Isolation circuit, automobile diagnostic equipment and automobile diagnostic system

Abstract

The present invention relates to the field of automobile diagnosis, and provides an isolation circuit, automobile diagnostic equipment and automobile diagnostic system. Among them, the isolation circuit includes: a first switch circuit, electrically connected between the OBD connector of the automobile to be diagnosed and the diagnostic device of the automobile diagnostic equipment, and the OBD connector is also electrically connected to the automobile power supply of the automobile to be diagnosed; a switch control circuit, electrically connected to the OBD connector and the first switch circuit respectively, for when it is detected that the OBD connector outputs a positive power signal and the OBD connector outputs a negative power signal, the switch control circuit does not work, so that the first switch circuit works in an off state to keep the diagnostic device not powered on; when it is detected that the OBD connector outputs a positive power signal and the OBD connector outputs a negative power signal, a control signal is output to make the first switch circuit work in an on state, so that the automobile power supply supplies power to the diagnostic device. The embodiment of the present invention can avoid poor grounding and improve the reliability of automobile diagnostic equipment.

Description

[Technical field]

[0001] The embodiments of the present invention relate to the field of automobile diagnosis, and in particular to an isolation circuit, an automobile diagnostic device and an automobile diagnostic system. [Background technology]

[0002] At present, the car diagnostic equipment is connected to the OBD connector of the car to be diagnosed to read the fault code of the car to be diagnosed and locate the location and cause of the fault. However, if the car to be diagnosed uses a non-standard OBD connector, although the car to be diagnosed has no fault, due to the deviation between the design size of the non-standard OBD connector and the design size of the standard OBD connector, it may cause poor grounding when the car diagnostic equipment is connected to the OBD connector, that is, the positive pole of the car power supply is connected to the car diagnostic equipment before the negative pole of the car power supply, causing the fault light on the dashboard of the car to be diagnosed to light up, which is easy to interfere with the judgment of the car maintenance personnel. [Summary of the invention]

[0003] The embodiments of the present invention aim to provide an isolation circuit, an automobile diagnostic device and an automobile diagnostic system, which can avoid poor grounding and improve the reliability of the automobile diagnostic device.

[0004] To solve the above technical problems, the embodiments of the present invention provide the following technical solutions:

[0005] In a first aspect, an embodiment of the present invention provides an isolation circuit, which is applied to an automobile diagnostic device, and the isolation circuit includes:

[0006] A first switch circuit is electrically connected between the OBD connector of the vehicle to be diagnosed and the diagnostic device of the vehicle diagnostic device, and the OBD connector is also electrically connected to the vehicle power supply of the vehicle to be diagnosed;

[0007] The switch control circuit is electrically connected to the OBD connector and the first switch circuit respectively, and is used for not operating the switch control circuit when it is detected that the OBD connector outputs a positive power signal and does not detect that the OBD connector outputs a negative power signal, so that the first switch circuit operates in an off state to keep the diagnostic device from being powered on; and outputting a control signal when it is detected that the OBD connector outputs a positive power signal and detects that the OBD connector outputs a negative power signal, so that the first switch circuit operates in an on state, so that the vehicle power supply powers the diagnostic device.

[0008] Optionally, the automobile power supply includes an automobile power positive electrode and an automobile power negative electrode, the automobile power positive electrode is used to output the power positive electrode signal, the automobile power positive electrode is used to output the power negative electrode signal, and the switch control circuit includes:

[0009] A bias circuit, electrically connected to the positive electrode of the vehicle power supply, for converting the power supply voltage output by the positive electrode of the vehicle power supply into a bias voltage;

[0010] A second switch circuit is electrically connected to the positive electrode of the automobile power supply;

[0011] a step-down chopper circuit, electrically connected to the second switch circuit, the negative electrode of the vehicle power supply and the first switch circuit respectively;

[0012] The controller is electrically connected to the positive electrode of the automobile power supply, the negative electrode of the automobile power supply, the bias circuit, the second switch circuit and the step-down chopper circuit respectively, and is used for not working when it is detected that the OBD connector outputs a positive power supply signal and does not detect that the OBD connector outputs a negative power supply signal; when it is detected that the OBD connector outputs a positive power supply signal and detects that the OBD connector outputs a negative power supply signal, detecting a current detection signal flowing through the second switch circuit, and outputting a pulse width modulation signal according to the bias voltage and the current detection signal to control the working state of the second switch circuit so that the step-down chopper circuit outputs the control signal.

[0013] Optionally, the bias circuit includes a first resistor and a first capacitor;

[0014] One end of the first resistor is connected to the positive electrode of the vehicle power supply, one end of the first capacitor and the second switch circuit, and the other end of the first resistor is connected to the other end of the first capacitor and the controller.

