LCD Timepiece Display Timing Around AC Polarity Reversal
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Solution Overview
Problem
Existing techniques for applying AC voltage to liquid crystal panels in digital timepieces face issues such as increased electrical load interference with image data writing, software complexity, and duty ratio imbalance, leading to potential overlap between polarity reversal and image data timing.
Innovation Solution
A time measurement device with a polarity control unit that reverses AC voltage at a constant cycle, an event reception unit to hold events, a display update determination unit to manage standby times, and an image data output control unit to write data at optimized times, ensuring non-overlapping polarity reversal and image data writing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the polarity of AC voltage is reversed at a constant cycle, then liquid crystal reliability is maintained, but the timing of polarity reversal may overlap with image data writing timing
Solution Approach 1:
The patent applies preliminary action by setting a transfer standby period before polarity reversal occurs. Image data transfer is prohibited during this standby period, preventing overlap between data writing and polarity reversal. The control unit determines whether to transfer image data based on the timing relationship with the polarity reversal, ensuring data is transferred only when it will not conflict with the AC voltage polarity reversal timing.
2Object-affected harmful factors
If image data transfer is delayed until after polarity reversal standby period, then overlap is prevented, but software complexity increases
Solution Approach 1:
The patent reduces software complexity by establishing a fixed transfer standby period before polarity reversal. This predetermined timing window simplifies the control logic, as the system only needs to check whether the current time falls within this predefined standby period rather than implementing complex real-time conflict detection and resolution algorithms.
3Object-affected harmful factors
If polarity reversal is delayed during enable signal output, then overlap is avoided, but duty ratio 50% cannot be maintained
Solution Approach 1:
The patent segments the AC voltage cycle into distinct phases: a transfer standby period before polarity reversal, and a second standby period after polarity reversal. By prohibiting image data transfer only during these specific segmented periods while maintaining the overall polarity reversal cycle, the system avoids timing overlap without compromising the 50% duty ratio of the AC voltage.
Data Source
AI summary
To prevent, with a simple configuration, a timing at which a polarity of an AC voltage applied to a liquid crystal panel is reversed at a constant polarity reversal cycle and a timing at which image data is written to the liquid crystal panel from overlapping each other. A time measurement device includes: an event holding unit configured to hold an event in periods of a certain first standby operation time immediately before the polarity of the AC voltage applied to the liquid crystal panel is reversed and a certain second standby operation time immediately after the polarity of the AC voltage is reversed; a display update determination unit configured to determine whether the holding event requires updating of the display on the liquid crystal panel after the periods of the first standby operation time and the second standby operation time elapse; and an image data output control unit configured to write, to the liquid crystal panel, image data of the event for which a determination is made that the updating of the display on the liquid crystal panel is required.