Active Matrix Display Driver Timing Control for Power-On Stability
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Solution Overview
Problem
Active matrix type display devices using organic electroluminescent elements face issues with horizontal emission lines during power-on or full screen signal application, affecting image quality due to variations in transistor characteristics across pixels.
Innovation Solution
A method involving a pixel select gate driver and an illumination on/off driver with a shift register and gate signal control circuit, where the illumination on/off driver starts its operation only after the output enable signal is applied to the gate signal output control circuit, ensuring stable power supply and controlled emission periods for each row of pixel circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If power supply voltages are stabilized before sequentially outputting scan signals and pixel select pulses, then power supply stability is improved, but horizontal emission lines still occur on the screen
Solution Approach 1:
The patent applies preliminary action by initializing the shift register with a start pulse before enabling the output enable signal. This preliminary initialization ensures that the first output signal corresponds to the first pixel row, preventing horizontal emission lines from appearing on the screen during power-on or full screen signal application.
Solution Approach 2:
The patent segments the power-on sequence into distinct phases: first stabilizing power supply voltages, then initializing the shift register with a start pulse, and finally enabling the output enable signal. This segmentation allows each phase to be properly executed in sequence, preventing image quality issues while maintaining power supply stability.
2Reliability
If threshold cancel type circuit or current copy type circuit is used, then transistor threshold variation effect is eliminated, but image quality upon power-on or full screen signal application deteriorates
Solution Approach 1:
The patent applies preliminary action by initializing the shift register with a start pulse before enabling the output enable signal. This preliminary initialization ensures that the first output signal corresponds to the first pixel row, preventing horizontal emission lines from appearing on the screen during power-on or full screen signal application.
Solution Approach 2:
The patent uses feedback by monitoring the power-on state and controlling the timing of the start pulse and output enable signal accordingly. The control circuit adjusts the initialization sequence based on the power supply stabilization status, ensuring that the shift register is properly initialized before signals are output, thus preventing image quality degradation.
Data Source
AI summary
Appropriate image quality is maintained when a display device is powered on or when a signal is applied. After a power supply is stabilized, a pixel select gate driver section scans all pixel circuits. A final illumination on/off driver outputs illumination on/off gate signals. In this case, a start pulse for an illumination on/off shift register is started when or after an output enable signal for an illumination on/off gate signal output control circuit is output. This prevents the illumination on/off gate signals, serving as scan signals, from being improperly supplied to the pixel circuits.