Scan Driver Inverter Circuit for OLED Flicker Suppression
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Solution Overview
Problem
Organic light emitting display devices face issues with internal compensation circuits leading to unexpected problems such as flicker due to residual charge accumulation in subpixels, which affects display quality and reliability.
Innovation Solution
A scan driver design that includes a shift register and an inverter connected to separate voltage lines, with the inverter using a variable voltage line to control the logical state of the output signal, preventing abnormal operation of compensation transistors and reducing flicker by maintaining an off voltage during power-on sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If internal compensation circuits are used in subpixels, then display quality is improved, but residual charge accumulation causes unexpected problems such as flicker
Solution Approach 1:
The patent extracts the problematic inversion operation from the main scan driver circuit and relocates it to a separate inverter circuit. This separation removes the source of residual charge accumulation from the compensation circuits, eliminating the flicker problem while preserving the display quality benefits of internal compensation.
Solution Approach 2:
The patent introduces an inverter circuit as an intermediary component between the scan driver output and the compensation circuits. This intermediary inverts the scan signal externally, preventing abnormal operation of compensation transistors and eliminating residual charge accumulation that causes flicker.
2Device complexity
If scan signal is inverted using shared voltage line, then device complexity is reduced, but abnormal operation occurs during power-on sequence
Solution Approach 1:
The patent segments the voltage line configuration by providing separate voltage lines for the shift register and inverter circuits. This segmentation allows independent voltage control, preventing abnormal operation during power-on sequences while maintaining manageable device complexity through modular design.
Solution Approach 2:
The patent implements dynamic voltage control by applying different voltages to the shift register and inverter during the power-on sequence. This dynamic approach ensures proper initialization of both circuits, preventing flicker and abnormal operation while adapting to different operational states.
3Reliability
If compensation transistors operate abnormally, then residual charge accumulates in subpixels, but display reliability decreases
Solution Approach 1:
The patent applies preliminary anti-action by inverting the scan signal before it reaches the compensation circuits. This pre-inversion prevents compensation transistors from operating abnormally, thereby preventing residual charge accumulation and eliminating flicker before these harmful effects can occur.
Solution Approach 2:
The patent implements a feedback mechanism where the inverter circuit monitors and corrects the scan signal to prevent abnormal compensation transistor operation. This feedback loop ensures that compensation circuits operate correctly, preventing residual charge accumulation and maintaining display reliability.
Data Source
AI summary
A circuit has a first portion configured to act as a shift register to provide an output signal via an output terminal, and a second portion configured to act as an inverter to invert the output signal at the output terminal of said first portion from a logic high state to a logic low state or vice versa. This is to forcibly turn off one or more transistors in a pixel circuit that provides subpixel or pixel-related control in an OLED display, such that an anode voltage of an organic light emitting diode does not exceed a turn-on voltage thereof.