Vehicle Ground Path Impedance Detection Circuit
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Solution Overview
Problem
Modern vehicles with dual control systems using master and slave microcontrollers face safety concerns due to increased complexity and cost with galvanically isolated grounds, and reduced functionality with common internal grounds, as a single failed ground return path can lead to voltage drops and system failures.
Innovation Solution
A circuit with shunt resistors and a bi-directional current sense amplifier is used to detect differences in ground path impedance between the master and slave sides, allowing for alerts and system adjustments to ensure safety, such as powering off systems or limiting current, without increasing circuit complexity or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanically isolated grounds are used for master and slave control systems, then safety and reliability are improved, but device complexity and cost increase
Solution Approach 1:
The patent introduces a current sense amplifier as an intermediary device that monitors ground path currents without requiring galvanic isolation. The amplifier detects current differences between master and slave ground paths, providing safety monitoring while maintaining a simpler common ground architecture.
Solution Approach 2:
The patent replaces the mechanical/electrical isolation approach (galvanic isolation) with an electronic sensing approach. Instead of physically isolating ground paths, the system uses electronic current sensing to monitor ground path integrity, achieving safety through measurement rather than isolation.
2Reliability
If galvanically isolated grounds are used for master and slave control systems, then safety and reliability are improved, but cost increases
Solution Approach 1:
The patent employs inexpensive current sense amplifiers and shunt resistors to monitor ground paths, replacing costly galvanic isolation components. The sensing approach uses low-cost electronic components to achieve the same safety objective.
Solution Approach 2:
The patent substitutes expensive galvanic isolation hardware with cheaper electronic sensing circuitry, achieving safety monitoring through measurement and detection rather than through costly isolated power supply architectures.
3Device complexity
If a common internal ground is used for master and slave control systems, then device complexity and cost are reduced, but reliability deteriorates due to voltage drops and system failures
Solution Approach 1:
The patent implements a feedback mechanism where the current sense amplifier continuously monitors ground path currents and provides information about ground path integrity. This feedback enables the system to detect ground path degradation and respond appropriately, maintaining reliability despite using a common ground architecture.
Solution Approach 2:
The patent performs preliminary detection of ground path issues before they lead to system failure. By continuously monitoring ground path currents, the system can identify problems early and take corrective action, preventing catastrophic failures that would occur without such monitoring.
4Device complexity
If ground path impedance differences are not detected, then system simplicity is maintained, but harmful factors increase due to undetected failures
Solution Approach 1:
The patent replaces complex isolation systems with simple electronic sensing, achieving both simplicity and safety. The current sense amplifier provides a straightforward electronic method to detect ground path issues without the complexity of isolated power supplies.
Solution Approach 2:
The current sense amplifier acts as an intermediary monitoring device that detects ground path problems without interfering with normal system operation. This intermediary provides safety monitoring while maintaining system simplicity and avoiding the need for complex isolated architectures.
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 enables early detection of ground path issues, preventing system failures and ensuring safety by alerting drivers or mechanics, while reducing the need for complex or costly solutions like increased wire harness capacity.
Implementation Method 1
determining a difference in ground path impedance between a master side and a slave side of a vehicle control circuit
Implementation Method 2
a first shunt resistor electrically coupled between the master ground terminal and a common internal ground, and a second shunt resistor electrically coupled between the slave ground terminal and the common internal ground
Data Source
AI summary
Circuits and methods are disclosed for determining a ground path impedance difference in a vehicle having master and slave control. An example circuit for detecting a difference in ground path impedance in a vehicle includes a master ground terminal and a slave ground terminal. The circuit also includes a first shunt resistor electrically coupled between the master ground terminal and a common internal ground, and a second shunt resistor electrically coupled between the slave ground terminal and the common internal ground. The circuit further includes a bi-directional current sense amplifier having as inputs the master ground terminal and the slave ground terminal.