Mini-LED Backlight Brightness Control Using PWM and Constant Current

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Solution Overview

Problem

Mini-LED backlight modules face issues with uneven brightness and difficulty in fine adjustment due to conventional control methods, leading to high power consumption and low display contrast in liquid crystal displays.

Innovation Solution

A backlight brightness control method and device that utilize pulse width modulation (PWM) waves with peak current and duty cycle adjustment coefficients to achieve uniform and fine-tuned brightness control by determining target peak current and duty cycle based on grayscale data, using a constant current integrated circuit to input current to backlight partitions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional constant voltage integrated circuits and passive matrices are used to control mini-LED backlight modules, then partial control of backlight is achieved, but uneven backlight brightness and difficulty of fine adjustment occur

Engineering Contradiction:

Improvebacklight control capabilityVSAvoidbacklight brightness uniformity

Core Design Contradiction:

Ease of operationVSManufacturing precision

Solution Approach 1:

The backlight module is divided into multiple independently controllable partitions, each with its own constant current integrated circuit. This segmentation allows precise individual control of each partition's brightness through PWM duty cycle adjustment, eliminating the uneven brightness caused by conventional unified control methods.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the control parameter from constant voltage to constant current, and introduces PWM duty cycle as an additional controllable parameter. By adjusting the duty cycle of PWM signals applied to each partition, the backlight brightness can be finely tuned, solving the difficulty of fine adjustment inherent in conventional methods.

Inventive Principle:

Principle #35Parameter changes

2Illumination intensity

If mini-LED backlight modules are used to achieve locally controllable backlight, then display contrast is improved, but power consumption increases

Engineering Contradiction:

Improvedisplay contrastVSAvoidpower consumption

Core Design Contradiction:

Illumination intensityVSUse of energy by moving object

Solution Approach 1:

Different backlight partitions can be controlled with different brightness levels according to the local requirements of display content. This local quality control allows high brightness in areas requiring detail while maintaining low brightness or turning off other areas, thereby improving display contrast while reducing overall power consumption.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

PWM (Pulse Width Modulation) technology is applied to control the backlight partitions periodically. By adjusting the duty cycle of periodic PWM signals, the average power consumption of each partition can be precisely controlled while maintaining the ability to achieve high brightness when needed, thus improving contrast without excessive power consumption.

Inventive Principle:

Principle #19Periodic action

3Device complexity

If conventional control methods are used for mini-LED backlight, then simple control structure is maintained, but fine adjustment of backlight brightness becomes difficult

Engineering Contradiction:

Improvecontrol structureVSAvoidbacklight brightness adjustment

Core Design Contradiction:

Device complexityVSEase of operation

Solution Approach 1:

The invention introduces dynamic PWM duty cycle control for each backlight partition, transforming the static constant voltage control into a dynamic system. This allows continuous and fine adjustment of brightness by varying the duty cycle parameter, making the control more flexible and precise while maintaining a relatively simple overall structure through software-based PWM generation.

Inventive Principle:

Principle #15Dynamics

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 improves the uniformity of backlight brightness and enables precise adjustment, ensuring required brightness levels for high grayscale images while optimizing power usage and enhancing display contrast.

Implementation Method 1

obtaining an initial duty cycle of pulse width modulation waves of backlight sources in the backlight partitions corresponding to the partition images

Methodology Applied

Scientific EffectPulse Width Modulation (PWM):

Implementation Method 2

mini light emitting diodes (mini-LEDs) backlight module have come into being

Methodology Applied

Scientific EffectLight Emitting Diode (LED): Light Emitting Diode

Data Source

PatentUS11790825B2Backlight brightness control method, backlight brightness control device, and display equipment

Publication Date: 2023.10.17 TCL CHINA STAR OPTOELECTRONICS TECHNOLOGY CO LTD

AI summary

A backlight brightness control method, a backlight brightness control device, and a display equipment are provided. By using a constant current integrated circuit to input constant current to backlight sources in backlight partitions, uniformity of backlight brightness is allowed to be improved. By determining a target peak current inputted to the backlight sources in the backlight partitions according to a grayscale level of partition images, not only can the backlight brightness required by a high grayscale level be ensured, but fine adjustment of the backlight brightness under a low grayscale level can also be ensured.