Display Control Circuit Frame Rate Brightness Compensation

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Solution Overview

Problem

LCD panels with variable refresh rates experience inconsistent current leakage times in pixel capacitors, leading to variations in image brightness and color, causing flickering and nonuniformity due to differing durations of voltage holding stages at different frame rates and pixel clock frequencies.

Innovation Solution

A control method and circuit that dynamically adjusts backlight brightness or image data pixel values based on the frame rate, using a receiving interface, image processing circuit, and backlight control circuit to generate control signals for the display panel, ensuring consistent image quality by compensating for frame rate changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If variable refresh rate display method is adopted to change frame rate by changing the number of vertical blanking intervals, then the frame rate can be adjusted, but the current leakage time of pixel capacitors becomes inconsistent causing brightness and color nonuniformity

Engineering Contradiction:

Improveframe rate adjustment capabilityVSAvoidimage brightness and color uniformity

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The patent changes the pixel clock frequency parameter dynamically according to the frame rate. When frame rate changes, the pixel clock frequency is adjusted proportionally (e.g., from 148.5 MHz at 60 Hz to 297 MHz at 120 Hz), which maintains consistent charging time for pixel capacitors across different frame rates, thereby resolving the brightness and color nonuniformity issue while preserving frame rate variability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent preemptively adjusts the pixel clock frequency before frame rate changes take effect, and applies compensation algorithms to pre-correct potential brightness and color deviations. This preliminary action prevents the nonuniformity problem from occurring in the first place, rather than correcting it after it appears

Inventive Principle:

Principle #9Preliminary anti-action

2Reliability

If different pixel clock frequencies are used to drive image content with the same frame rate, then the frame rate remains constant, but the voltage holding stage duration varies causing brightness and color differences

Engineering Contradiction:

Improveframe rate stabilityVSAvoidimage brightness and color consistency

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent establishes a fixed relationship between pixel clock frequency and frame rate, where the pixel clock frequency is set to a specific multiple of the frame rate (e.g., 4.5 times). This parameter coordination ensures that when frame rate remains constant, the pixel clock frequency also remains constant, thereby maintaining consistent voltage holding stage duration and eliminating brightness and color variations

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11615753B2Control circuit applied to display and associated control method

Publication Date: 2023.03.28 REALTEK SEMICON CORP

AI summary

A control circuit applied to a display includes a receiving interface, an image processing circuit, and a backlight control circuit. The receiving interface is arranged to receive an image data from an image source, wherein the image data has an unfixed frame rate. The image processing circuit is arranged to receive the image data from the receiving interface and determine a frame rate of the image data. The backlight control circuit is arranged to generate a control signal to a display panel according to the frame rate, to control brightness of a backlight module of the display panel.