Pixel Circuit Segmentation for Stable Luminance Dimming
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Solution Overview
Problem
Display devices experience luminance inversion phenomena due to variations in light emitting element initialization times when using dimming techniques that adjust light emitting periods based on set luminance levels, as they do not store the length of the light emitting period for all luminance levels.
Innovation Solution
A pixel circuit design incorporating a first emission signal with a variable off-duty ratio and a second emission signal with a fixed off-duty ratio, along with a driving transistor and initialization transistors, to control voltage application time and fix light emitting and initialization times, preventing luminance inversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the dimming technique for adjusting the length of the light emitting period is used, then luminance can be controlled according to set luminance levels, but luminance inversion phenomenon occurs at luminance levels other than representative luminance levels due to variations in light emitting element initialization times
Solution Approach 1:
The patent divides the control of light emitting period into two separate signals: a first emission signal for controlling the light emitting period length (with variable off-duty ratio for luminance adjustment) and a second emission signal for controlling the light emitting element initialization (with fixed off-duty ratio). This segmentation prevents the initialization time from varying when luminance is adjusted, eliminating the luminance inversion phenomenon while maintaining luminance control capability.
2Use of energy by moving object
If the light emitting period length is adjusted for dimming, then power consumption can be reduced at lower luminance levels, but the light emitting element initialization time varies causing luminance inversion
Solution Approach 1:
The patent separates the control functions into two independent emission signals, allowing the light emitting period (and thus power consumption) to be adjusted via the first emission signal while the initialization time remains fixed through the second emission signal. This enables energy-efficient dimming without luminance inversion.
3Adaptability or versatility
If interpolation method is used to determine light emitting period for non-representative luminance levels, then all luminance levels can be supported, but luminance inversion occurs due to varying initialization times
Solution Approach 1:
The patent maintains adaptability across all luminance levels by using the first emission signal with variable off-duty ratio for luminance control, while the second emission signal with fixed off-duty ratio ensures consistent initialization timing. This segmentation allows interpolation for non-representative luminance levels without causing luminance inversion.
Data Source
AI summary
A pixel circuit includes a light emitting element, a driving transistor, a first emission transistor applying a first power voltage to the driving transistor in response to a first emission signal, a second emission transistor applying the driving current to the light emitting element in response to a second emission signal, a first initialization transistor applying a first initialization voltage to an anode electrode of the light emitting element in response to the second emission signal, a data write transistor, a compensation transistor, a second initialization transistor, and a storage capacitor. A first off-duty ratio which is a ratio of a high voltage level period of the first emission signal in one frame is determined according to a set luminance level, and a second off-duty ratio which is a ratio of a high voltage level period of the second emission signal in the one frame is fixed.