Backlight Modulation Selection Unit for LCD Efficiency
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Solution Overview
Problem
Existing liquid crystal display apparatuses using Content Adaptive Brightness Control (CABC) technology face inefficiencies in backlight driving, particularly with low duty ratios in PWM dimming modes, which reduce overall system energy usage when small backlight brightness is required.
Innovation Solution
Incorporating a dual-modulation approach with both Pulse-Width Modulation (PWM) and Pulse-Frequency Modulation (PFM) modules in the backlight driving unit, where the average pixel brightness is detected and compared to a reference value to select between PWM and PFM modes, optimizing dimming efficiency based on brightness needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If PWM dimming is used for backlight control, then high conversion efficiency is achieved when required backlight brightness is large, but duty ratio becomes very low when required backlight brightness is small, greatly reducing efficiency of backlight driving
Solution Approach 1:
The patent dynamically switches between PWM and PFM dimming modes based on the required backlight brightness level. When brightness requirement is high, PWM mode is used; when brightness requirement is low, PFM mode is used. This dynamic adaptation resolves the contradiction by selecting the appropriate modulation strategy for each operating condition, maintaining high conversion efficiency across the full brightness range.
Solution Approach 2:
The patent changes the modulation parameter (from pulse width in PWM to pulse frequency in PFM) based on the operating conditions. By switching from PWM to PFM when brightness drops below a threshold, the system maintains optimal efficiency. This parameter change allows the system to overcome the duty ratio limitation of PWM at low brightness levels.
2Loss of energy
If single mode PWM dimming is used, then结构简单 (structure is simple), but overall efficiency of backlight driving is reduced when small backlight brightness is required
Solution Approach 1:
The patent segments the backlight control function into two distinct modules: PWM dimming module for high brightness scenarios and PFM dimming module for low brightness scenarios. This segmentation allows each module to be optimized for its specific operating range, improving overall energy efficiency while keeping each individual module relatively simple in structure.
Solution Approach 2:
The backlight control unit is designed with multi-functionality, incorporating both PWM and PFM dimming capabilities within a single integrated structure. This universal design allows the system to handle both high and low brightness requirements efficiently, achieving improved energy efficiency without proportionally increasing device complexity.
Data Source
AI summary
There provides a liquid crystal display apparatus and a backlight control method thereof. The liquid crystal display apparatus includes an image data acquisition part, a liquid crystal panel, a panel driving unit, a backlight module and a backlight driving unit; wherein the panel driving unit drives the liquid crystal panel and generates a backlight driving signal; the backlight driving unit includes a PWM module and a PFM module to modulate the backlight driving signal, thereby forming driving powers supplied to the backlight module; the liquid crystal display apparatus further includes a backlight modulation selection unit used to detect and calculate an average pixel brightness value A of the image data, and a reference pixel brightness value A0 is further set therein; when A≥A0, the backlight modulation selection unit selects to enable the PWM module; and when A<A0, the backlight modulation selection unit selects to enable the PFM module.