[0015] Optionally, the second switching circuit includes a PMOS tube, a gate of the PMOS tube is connected to the controller, a source of the PMOS tube is connected to the positive electrode of the automobile power supply, and a drain of the PMOS tube is connected to the controller and the step-down chopper circuit.

[0016] Optionally, the step-down chopper circuit includes:

[0017] A freewheeling circuit, electrically connected to the second switch circuit and the negative electrode of the vehicle power supply, and configured to operate in an off state when the second switch circuit operates in an on state, and operate in an on state when the second switch circuit operates in an off state;

[0018] The charging and discharging circuit is electrically connected to the second switch circuit, the freewheeling circuit, the negative electrode of the vehicle power supply and the first switch circuit respectively, and is used to implement charging when the freewheeling circuit is in an off state and to implement discharging when the freewheeling circuit is in an on state, so as to output the control signal and send the control signal to the first switch circuit when the OBD connector outputs a positive power signal and a negative power signal.

[0019] Optionally, the freewheeling circuit includes a diode, an anode of the diode is connected to the negative electrode of the automobile power supply, and a cathode of the diode is connected to the drain of the PMOS tube and the charge and discharge circuit.

[0020] Optionally, the charging and discharging circuit includes an inductor and a second capacitor;

[0021] One end of the inductor is connected to the cathode of the diode and the drain of the PMOS tube, and the other end of the inductor is connected to one end of the second capacitor and the first switch circuit; the other end of the second capacitor is connected to the negative electrode of the car power supply.

[0022] Optionally, the switch control circuit also includes a voltage sampling circuit, which is electrically connected to the negative electrode of the vehicle power supply, the step-down chopper circuit, the first switch circuit and the controller respectively, and is used to sample the control signal so that the controller can feedback and adjust the control signal.

[0023] Optionally, the voltage sampling circuit includes a second resistor and a third resistor;

[0024] One end of the second resistor is connected to the step-down chopper circuit and the first switch circuit, and the other end of the second resistor is connected to one end of the third resistor and the controller; the other end of the third resistor is connected to the negative electrode of the vehicle power supply.

[0025] Optionally, the switch control circuit further includes an input filter circuit electrically connected between the positive electrode of the automobile power supply and the negative electrode of the automobile power supply, for filtering the power supply voltage.

[0026] Optionally, the input filter circuit includes a third capacitor, one end of the third capacitor is connected to the positive electrode of the vehicle power supply, and the other end of the third capacitor is connected to the negative electrode of the vehicle power supply.

[0027] Optionally, the isolation circuit also includes a slow-start circuit, which is electrically connected to the first switch circuit and the diagnostic device respectively, and is used to delay processing of the power supply voltage output by the vehicle power supply when the working state of the first switch circuit is switched to the on state.

[0028] Optionally, the first switch circuit includes:

[0029] A first switch, electrically connected between the positive electrode of the vehicle power supply and the diagnostic device, and also electrically connected to the switch control circuit, for operating in a conducting state according to the control signal;

[0030] The second switch is electrically connected between the negative electrode of the vehicle power supply and the diagnostic device, and is also electrically connected to the switch control circuit, and is used to work in a conducting state according to the control signal.

[0031] In a second aspect, an embodiment of the present invention provides an automobile diagnostic device, comprising:

[0032] An isolation circuit as described in any one of the above items;

[0033] The diagnostic device is electrically connected to the isolation circuit and is also in communication connection with the vehicle to be diagnosed. When the isolation circuit is in an on state, the diagnostic device operates according to the power supply voltage provided by the vehicle power supply of the vehicle to be diagnosed, and obtains the diagnostic data of the vehicle to be diagnosed.

[0034] In a third aspect, an embodiment of the present invention provides an automobile diagnostic system, comprising:

[0035] Automotive diagnostic equipment as described above;

[0036] The host computer is connected to the automobile diagnostic device for displaying the diagnostic data sent by the automobile diagnostic device.

[0037] The beneficial effects of the present invention are as follows: compared with the prior art, the embodiments of the present invention provide an isolation circuit, an automobile diagnostic device and an automobile diagnostic system, which are electrically connected between the OBD connector of the automobile to be diagnosed and the diagnostic device of the automobile diagnostic device through a first switch circuit, the OBD connector is also electrically connected to the automobile power supply of the automobile to be diagnosed, and the switch control circuit is electrically connected to the OBD connector and the first switch circuit respectively, and is used for not operating the switch control circuit when it is detected that the OBD connector outputs a positive power signal and does not detect that the OBD connector outputs a negative power signal, so that the first switch circuit operates in an off state to keep the diagnostic device from being powered on, and outputting a control signal when it is detected that the OBD connector outputs a positive power signal and detects that the OBD connector outputs a negative power signal, so that the first switch circuit operates in an on state to enable the automobile power supply to power the diagnostic device. Therefore, the embodiments of the present invention can avoid poor grounding and improve the reliability of the automobile diagnostic device.

