Scan Driver EMI Mitigation via Variable Clock Frequency
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Solution Overview
Problem
Display devices such as LCDs and OLEDs face issues with electromagnetic interference (EMI) due to fixed clock signal frequencies in their scan drivers, which affects the reliability and performance of the display.
Innovation Solution
A scan driver is designed with a level shifter that outputs clock signals with varying frequencies for at least two consecutive periods, and a shift register that operates based on these signals, dispersing the scan signals across diverse frequency bands to mitigate EMI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed frequency clock signal is used in the scan driver, then the circuit operation is stable and simple, but electromagnetic interference (EMI) problems occur
Solution Approach 1:
The patent applies dynamics by making the clock signal frequency variable rather than fixed. The level shifter dynamically adjusts the clock signal frequency based on control signals, transforming the static frequency into a dynamic parameter that can adapt to different operating conditions, thereby reducing EMI while maintaining operational stability
Solution Approach 2:
The patent changes the frequency parameter of the clock signal from a fixed value to a variable value. By using a level shifter to modify the clock signal frequency according to control signals, the system alters the temporal characteristics of the signal to mitigate EMI effects while preserving circuit reliability
2Object-affected harmful factors
If the clock signal frequency is varied to reduce EMI, then electromagnetic interference is reduced, but the device complexity increases due to the level shifter
Solution Approach 1:
The patent introduces a level shifter as an intermediary component between the clock signal source and the shift register. This mediator component specifically handles the frequency adjustment function, isolating the complexity from the main scan driver circuit while achieving EMI reduction through controlled frequency variation
3Object-affected harmful factors
If clock signals are dispersed across diverse frequency bands, then EMI vulnerability is reduced, but the control complexity increases
Solution Approach 1:
The patent employs periodic action by varying the clock signal frequency in a controlled periodic manner. The level shifter generates frequency-varied clock signals that operate in distinct periods, creating temporal dispersion of the signal energy across different frequency bands, which reduces EMI vulnerability while maintaining manageable control complexity through rhythmic signal patterns
Data Source
AI summary
A scan driver comprises a level shifter configured to output varied clock signals that have different frequencies for at least two consecutive periods; and a shift register operating based on the varied clock signals output from the level shifter and outputting scan signals.