Pixel Circuit Temperature Compensation for Uniform Display Luminance
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Solution Overview
Problem
Display devices experience luminance differences between sub-pixels due to temperature variations, leading to inconsistent image quality.
Innovation Solution
Incorporation of a temperature compensation transistor and anode initialization transistor in the pixel circuit to regulate the voltage and current flow, reducing luminance differences by adjusting the channel width-to-length ratio of transistors based on temperature changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit without temperature compensation is used, then the device complexity is low, but luminance difference between sub-pixels occurs due to temperature variations
Solution Approach 1:
A temperature compensation transistor is introduced as an intermediary component in the pixel circuit. This transistor is configured to compensate for temperature-induced threshold voltage changes in the driving transistor, thereby maintaining consistent driving current and luminance across sub-pixels despite temperature variations. The compensation transistor acts as a mediator that counteracts the harmful thermal effects without requiring external temperature sensors or complex control systems.
2Reliability
If the channel width-to-length ratio of transistors is adjusted for temperature compensation, then luminance consistency improves, but manufacturing precision requirements increase
Solution Approach 1:
The channel width-to-length ratio (W/L ratio) of the temperature compensation transistor is specifically designed and optimized to provide effective temperature compensation. By carefully selecting and fixing this geometric parameter during the design phase, the circuit achieves temperature insensitivity. The W/L ratio is chosen such that the compensation transistor's threshold voltage change with temperature counterbalances the driving transistor's threshold voltage drift, thereby maintaining stable driving current across temperature ranges without requiring active control or complex manufacturing processes.
3Reliability
If additional transistors are added to the pixel circuit for temperature compensation, then current distribution control improves, but the area of the pixel circuit increases
Solution Approach 1:
The temperature compensation transistor is integrated into the existing pixel circuit architecture by sharing nodes and pathways with other circuit components. Specifically, the compensation transistor is connected to the same power supply nodes and control signals as the driving transistor, allowing it to perform temperature compensation without requiring entirely separate circuit paths. This merging approach enables effective temperature compensation while minimizing the additional area required, as the compensation functionality is embedded within the existing circuit framework rather than added as a completely separate block.
Data Source
AI summary
A display device includes a first pixel circuit and a second pixel circuit. The first pixel circuit includes a driving transistor generating a driving current, a temperature compensation transistor connected to the driving transistor, and a light emitting element connected to the temperature compensation transistor and emitting light according to the driving current.