Shift Register Q Node Voltage Control for Line Dim Reduction
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Solution Overview
Problem
In touch sensor integrated display devices, the division of display and touch sensing periods leads to a longer Q standby period, causing line dim phenomena due to increased discharge time of the Q node, which affects display quality.
Innovation Solution
A shift register configuration is implemented with a variable low potential voltage line connected to stages during touch sensing periods to prevent Q node discharge, maintaining the voltage level and reducing leakage currents, thereby minimizing line dim issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the display period is divided into multiple panel blocks with touch sensing periods allocated between them, then touch sensing capability is improved, but the Q standby period increases causing line dim phenomena
Solution Approach 1:
The shift register is divided into multiple stages corresponding to different panel blocks, with each stage independently controlling its associated panel block. This segmentation allows the display period to be divided into multiple sub-periods, enabling touch sensing operations to be performed between display periods for different blocks without affecting the overall display quality.
Solution Approach 2:
The patent dynamically adjusts the Q standby period for different stages based on their position in the shift register. Stages corresponding to panel blocks that are displayed during periods when touch sensing is active have their Q standby periods extended, while other stages maintain normal Q standby periods. This dynamic adjustment prevents line dim phenomena while maintaining touch sensing capability.
2Adaptability or versatility
If the Q standby period is extended to accommodate touch sensing periods, then touch sensing operation is enabled, but discharge time of Q node increases causing line dim on first line
Solution Approach 1:
Different stages of the shift register are assigned different Q standby period lengths according to their specific functions. Stages that need to operate during touch sensing periods have extended Q standby periods, while stages dedicated to display periods maintain normal Q standby periods. This local differentiation eliminates line dim phenomena by ensuring that only necessary stages have extended standby periods.
Solution Approach 2:
The Q node is pre-charged to an appropriate voltage level before the touch sensing period begins, ensuring that even with the extended Q standby period, the voltage remains sufficient to prevent line dim phenomena. This preliminary charging action compensates for the longer discharge time during touch sensing operations.
Data Source
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AI summary
A shift register for a touch sensor integrated type display device comprises a first plurality of cascaded stages (STG[1], ..., STG[i-1]) and a second plurality of cascaded stages (STG[i], ..., STG[2i-1]), each of the stages comprising at least a first discharge transistor (T2; T4), a pull-up transistor (Tpu), a pull-down transistor (Tpd), and an output node (Nout) interconnecting the pull-up transistor (Tpu) and the pull-down transistor (Tpd), the pull-down transistor (Tpd) being further connected to a first low potential voltage line (VSS), and a gate electrode of the pull-up transistor (Tpu) constituting a control node (Q), wherein the control node (Q) of the first stage (STG[i]) of the second plurality of cascaded stages (STG[i], ..., STG[2i-1]) is connected to a second low potential voltage line (A_VSS), electrically separate from the first low potential voltage line (VSS), through the first discharge transistor (T2, T4) of said first stage.