OLED Driving Circuit Bias Control for VRR Luminance Stability

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Solution Overview

Problem

The change in refresh rate in electroluminescent display devices using a variable refresh rate (VRR) can cause unnatural perception of luminance differences, which is undesirable for viewers.

Innovation Solution

The display device incorporates a pixel circuit with a driving transistor, compensation transistor, first and second bias transistors, and a driver that dynamically controls bias voltages before and after switching refresh rates to maintain consistent luminance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the refresh rate is changed in VRR mode, then power consumption and driving speed are optimized, but luminance difference occurs causing unnatural perception

Engineering Contradiction:

Improverefresh rateVSAvoidluminance

Core Design Contradiction:

ProductivityVSIllumination intensity

Solution Approach 1:

The patent applies parameter changes by dynamically adjusting the bias voltage applied to the electroluminescent device based on the refresh rate. When the refresh rate changes, the bias voltage is modified to compensate for luminance variations, ensuring consistent visual perception across different refresh rates while maintaining the benefits of variable refresh rate operation.

Inventive Principle:

Principle #35Parameter changes

2Speed

If the refresh rate is increased for high-speed driving, then response speed is improved, but power consumption increases

Engineering Contradiction:

Improverefresh rateVSAvoidpower consumption

Core Design Contradiction:

SpeedVSUse of energy by moving object

Solution Approach 1:

The patent implements dynamics by enabling the display device to operate at variable refresh rates according to content requirements. The system dynamically switches between different refresh rates (e.g., 1Hz to 120Hz) based on whether the content is static or changing, allowing high-speed driving when needed while reducing power consumption during static displays.

Inventive Principle:

Principle #15Dynamics

3Use of energy by moving object

If the refresh rate is reduced for power saving, then power consumption is decreased, but luminance consistency deteriorates

Engineering Contradiction:

Improvepower consumptionVSAvoidluminance consistency

Core Design Contradiction:

Use of energy by moving objectVSStability of the object's composition

Solution Approach 1:

The patent compensates for luminance inconsistency at reduced refresh rates by adjusting the bias voltage parameter. When operating at low refresh rates for power saving, the system modifies the bias voltage to maintain proper charge accumulation in the electroluminescent device, ensuring luminance consistency is preserved even during extended hold periods between refresh cycles.

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The solution effectively reduces luminance differences during refresh rate changes, ensuring a smooth transition and preventing viewer perception of rate changes.

Implementation Method 1

an electroluminescent display device using a variable refresh rate (VRR) mode

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentUS20260024496A1Driving Circuit and Display Device Using the Same

Publication Date: 2026.01.22 LG DISPLAY CO LTD

AI summary

Disclosed is an electroluminescent display device using a variable refresh rate (VRR) mode. The purpose of the present disclosure is to reduce the occurrence of a difference in luminance at a time point of a refresh rate change, thereby preventing viewers from perceiving the variation of the refresh rate.