OLED Variable Frame Luminance Control via Voltage Step
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Solution Overview
Problem
In OLED display devices operating in variable frame mode, the increased time length of the variable blank period leads to luminance reduction due to leakage current and increased gray levels, causing image quality degradation.
Innovation Solution
The OLED display device determines an initial power supply voltage level based on panel load and gray levels, and gradually increases the voltage level during the variable blank period using a step code, ensuring consistent luminance by adjusting the power supply voltage accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the time length of the variable blank period is increased to support variable frame mode, then the frame frequency mismatch is reduced and tearing phenomenon is prevented, but the luminance of the display panel is reduced due to leakage current
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the power supply voltage level during the variable blank period. Instead of maintaining a constant voltage, the system modifies the voltage parameter in response to the extended blank period duration, thereby compensating for luminance reduction caused by leakage current while preserving the benefits of variable frame mode operation
Solution Approach 2:
The patent implements preliminary action by pre-charging or pre-adjusting the power supply voltage before the variable blank period begins. This preliminary adjustment ensures that when the blank period extends, the voltage is already optimized to counteract the expected leakage current effects, maintaining luminance stability throughout the extended period
2Illumination intensity
If the gray level of image data is increased to improve image quality, then the luminance of the display panel is enhanced, but the luminance reduction in the variable blank period is further exacerbated
Solution Approach 1:
The patent dynamically adjusts the power supply voltage parameter based on the gray level of image data. When high gray levels are detected, the system modifies the voltage during the variable blank period to compensate for the increased leakage current, thereby maintaining luminance without excessive energy loss
Solution Approach 2:
The patent introduces dynamics by making the power supply voltage adjustable and responsive to real-time conditions. The voltage is not fixed but dynamically modified based on the gray level and blank period duration, allowing the system to optimize the balance between luminance and energy consumption under varying operating conditions
Data Source
AI summary
An organic light emitting diode (“OLED”) display device, which operates in a variable frame mode, includes a display panel including a plurality of pixels, a power management circuit which supplies a power supply voltage to the plurality of pixels, and a controller which determines a panel load, a first representative gray level and a second representative gray level by analyzing input image data, determines an initial level of the power supply voltage based on the panel load and the first representative gray level, and determines a step level of the power supply voltage based on the panel load and the second representative gray level. The power management circuit generates the power supply voltage having the initial level during an active period, and gradually increases a voltage level of the power supply voltage from the initial level based on the step level during a variable blank period.