Backlight Unit Controller for LED String Fault Detection

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Solution Overview

Problem

Backlight units in liquid crystal displays face issues with non-uniform brightness and color distribution, and are prone to damage due to over-current flow when one LED string is open, leading to malfunction.

Innovation Solution

A backlight unit with a power converter and a controller that generates a light driving voltage, where the controller detects the operation state of light emitting strings using a detection circuit and logic circuit, and stops the power converter when an abnormal state is detected, preventing over-current flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If LED strings are used to generate brightness, then power consumption is reduced and size is minimized, but non-uniform brightness and color distribution occur

Engineering Contradiction:

Improvepower consumptionVSAvoidbrightness uniformity

Core Design Contradiction:

Use of energy by moving objectVSIllumination intensity

Solution Approach 1:

The backlight unit is divided into multiple independently controllable LED strings, each receiving individual current control signals from the controller. This segmentation allows separate regulation of each string's brightness, enabling uniform overall illumination while maintaining low power consumption and compact size characteristics of LED technology

Inventive Principle:

Principle #1Segmentation

2Use of energy by moving object

If multiple LED strings are used to generate required brightness, then power consumption is reduced, but over-current damage occurs when one LED string is open

Engineering Contradiction:

Improvepower consumptionVSAvoiddamage resistance

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The controller receives feedback signals from each LED string indicating its operational state. When an open circuit is detected in one string, the controller automatically adjusts current distribution to other strings, preventing over-current conditions and maintaining system reliability while continuing to operate at low power consumption

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The controller proactively monitors the operational state of each LED string before over-current damage can occur. By detecting open circuits in advance and preemptively adjusting current distribution, the system prevents damage while maintaining efficient power consumption characteristics

Inventive Principle:

Principle #10Preliminary action

3Volume of moving object

If LED strings are used for backlight, then device size is minimized, but non-uniform color distribution occurs

Engineering Contradiction:

Improvedevice sizeVSAvoidcolor uniformity

Core Design Contradiction:

Volume of moving objectVSIllumination intensity

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different current control signals are applied to different LED strings based on their specific characteristics and positions. This local quality approach allows each string to be optimized individually, ensuring uniform color distribution across the entire backlight while maintaining the compact size advantage of LED technology

Inventive Principle:

Principle #3Local quality

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

Ensures uniform brightness and prevents damage to the backlight unit by detecting and addressing abnormal states in the light emitting strings, maintaining the display's performance and longevity.

Implementation Method 1

a power converter that generates a light driving voltage in response to a voltage control signal with a first level

Methodology Applied

Scientific EffectPower conversion:

Implementation Method 2

a plurality of light emitting strings, wherein each of the light emitting strings receives the light driving voltage

Methodology Applied

Scientific EffectLight emitting diode effect: Light Emitting Diode

Implementation Method 3

the controller is connected to a second end of at least one of the light emitting strings and detects a level of a signal at the connected second end to detect an operation state of the light emitting strings

Methodology Applied

Scientific EffectVoltage detection:

Data Source

PatentUS9288883B2Backlight unit and a display apparatus having the same

Publication Date: 2016.03.15 SAMSUNG DISPLAY CO LTD

AI summary

A backlight unit includes a power converter which generates a light driving voltage in response to a voltage control signal with a first level, a plurality of light emitting strings, wherein each of the light emitting strings receives the light driving voltage through a first end thereof, and a controller which generates the voltage control signal. The controller is connected to a second end of at least one of the light emitting strings and detects a level of a signal at the connected second end to detect an operation state of the light emitting strings. The controller generates the voltage control signal with a second level to stop the power converter from generating the light driving voltage when the operation state of the light emitting strings is in an abnormal state.