OLED Pixel Circuit with Initialization Transistor for Low-Frequency Driving
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Solution Overview
Problem
Low-frequency driving of display devices leads to image quality deterioration due to data signal distortion caused by leakage currents in transistors, resulting in decreased luminance of organic light emitting diodes, especially at low and high gray levels.
Innovation Solution
The pixel configuration includes an organic light emitting diode, driving and switching transistors, dual gate transistors, and additional switching transistors to manage power supply voltages and initialization signals, ensuring the organic light emitting diode's luminance is maintained across all gray levels by reducing hysteresis and voltage fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If low-frequency driving is used to reduce power consumption, then power consumption is reduced, but data signal distortion occurs due to leakage current
Solution Approach 1:
The patent applies preliminary action by initializing the organic light emitting diode before low-frequency driving occurs. The initialization transistor sets the OLED to a known state (turning it off or setting a reference voltage) before the actual display operation begins, which compensates for the leakage current effects that will occur during low-frequency driving. This preliminary initialization prevents data signal distortion without requiring continuous high-frequency updates.
2Loss of energy
If low-frequency driving is used to reduce power consumption, then power consumption is reduced, but luminance decreases at low and high gray levels
Solution Approach 1:
The initialization transistor performs a preliminary action by setting the OLED to a reference state before low-frequency driving. This initialization compensates for the voltage drops and leakage currents that would otherwise cause luminance degradation at extreme gray levels, allowing the display to maintain proper luminance output while operating at low frequencies for power savings.
3Illumination intensity
If additional transistors and circuit elements are added to maintain luminance, then luminance stability is improved, but device complexity increases
Solution Approach 1:
The patent segments the pixel circuit into distinct functional blocks: the initialization transistor separate from the driving transistor, with dedicated connections to power supply lines and the OLED. This segmentation allows each component to perform its specific function efficiently - the initialization transistor handles luminance stability while the driving transistor handles current control - reducing the need for additional complex circuitry to manage interactions between functions.
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 effectively maintains the luminance of organic light emitting diodes during low-frequency driving, preventing luminance decrease at low and high gray levels, and reduces flicker phenomena by managing voltage levels and hysteresis.
Implementation Method 1
an organic light emitting diode configured to output a light based on a driving current
Data Source
AI summary
A pixel includes an organic light emitting diode that is configured to output light based on a driving current, and includes a first terminal and a second terminal. A driving transistor is configured to generate the driving current, and includes a first terminal to which a first power supply voltage and a bias power supply voltage are applied, a second terminal connected to the first terminal of the organic light emitting diode, and a gate terminal to which a first initialization voltage is applied. The first dual gate transistor is connected between the gate terminal of the driving transistor and the second terminal of the driving transistor. The first switching transistor includes a first terminal to which the bias power supply voltage is applied, a second terminal connected to the first terminal of the driving transistor, and a gate terminal to which a light emitting diode initialization signal is applied.