Display Panel Ripple Frequency Control to Prevent Waterfall Effect

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Solution Overview

Problem

Existing display devices experience luminance differences due to residual ripple voltages from rectified AC power, leading to phenomena like the 'waterfall effect' where horizontal lines are visible due to varying luminance between pixel rows.

Innovation Solution

The display device incorporates a timing controller that sets the ripple frequency of the power voltage to deviate from the scan frequency by a predetermined reference ratio, typically 5%, ensuring the ripple frequency does not align with integer multiples of the scan frequency, thereby reducing luminance differences and preventing the waterfall effect.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If AC voltage is rectified to generate DC power voltage, then power voltage is generated for driving pixels, but ripple voltage remains causing luminance differences

Engineering Contradiction:

Improvepower voltageVSAvoidluminance difference

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent changes the frequency parameter of the power voltage by adjusting the switching frequency of the power voltage generator to deviate from the scan frequency, thereby transforming the ripple voltage characteristics to minimize luminance differences caused by frequency alignment between ripple and scan signals

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent converts the harmful ripple voltage into a beneficial effect by deliberately adjusting its frequency to mismatch with the scan frequency, transforming the potential source of luminance differences into a solution that prevents the waterfall phenomenon while maintaining efficient power conversion

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Productivity

If ripple frequency aligns with scan frequency, then power conversion is efficient, but luminance differences cause waterfall phenomenon

Engineering Contradiction:

Improvepower conversion efficiencyVSAvoidwaterfall phenomenon

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the frequency parameter of the power voltage by adjusting the switching frequency to deviate from the scan frequency, thereby transforming the ripple voltage characteristics to minimize luminance differences caused by frequency alignment between ripple and scan signals

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent dynamically adjusts the switching frequency of the power voltage generator based on the scan frequency, making the system adaptive to different operating conditions while maintaining frequency mismatch to prevent the waterfall phenomenon

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12548520B2Display device, method of driving the same, and electronic device

Publication Date: 2026.02.10 SAMSUNG DISPLAY CO LTD

AI summary

A display device includes a display panel including pixels, a gate driver which sequentially applies scan signals to pixel rows including the pixels at a scan frequency, a data driver which applies data voltages to the pixels, a power voltage generator which applies a power voltage to the pixels, and a timing controller which sets a ripple frequency of the power voltage to deviate from the scan frequency by a predetermined reference ratio or more.