OLED Pixel Circuit with Overlapped Scan and Emission
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Solution Overview
Problem
Large-sized and high-resolution display devices face challenges in driving pixels efficiently, particularly when displaying stereoscopic images, due to increased RC delay and high driving frequencies, which lead to increased production costs and potential motion artifacts.
Innovation Solution
A display device with pixels comprising an organic light emitting diode (OLED), a driving transistor, a compensation capacitor, and a storage capacitor, where the scan and light emitting periods are temporally overlapped, and the pixels are divided into groups to reduce driving frequency and prevent motion artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the display device operates at high driving frequency to display stereoscopic images, then the stereoscopic image display capability is improved, but the production cost increases
Solution Approach 1:
The pixel circuit is divided into multiple capacitors (compensation capacitor CTH, storage capacitor CST, and additional capacitor CX) that work in sequence during different time periods. This segmentation allows the circuit to perform multiple functions (threshold compensation, data storage, and voltage transformation) without requiring a single complex high-frequency driver, thereby reducing production costs while maintaining stereoscopic display capability
Solution Approach 2:
The compensation capacitor CTH performs threshold voltage compensation in advance during the compensation period before the light emitting period begins. This preliminary action ensures that the driving transistor is properly compensated before high-frequency operation for stereoscopic display, avoiding the need for expensive real-time correction circuits
2Manufacturing precision
If the scan period is extended to complete data writing, then the data writing accuracy is improved, but the motion artifacts increase
Solution Approach 1:
The pixel circuit operates with periodic action by using multiple capacitors that charge and discharge in sequence during different time periods (compensation period, light emitting period, reset period). This periodic operation allows data writing to be completed accurately across multiple cycles without extending the overall frame time, thereby preventing motion artifacts while ensuring data writing accuracy
Solution Approach 2:
The storage capacitor CST maintains the data voltage continuously throughout the light emitting period, ensuring uninterrupted data writing accuracy. Simultaneously, the compensation capacitor CTH continuously compensates for threshold voltage variations, allowing the circuit to operate efficiently without extending the scan period, thus avoiding motion artifacts
3Manufacturing precision
If the display device displays stereoscopic images with 60 frames per second, then the image quality is improved, but the driving frequency must be doubled which increases complexity
Solution Approach 1:
The pixel circuit uses dynamic operation by switching between different capacitor configurations during different time periods. The compensation capacitor CTH is connected during the compensation period, while the storage capacitor CST is active during the light emitting period. This dynamic switching allows the circuit to maintain high image quality for stereoscopic display without requiring a permanently doubled driving frequency, thereby reducing overall system complexity
Solution Approach 2:
The circuit changes its operational parameters by using different capacitors at different times. The compensation capacitor CTH provides threshold compensation with specific capacitance values, while the storage capacitor CST holds data with different voltage levels. These parameter changes allow the circuit to achieve high image quality for stereoscopic display without requiring uniformly high driving frequencies across all operations, reducing complexity
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 solution allows for efficient data writing and light emitting periods, reducing production costs and improving image quality by minimizing motion artifacts and enabling stereoscopic image display.
Implementation Method 1
an organic light emitting diode (OLED)
Data Source
AI summary
A pixel, a display device including the same, and a driving method thereof. After the anode voltage of an organic light emitting diode (OLED) is discharged and reset, a first voltage corresponding to a data voltage applied to a storage capacitor is transmitted to a compensation capacitor. A voltage corresponding to the threshold voltage of the driving transistor is transmitted to the compensation capacitor. The data voltage is stored according to a data signal corresponding to the storage capacitor. The organic light emitting diode (OLED) emits light according to a driving current flowing to the driving transistor by the voltage stored to the compensation capacitor. Here, the light emitting steps of a plurality of pixels are concurrently generated, and a scan step and the light emitting step are temporally overlapped.