OLED Pixel Circuit Diode Initialization for Flicker Reduction
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Solution Overview
Problem
Light emitting display devices, such as OLEDs, experience luminance differences when driven at different frequencies due to varying emission and non-emission periods, leading to flicker issues and inconsistent brightness.
Innovation Solution
A pixel design incorporating a switching transistor, storage capacitor, driving transistor, emission transistor, light emitting diode, and diode initialization transistor, where the diode initialization transistor is turned on for the entire non-emission period, ensuring consistent luminance across different driving frequencies by maintaining uniform initialization of the light emitting diode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the driving frequency of the display panel is changed to adapt to different image characteristics, then the adaptability of the display device is improved, but the luminance consistency deteriorates causing flicker
Solution Approach 1:
The patent applies preliminary action by initializing the light emitting diode at the beginning of each non-emission period before the next emission period starts. The diode initialization transistor transfers an initialization voltage to the light emitting diode during non-emission periods, ensuring the diode is properly prepared before each emission cycle regardless of driving frequency changes. This preliminary initialization prevents luminance inconsistency and flicker that would otherwise occur when switching between different driving frequencies.
2Stability of the object's composition
If the diode initialization transistor is activated during non-emission periods to maintain luminance consistency, then the luminance stability is improved, but the device complexity increases
Solution Approach 1:
The diode initialization transistor serves multiple functions: it initializes the light emitting diode during non-emission periods to prevent undesired emissions, and it prepares the diode for the next emission period. By making this single transistor perform both initialization and preparation functions across different emission cycles, the patent avoids adding separate circuits for each function, thereby maintaining luminance stability without significantly increasing device complexity.
Solution Approach 2:
The patent implements periodic action by activating the diode initialization transistor during each non-emission period in a repeating cycle. This periodic initialization occurs at regular intervals corresponding to the frame period, ensuring consistent luminance output across multiple frames while using a simple repeating pattern rather than complex continuous control mechanisms.
3Illumination intensity
If the emission transistor is turned on during emission periods to enable light output, then the brightness is improved, but undesired emissions during non-emission periods may occur
Solution Approach 1:
The patent applies preliminary anti-action by initializing the light emitting diode during non-emission periods through the diode initialization transistor before the emission period begins. This preliminary initialization sets the diode in a proper state that prevents undesired emissions from occurring during non-emission periods, while still allowing normal bright emission during designated emission periods when the emission transistor is activated.
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
The solution maintains substantially constant luminance at different driving frequencies, preventing undesired emissions during non-emission periods and ensuring consistent brightness, thereby addressing flicker issues and luminance inconsistencies.
Implementation Method 1
a light emitting diode which emits light based on the driving current
Data Source
AI summary
A pixel of a light emitting display device includes: a switching transistor which transfers a data voltage in response to a gate writing signal, a storage capacitor which stores a storage voltage, a driving transistor which generates a driving current based on the storage voltage stored in the storage capacitor, an emission transistor which selectively forms a path of the driving current in response to an emission signal, a light emitting diode which emits light based on the driving current, and a diode initialization transistor which transfers an initialization voltage to the light emitting diode in response to the emission signal. The storage voltage corresponds to a value obtained by subtracting a threshold voltage of the driving transistor from the data voltage.