connected to the input terminal of the second voltage-reducing unit U1, and the output terminal of the second voltage-reducing unit U1 sequentially passes through the seventh filtering unit and the eighth filtering unit to be electrically connected to the input terminal of the first switch circuit 61 of the first power supply module 6.

Specifically, after the vehicle fault diagnosis seat on the vehicle with the OBD interface 1 is mounted, the 12V voltage or the 24V voltage output by the vehicle power supply can be connected to the diagnosis device through the power pin 12.

Specifically, the second voltage reduction unit U1 is configured to reduce the voltage input by the external power source through the power pin 12 of the OBD interface 1, and in this embodiment, the second voltage reduction unit U1 reduces the voltage input by the external power source through the power pin 12 of the OBD interface 1 to 5V. The second pressure reducing unit U1 may be a TPS54380 or the like.

Specifically, the fifth filtering unit is configured to decouple and filter the voltage from the power pin 12 to stabilize the input value of the second voltage-reducing unit U1. The fifth filtering unit includes at least one capacitor, the capacitor is connected between the power supply pin 12 of the OBD interface 1 and the input end of the second voltage reduction unit U1, and the capacitor is connected in parallel between the power supply pin 12 of the OBD interface 1 and the ground. In this embodiment, the fifth filtering unit includes a sixth capacitor C2, a seventh capacitor C3, an eighth capacitor C6, a ninth capacitor C7, and a tenth capacitor C8, where the sixth capacitor C2, the seventh capacitor C3, the eighth capacitor C6, the ninth capacitor C7, and the tenth capacitor C8 are sequentially connected between the power pin 12 of the OBD interface 1 and the input end of the sixth filtering unit, and two ends of the sixth capacitor C2, the seventh capacitor C3, the eighth capacitor C6, the ninth capacitor C7, and the tenth capacitor C8 are connected across between the positive electrode and the negative electrode of the power pin 12 of the OBD interface 1.

Specifically, the sixth filtering unit is used for filtering the electromagnetic interference signal of the common mode. The sixth filtering unit includes a third common mode choke L2, an input terminal of the third common mode choke L2 is electrically connected to an output terminal of the fifth filtering unit, and an output terminal of the third common mode choke L2 is electrically connected to an input terminal of the second voltage dropping unit U1. The third common mode choke L2 is composed of two identical coils wound in opposite directions around a core, and when a load current passes through the third common mode choke L2, the magnetic lines of force generated by the coils connected in series to the positive line and the magnetic lines of force generated by the coils connected in series to the negative line are opposite in direction, and they cancel each other in the core. Therefore, even in the case of a large load current, the magnetic core is not saturated. For common-mode interference current, the magnetic fields generated by the two coils are in opposite directions, and larger inductance is presented, so that the common-mode interference signal is attenuated.

Specifically, the seventh filtering unit is configured to perform a suppression process of high-frequency noise and spike interference on the voltage output by the second voltage-reducing unit U1. The seventh filtering unit includes a fourth common mode choke L1, an input terminal of the fourth common mode choke L1 is electrically connected to an output terminal of the second voltage dropping unit U1, and an output terminal of the fourth common mode choke L1 is electrically connected to an input terminal of the eighth filtering unit.

Specifically, the eighth filtering unit is configured to decouple and filter the output voltage of the second voltage-reducing unit U1, so as to stabilize the input voltage to the first power supply module 6. The eighth filtering unit includes at least one capacitor, the capacitor is connected between the seventh filtering unit and the input end of the first power supply module 6, and the capacitor is connected between the output end of the seventh filtering unit and the ground end in parallel. In this embodiment, the eighth filtering unit includes an eleventh capacitor C12, a twelfth capacitor C13, a thirteenth capacitor C14, a fourteenth capacitor C15, a fifteenth capacitor C16, and a sixteenth capacitor C17, wherein the eleventh capacitor C12, the twelfth capacitor C13, the thirteenth capacitor C14, the fourteenth capacitor C15, the fifteenth capacitor C16, and the sixteenth capacitor C17 are all connected between the output end of the seventh filtering unit and the input end of the first power supply module 6, and two ends of the eleventh capacitor C12, the twelfth capacitor C13, the thirteenth capacitor C14, the fourteenth capacitor C15, the fifteenth capacitor C16, and the sixteenth capacitor C17 are all connected in parallel between the output end of the seventh filtering unit and the ground end.

