Column Driver Multiplexer Parasite Capacitor Discharge
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Solution Overview
Problem
Ghost images occur in display devices due to parasite capacitors in the row and column drivers, causing incorrect lighting of luminescent devices and degrading display quality.
Innovation Solution
A column driver with two multiplexers and select switches is used to control signal transmission paths, where one multiplexer supplies power to a luminescent device and the other discharges the parasite capacitor in the select switch during specific driving periods, ensuring proper charging and discharging of luminescent devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a multi-column scan driving scheme is used to drive the luminescent array, then the display device can efficiently control multiple luminescent devices, but parasite capacitors in the row driver and column driver cause ghost images that degrade display quality
Solution Approach 1:
The patent extracts the harmful residual charges from the parasite capacitors by introducing a dedicated discharge path through the second multiplexer. This allows the harmful charges to be removed separately from the normal driving operation, eliminating the ghost image effect while preserving the efficient multi-column scan driving capability.
Solution Approach 2:
The patent introduces a second multiplexer as an intermediary component that provides a dedicated discharge path for the parasite capacitors. This intermediary structure mediates between the driving signal and the luminescent devices, allowing controlled discharge of residual charges without interfering with the main driving function.
2Ease of operation
If select switches are used to control signal transmission paths in the column driver, then individual column control is achieved, but residual charges in the parasite capacitors of select switches charge wrong luminescent devices
Solution Approach 1:
The patent segments the control function into two separate multiplexers: the first multiplexer handles the driving signal transmission for normal operation, while the second multiplexer specifically manages the discharge of parasite capacitors. This segmentation allows independent optimization of each function, maintaining ease of column control while improving display accuracy.
Solution Approach 2:
The patent implements preliminary discharge action by using the second multiplexer to clear residual charges from the parasite capacitors before the next driving cycle begins. This preliminary action prevents the accumulation of harmful charges that would otherwise cause incorrect luminescent device activation.
3Device complexity
If the same word line is used for multiple luminescent devices in a row, then row-level addressing is simplified, but residual charges can affect adjacent luminescent devices in subsequent rows
Solution Approach 1:
The patent extracts the harmful residual charges from the shared word line structure by providing a dedicated discharge path through the second multiplexer. This allows the simplified row-level addressing to function correctly without the harmful side effect of charge interference affecting adjacent luminescent devices.
Data Source
AI summary
A display device includes a luminescent array and a column driver. The cathodes of the first row of luminescent devices are coupled to a first word line. The anodes of the second row of luminescent devices are coupled to a second word line. In the mth column of luminescent devices, the anode of a first luminescent device in the first row is coupled to the cathode of a second luminescent device in the second row. The column driver includes a switch and two multiplexers. The switch controls the path between input signal and the mth column of luminescent devices. The first multiplexer provides a first driving signal for charging the parasite capacitor in the switch and the first luminescent device during a first period. The second multiplexer provides a second driving signal for charging the second luminescent device and discharging the parasite capacitor in the switch during a second period.