Bidirectional Shift Register End Stage Multi-Output Prevention
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Solution Overview
Problem
Bidirectional shift registers experience multi-output issues during forward and reverse driving, leading to uneven pixel luminance and the 'end line brightening phenomenon', particularly at high temperatures, due to floating set nodes in the last and first stages.
Innovation Solution
A bidirectional shift register design where only the first stage is set in forward driving and only the last stage is set in reverse driving, utilizing forward and reverse scan controllers, output units, and deactivation prevention switching devices to prevent multi-outputs by synchronizing clock pulses and start pulses, ensuring proper node activation and deactivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a start pulse is supplied to both first stage and last stage at the beginning of driving, then bidirectional driving capability is achieved, but multi-output problem occurs causing end line brightening phenomenon
Solution Approach 1:
The patent applies local quality by making the first stage and last stage structurally different. The first stage includes a forward scan controller that prevents multi-output in forward driving, while the last stage includes a reverse scan controller that prevents multi-output in reverse driving. This asymmetric design allows bidirectional driving capability while preventing the harmful multi-output effect at each end stage.
Solution Approach 2:
The patent segments the bidirectional shift register into distinct functional components: forward scan controllers in the first stage, reverse scan controllers in the last stage, and intermediate stages. This segmentation allows independent control of forward and reverse driving operations, preventing the start pulse from causing multi-output at both ends simultaneously.
2Adaptability or versatility
If start pulse is supplied to last stage in forward driving, then reverse driving capability is enabled, but set node floats causing multi-output from last stage
Solution Approach 1:
The patent applies preliminary action by equipping the last stage with a reverse scan controller that is prepared in advance. When forward driving occurs, this reverse scan controller actively prevents the set node from floating by maintaining proper voltage levels, thereby preventing multi-output before it can occur. The protective mechanism is already in place and active during forward driving operations.
3Adaptability or versatility
If start pulse is supplied to first stage in reverse driving, then forward driving capability is enabled, but set node floats causing multi-output from first stage
Solution Approach 1:
The patent applies preliminary action by equipping the first stage with a forward scan controller that is prepared in advance. When reverse driving occurs, this forward scan controller actively prevents the set node from floating by maintaining proper voltage levels, thereby preventing multi-output before it can occur. The protective mechanism is already in place and active during reverse driving operations.
Data Source
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AI summary
Disclosed herein is a bidirectional shift register, which is capable of preventing multi-outputs from both end stages. The shift register includes a plurality of stages for outputting scan pulses forward or reversely based on a start pulse and a plurality of clock pulses with a phase difference. A last one of the stages includes a forward scan controller for making a set node active and a reset node inactive based on any one of the clock pulses and a scan pulse from an upstream stage, a reverse scan controller for making the set node active and the reset node inactive based on any one of the clock pulses and the start pulse, and an output unit for outputting any one of a corresponding scan pulse and a deactivation voltage based on a voltage at the set node, a voltage at the reset node and any one of the clock pulses.