After the OBD interface 1 is inserted into an automobile fault diagnosis seat of an automobile, the 12V voltage of the OBD interface 1 is subjected to decoupling filtering processing by a sixth capacitor C2, a seventh capacitor C3, an eighth capacitor C6, a ninth capacitor C7 and a tenth capacitor C8, and then is subjected to common-mode electromagnetic interference signal filtering by a third common-mode choke coil L2, so that a stable voltage is input to the second voltage reduction unit U1; then, the voltage of 5V is output through the voltage reduction processing of the second voltage reduction unit U1, the voltage of 5V firstly passes through the fourth common mode choke coil L1 to suppress high frequency noise and spike interference, and then passes through the decoupling filtering processing of the eleventh capacitor C12, the twelfth capacitor C13, the thirteenth capacitor C14, the fourteenth capacitor C15, the fifteenth capacitor C16, and the sixteenth capacitor C17, so that the automotive power supply can output a stable voltage of 5V to the electronic components of the diagnostic apparatus, and reliable and stable power supply is provided.

Referring to fig. 1 and 5, the diagnostic device further comprises an internal dc power supply 8. The second power supply module 7 includes a ninth filtering unit. The internal direct-current power supply 8 is electrically connected with the second switch module 5 and the second power supply module 7 respectively, and the internal direct-current power supply 8 supplies power to the second switch module 5 and the second power supply module 7; in this embodiment, the internal dc power supply 8 provides 12V to the second power supply module 7, and the internal dc power supply 8 may be a lithium battery or the like. The ninth filtering unit is used for decoupling and filtering the output voltage of the OBD interface 1 or the internal dc power supply 8. The ninth filtering unit includes at least one capacitor, the capacitor is connected between the internal dc power supply 8 and the second voltage-reducing unit U1, the capacitor is connected between the sixth filtering unit and the second voltage-reducing unit U1, and the capacitor is connected in parallel between the input end of the second voltage-reducing unit U1 and the ground end; in this embodiment, the ninth filtering unit includes a seventeenth capacitor C4, an eighteenth capacitor C5, a nineteenth capacitor C9, a twentieth capacitor C10 and a twenty-first capacitor C11, wherein the seventeenth capacitor C4, the eighteenth capacitor C5, the nineteenth capacitor C9, the twentieth capacitor C10 and the twenty-first capacitor C11 are all connected between the internal dc power supply 8 and the second voltage-dropping unit U1, the seventeenth capacitor C4, the eighteenth capacitor C5, the nineteenth capacitor C9, the twentieth capacitor C10 and the twenty-first capacitor C11 are all connected between the sixth filtering unit and the second voltage-dropping unit U1, and the seventeenth capacitor C4, the eighteenth capacitor C5, the nineteenth capacitor C9, the twentieth capacitor C10 and the twenty-first capacitor C11 are all connected between the input end of the second voltage-dropping unit U1 and the ground end.

In addition, it should be noted that the input voltage of the OBD interface 1 and the input voltage of the internal dc power supply 8 are not simultaneously connected to the second power supply module 7. Moreover, the internal dc power supply 8 also supplies power to the second switch module 5, and specifically, the internal dc power supply 8 is electrically connected to the input end of the second switch module 5.

