Display Drive Device Gate Signal ON/OFF Ratio Stabilization
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Solution Overview
Problem
Conventional display devices experience fluctuations in the ON/OFF ratio of gate signal lines when changing refresh rates, leading to variations in threshold voltage of switching elements, which can cause operational defects, especially with increased image resolution and refresh rate adjustments.
Innovation Solution
A drive device that includes refresh rate changing means and drive amount control means to adjust the ratio of scan periods to pause periods, ensuring the ON/OFF ratio of each gate signal line remains constant by controlling the drive time during scan periods, thereby stabilizing the threshold voltage of switching elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refresh rate is increased to improve display image quality, then the smoothness of movement and reduction of flicker are improved, but the electric power consumption increases
Solution Approach 1:
The patent applies dynamics by making the refresh rate adjustable rather than fixed. The display device can dynamically change the refresh rate between a first value (higher) and a second value (lower) based on display conditions, allowing optimization between image quality and power consumption for different usage scenarios
Solution Approach 2:
The patent changes the refresh rate parameter between two distinct values. By switching between a first refresh rate (for high image quality) and a second refresh rate (for lower power consumption), the system can adapt to different display requirements and usage conditions
2Speed
If the write time is shortened due to increased resolution, then the scanning speed is improved, but the voltage retention rate of liquid crystals decreases leading to reduced contrast ratio
Solution Approach 1:
The patent applies preliminary action by performing a preliminary write operation before the main write operation. The first write operation (performed during the first scan period) prepares the liquid crystal state in advance, ensuring sufficient voltage retention and contrast ratio even when the second write operation uses shortened write time for high resolution
3Adaptability or versatility
If the refresh rate is changed by adjusting scan periods only, then the refresh rate is modified, but the ON/OFF ratio of gate signal lines fluctuates causing threshold voltage variations
Solution Approach 1:
The patent changes multiple parameters simultaneously - both the refresh rate (by adjusting scan period ratio) and the drive time of gate signal lines. By coordinating these parameter changes, the system maintains a constant ON/OFF ratio for switching elements even when refresh rate changes, preventing threshold voltage variations
Solution Approach 2:
The patent implements feedback by monitoring the relationship between scan periods and pause periods, and automatically adjusting the drive time of gate signal lines to maintain constant ON/OFF ratio. This closed-loop control ensures threshold voltage stability during refresh rate transitions
Data Source
AI summary
Included are: refresh a rate changing section (15) for changing a refresh rate of a display panel (2) by configuring settings for scan periods during each of which a plurality of gate signal lines (G) of the display panel (2) are sequentially scanned and for pause periods during each of which sequential scanning of the plurality of gate signal lines (G) is suspended; and a drive amount control section (20) for controlling, in accordance with a ratio of the scan periods to the pause periods, drive time during which each of the gate signal lines is driven in each of the scan periods.