Current Sensing Line Fault Detector for Automotive Systems
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Solution Overview
Problem
Existing fault detection systems in automotive systems, which use serial cables to multiplex parallel video, struggle to detect line-to-line shorts in twisted pair transmission lines and require additional voltage supplies and external resistors, leading to reliability issues and increased costs due to high current requirements for electric car applications.
Innovation Solution
The implementation of current sensing fault detectors that use reference current sources, operational amplifiers, and current-mode analog-to-digital converters to detect fault conditions such as short-to-ground, short-to-battery, and open by sensing currents instead of voltages, allowing for the detection of line-to-line shorts in differential transmission lines without additional voltage supplies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If voltage-based fault detection is used, then fault conditions can be detected, but additional voltage supplies and external resistors are required, increasing device complexity
Solution Approach 1:
The patent extracts the voltage supply requirement from the fault detection system by using current-mode sensing that operates with single-ended or differential currents without needing additional voltage supplies. The fault detection function is achieved by sensing current levels and transitions rather than measuring voltages, thereby eliminating the need for separate voltage reference supplies and external resistors.
Solution Approach 2:
The current sensing mechanism serves multiple functions: it detects short-to-ground faults, short-to-battery faults, open circuit faults, and line-to-line shorts in differential pairs. By using a universal current sensing approach that monitors current flow characteristics, the system achieves comprehensive fault detection without requiring different detection mechanisms for each fault type, thereby reducing overall device complexity.
2Reliability
If clamping diodes are added for short-to-battery detection, then IC pin voltage protection is achieved, but area and cost increase due to high current capacity requirements
Solution Approach 1:
The patent replaces the mechanical/clamping diode-based protection approach with a current-mode sensing and detection system. Instead of using clamping diodes that physically limit voltage by conducting high currents, the system uses operational amplifiers and current mirrors to sense voltage conditions through current measurements. This substitution eliminates the need for high-current-capacity clamping diodes, thereby reducing the area required for protection components while maintaining reliability.
3Adaptability or versatility
If current sensing is used instead of voltage sensing, then line-to-line shorts in twisted pair transmission lines can be detected, but additional sensing circuitry is required
Solution Approach 1:
The patent merges the current sensing function with the existing fault detection logic by using the same operational amplifiers and comparator circuits for both voltage-based and current-based detection. The current sensing circuitry is integrated into the existing fault detection architecture, where current mirrors and operational amplifiers that were previously used for voltage sensing now also perform current measurement functions. This merging approach enables line-to-line short detection in differential pairs without requiring completely separate sensing circuitry, thereby managing device complexity while expanding detection capabilities.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively detects various fault conditions, including line-to-line shorts, without the need for additional voltage supplies, reducing complexity and cost while improving reliability by using current sensing instead of voltage-based methods.
Implementation Method 1
Sense lines sense the voltage on the line through a resistor network
Data Source
AI summary
A current sensing line fault detector includes a unity gain buffer coupling a reference voltage to an IC pin, a current controlled current source coupled to the buffer, a current mode A/D converter developing a digital signal representative of the IC pin current, and logic for determining the state of a transmission line coupled to the IC pin. An alternative current sensing line fault detector includes an OPAMP having a first input coupled to an input node and to a reference current source and having a second input coupled to a reference voltage source. A voltage controlled current source (VCCS) is coupled between the first input of the OPAMP and ground and is controlled by an output of the OPAMP. An A/D converter is coupled to the output of the OPAMP to develop a digital output signal representative of the current flowing through the current sensor.