After the OBD interface 1 is inserted into an automobile fault diagnosis seat of an automobile, the 12V voltage of the OBD interface 1 is subjected to decoupling filtering processing by a sixth capacitor C2, a seventh capacitor C3, an eighth capacitor C6, a ninth capacitor C7 and a tenth capacitor C8, then a common-mode electromagnetic interference signal is filtered by a third common-mode choke coil L2, and further subjected to decoupling filtering processing by a seventeenth capacitor C4, an eighteenth capacitor C5, a nineteenth capacitor C9, a twentieth capacitor C10 and a twenty-first capacitor C11, so that a stable voltage is input to the second voltage reduction unit U1; then, the voltage of 5V is output through the voltage reduction processing of the second voltage reduction unit U1, the voltage of 5V firstly passes through the fourth common mode choke coil L1 to suppress high frequency noise and spike interference, and then passes through the decoupling filtering processing of the eleventh capacitor C12, the twelfth capacitor C13, the thirteenth capacitor C14, the fourteenth capacitor C15, the fifteenth capacitor C16, and the sixteenth capacitor C17, so that the automobile power supply can output a stable voltage of 5V to the electronic components of the diagnostic apparatus, and reliable and stable power supply is provided.

When the input voltage of the internal dc power supply 8 is connected to the second power supply module 7, the 12V voltage of the internal dc power supply 8 passes through decoupling filtering processing of a seventeenth capacitor C4, an eighteenth capacitor C5, a nineteenth capacitor C9, a twentieth capacitor C10 and a twenty-first capacitor C11, so as to input a stable voltage to the second voltage reduction unit U1; then, the voltage of 5V is output through the voltage reduction processing of the second voltage reduction unit U1, the voltage of 5V firstly passes through the fourth common mode choke coil L1 to suppress high frequency noise and spike interference, and then passes through the decoupling filtering processing of the eleventh capacitor C12, the twelfth capacitor C13, the thirteenth capacitor C14, the fourteenth capacitor C15, the fifteenth capacitor C16, and the sixteenth capacitor C17, so that the automobile power supply can output a stable voltage of 5V to the electronic components of the diagnostic apparatus, and reliable and stable power supply is provided.

The above-mentioned embodiments only express several embodiments of the present invention, 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 inventive concept, which falls within the scope of the present invention.

Claims (10)

1. A diagnostic apparatus having a digital-to-analog conversion function, the diagnostic apparatus comprising:

an OBD interface (1), said OBD interface (1) comprising at least two ports (11);

the digital-to-analog conversion module (3), the digital-to-analog conversion module (3) is electrically connected with the port (11), and the digital-to-analog conversion module (3) is used for converting a digital signal into an analog signal;

the first switch module (2), the first switch module (2) is connected between the port (11) and the digital-to-analog conversion module (3), and the first switch module (2) is used for controlling the connection and disconnection between the port (11) and the digital-to-analog conversion module (3);

the control module (4), the control module (4) respectively with digital-to-analog conversion module (3), first switch module (2) electric connection.

2. The diagnostic apparatus having a digital-to-analog conversion function according to claim 1, wherein: the first switch module (2) comprises a first controlled switch (Q11) and a second controlled switch (Q10), the controlled end of the first controlled switch (Q11) is electrically connected with the control module (4), the output end or the input end of the first controlled switch (Q11) is electrically connected with the controlled end of the second controlled switch (Q10), the input end of the second controlled switch (Q10) is electrically connected with the digital-to-analog conversion module (3), and the output end of the second controlled switch (Q10) is electrically connected with the port (11).

3. The diagnostic apparatus having a digital-to-analog conversion function according to claim 2, wherein: the first controlled switch (Q11) is a triode, and the second controlled switch (Q10) is a triode.

4. The diagnostic apparatus with digital-to-analog conversion function according to claim 1, wherein the digital-to-analog conversion module (3) comprises:

a linear regulator (U14), an output terminal of the linear regulator (U14) is electrically connected with the port (11);

a DC-DC converter (U13), a voltage output end of the DC-DC converter (U13) is electrically connected with a voltage input end of the linear voltage regulator (U14);

digital potentiometer (U15), digital potentiometer's (U15) input with control module (4) electric connection, digital potentiometer's (U15) output with linear voltage regulator's (U14) resistance regulation end electric connection.

5. The diagnostic apparatus having a digital-to-analog conversion function according to claim 4, wherein: the linear voltage regulator (U14) is a low-voltage linear voltage regulator (U14).

6. The diagnostic apparatus having a digital-to-analog conversion function according to claim 4, wherein: the DC-DC converter (U13) is used for boosting the system voltage to be more than 20V.