Brief Description of the Drawings

[0038] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0039] Figure 1 A schematic diagram of the structure of an automobile diagnostic system provided by an embodiment of the present invention;

[0040] Figure 2 A schematic diagram of the structure of an automobile diagnostic device provided by an embodiment of the present invention;

[0041] Figure 3 A schematic diagram of the structure of an isolation circuit provided by an embodiment of the present invention;

[0042] Figure 4 A schematic diagram of the structure of an isolation circuit provided by another embodiment of the present invention;

[0043] Figure 5 A schematic diagram of the structure of a switch control circuit provided by an embodiment of the present invention;

[0044] Figure 6 A circuit connection diagram of a switch control circuit provided by an embodiment of the present invention. [Specific implementation method]

[0045] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "connected" to another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. In addition, the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0046] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0047] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0048] See also Figure 1 , is a schematic diagram of the structure of an automobile diagnostic system provided by an embodiment of the present invention. Figure 1As shown, the automobile diagnostic system 500 includes an automobile diagnostic device 300 and a host computer 400 as described in the following device embodiment. The host computer 400 is communicatively connected with the automobile diagnostic device 300 to display the diagnostic data sent by the automobile diagnostic device 300.

[0049] An automobile diagnostic system provided by an embodiment of the present invention avoids the phenomenon of poor grounding through automobile diagnostic equipment, thereby improving diagnostic reliability.

[0050] See also Figure 2 , is a schematic diagram of the structure of an automobile diagnostic device provided by an embodiment of the present invention. Figure 2 As shown, the automobile diagnostic device 300 includes an isolation circuit 100 and a diagnostic device 200 as described in the following circuit embodiment. The diagnostic device 200 is electrically connected to the isolation circuit 100 and is also in communication connection with the automobile to be diagnosed 11, and is used to work according to the power supply voltage provided by the automobile power supply 112 of the automobile to be diagnosed 11 when the isolation circuit 100 is in the on state, and obtain the diagnostic data of the automobile to be diagnosed 11.

[0051] The vehicle to be diagnosed 11 includes an OBD connector 111, a vehicle power supply 112, and an on-board automatic diagnostic system (not shown). The vehicle power supply 112 includes a positive electrode and a negative electrode, the positive electrode is used to output the positive electrode signal, and the positive electrode is used to output the negative electrode signal.

[0052] Inside the car to be diagnosed 11, the OBD connector 111 is electrically connected to the positive pole of the car power supply and the negative pole of the car power supply, respectively. When the car diagnostic device 300 is connected to the car to be diagnosed 11, the OBD connector 111 is electrically connected to the isolation circuit 100 and is communicatively connected to the diagnostic device 200. If the OBD connector 111 is normally connected to the isolation circuit 100, the isolation circuit 100 is used to enable the car power supply 112 to provide power to the diagnostic device 200 through the isolation circuit 100. When the diagnostic device 200 is powered on, the diagnostic data of the car to be diagnosed 11 is obtained through the OBD connector 111; if the OBD connector 111 and the isolation circuit 100 are poorly grounded, the isolation circuit 100 is used to cut off the power supply circuit between the car power supply 112 and the diagnostic device 200 to keep the diagnostic device 200 not powered on.

[0053] The vehicle power supply 112 is used to provide a low-voltage DC power supply (usually 12V for gasoline vehicles and 24V for diesel vehicles) for all electrical devices in the vehicle to be diagnosed 11, so that all parts of the vehicle to be diagnosed 11 can work normally. When the vehicle diagnostic device 300 is connected to the vehicle to be diagnosed 11, the vehicle power supply 112 is also used to provide power for the vehicle diagnostic device 300.

[0054] The on-board automatic diagnostic system is also electrically connected to the OBD connector 111 (not shown) to monitor the vehicle to be diagnosed 11, generate diagnostic data, and, when the diagnostic device 200 is powered on, send the diagnostic data to the diagnostic device 200 through the OBD connector 111.

[0055] Specifically, the positive power signal and the negative power signal reach the isolation circuit 100 through the OBD connector 111. The isolation circuit 100 is used to detect the positive power signal and the negative power signal. When it is detected that the OBD connector 111 outputs a positive power signal and it is not detected that the OBD connector 111 outputs a negative power signal, the diagnostic device 200 is kept unpowered; when it is detected that the OBD connector 111 outputs a positive power signal and it is detected that the OBD connector 111 outputs a negative power signal, the vehicle power supply 112 is used to power the diagnostic device 200.

[0056] An automobile diagnostic device provided by an embodiment of the present invention can avoid poor grounding of the automobile diagnostic device through an isolation circuit, thereby improving the reliability of the automobile diagnostic device.

