LCD Backlight LED Strings with Periodic Square-Wave Driving
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Solution Overview
Problem
Large-sized liquid crystal display devices require high backlight brightness, leading to increased heat and reduced service life of LED lamp beads due to prolonged light emitting time, which affects color gamut and overall light quality.
Innovation Solution
A backlight system for liquid crystal display devices using a LED lamp bead group with strings connected in opposite directions, driven by a periodic square-wave voltage signal, allowing alternate emission of light and adjusting brightness through current control, with frequencies greater than 50 Hz to simulate continuous light perception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If higher driving current is used to increase backlight brightness for large-sized display panels, then the brightness requirement is met, but the heat generated increases and service life of LED lamp beads is shortened
Solution Approach 1:
The patent applies periodic square-wave voltage signals to drive the LED lamp beads in alternating positive and negative direction strings. This periodic driving method allows each string to emit light only during its designated time interval, effectively reducing the total light emitting time and heat generation while maintaining required brightness through temporal multiplexing
2Illumination intensity
If the light emitting time of LED lamp beads is prolonged to achieve high backlight brightness, then the brightness requirement is met, but the ambient temperature rises and operation property changes
Solution Approach 1:
The patent uses periodic square-wave voltage signals with alternating polarity to drive different strings of LED lamp beads at different time intervals. This temporal separation reduces cumulative light emitting time and heat generation, thereby controlling ambient temperature while maintaining brightness through efficient time-multiplexed operation
Solution Approach 2:
The LED lamp bead group is divided into multiple strings connected in opposite directions (positive and negative directions). Each string is driven independently during specific time intervals, allowing the system to segment the total brightness requirement across multiple discrete lighting events rather than continuous operation, thus reducing heat accumulation
3Illumination intensity
If the light emitting time of LED lamp beads is extended for high brightness, then backlight brightness is improved, but color gamut changes and light emitting quality is declined
Solution Approach 1:
The patent employs periodic square-wave voltage signals to alternately drive positive and negative direction LED string groups. Each string emits light during its designated time interval within each period, reducing cumulative operation time and preventing color gamut degradation while maintaining perceived brightness through temporal multiplexing and human visual persistence
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
This approach reduces the light emitting time of LED lamp beads, prolongs their service life, and maintains color accuracy by utilizing the afterglow effect to create a continuous light impression without compromising energy efficiency.
Implementation Method 1
the LED lamp beads are typically driven by direct current, and the brightness of emitted light of the LED lamp beads depends on the magnitude of the driving current
Implementation Method 2
the voltage signal may be configured as more than one serials of periodic square-wave signal, under the action of which a string of LED lamp bead of positive direction and a string of LED lamp bead of negative direction emit light in an alternate manner
Data Source
AI summary
The present invention relates to a backlight of a liquid crystal display device and a driving method thereof. The backlight comprises a LED lamp bead group and a backlight driving module. The LED lamp bead group includes a plurality of strings of LED lamp bead which are opposite in term of positive and negative directions. The backlight driving module is electrically connected to the LED lamp bead group to output a voltage signal and a current signal to drive the LED lamp bead group, wherein the voltage signal is configured as more than one serials of periodic square-wave signal, under the action of which a string of LED lamp bead of positive direction and a string of LED lamp bead of negative direction emit light in an alternate manner, and the brightness of emitted light is determined by the magnitude of the current signal.