Backlight Unit CPWAM LED Drive for LCD Dimming

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Solution Overview

Problem

Existing backlight units for liquid crystal displays face issues with high power consumption, electromagnetic interference, heat generation, noise, and wavy noise due to the limitations of the PWM control method, which also restrict their ability to perform both backlight scanning and local dimming drives.

Innovation Solution

A backlight unit utilizing a conditional pulse width and amplitude modulation (CPWAM) signal with variable pulse amplitude and width, generated based on luminance control information, to drive LED channels, allowing for both backlight scanning and local dimming while reducing power consumption, electromagnetic interference, heat generation, and noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If PWM control method is used to control LED luminance, then backlight scanning drive and local dimming drive are enabled, but power consumption, electromagnetic interference, heat generation, and noise increase

Engineering Contradiction:

Improvebacklight scanning drive and local dimming drive capabilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by stationary object

Solution Approach 1:

The patent applies parameter changes by transitioning from fixed-amplitude PWM control to variable-amplitude CPWAM control. The pulse amplitude is dynamically adjusted based on the required luminance level, allowing the system to reduce power consumption during low-luminance operations while maintaining the ability to perform backlight scanning and local dimming drives when needed.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamics by making the pulse amplitude variable rather than fixed. The CPWAM signal dynamically adjusts both pulse width and amplitude based on real-time luminance requirements, enabling the system to adaptively balance between power consumption and drive capability for different operating modes.

Inventive Principle:

Principle #15Dynamics

2Adaptability or versatility

If PWM control method is used to control LED luminance, then backlight scanning drive and local dimming drive are enabled, but electromagnetic interference and heat generation increase

Engineering Contradiction:

Improvebacklight scanning drive and local dimming drive capabilityVSAvoidelectromagnetic interference and heat generation

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The patent reduces electromagnetic interference and heat generation by changing the amplitude parameter of the drive signal. By using variable amplitude CPWAM control instead of fixed amplitude PWM, the system lowers the current levels during low-luminance operation, thereby reducing electromagnetic interference and heat generation while preserving the capability for full-luminance drives.

Inventive Principle:

Principle #35Parameter changes

3Illumination intensity

If PWM control method is used to control LED luminance, then low luminance is easily achieved, but noise and wavy noise increase

Engineering Contradiction:

Improvelow luminance achievementVSAvoidnoise and wavy noise

Core Design Contradiction:

Illumination intensityVSObject-generated harmful factors

Solution Approach 1:

The patent addresses noise issues by changing both the amplitude and width parameters of the drive signal. The variable amplitude CPWAM control allows for smoother transitions and reduced current fluctuations compared to fixed amplitude PWM, thereby reducing noise and wavy noise while maintaining the ability to achieve low luminance levels.

Inventive Principle:

Principle #35Parameter changes

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

The CPWAM signal effectively modulates luminance, enabling both backlight scanning and local dimming drives while reducing power consumption, electromagnetic interference, heat generation, and noise, thereby improving the performance and efficiency of the liquid crystal display.

Implementation Method 1

a light source having at least one LED channel

Methodology Applied

Scientific EffectLight emitting diode: Light Emitting Diode

Implementation Method 2

The LED is more eco-friendly and has a faster response time than the fluorescent lamps

Methodology Applied

Scientific EffectElectroluminescence: Electroluminescence

Data Source

PatentEP2869293B1Backlight unit and liquid crystal display using the same

Publication Date: 2019.01.16 LG DISPLAY CO LTD

Figure 1~2
Figure 3A
Figure 3B

AI summary

A liquid crystal display (LCD) device having an LCD panel (10) with a plurality of pixels is disclosed. The LCD device includes gate and data driving circuits (13,12) to provide a gate pulse and a data voltage to the pixels, respectively, and a timing controller (11) to control the gate and data driving circuits (13, 12). The LCD device also includes a backlight unit (40) to provide light to the liquid crystal display panel (10). The backlight unit (40) includes a light source having at least one LED channel (CH1- CHn), a driving voltage generator (100) to supply a driving voltage to the LED channel, and an LED driver (200) to supply a conditional pulse width and amplitude modulation (CPWAM) signal to the LED channel. The CPWAM signal has a pulse with an amplitude and a width that are both variable from one period of a predetermined length to another period of the predetermined length.