[0057] See also Figure 3 , is a schematic diagram of the structure of an isolation circuit provided by an embodiment of the present invention. Figure 3 As shown, the isolation circuit 100 is applied to an automobile diagnostic device 300 , and includes a first switch circuit 10 and a switch control circuit 20 .

[0058] The first switch circuit 10 is electrically connected between the OBD connector 111 of the vehicle 11 to be diagnosed and the diagnoser 200 of the vehicle diagnostic device 300 , and the OBD connector 111 is also electrically connected to the vehicle power supply 112 of the vehicle 11 to be diagnosed.

[0059] See also Figure 4 and Figure 5 The first switch circuit 10 includes a first switch 101 and a second switch 102 .

[0060] The first switch 101 is electrically connected between the positive electrode of the vehicle power supply and the diagnostic device 200, and is also electrically connected to the switch control circuit 20, and is used to operate in a conducting state according to the control signal.

[0061] The second switch 102 is electrically connected between the negative electrode of the vehicle power supply and the diagnostic device 200, and is also electrically connected to the switch control circuit 20, and is used to operate in a conducting state according to the control signal.

[0062] In this embodiment, the first switch 101 and the second switch 102 are normally closed switches, which operate in a conducting state according to the control signal, and return to a normally closed state when the controller 204 is not operating.

[0063] It can be understood that when the first switch 101 and the second switch 102 are both operating in the on state, the first switch 101 and the second switch 102 are electrically connected to the positive electrode of the vehicle power supply and the negative electrode of the vehicle power supply respectively through the OBD connector 111 of the vehicle to be diagnosed 11, so that the power supply voltage provided by the vehicle power supply 112 of the vehicle to be diagnosed 11 passes through the OBD connector 111 to reach the first switch 101, the second switch 102 and the switch control circuit 20, thereby providing power for the first switch 101, the second switch 102 and the switch control circuit 20.

[0064] In some embodiments, the first switch 101 and the second switch 102 include a switch circuit composed of a metal-oxide semiconductor field effect transistor, a bipolar transistor, a relay, or other transistors. At this time, when the controller 204 is not working, the output pins of the controller 204 corresponding to the first switch 101 and the second switch 102 are set low, and the switch control circuit 20 does not output a control signal, so that the first switch 101 and the second switch 102 work in an off state; when the controller 204 is working, the output pins of the controller 204 corresponding to the first switch 101 and the second switch 102 output a pulse width modulation signal, and the switch control circuit 20 outputs a control signal, so that the first switch 101 and the second switch 102 work in an on state.

[0065] The switch control circuit 20 is electrically connected to the OBD connector 111 and the first switch circuit 10 respectively, and is used for not working when it is detected that the OBD connector 111 outputs a positive power signal and it is not detected that the OBD connector 111 outputs a negative power signal, so that the first switch circuit 10 works in an off state to keep the diagnostic device 200 not powered on; when it is detected that the OBD connector 111 outputs a positive power signal and it is detected that the OBD connector 111 outputs a negative power signal, outputting a control signal to make the first switch circuit 10 work in an on state, so that the vehicle power supply 112 supplies power to the diagnostic device 200.

[0066] The switch control circuit 20 detects that the OBD connector 111 outputs a positive power signal, and does not detect that the OBD connector 111 outputs a negative power signal, including the following situations: the positive pole of the vehicle power supply is connected to the isolation circuit 100 before the negative pole of the vehicle power supply. The switch control circuit 20 detects that the OBD connector outputs a positive power signal, and detects that the OBD connector outputs a negative power signal, including the following two situations: 1. The positive pole of the vehicle power supply and the negative pole of the vehicle power supply are connected to the isolation circuit 100 at the same time; 2. The positive pole of the vehicle power supply is connected to the isolation circuit 100 after the negative pole of the vehicle power supply.

[0067] It can be seen that when the switch control circuit 20 detects that the OBD connector 111 outputs a positive power signal and does not detect that the OBD connector 111 outputs a negative power signal, at this time, the positive pole of the vehicle power supply provides an input voltage to the switch control circuit 20. Since the switch control circuit 20 is not grounded, the switch control circuit 20 does not work, so that the first switch circuit 10 works in the off state to cut off the power supply circuit between the vehicle power supply 112 and the diagnostic device 200, and keep the diagnostic device 200 unpowered. Next, the connection between the automobile diagnostic device 300 and the OBD connector 111 is manually adjusted, for example, the automobile diagnostic device 300 is replugged, so that when the switch control circuit 20 detects that the OBD connector outputs a positive power signal and detects that the OBD connector outputs a negative power signal, at this time, the positive pole of the automobile power supply provides input voltage to the switch control circuit 20, the switch control circuit 20 is grounded, and the switch control circuit 20 outputs a control signal, so that the first switch circuit 10 works in a conducting state according to the control signal, so that the automobile power supply 112 provides power to the diagnostic device 200 through the isolation circuit 100. Thus, the problem of voltage floating or spark discharge caused by poor grounding is avoided, which causes the automobile 11 to be diagnosed to detect an external high voltage pulse and trigger an alarm.

