Avionics LCD Fault Tolerance via Isolation FETs
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Solution Overview
Problem
Existing avionics systems with LCD displays face limitations in fault tolerance, as they often lose functionality when a driver circuit fails, and attempts to address this through redundant circuits can lead to premature failure due to parasitic impedance from inactive driver circuits.
Innovation Solution
The implementation of fault-tolerant LCD systems with redundant driver circuits and isolation FETs directly on the panel glass, which electrically isolate inactive driver circuits to prevent back biasing and ensure continued full-screen functionality even in the presence of failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant driver circuits are added to improve fault tolerance, then reliability is improved, but device complexity increases
Solution Approach 1:
The display panel is divided into multiple independently controllable segments, each with its own driver circuit. The first display region has a first driver circuit and the second display region has a second driver circuit, allowing independent operation of each segment. This segmentation enables fault isolation while maintaining overall system functionality.
Solution Approach 2:
Isolation switches are pre-configured in each driver circuit to enable rapid disconnection of faulty segments. The switches are positioned to allow the system to proactively isolate potential failure points before they propagate, enabling quick transition to standby circuits or alternative display modes without waiting for actual failure detection.
2Device complexity
If inactive driver circuits are left connected to signal lines, then device complexity is reduced, but reliability deteriorates due to back biasing and premature failure
Solution Approach 1:
The harmful back biasing effect is extracted and eliminated by introducing isolation switches that physically disconnect inactive driver circuits from the signal lines. This removes the parasitic impedance pathway that causes premature failure, allowing inactive circuits to be completely isolated rather than left connected with harmful electrical interactions.
Solution Approach 2:
Isolation switches serve as intermediary components between active and inactive driver circuits. These switches act as controllable barriers that can be activated to prevent harmful electrical interactions (back biasing) while allowing normal operation when not needed. The switches mediate the connection state based on circuit activity, protecting inactive circuits from damage.
Data Source
AI summary
Fault-tolerant liquid crystal displays are delineated for avionics systems. At least some example embodiments are methods including providing an avionics display full screen on the LCD, the providing being implemented by driving source signal lines of the LCD by way of a first source driver circuit through a first set of FETs; driving gate signal lines of the LCD by way of a first gate driver circuit through a second set of FETs; preventing back biasing of a second source driver circuit by electrically isolating the source signal lines from the second source driver circuit; and preventing back biasing of a second gate driver circuit by electrically isolating the gate signal lines from the second gate driver circuit.