Touch Panel Display Driving With Oxide TFT Image Retention
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Solution Overview
Problem
Existing semiconductor display devices with touch panels or photosensors face high power consumption, especially in portable devices, leading to short operation times, and existing solutions limit versatility and cause image quality loss due to the need for specific liquid crystal materials and multiple display layers.
Innovation Solution
Implement a semiconductor display device with a pixel portion using transistors having a channel formation region made of an oxide semiconductor with a wide band gap and low intrinsic carrier density, and adjust driving frequency based on image type (still vs. moving) to reduce power consumption while maintaining image quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the driving of liquid crystal display panel is stopped when there is no touch panel key operation, then power consumption is reduced, but versatility is low due to limiting the kinds of liquid crystal materials
Solution Approach 1:
The patent implements dynamic driving frequency adjustment based on the type of image being displayed. When still images are detected, the driving frequency is reduced to save power; when moving images are detected, the driving frequency returns to normal. This dynamic adaptation resolves the contradiction by making the system flexible enough to work with different liquid crystal materials while optimizing power consumption for still images.
Solution Approach 2:
The patent changes the driving frequency parameter dynamically based on image type detection. By detecting whether the displayed image is static or moving and adjusting the frame rate accordingly, the system achieves power savings without limiting liquid crystal material choices, as the parameter adjustment works universally across different material types.
2Illumination intensity
If display layers corresponding to respective colors are stacked to display full color image, then color display capability is improved, but loss of light inside the panel is large and display is dark
Solution Approach 1:
The patent employs periodic refresh at reduced frequency for still images. Instead of continuously refreshing at high frequency with multiple color layers causing light loss, the system detects still images and reduces refresh frequency, thereby reducing cumulative light loss while maintaining acceptable display brightness and color performance.
3Use of energy by moving object
If driving frequency is reduced to reduce power consumption, then power consumption is reduced, but image quality may be degraded
Solution Approach 1:
The patent implements a feedback mechanism that detects the type of image being displayed (still or moving) and adjusts the driving frequency accordingly. This feedback loop ensures that image quality is maintained for moving images while allowing power-saving reduced frequency for still images, thus resolving the contradiction between power consumption and image quality.
Solution Approach 2:
The system dynamically adjusts driving frequency based on real-time detection of image characteristics. For still images, lower frequency maintains quality while saving power; for moving images, higher frequency preserves quality. This dynamic behavior resolves the static contradiction by adapting to actual display needs.
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 reduces power consumption by extending the voltage retention period and decreasing the number of writing operations during still image display, thereby maintaining image quality and extending device operation time.
Implementation Method 1
The pixel portion includes a display element which performs display in accordance with voltage of an image signal to be input and a transistor used for controlling retention of the voltage. A channel formation region of the transistor contains a semiconductor material whose band gap is wider than that of a silicon semiconductor and whose intrinsic carrier density is lower than that of silicon
Data Source
AI summary
It is an object to provide a semiconductor display device having a touch panel, which can reduce power consumption. The semiconductor display device includes a panel which is provided with a pixel portion and a driver circuit which controls an input of the image signal to the pixel portion, and a touch panel provided in a position overlapping with the panel in the pixel portion. The pixel portion includes a display element configured to perform display in accordance with voltage of the image signal to be input, and a transistor configured to control retention of the voltage. The transistor includes an oxide semiconductor in a channel formation region. The driving frequency of the driver circuit, that is, the number of writing operations of the image signal for a certain period is changed in accordance with an operation signal from a touch panel.