[0068] Please refer again Figure 5 The switch control circuit 20 includes a bias circuit 201 , a second switch circuit 202 , a step-down chopper circuit 203 , a controller 204 , a voltage sampling circuit 205 and an input filter circuit 206 .

[0069] The bias circuit 201 is electrically connected to the positive electrode of the vehicle power supply and is used to convert the power supply voltage output by the positive electrode of the vehicle power supply into a bias voltage.

[0070] Please also read Figure 6 , the bias circuit 201 includes a first resistor R1 and a first capacitor C1.

[0071] One end of the first resistor R1 is connected to the positive electrode of the car power supply, one end of the first capacitor C1 and the second switch circuit 202 , and the other end of the first resistor R1 is connected to the other end of the first capacitor C1 and the controller 204 .

[0072] The controller 204 includes a constant current source for providing a constant current i, which forms a voltage drop on the first resistor R1, i.e., a bias voltage V, wherein the bias voltage V=R1*i, and the bias voltage V is sent to the controller 204. In addition, the power supply voltage is slowly started under the volume effect of the first resistor R1 and the first capacitor C1, so as to avoid the influence of the peak voltage on the controller 204 and protect the controller 204 from being burned out.

[0073] The second switch circuit 202 is electrically connected to the positive electrode of the vehicle power supply.

[0074] The second switch circuit 202 includes a PMOS tube Q1, a gate of the PMOS tube Q1 is connected to the controller 204, a source of the PMOS tube Q1 is connected to the positive electrode of the car power supply, and a drain of the PMOS tube Q1 is connected to the controller 204 and the step-down chopper circuit 203.

[0075] In some embodiments, the second switch circuit 202 further includes components such as resistors and / or capacitors, which are used to limit the gate-source voltage of the PMOS transistor Q1 to prevent the PMOS transistor Q1 from being broken down due to excessive gate-source voltage.

[0076] The step-down chopper circuit 203 is electrically connected to the second switch circuit 202 , the negative electrode of the vehicle power supply, and the first switch circuit 10 , respectively.

[0077] In this embodiment, the step-down chopper circuit 203 includes a freewheeling circuit 2031 and a charge-discharge circuit 2032 .

[0078] The freewheeling circuit 2031 is electrically connected to the second switch circuit 202 and the negative electrode of the vehicle power supply, and is used for operating the freewheeling circuit 2031 in an off state when the second switch circuit 202 operates in an on state, and operating the freewheeling circuit 2031 in an on state when the second switch circuit 202 operates in an off state.

[0079] like Figure 6 As shown, the freewheeling circuit 2031 includes a diode D1 , an anode of the diode D1 is connected to the negative electrode of the vehicle power supply, and a cathode of the diode D1 is connected to the drain of the PMOS tube Q1 and the charge and discharge circuit 2032 .

[0080] The charge and discharge circuit 2032 is electrically connected to the second switch circuit 202, the freewheeling circuit 2031, the negative pole of the vehicle power supply and the first switch circuit 10 respectively, and is used to implement charging when it is detected that the OBD connector 111 outputs a positive power supply signal and detects that the OBD connector 111 outputs a negative power supply signal, and when the freewheeling circuit 2031 operates in the off state, implement discharging when the freewheeling circuit 2031 operates in the on state, so as to output the control signal and send the control signal to the first switch circuit 10.

[0081] like Figure 6 As shown, the charge and discharge circuit 2032 includes an inductor L1 and a second capacitor C2.

[0082] Among them, one end of the inductor L1 is connected to the cathode of the diode D1 and the drain of the PMOS tube Q1, and the other end of the inductor L1 is connected to one end of the second capacitor C2 and the first switch circuit 10; the other end of the second capacitor C2 is connected to the negative electrode of the car power supply.

[0083] Specifically, the pulse width modulation signal is used to modulate the duty cycle of the PMOS tube Q1. When the PMOS tube Q1 is in the on-time ton period, the diode D1 is reverse biased, and the power supply voltage is charged through the inductor L1 to charge the first switch circuit 10. At this time, the current iL flowing through the inductor L1 increases, and the energy storage of the inductor L1 increases. Assuming that the power supply voltage is E and the voltage across the first switch circuit 10 is u0, there is a forward voltage Ul=E-u0 across the two ends of the inductor L1, and Ul makes the current iL increase linearly. When the PMOS tube Q1 is in the off-time toff period, the inductor L1 generates an induced electromotive force, the diode D1 is turned on, and the current iL continues to flow through the diode D1. At this time, Ul=-u0, the inductor L1 supplies power to the first switch circuit 10, the inductor energy storage is gradually consumed, and the current iL decreases linearly.

