Display Driver Leakage Current Control for Still Images
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Solution Overview
Problem
Display devices face high power consumption when displaying still images, leading to flickering due to leakage current, as existing methods to reduce power consumption, such as lowering driving frequency, result in deteriorated display quality.
Innovation Solution
A display device with a signal controller that drives data and gate drivers at different frequencies for moving and still images, using a gate-off voltage generator to apply varying gate-off voltages based on a representative value of the image data, ensuring equal voltage differences between the source and gate for both positive and negative data voltages, thereby minimizing leakage current and flickering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the driving frequency is lowered to reduce power consumption, then energy efficiency improves, but display quality deteriorates due to flickering from leakage current
Solution Approach 1:
The patent changes the gate-off voltage parameter dynamically based on the data voltage applied to pixels. By adjusting the gate-off voltage to maintain a constant voltage difference (Vgs) between source and gate, the invention compensates for leakage current variations at different driving frequencies, thereby maintaining display quality while enabling low-power operation.
Solution Approach 2:
The invention introduces dynamic adjustment of gate-off voltage levels based on operating conditions. The gate-off voltage generator dynamically selects between first and second gate-off voltages depending on whether positive or negative data voltages are applied, and adjusts these voltages based on representative image data values, enabling adaptive compensation for leakage current at varying driving frequencies.
2Use of energy by stationary object
If the driving frequency is lowered for still images, then power consumption decreases, but leakage current causes flickering
Solution Approach 1:
The patent modifies the gate-off voltage parameter in response to changes in driving frequency and data voltage polarity. By calculating a representative value from image data and adjusting gate-off voltages accordingly, the invention maintains consistent Vgs conditions that minimize leakage current effects, preventing flickering even at reduced driving frequencies for still image display.
Solution Approach 2:
The signal controller implements feedback by monitoring the data voltage applied to pixels and adjusting the gate-off voltage accordingly. The gate-off voltage generator receives feedback about the current operating state (positive or negative data voltage, representative image value) and dynamically adjusts gate-off voltages to compensate for leakage current, thereby eliminating flickering at low driving frequencies.
3Reliability
If different gate-off voltages are applied based on data voltage polarity, then leakage current is minimized, but device complexity increases
Solution Approach 1:
The gate driver is segmented into functional parts: a gate-off voltage generator that produces different gate-off voltages based on data voltage polarity, and a gate driver circuit that applies these voltages selectively. This segmentation allows complex leakage current compensation functionality to be implemented through modular components, managing device complexity while achieving improved leakage current control.
Data Source
AI summary
A controller controls the driving frequency and voltages for a display device. If image data corresponds to a moving picture, the controller drives a data driver and a gate driver at a moving picture frequency. If image data corresponds to a still image, drives the data driver and the gate driver at a still image frequency lower frequency than the moving picture frequency. When the still image is to be displayed, the signal controller also controls leakage current of a thin film transistor of a pixel based on a representative value of the image data, such that positive leakage current applied for a positive data voltage is equal to negative leakage current applied for a negative data voltage.