Backlight Driving Control Method for LCD TVs
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Solution Overview
Problem
Existing backlight driving control methods for LCD TVs using LED backlighting suffer from poor lighting efficacy and reduced picture display contrast due to the need for high production costs and reduced energy efficiency, as they adjust brightness by modifying both PWM duty cycle and LED reference current simultaneously.
Innovation Solution
A backlight driving control method and system that utilizes a micro control unit (MCU) to demodulate electrical signals, compare brightness values across driving ICs, divide them into intervals, and determine corresponding current values, allowing for independent adjustment of LED light brightness without increasing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If both PWM duty cycle and LED reference current are adjusted to control brightness, then brightness control precision is improved, but device complexity and production cost increase due to requiring digital-to-analog converter for each channel
Solution Approach 1:
The patent extracts the digital-to-analog conversion function from each individual channel and consolidates it into a single reference current generation module. This allows the MCU to control brightness by adjusting only the PWM duty cycle while the reference current is generated centrally based on the maximum brightness value, eliminating the need for multiple DACs and reducing system complexity.
Solution Approach 2:
The patent makes the single reference current generation module serve all LED channels universally. Instead of having separate current control for each channel, one reference current source provides the current reference for all channels, and the PWM duty cycle independently controls the effective current. This multi-functional approach reduces component count while maintaining brightness control capability.
2Device complexity
If fixed maximum current is used and only PWM is adjusted to control brightness, then device complexity is reduced, but lighting efficacy decreases and energy saving is compromised due to voltage increase
Solution Approach 1:
The patent introduces dynamic adjustment of the reference current based on the maximum brightness value detected from different LED groups. Instead of using a fixed maximum current for all channels, the system dynamically optimizes the reference current for each channel according to its actual brightness requirements, thereby improving lighting efficacy while maintaining simple hardware architecture.
Solution Approach 2:
The patent applies local quality optimization by allowing each LED channel to have its own reference current value tailored to its specific brightness requirements. The MCU determines the maximum brightness value for each channel and sets the reference current accordingly, so that each channel operates at optimal efficiency rather than all channels using a uniform fixed current.
3Illumination intensity
If LED current is increased to improve brightness, then picture display contrast is improved, but voltage increases which reduces lighting efficacy and energy saving
Solution Approach 1:
The patent implements dynamic reference current adjustment that adapts to the actual brightness requirements of each LED channel. By detecting the maximum brightness value and setting the reference current accordingly, the system achieves the necessary picture display contrast without unnecessarily increasing the voltage and current beyond what is required, thereby maintaining optimal lighting efficacy and energy efficiency.
Data Source
AI summary
Disclosed is a backlight driving control method and system applied to a display terminal having an LCD. The display terminal includes a MCU and a backlight, the backlight includes multiple light bars composed of LED lights and multiple driving ICs, each driving IC controls one or more light bars. The method includes: in response to reception of respective electrical signals of the LED lights, demodulating, by the MCU, the electrical signals to obtain respective brightness values of the LED lights; comparing the respective brightness values of the LED lights in each driving IC to obtain a maximum brightness value of the LED lights in the driving IC; and dividing the maximum brightness values of the LED lights in the driving ICs into multiple brightness intervals, determining a current value corresponding to each brightness interval, and controlling the brightness of the LED lights in the driving ICs according to the current values.