[0084] It can be understood that the inductance value of the inductor L1 and the capacitance value of the second capacitor C2 need to be set slightly larger. In this embodiment, when the controller 204 detects that the OBD connector 111 outputs a positive power signal and detects that the OBD connector 111 outputs a negative power signal, it outputs the pulse width modulation signal to modulate the PMOS tube Q1 so that the charge and discharge circuit 2032 outputs the control signal according to the duty cycle of the PMOS tube Q1. Wherein, the control signal is a sine wave signal, and the amplitude of the control signal can be changed by setting the duty cycle of the pulse width modulation signal.

[0085] The controller 204 is electrically connected to the positive electrode of the automobile power supply, the negative electrode of the automobile power supply, the bias circuit 201, the second switch circuit 202 and the step-down chopper circuit 203 respectively, and is used for not working when it is detected that the OBD connector 111 outputs a positive power supply signal and the OBD connector 111 outputs a negative power supply signal; when it is detected that the OBD connector 111 outputs a positive power supply signal and the OBD connector 111 outputs a negative power supply signal, detecting the current detection signal flowing through the second switch circuit 202, and outputting a pulse width modulation signal according to the bias voltage and the current detection signal to control the working state of the second switch circuit 202, so that the step-down chopper circuit 203 outputs the control signal.

[0086] It can be understood that the controller 204 calculates the internal voltage drop of the PMOS transistor Q1 in the controller 204 according to the current detection signal, and the controller 204 outputs a pulse width modulation signal according to the bias voltage and the internal voltage drop of the PMOS transistor Q1.

[0087] In this embodiment, the controller 204 includes a single chip microcomputer, and the single chip microcomputer can be a 51 series, an Arduino series, an STM32 series, etc.

[0088] The single chip microcomputer includes an input pin, an adjustable voltage pin, a current detection pin, an output pin, a power ground pin, a controller ground pin and a feedback pin. The input pin is electrically connected to the positive electrode of the automobile power supply for receiving the power supply voltage; the adjustable voltage pin is electrically connected to the bias circuit 201 for receiving the bias voltage; the current detection pin is electrically connected to the second switch circuit 202 and the step-down chopper circuit 203 for obtaining the current detection signal; the output pin is electrically connected to the second switch circuit 202 for outputting the pulse width modulation signal; the power ground pin is connected to the negative electrode of the automobile power supply; the controller ground pin is connected to the negative electrode of the automobile power supply; the feedback pin is electrically connected to the voltage sampling circuit 205 for receiving the voltage sampling signal sent by the voltage sampling circuit 205.

[0089] In some embodiments, the controller 204 may also be a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), an ARM (Acorn RISC Machine) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination of these components; it may also be any conventional processor, controller, microcontroller, or state machine; it may also be implemented as a combination of computing devices, for example, a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors combined with a DSP core, or any other such configuration.

[0090] The voltage sampling circuit 205 is electrically connected to the negative electrode of the vehicle power supply, the step-down chopper circuit 203 , the first switch circuit 10 and the controller 204 respectively, and is used to sample the control signal so that the controller 204 can feedback and adjust the control signal.

[0091] like Figure 6 As shown, the voltage sampling circuit 205 includes a second resistor R2 and a third resistor R3.

[0092] Among them, one end of the second resistor R2 is connected to the step-down chopper circuit 203 and the first switch circuit 10, and the other end of the second resistor R2 is connected to one end of the third resistor R3 and the controller 204; the other end of the third resistor R3 is connected to the negative electrode of the vehicle power supply.

[0093] Specifically, the second resistor R2 and the third resistor R3 form a voltage divider circuit, which performs voltage division processing on the control signal, outputs a voltage sampling signal, and sends the voltage sampling signal to the controller 204, so that the controller 204 feedback-adjusts the control signal according to the voltage sampling signal.

[0094] The input filter circuit 206 is electrically connected between the positive electrode of the automobile power supply and the negative electrode of the automobile power supply, and is used for filtering the power supply voltage.

[0095] The input filter circuit 206 includes a third capacitor C3, one end of the third capacitor C3 is connected to the positive electrode of the vehicle power supply, and the other end of the third capacitor C3 is connected to the negative electrode of the vehicle power supply. The third capacitor C3 is specifically used to filter out the spike pulse and ripple voltage input by the vehicle power supply 112, so that the signal waveform of the power supply voltage input to the bias circuit 201 and the second switch circuit 202 is smooth.

