Display Driving Controller Luminance Compensation Variable Frame Rate

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Solution Overview

Problem

Display devices operating at variable frame rates experience luminance drops due to capacitive discharge, leading to noticeable image quality degradation when switching between high and low frame rates, especially when the frame length increases, causing flicker and decreased luminance.

Innovation Solution

A display device with a driving controller that adjusts image signals by adding compensation values based on the operation frequency, using dithering circuits and gamma correction, and varying driving voltages to maintain consistent image quality across different frame rates, thereby reducing luminance variations and flicker.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If the frame rate is reduced to conserve power or support variable frame rate rendering, then power consumption is reduced and rendering requirements are met, but luminance drops due to capacitive discharge and image quality deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidluminance

Core Design Contradiction:

Use of energy by stationary objectVSIllumination intensity

Solution Approach 1:

The patent applies preliminary action by pre-charging the pixel capacitor to a higher voltage level before the display period when operating at low frame rates. The driving controller detects the frame rate and adjusts the initialization voltage accordingly, ensuring sufficient luminance is maintained throughout the extended frame period despite capacitive discharge.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the electrical parameter (initialization voltage level) based on the operating frame rate. When low frame rate is detected, the controller increases the initialization voltage to compensate for the longer discharge period, thereby maintaining consistent luminance across different frame rates.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the frame rate is reduced to support variable frame rate rendering, then rendering time requirements are met, but noticeable luminance variation and flicker occur when switching between high and low frame rates

Engineering Contradiction:

Improvevariable frame rate supportVSAvoidluminance consistency

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The patent implements dynamics by making the initialization voltage adaptive and variable based on the detected frame rate. The driving controller dynamically adjusts the voltage level in response to frame rate changes, ensuring smooth transitions without noticeable luminance variations or flicker between different frame rate modes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses feedback by having the driving controller detect the actual frame rate being used and adjust the initialization voltage accordingly. This closed-loop approach ensures that luminance consistency is maintained across different frame rates by continuously adapting to the operating conditions.

Inventive Principle:

Principle #23Feedback

3Adaptability or versatility

If the frame period is increased at low frame rates, then variable frame rate operation is enabled, but the blank period becomes longer causing increased capacitive discharge and luminance drop

Engineering Contradiction:

Improvevariable frame rate operationVSAvoidblank period duration

Core Design Contradiction:

Adaptability or versatilityVSDuration of action of stationary object

Solution Approach 1:

The patent applies the counterweight principle by introducing an opposing action (increased initialization voltage) to compensate for the harmful effect (increased capacitive discharge during extended blank period). The higher initial voltage counteracts the greater voltage drop that occurs during the longer blank period at low frame rates.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

Data Source

PatentUS10839755B2Display device capable of changing luminance depending on operating frequency

Publication Date: 2020.11.17 SAMSUNG DISPLAY CO LTD

AI summary

A display device includes a display panel including gate lines, data lines, and pixels individually connected to a corresponding gate line and data line, a gate driver driving the gate lines, a data driver driving the data lines, and a driving controller. The driving controller receives, from an external source, first image signals and a variable frequency signal indicating an operation frequency (frame rate) for the display device. The driving controller converts the first image signals to second image signals by adding a compensation value corresponding to the operation frequency to the first image signals, and outputs the second image signals to the data driver. Embodiments may compensate for luminance reduction/variation and reduce image artifacts that otherwise occur due to variable frequency operation. An alternative embodiment dynamically controls an amount of light output from a backlight according to the variable frequency signal.