Data Driver DAC Error Diffusion for Uniform Brightness
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Solution Overview
Problem
Conventional data drivers for light emitting display devices often generate non-uniform data signals due to deviations in digital-to-analog converters (DACs), leading to images with non-uniform brightness and noise in the form of vertical lines.
Innovation Solution
A data driver design that includes a holding latch unit, a signal generator with multiple DACs, and switching units that alter the coupling between holding latches and DACs between horizontal periods, ensuring that data signals are generated by different DACs each period, thereby diffusing errors and achieving uniform brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional data drivers use fixed DAC assignments for each data line, then the circuit structure is simple, but non-uniform brightness and vertical line noise occur due to DAC deviations
Solution Approach 1:
The patent applies dynamics by making the DAC assignment dynamic rather than fixed. Switching units dynamically reassign which DAC serves which data line on a per-horizontal-period basis. This dynamic reassignment ensures that no single DAC's deviation consistently affects the same data line, thereby uniforming brightness across the display while managing the complexity through systematic switching control.
Solution Approach 2:
The patent implements periodic action by cycling through different DAC assignments for each horizontal period. During each horizontal period, a specific mapping between DACs and data lines is applied, and this mapping changes in subsequent periods. This periodic reassignment pattern ensures that DAC deviations are distributed uniformly across all data lines over time, eliminating persistent vertical line noise while maintaining manageable circuit complexity through repetitive switching sequences.
2Manufacturing precision
If the same DAC is always used for a specific data line, then the circuit control is simple, but brightness non-uniformity occurs due to DAC manufacturing deviations
Solution Approach 1:
The patent makes the signal generation process dynamic by continuously changing which DAC generates the signal for each data line. Instead of a static one-to-one mapping, the system dynamically routes data signals through different DACs based on the current horizontal period. This dynamic approach ensures that manufacturing deviations in any single DAC do not persistently affect the same data line, improving signal uniformity while the switching control manages the operational complexity.
Solution Approach 2:
The patent applies periodic action by implementing a cyclic pattern of DAC assignments. Each horizontal period uses a specific DAC assignment pattern, and this pattern systematically changes in subsequent periods. This periodic reassignment ensures that over the course of multiple horizontal periods, each data line receives signals from multiple different DACs, averaging out manufacturing deviations and achieving uniformity while the repetitive nature of the switching maintains operational manageability.
Data Source
AI summary
A data driver adapted to display an image with substantially uniform brightness is provided. The data driver includes a holding latch unit including holding latches for storing data, a signal generator including digital-analog converters for receiving the data to generate data signals, a first switching unit provided between the holding latch unit and the signal generator, and a second switching unit coupled to the signal generator to transmit the data signals to data lines. The first switching unit couples the holding latches to the digital-analog converters during a horizontal period in a manner different from the manner in which the holding latches and the digital-analog converters are coupled to each other during a previous horizontal period. Therefore, errors of the digital-analog converters are diffused so that it is possible to display an image with substantially uniform brightness.