Scan Line Driving Circuit High Impedance Suppression
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Solution Overview
Problem
In electro-optical devices, the demultiplexer type scan line driving circuit results in a prolonged high impedance state when scan lines are not selected, leading to potential noise-induced off-leaks and stripe patterns on the display, degrading display quality.
Innovation Solution
A scan line driving circuit that divides scan lines into blocks and uses an address signal output circuit and demultiplexer to selectively activate scan lines, ensuring that only selected lines are connected, while unselected lines are grounded, thereby shortening the high impedance state and stabilizing non-active levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a demultiplexer type scan line driving circuit is used to sequentially select scan lines, then the circuit complexity is reduced and manufacturing efficiency is improved, but the scan lines remain in a high impedance state for a prolonged period during non-selection, causing noise-induced off-leaks and stripe patterns that deteriorate display quality
Solution Approach 1:
The patent applies preliminary action by grounding the scan lines before they are selected. The ground selection circuit预先 connects unselected scan lines to ground potential, so when they transition to the selected state, they do not experience a prolonged high impedance period. This preliminary grounding action prevents noise-induced off-leaks and stripe patterns while maintaining the simplified demultiplexer circuit structure.
2Device complexity
If scan lines are left in a high impedance state during non-selection periods, then the circuit structure is simplified, but the uniformity of scan line voltages deteriorates due to noise-induced off-leaks in pixels
Solution Approach 1:
The patent applies equipotentiality by maintaining all scan lines at ground potential during non-selection periods through the ground selection circuit. This ensures that unselected scan lines are at a defined potential rather than floating in a high impedance state, preventing voltage fluctuations and noise-induced off-leaks. The equipotential grounding maintains uniform scan line voltages while keeping the circuit structure simple.
3Productivity
If the high impedance period of scan lines is prolonged in a demultiplexer driving circuit, then manufacturing efficiency is improved, but noise-induced off-leaks become more severe, generating stripe patterns on the display screen
Solution Approach 1:
The patent converts the potentially harmful high impedance state into a beneficial grounded state. Instead of allowing scan lines to float in high impedance during non-selection, the ground selection circuit actively grounds them, transforming what would be a harmful condition (prolonged high impedance causing off-leaks) into a beneficial condition (defined ground potential that suppresses noise and prevents stripe patterns).
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
This approach reduces the duration of the high impedance state, enhances the uniformity of scan line voltages, and improves display quality by minimizing noise-induced off-leaks and stripe patterns.
Implementation Method 1
a plurality of switches 140 are provided in correspondence with the plurality of scan lines 112, each having one end being connected to a scan line corresponding thereto and the other end being commonly grounded
Data Source
AI summary
The object of the present invention is to suppress a high impedance state of scan lines in a case where the scan lines are driven by using a demultiplexer. A logic AND circuit 34 outputs signals resulting from logical product of block selection signals Y-1, Y-2, and Y-3, . . . , and Y-80 and a signal Enb as address signals Ad-1, Ad-2, and Ad-3, . . . , and Ad-80. A demultiplexer 40 distributes address signals Ad-1, Ad-2, Ad-3, . . . , and Ad-80 to scan lines 112 in accordance with selection signals Sel-1, Sel-2, and Sel-3. Drains of TFTs 140 are connected to the scan lines 112. The TFTs 140 are controlled to be turned on/off, for example, by using a signal Sel-all that is a logically inverted signal of the signal Enb, and when the TFTs are turned on, level L is determined.