Display Device Multi-Frequency Driving for Hysteresis Reduction
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Solution Overview
Problem
Existing display devices face challenges in maintaining display quality when driven at low frequencies, particularly in terms of power consumption and efficiency, leading to issues like hysteresis differences and afterimage phenomena between pixels.
Innovation Solution
The display device employs a multi-frequency driving method, utilizing separate scan and emission drivers to manage scan signals and emission control signals at different frequencies, with a timing controller coordinating the drivers to ensure proper pixel operation, including the use of n-type and p-type transistors and a storage capacitor to manage biasing and emission control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If the display device is driven at a low frequency to improve driving efficiency and minimize power consumption, then power consumption is reduced, but display quality deteriorates due to hysteresis differences and afterimage phenomena
Solution Approach 1:
The patent segments the scan signal generation into two independent paths: a first scan driver that generates scan signals at a first frequency (higher than image refresh rate) and a second scan driver that generates scan signals at a second frequency (image refresh rate). This segmentation allows the display to operate at low image refresh rates while maintaining high-frequency scan signaling to prevent hysteresis and afterimage effects, thus resolving the contradiction between low power consumption and display quality.
Solution Approach 2:
The patent changes the frequency parameter of scan signals independently from the image refresh rate parameter. By decoupling these two parameters and allowing the scan signal frequency to remain high while the image refresh rate is reduced, the system achieves both low power consumption and maintained display quality. The emission control signals are also adjusted at the first frequency to compensate for threshold voltage shifts.
2Productivity
If the display device is driven at a low frequency to minimize power consumption, then energy efficiency is improved, but hysteresis differences and afterimage phenomena occur between pixels
Solution Approach 1:
The patent implements feedback mechanisms through emission control signals that are generated at the first frequency (higher than image refresh rate). These emission control signals provide continuous feedback to compensate for threshold voltage shifts in the transistors, preventing hysteresis differences and afterimage phenomena even when operating at low image refresh rates. The timing controller coordinates these feedback signals to maintain pixel uniformity.
Solution Approach 2:
The first scan driver and emission driver operate at a higher frequency than the image refresh rate, performing preliminary actions before each image update. This preliminary scanning and emission control at high frequency ensures that threshold voltage shifts are compensated in advance, preventing hysteresis and afterimage effects from manifesting during low-frequency operation.
3Reliability
If separate scan and emission drivers are used to supply signals at different frequencies, then display quality is maintained at low frequencies, but device complexity increases
Solution Approach 1:
The timing controller serves multiple functions by coordinating both the first scan driver and second scan driver, as well as the emission driver. It generates gate start pulses for both scan drivers and emission start pulses for the emission driver, all while managing the frequency differences between signal paths. This multi-functionality reduces the need for separate control circuits and minimizes overall device complexity despite the multi-frequency operation.
Data Source
AI summary
A display device includes pixels which are connected to first scan lines, second scan lines, third scan lines, emission control lines, and data lines; a scan driver which supplies a bias scan signal to each of the third scan lines at a first frequency and supplies a scan signal to each of the first scan line and the second scan line at a second frequency which corresponds to an image refresh rate of each of the pixels; an emission driver which supplies an emission control signal to each of the emission control lines at the first frequency; a data driver which supplies a data signal to each of the data lines at the second frequency; and a timing controller which controls driving of the scan driver, the emission driver, and the data driver.