TFT LCD Common Signal Waveform Adjustment for Contrast and Power

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Solution Overview

Problem

In electronic devices with TFT liquid crystal displays, contrast differences between images are emphasized by intense light, leading to user discomfort, especially when the light source is activated for viewing in dark conditions.

Innovation Solution

An electronic device with a TFT liquid crystal panel and a light source that emits light onto the back face of the panel, featuring a processor that generates distinct common signals for when the light source is lit and when it is not, with different waveforms to manage power consumption and contrast differences.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the inversion period of the common signal is extended to reduce power consumption, then power consumption is reduced, but contrast difference between images increases during inversion

Engineering Contradiction:

Improvepower consumptionVSAvoidcontrast difference

Core Design Contradiction:

Use of energy by moving objectVSManufacturing precision

Solution Approach 1:

The patent applies dynamics by making the common signal waveform adjustable based on operating conditions. The signal processing unit changes the common signal waveform according to the backlight duty ratio, transitioning from a fixed waveform to a dynamic one that adapts to different lighting conditions, thereby resolving the contradiction between power consumption and contrast difference

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameters of the common signal waveform (such as voltage levels, pulse width, or frequency characteristics) based on the backlight duty ratio. By adjusting these signal parameters dynamically, the system maintains low power consumption while compensating for contrast differences that occur during inversion periods

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If a TFT liquid crystal panel with extended inversion period is used to achieve low power consumption, then power consumption is reduced, but contrast differences between images are emphasized when intense light strikes the panel

Engineering Contradiction:

Improvepower consumptionVSAvoidcontrast difference emphasis under intense light

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a signal processing unit as an intermediary between the backlight control and the common signal generation. This intermediary component analyzes the backlight duty ratio and accordingly adjusts the common signal waveform, serving as a mediator that coordinates between power consumption requirements and contrast quality under intense lighting conditions

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system performs preliminary anti-action by pre-adjusting the common signal waveform based on the anticipated backlight duty ratio. Before intense light conditions fully manifest their harmful effects, the common signal is already optimized to counteract potential contrast differences, preventing the emphasis of contrast artifacts before they occur

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS10824117B2Electronic device, electronic timepiece, display control method, and storage medium

Publication Date: 2020.11.03 CASIO COMPUTER CO LTD

AI summary

An electronic device includes: a TFT liquid crystal panel; a light source that emits light to be radiated onto a back face of the TFT liquid crystal panel; and a processor that generates a common signal to be input to a common electrode of the TFT liquid crystal panel. The processor generates the common signal so as to have a waveform that differs between when the light source is not lit and when the light source is lit.