7. The diagnostic apparatus having a digital-to-analog conversion function according to claim 4, wherein: the diagnosis device further comprises a second switch module (5) and an internal direct-current power supply (8), wherein the input end of the second switch module (5) is electrically connected with the internal direct-current power supply (8), the output end of the second switch module (5) is electrically connected with the input end of the DC-DC converter (U13), and the controlled end of the second switch module (5) is electrically connected with the control module (4).

8. The diagnostic apparatus having a digital-to-analog conversion function according to claim 7, wherein: the second switch module (5) comprises a third controlled switch (Q8) and a fourth controlled switch (Q7), wherein a controlled end of the third controlled switch (Q8) is electrically connected with the control module (4), an output end or an input end of the third controlled switch (Q8) is electrically connected with a controlled end of the fourth controlled switch (Q7), an input end of the fourth controlled switch (Q7) is electrically connected with the internal direct-current power supply (8), and an output end of the fourth controlled switch (Q7) is electrically connected with an input end of the DC-DC converter (U13).

9. The diagnostic apparatus having a digital-to-analog conversion function according to claim 8, wherein: the third controlled switch (Q8) is a triode and the fourth controlled switch (Q7) is a triode.

10. The diagnostic apparatus having a digital-to-analog conversion function according to claim 7, wherein:

the diagnosis device further comprises a first power supply module (6), wherein the first power supply module (6) is used for supplying power to the control module (4) or the digital potentiometer (U15);

the first power supply module (6) comprises a first switch circuit (61) and a voltage reduction circuit (62), wherein a controlled end of the first switch circuit (61) is electrically connected with the control module (4), an output end of the first switch circuit (61) is electrically connected with an input end of the voltage reduction circuit (62), and an output end of the voltage reduction circuit (62) is electrically connected with the control module (4) or the digital potentiometer (U15);

the first switch circuit (61) comprises a fifth controlled switch (Q3) and a sixth controlled switch (Q2), a controlled end of the fifth controlled switch (Q3) is electrically connected with the control module (4), an output end or an input end of the fifth controlled switch (Q3) is electrically connected with a controlled end of the sixth controlled switch (Q2), and an output end of the sixth controlled switch (Q2) is electrically connected with an input end of the voltage reduction circuit (62);

the fifth controlled switch (Q3) is a triode, and the sixth controlled switch (Q2) is an MOS (metal oxide semiconductor) transistor;

The voltage reduction circuit (62) comprises a first voltage reduction unit (U11), a first filtering unit, a second filtering unit, a third filtering unit and a fourth filtering unit, the output end of the first switch circuit (61) sequentially passes through the first filtering unit and the second filtering unit and then is electrically connected with the input end of the first voltage reduction unit (U11), and the output end of the first voltage reduction unit (U11) sequentially passes through the third filtering unit and the fourth filtering unit and then is electrically connected with the control module (4) or the digital potentiometer (U15);

the first filtering unit comprises a first common mode choke (L7), an input end of the first common mode choke (L7) is electrically connected with an output end of the first switching circuit (61), and an output end of the first common mode choke (L7) is electrically connected with an input end of the second filtering unit;

the second filtering unit comprises a first capacitor (C49) and a second capacitor (C51), the first capacitor (C49) and the second capacitor (C51) are sequentially connected between the output end of the first filtering unit and the input end of the first voltage reduction unit (U11), and two ends of the first capacitor (C49) and the second capacitor (C51) are both connected in parallel between the output end and the ground end of the first filtering unit;

