Amplifier Offset Polarity Reversal for Display Panel Uniformity
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Solution Overview
Problem
Liquid crystal display devices suffer from 'inter-block unevenness' due to variations in offset voltages of amplifiers within grayscale generation power supply circuits, leading to inconsistent gamma characteristics and visible boundaries between regions driven by adjacent data drivers.
Innovation Solution
The display device incorporates a grayscale voltage generation circuit with amplifiers that have reversible offset voltage polarity, which is controlled to be opposite between frame periods, effectively canceling voltage level errors and reducing inter-block unevenness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If grayscale generation power supply circuits are individually integrated in each data driver, then cost is reduced and component count is decreased, but variations in amplifier offset voltages cause inter-block unevenness and inconsistent gamma characteristics
Solution Approach 1:
The patent changes the polarity parameter of the amplifier offset voltage periodically between frame periods. By inverting the offset polarity, the system compensates for the fixed offset variations in integrated amplifiers, thereby maintaining consistent gamma characteristics across different data drivers while keeping the integrated structure for cost efficiency
Solution Approach 2:
The patent applies periodic inversion of the amplifier offset polarity at each frame period. This periodic action ensures that the offset errors are averaged out over time, eliminating inter-block unevenness while maintaining the benefits of integrated grayscale generation circuits
2Ease of operation
If amplifier offset voltage polarity is kept constant, then circuit operation is simple, but voltage level errors accumulate and cause visible boundaries between display regions
Solution Approach 1:
The patent inverts the amplifier offset polarity between frame periods instead of keeping it constant. This inversion approach cancels out the accumulated voltage level errors that would otherwise cause visible boundaries, while adding minimal complexity to the circuit operation through simple polarity switching
Data Source
AI summary
A data driver used for driving a display panel is provided with a grayscale voltage generator circuit generating a plurality of grayscale voltages; and a drive circuitry selecting a selected grayscale voltage from the plurality of grayscale voltages in response to input display data, and outputting a data signal having a voltage level corresponding to the selected grayscale voltage to the display panel. The grayscale voltage generator circuit comprises an amplifier generating a voltage bias; and a voltage generator circuit generating the plurality of grayscale voltages from the voltage bias. The amplifier is designed so that a polarity of an offset voltage of the amplifier is reversible. The polarity of the offset voltage of the amplifier is controlled so that the polarity of the offset voltage of the amplifier used for driving a specific pixel of the display panel in a certain frame period is opposite to that of the offset voltage of the amplifier used for driving the c specific pixel in another frame period.