[0096] In some embodiments, the input filter circuit 206 is composed of reactive elements, for example, a capacitor connected in parallel across the load, or an inductor connected in series with the load, as well as various complex filter circuits composed of capacitors and inductors.

[0097] It can be understood that the voltage sampling circuit 205 and / or the input filtering circuit 206 can be omitted.

[0098] In some embodiments, see Figure 4 The isolation circuit 100 also includes a slow-start circuit 40, which is electrically connected to the first switch circuit 10 and the diagnostic device 200, respectively, and is used to delay processing of the power supply voltage output by the vehicle power supply 112 when the working state of the first switch circuit 10 is switched to the on state.

[0099] It can be understood that when the first switch circuit 10 is turned on, a high-voltage spike pulse is generated. If the power supply voltage output by the vehicle power supply 112 directly acts on the diagnostic device 200 through the first switch circuit 10, the high-voltage spike pulse is also input to the diagnostic device 200, which may burn out or break down the internal components of the diagnostic device 200. The slow-start circuit 40 is used to delay the power supply voltage output by the vehicle power supply 112 to prevent the high-voltage spike pulse from reaching the diagnostic device 200, thereby improving the safety of the isolation circuit 100.

[0100] An embodiment of the present invention provides an isolation circuit, which is electrically connected between an OBD connector of a vehicle to be diagnosed and a diagnostic device of a vehicle diagnostic device through a first switch circuit. The OBD connector is also electrically connected to a vehicle power supply of the vehicle to be diagnosed. A switch control circuit is electrically connected to the OBD connector and the first switch circuit respectively. When it is detected that the OBD connector outputs a positive power signal and the OBD connector outputs a negative power signal, the switch control circuit does not work so that the first switch circuit works in an off state to keep the diagnostic device from being powered on. When it is detected that the OBD connector outputs a positive power signal and the OBD connector outputs a negative power signal, a control signal is output so that the first switch circuit works in an on state so that the vehicle power supply supplies power to the diagnostic device. Therefore, the embodiment of the present invention can avoid poor grounding and improve the reliability of the vehicle diagnostic device.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other changes in different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An isolation circuit, applied to automotive diagnostic equipment, characterized in that: The isolation circuit comprises: a first switch circuit, wherein a first end of the first switch circuit is electrically connected to an OBD connector of the vehicle to be diagnosed, a second end of the first switch circuit is electrically connected to a diagnostic device of the vehicle diagnostic device, and the OBD connector is also electrically connected to a vehicle power supply of the vehicle to be diagnosed; A switch control circuit is electrically connected to the OBD connector and the third end of the first switch circuit respectively, and is used for, when it is detected that the OBD connector outputs a positive power signal and it is not detected that the OBD connector outputs a negative power signal, the switch control circuit does not work, so that the first switch circuit works in an off state to keep the diagnostic device unpowered; when it is detected that the OBD connector outputs a positive power signal and it is detected that the OBD connector outputs a negative power signal, outputting a control signal to make the first switch circuit work in an on state, so that the vehicle power supply supplies power to the diagnostic device, wherein the control signal is a sine wave signal; The automobile power supply comprises an automobile power positive electrode and an automobile power negative electrode, wherein the automobile power positive electrode is used to output the power positive electrode signal, and the automobile power negative electrode is used to output the power negative electrode signal. The switch control circuit comprises: A bias circuit, wherein a first end of the bias circuit is electrically connected to the positive electrode of the vehicle power supply and is used to convert a power supply voltage outputted by the positive electrode of the vehicle power supply into a bias voltage; a second switch circuit, wherein a first end of the second switch circuit is electrically connected to the positive electrode of the vehicle power supply; a step-down chopper circuit, wherein a first end of the step-down chopper circuit is electrically connected to a second end of the second switch circuit and a third end of the first switch circuit respectively, and a second end of the step-down chopper circuit is electrically connected to a negative electrode of the vehicle power supply; A controller, the controller is electrically connected to the positive electrode of the automobile power supply, the negative electrode of the automobile power supply, the second end of the bias circuit, the control end of the second switch circuit and the second end of the step-down chopper circuit, and is used for not working when it is detected that the OBD connector outputs a positive power supply signal and does not detect that the OBD connector outputs a negative power supply signal; when it is detected that the OBD connector outputs a positive power supply signal and detects that the OBD connector outputs a negative power supply signal, detecting a current detection signal flowing through the second switch circuit, and outputting a pulse width modulation signal according to the bias voltage and the current detection signal to control the working state of the second switch circuit so that the step-down chopper circuit outputs the control signal.

2. The isolation circuit according to claim 1, characterized in that: The bias circuit includes a first resistor and a first capacitor; The first end of the first resistor is connected to the positive electrode of the vehicle power supply, the first end of the first capacitor and the first end of the second switch circuit, and the second end of the first resistor is connected to the second end of the first capacitor and the first end of the controller.

