Demux Switch Signal Segmentation for AMOLED Brightness Uniformity
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Solution Overview
Problem
The issue of uneven brightness at the sides and middle positions of small-sized AMOLED display panels due to limited wiring and the resulting S-direction mura (column direction defects) in Demux circuits, which affects product yield.
Innovation Solution
A method for driving a display panel with a Demux circuit by setting a switch signal with a two-phase rise time period, where the switch remains on during the rise time, ensuring uniform voltage distribution across the panel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the wiring width is reduced to meet small size requirements, then the display panel size is reduced, but uneven brightness and S-direction mura occur at side and middle positions
Solution Approach 1:
The rise time period of the switch signal is segmented into two distinct phases: a first phase where the switch signal transitions from low electrical level to predetermined electrical level, and a second phase where it transitions from predetermined electrical level to high electrical level. This segmentation allows different portions of the wiring (side positions vs. middle position) to receive appropriately timed signals, compensating for the uneven voltage distribution caused by reduced wiring width.
Solution Approach 2:
The switch signal is activated in advance during the rise time period before the actual switching operation. By dividing this preliminary action into two phases with the switch remaining on throughout, the system pre-charges or pre-discharges the wiring capacitance uniformly across all positions, preventing the voltage drop that would otherwise occur at the middle position due to longer signal transmission paths in reduced-width wiring.
2Manufacturing precision
If the wiring width is reduced to meet high resolution requirements, then the display panel resolution is improved, but S-direction mura occurs at the middle position
Solution Approach 1:
The switch signal waveform is segmented into two phases during the rise time period, allowing precise control over voltage distribution. The first phase (low to predetermined level) and second phase (predetermined to high level) enable differentiated charging characteristics that compensate for the increased wiring resistance and capacitance effects in high-resolution panels with narrower wiring.
Solution Approach 2:
The electrical level parameters of the switch signal are changed and divided into three levels: low electrical level, predetermined electrical level (intermediate), and high electrical level. By introducing the predetermined electrical level as an intermediate state and maintaining the switch on throughout the transition, the signal parameters are optimized to ensure uniform voltage distribution across the reduced wiring width in high-resolution displays.
3Speed
If the switch signal transitions directly from low to high electrical level, then the switching speed is improved, but uneven voltage distribution and mura occur
Solution Approach 1:
The single transition is segmented into two phased transitions during the rise time period. The first phase transitions from low to predetermined electrical level, and the second phase transitions from predetermined to high electrical level. The switch remains on throughout both phases, ensuring continuous current flow that uniformly charges the wiring capacitance while maintaining fast overall switching speed.
Solution Approach 2:
The switch signal employs periodic phase transitions within the rise time period, with the switch oscillating between on states during the two phases. This periodic action ensures continuous charging current delivery to all wiring segments, preventing voltage distribution unevenness while maintaining the required switching speed for display operation.
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 ensures even brightness across the display panel by minimizing the difference in feedthrough voltages at side and middle positions, effectively alleviating the occurrence of S-direction mura.
Implementation Method 1
At the end of the first phase, the switch signal transforms from the low electrical level to the predetermined electrical level to generate a feedthrough voltage
Data Source
AI summary
A method for driving a display panel includes controlling a signal of ON/OFF state of a switch in a Demux circuit as a switch signal, and dividing each rising time period in the switch signal into two phases (T, T1), so that the abrupt change effect of voltage generated on both side positions of the display panel and a middle position of the display panel is relatively uniform, ensuring that the charging effect of the display panel at different positions is substantially the same, the brightness of the display panel is even after being driven, and the problem of bright lines in the column direction of the display panel is effectively improved.