The third filtering unit comprises a third capacitor (C50), a fourth capacitor (C52) and a fifth capacitor (C53), the third capacitor (C50), the fourth capacitor (C52) and the fifth capacitor (C53) are sequentially connected between the output end of the first voltage reduction unit (U11) and the input end of the fourth filtering unit, and two ends of the third capacitor (C50), the fourth capacitor (C52) and the fifth capacitor (C53) are all connected between the output end of the first voltage reduction unit (U11) and a ground end in parallel;

the fourth filtering unit comprises a second common mode choke (L8), an input end of the second common mode choke (L8) is electrically connected with an output end of the third filtering unit, and an output end of the second common mode choke (L8) is electrically connected with the control module (4) or the digital potentiometer (U15);

the diagnostic device further comprises a second power supply module (7), wherein the second power supply module (7) is used for supplying power to the first power supply module (6);

a power supply pin (12) is arranged on the OBD interface (1);

the second power supply module (7) comprises a second voltage reduction unit (U1), a fifth filtering unit, a sixth filtering unit, a seventh filtering unit and an eighth filtering unit, the power supply pin (12) sequentially passes through the fifth filtering unit and the sixth filtering unit and then is electrically connected with the input end of the second voltage reduction unit (U1), and the output end of the second voltage reduction unit (U1) sequentially passes through the seventh filtering unit and the eighth filtering unit and then is electrically connected with the input end of the first switch circuit (61);

The fifth filtering unit comprises a sixth capacitor (C2), a seventh capacitor (C3), an eighth capacitor (C6), a ninth capacitor (C7) and a tenth capacitor (C8), the sixth capacitor (C2), the seventh capacitor (C3), the eighth capacitor (C6), the ninth capacitor (C7) and the tenth capacitor (C8) are sequentially connected between the power supply pin (12) and the input end of the sixth filtering unit, and two ends of the sixth capacitor (C2), the seventh capacitor (C3), the eighth capacitor (C6), the ninth capacitor (C7) and the tenth capacitor (C8) are connected between the anode and the cathode of the OBD interface (1) in a bridging manner;

the sixth filtering unit comprises a third common mode choke (L2), an input terminal of the third common mode choke (L2) is electrically connected with an output terminal of the fifth filtering unit, and an output terminal of the third common mode choke (L2) is electrically connected with an input terminal of the second voltage reducing unit (U1);

the seventh filtering unit comprises a fourth common mode choke (L1), an input end of the fourth common mode choke (L1) is electrically connected with an output end of the second voltage reduction unit (U1), and an output end of the fourth common mode choke (L1) is electrically connected with an input end of the eighth filtering unit;

The eighth filter unit comprises an eleventh capacitor (C12), a twelfth capacitor (C13), a thirteenth capacitor (C14), a fourteenth capacitor (C15), a fifteenth capacitor (C16) and a sixteenth capacitor (C17), wherein the eleventh capacitor (C12), the twelfth capacitor (C13), the thirteenth capacitor (C14), the fourteenth capacitor (C15), the fifteenth capacitor (C16) and the sixteenth capacitor (C17) are all connected between an output end of the seventh filter unit and an input end of the first switch circuit (61), and two ends of the eleventh capacitor (C12), the twelfth capacitor (C13), the thirteenth capacitor (C14), the fourteenth capacitor (C15), the fifteenth capacitor (C16) and the sixteenth capacitor (C17) are all connected between an output end and a ground end of the seventh filter unit in parallel;

the second power supply module (7) further comprises a ninth filtering unit arranged between the sixth filtering unit and the second voltage reducing unit (U1), the ninth filtering unit being arranged between the internal DC power supply (8) and the second voltage reducing unit (U1);

the ninth filtering unit includes a seventeenth capacitor (C4), an eighteenth capacitor (C5), a nineteenth capacitor (C9), a twentieth capacitor (C10), and a twenty-first capacitor (C11), the seventeenth capacitor (C4), the eighteenth capacitor (C5), the nineteenth capacitor (C9), the twentieth capacitor (C10), and the twenty-first capacitor (C11) are all connected between the internal dc power supply (8) and the second voltage-reducing unit (U1), the seventeenth capacitor (C4), the eighteenth capacitor (C5), the nineteenth capacitor (C9), the twentieth capacitor (C10), and the twenty-first capacitor (C11) are all connected between the sixth filtering unit and the second voltage-reducing unit (U1), the seventeenth capacitor (C4), the eighteenth capacitor (C5), the nineteenth capacitor (C9), and the twentieth capacitor (C10), The twenty-first capacitors (C11) are all connected in parallel between the input end of the second voltage reduction unit (U1) and the ground end.

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