3. The isolation circuit according to claim 1, characterized in that: The second switch circuit includes a PMOS tube, a gate of the PMOS tube is connected to the second end of the controller, a source of the PMOS tube is connected to the positive electrode of the car power supply, and a drain of the PMOS tube is connected to the third end of the controller and the step-down chopper circuit.

4. The isolation circuit according to claim 3, characterized in that: The step-down chopper circuit comprises: A freewheeling circuit, wherein a first end of the freewheeling circuit is electrically connected to a second end of the second switch circuit, and a second end of the freewheeling circuit is electrically connected to a negative electrode of the vehicle power supply, and is configured to operate in an off state when the second switch circuit operates in an on state, and in an on state when the second switch circuit operates in an off state; A charge and discharge circuit, wherein the first end of the charge and discharge circuit is electrically connected to the second end of the second switch circuit, the first end of the freewheeling circuit and the third end of the first switch circuit respectively, and the second end of the charge and discharge circuit is electrically connected to the second end of the freewheeling circuit and the negative pole of the vehicle power supply respectively, and is used for, when it is detected that the OBD connector outputs a positive power supply signal and detects that the OBD connector outputs a negative power supply signal, when the freewheeling circuit operates in an off state, to implement charging, and when the freewheeling circuit operates in an on state, to implement discharging, so as to output the control signal, and send the control signal to the first switch circuit.

5. The isolation circuit according to claim 4, characterized in that: The freewheeling circuit comprises a diode, the anode of the diode is connected to the negative electrode of the automobile power supply, and the cathode of the diode is connected to the drain of the PMOS tube and the charging and discharging circuit.

6. The isolation circuit according to claim 5, characterized in that: The charging and discharging circuit includes an inductor and a second capacitor; One end of the inductor is connected to the cathode of the diode and the drain of the PMOS tube, and the other end of the inductor is connected to one end of the second capacitor and the third end of the first switch circuit; the other end of the second capacitor is connected to the negative electrode of the car power supply.

7. The isolation circuit according to claim 1, characterized in that: The switch control circuit also includes a voltage sampling circuit, a first end of the voltage sampling circuit is electrically connected to the first end of the step-down chopper circuit and the third end of the first switch circuit respectively, a second end of the voltage sampling circuit is electrically connected to the second end of the step-down chopper circuit and the negative electrode of the automobile power supply respectively, and a third end of the voltage sampling circuit is electrically connected to the fourth end of the controller for sampling the control signal so that the controller can feedback and adjust the control signal.

8. The isolation circuit according to claim 7, characterized in that: The voltage sampling circuit includes a second resistor and a third resistor; The first end of the second resistor is connected to the first end of the step-down chopper circuit and the third end of the first switch circuit respectively, the second end of the second resistor is connected to the first end of the third resistor and the fourth end of the controller; the second end of the third resistor is connected to the negative electrode of the vehicle power supply.

9. The isolation circuit according to claim 7, characterized in that: The switch control circuit also includes an input filter circuit, which is electrically connected between the positive electrode of the automobile power supply and the negative electrode of the automobile power supply and is used for filtering the power supply voltage.

10. The isolation circuit according to claim 9, characterized in that: The input filter circuit includes a third capacitor, one end of the third capacitor is connected to the positive electrode of the vehicle power supply, and the other end of the third capacitor is connected to the negative electrode of the vehicle power supply.

11. The isolation circuit according to any one of claims 1 to 10, characterized in that: The isolation circuit also includes a slow-start circuit, which is electrically connected to the second end of the first switch circuit and the diagnostic device respectively, and is used to delay processing of the power supply voltage output by the vehicle power supply when the working state of the first switch circuit is switched to the on state.

12. The isolation circuit according to any one of claims 2 to 10, characterized in that: The first switch circuit comprises: A first switch, electrically connected between the positive electrode of the vehicle power supply and the diagnostic device, and also electrically connected to the switch control circuit, for operating in a conducting state according to the control signal; The second switch is electrically connected between the negative electrode of the vehicle power supply and the diagnostic device, and is also electrically connected to the switch control circuit, and is used to work in a conducting state according to the control signal.

13. An automobile diagnostic device, characterized in that: include: The isolation circuit as claimed in any one of claims 1 to 12; The diagnostic device is electrically connected to the isolation circuit and is also in communication connection with the vehicle to be diagnosed. When the isolation circuit is in an on state, the diagnostic device operates according to the power supply voltage provided by the vehicle power supply of the vehicle to be diagnosed, and obtains the diagnostic data of the vehicle to be diagnosed.

14. An automobile diagnostic system, characterized in that: include: The automotive diagnostic device as claimed in claim 13; The host computer is connected to the automobile diagnostic device for displaying the diagnostic data sent by the automobile diagnostic device.

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