OLED Pixel Circuit with Dual-Size Elements for Low-Tone Brightness Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing organic EL display devices face challenges in precisely controlling brightness for low-tone representations, as current density reductions below a certain level make brightness control difficult, especially in achieving accurate color balance and hue.
Innovation Solution
The implementation of an organic EL display device with a current control circuit that selectively supplies current to either a small or large light emitting element based on tone levels, using a drive transistor to regulate current flow, ensuring monotonic increases in current with tone increases, thereby maintaining adequate current density for precise brightness and color expression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the current flowing in a light emitting element is reduced to express a low tone, then the brightness control becomes difficult when the current density drops below a certain level
Solution Approach 1:
The light emitting element is divided into two distinct segments: a large light emitting element and a small light emitting element. This segmentation allows the system to switch between different current density regimes - using the small element for low-tone expressions where high current density is needed, and the large element for high-tone expressions where lower current density is acceptable, thereby resolving the brightness control difficulty at low tones.
Solution Approach 2:
The invention changes the effective light emitting area parameter by switching between two different light emitting elements with different sizes. This parameter change allows the current density to be maintained above the critical threshold level even when expressing low tones, as the same current produces higher current density in the smaller element area.
2Adaptability or versatility
If a current programming system is used for multiple tone representation, then the device complexity increases with the need for precise current control circuits
Solution Approach 1:
The invention implements a dynamic switching mechanism between two light emitting elements based on the tone level being expressed. The current control circuit dynamically selects which element to activate (small element for low tones, large element for high tones), providing versatile tone representation while keeping the control logic relatively simple compared to continuously adjustable current control systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for more precise brightness control and color hue expression, especially at low tones, by suppressing current density reductions and maintaining color balance, thus enhancing the display's ability to accurately represent tones and hues.
Implementation Method 1
In the organic EL (electro-luminescence) light emitting element, if the current density drops below a certain level, the brightness control becomes difficult
Data Source
AI summary
An organic EL display device includes a first pixel circuit for displaying a first color. The first pixel circuit includes a large light emitting element, a small light emitting element, and a current control circuit that controls whether a current is supplied to the small light emitting element and the large light emitting element or not respectively, and the amount of the current to be supplied to at least one of the small light emitting element and the large light emitting element, according to a tone to be displayed by the first pixel circuit. The current control circuit supplies the current to the small light emitting element if the tone is equal to or smaller than a threshold value, and supplies the current to at least the large light emitting element if the tone is larger than the threshold value.