Pixel Circuit Timing for Stable Luminance at High Refresh Speed
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Solution Overview
Problem
Display devices experience instability in pixel luminance during high-speed operation, leading to deterioration in image quality.
Innovation Solution
A pixel circuit design incorporating specific transistors and capacitors, including a fifth transistor connected to a first power voltage and a fourth node, and a sixth transistor controlled by emission control lines, along with initialization and threshold voltage compensation operations, ensures stable luminance by managing node voltages during emission and non-emission periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the display device operates at high speed, then the productivity is improved, but the stability of node voltages deteriorates
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage compensation operations before the emission period. The fifth transistor is turned on during a compensation period to adjust the threshold voltage of the first transistor before the light emitting element needs to operate. This preliminary adjustment ensures that when high-speed operation begins, the node voltages are already stabilized and the system is ready to maintain stable luminance without requiring continuous adjustment during operation.
2Speed
If the sixth transistor is turned on simultaneously with the fifth transistor, then the emission response time is reduced, but the node voltage instability increases
Solution Approach 1:
The patent uses preliminary action by turning on the fifth transistor before the sixth transistor during the emission period. The fifth transistor is activated first to establish stable node voltages, and only after this preliminary stabilization does the sixth transistor turn on to enable the light emitting element. This sequential activation prevents voltage instability while maintaining fast emission response.
Solution Approach 2:
The patent applies segmentation by dividing the transistor activation process into distinct sequential steps rather than simultaneous activation. The fifth transistor activation is separated from the sixth transistor activation in time, with the fifth transistor turning on first to prepare the voltage conditions, then the sixth transistor turning on subsequently to complete the emission enablement. This temporal segmentation resolves the contradiction between speed and stability.
Data Source
AI summary
A pixel including: a fifth transistor between a power voltage and a fourth node, and including a gate electrode connected to a first emission control line; a first transistor between the power voltage and a second node, and including a gate electrode connected to a first node; a second transistor between a data line and the first node, and including a gate electrode connected to a second scan line; a sixth transistor between the second node and a third node, and including a gate electrode connected to a second emission control line; a capacitor between the first node and the second node; and a light emitting element between the third node and a power voltage, in a non-emission period, the sixth transistor is turned off after the fifth transistor is turned off, and in an emission period, the sixth transistor is turned on after the fifth transistor is turned on.