OBD Isolation Circuit for Poor-Grounding Prevention
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Solution Overview
Problem
Poor grounding occurs when a non-standard OBD connector is used for automobile diagnosis, leading to incorrect illumination of fault lamps and interference with maintenance judgment.
Innovation Solution
An isolation circuit with a switch control circuit that ensures power is only supplied to the diagnostic device when both positive and negative electrodes of the automobile power supply are correctly connected, preventing improper grounding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a nonstandard OBD connector is used for automobile diagnosis, then the diagnostic device can be connected to the automobile, but poor grounding occurs leading to incorrect fault lamp illumination and interference with maintenance judgment
Solution Approach 1:
The control circuit detects the connection status of the OBD connector before enabling power supply to the diagnostic device. When both positive and negative electrodes are properly connected, the control circuit activates the switching circuit to enable power supply. This preliminary detection action prevents poor grounding issues by ensuring proper connection before operation.
Solution Approach 2:
A control circuit is introduced as an intermediary between the OBD connector and the diagnostic device power supply. This control circuit detects the connection status and controls the switching circuit accordingly, acting as a mediator that ensures proper grounding through the negative electrode before allowing the diagnostic device to operate.
2Ease of operation
If the positive electrode is connected before the negative electrode during OBD connector connection, then the diagnostic device may power on prematurely, but this causes incorrect fault lamp illumination and poor grounding
Solution Approach 1:
The control circuit performs preliminary detection of the negative electrode connection status before enabling power supply. Even if the positive electrode is connected first, the switching circuit remains inactive until the control circuit confirms proper negative electrode connection, preventing premature power-on and ensuring reliable power supply sequence.
Solution Approach 2:
The control circuit continuously monitors the connection status of both positive and negative electrodes, and provides feedback control to the switching circuit. When the negative electrode is properly connected, the control circuit enables power supply; when disconnected, it disables power supply, creating a closed-loop feedback system that ensures stable and reliable power supply.
Data Source
AI summary
The present invention relates to the field of automobile diagnosis, and provides an isolation circuit, an automobile diagnosis device and an automobile diagnosis system. The isolation circuit comprises: a first switch circuit electrically connected between an OBD connector of an automobile to be diagnosed and a diagnostic device of the automobile diagnosis device, wherein the OBD connector is further electrically connected to an automobile power supply of the automobile to be diagnosed; and a switch control circuit electrically connected to the OBD connector and the first switch circuit respectively, wherein the switch control circuit does not operate when it is detected that the OBD connector outputs a power supply positive electrode signal and it is not detected that the OBD connector outputs a power supply negative electrode signal, so that the first switch circuit operates in an off state to ensure that the diagnostic device is not powered on; and the switch control circuit outputs a control signal when it is detected that the OBD connector outputs a power supply positive electrode signal and that the OBD connector outputs a power supply negative electrode signal, so that the first switch circuit operates in an on state so as to enable the automobile power supply to supply power to the diagnostic device. Embodiments of the present invention can avoid poor grounding and improve the reliability of automobile diagnosis device.