Luminance Controller Voltage Adjustment for OLED Delay and Color Shift
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing luminance controllers in organic light emitting display devices face challenges with light emission delays and color shifts in low luminance or low grayscale ranges due to parasitic elements and differences in luminance efficiency between red, green, and blue pixels, particularly when using the black current bypass (BCB) driving method.
Innovation Solution
A luminance controller that adjusts initialization and common voltages based on target luminance by selecting appropriate gamma sets, initialization voltage offsets, and common voltage offsets, and interpolating between them to minimize voltage differences and move the BCB operation closer to the threshold voltage, thereby reducing light emission delays and eliminating color shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If black current bypass (BCB) driving method is used to improve black luminance performance, then black image performance is improved, but light emission delay occurs in low luminance range due to parasitic capacitance
Solution Approach 1:
The patent applies preliminary action by initializing the organic light emitting diode before the display operation begins. The initialization voltage is applied to the anode through the initialization transistor during a specific time period (from the start of the display operation to a predetermined time before the end), which prepares the pixel by discharging parasitic capacitance in advance, thereby preventing light emission delay during actual display without affecting black luminance performance.
2Illumination intensity
If BCB driving method is used to improve black luminance performance, then black image performance is improved, but color shift occurs due to differences in luminance efficiency of red/green/blue pixels
Solution Approach 1:
The patent applies local quality by providing different initialization voltages to different color sub-pixels (red, green, blue) based on their individual characteristics. The initialization voltage generator generates separate initialization voltages for each color, allowing tailored compensation for the specific luminance efficiency characteristics of each color pixel, thereby eliminating color shift while maintaining black luminance performance.
3Ease of operation
If fixed initialization voltage is applied to initialize OLED, then initialization is simplified, but light emission delay and color shift cannot be effectively corrected across different luminance ranges
Solution Approach 1:
The patent applies dynamics by making the initialization voltage variable rather than fixed. The initialization voltage generator dynamically adjusts the initialization voltage based on the grayscale value or luminance range, selecting different voltage levels (first, second, or third initialization voltage) depending on the current display conditions. This dynamic adjustment enables effective correction of light emission delay and color shift across different luminance ranges while maintaining operational simplicity through automated control.
Data Source
AI summary
A luminance controller according to example embodiments includes a gamma set selector to select a reference gamma set from among first through N-th gamma sets respectively corresponding to first through N-th reference luminances, based on a target luminance of a display panel; an initialization voltage selector to select an initialization voltage corresponding to the reference gamma set, from among first through N-th initialization voltage offsets respectively corresponding to the first through N-th gamma sets; a common voltage selector to select a common voltage corresponding to the reference gamma set from among first through N-th common voltage offsets respectively corresponding to the first through N-th gamma sets; and a determiner to determine a target initialization voltage based on the target luminance and the initialization voltage, and to determine a target common voltage based on the target luminance and the common voltage.