Display Pixel Circuit with Bias Frames for Stable Luminance
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Solution Overview
Problem
Existing organic light-emitting display devices experience degradation in display quality when the driving frequency is changed, leading to noticeable changes in luminance due to the hysteresis effect of transistors.
Innovation Solution
A pixel structure is designed with specific transistor configurations and capacitors to stabilize the gate voltage of transistors, incorporating P-type and N-type transistors, and utilizing bias frames to initialize the transistors, minimizing luminance changes by controlling scan and emission control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the driving frequency of the display device is changed, then the display device can adapt to different refresh rates and power consumption requirements, but the luminance of the display degrades due to the hysteresis effect of transistors
Solution Approach 1:
The patent applies preliminary action by introducing a bias frame that occurs before the driving frame. In the bias frame, the data line is initialized to a reference voltage level, and the transistor gate voltage is pre-adjusted to compensate for hysteresis effects. This preliminary initialization ensures that when the driving frame begins, the transistor is in a known state, eliminating luminance degradation caused by frequency changes. The bias frame effectively prepares the pixel circuit in advance to maintain stable luminance across different driving frequencies.
2Illumination intensity
If a bias frame is added to initialize transistors before driving frames, then luminance consistency is improved, but the device complexity increases due to additional transistor configurations and signal control lines
Solution Approach 1:
The patent applies universality by designing the pixel circuit to serve multiple functions through shared components. The same transistor configuration used in the driving frame also functions during the bias frame. The data line serves dual purposes: receiving data signals during driving frames and receiving bias/initialization signals during bias frames. The scan lines and emission control lines are used for both bias frame and driving frame operations. This multi-functionality reduces the need for separate dedicated components, thereby limiting the increase in device complexity while achieving luminance consistency.
Solution Approach 2:
The patent applies periodic action by implementing a repeating sequence of bias frame followed by driving frame. This periodic structure allows the pixel circuit to be initialized regularly before each driving sequence, ensuring consistent luminance. The periodic bias frame acts as a reset mechanism that maintains transistor state stability across multiple frames, especially when driving frequency changes occur. This rhythmic alternation between bias and driving modes creates a predictable cycle that simplifies control logic.
3Manufacturing precision
If multiple scan signals are used to control transistor switching in the pixel circuit, then the precision of current control is improved, but the difficulty of detecting and measuring increases due to complex signal timing requirements
Solution Approach 1:
The patent applies feedback by incorporating emission control lines that receive emission control signals. These signals provide feedback control over the light emission process by adjusting the current through the light emitting diode based on the actual emission requirements. The emission control signals are generated based on the data signal and scan signal timing, creating a closed-loop system that precisely controls luminance. This feedback mechanism compensates for variations in transistor characteristics and maintains consistent display performance.
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 consistent display quality by minimizing luminance changes even when the driving frequency is varied, thereby enhancing the display performance.
Implementation Method 1
an organic light emitting diode that generates light by recombination of electrons and holes
Implementation Method 2
a first capacitor connected between a first node and the gate electrode of the first transistor
Data Source
AI summary
A pixel of a display device includes a light emitting diode, a capacitor, and first to fourth transistors, where the first transistor is connected to the light emitting diode, and the second transistor is connected between the first transistor and a data line. A first electrode of the first transistor receives a data signal during a driving frame and a bias signal during a bias frame through the data line and the second transistor.