LCD Backlight Sync Circuit for Flicker-Free Frequency Tracking
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Solution Overview
Problem
Conventional backlight drivers for liquid crystal display devices face difficulties in synchronizing input and output synchronization signals due to sudden frequency changes, leading to brightness fluctuations and flickering issues.
Innovation Solution
A method and circuit that synchronize input and output synchronization signals by setting the output period based on a comparison between the input period and the previous output period, and limiting the output period within a predefined range, using a period limiter and low pass filtering to stabilize the internal clocks and prevent sudden changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the output period is calculated based on sudden frequency change of input VSYNC signal, then the backlight driver can respond to frequency change, but the output period cannot be properly set and internal clocks cannot be generated
Solution Approach 1:
The patent implements dynamic adjustment of the output period by comparing the current input period with the previous output period and calculating the difference. The system dynamically updates the output period based on frequency changes while maintaining stability through controlled adaptation, allowing the backlight driver to respond to frequency changes without losing reliability in period setting.
Solution Approach 2:
The patent uses feedback mechanisms by continuously monitoring the input VSYNC signal frequency, comparing it with the previous output period, and adjusting the current output period accordingly. This feedback loop ensures that the system can adapt to frequency changes while maintaining stable internal clock generation by using the difference between current input period and previous output period to calculate the new output period.
2Adaptability or versatility
If the output period is suddenly changed due to frequency change of input signal, then the system can track frequency changes, but brightness fluctuation and flickering occur
Solution Approach 1:
The patent implements dynamic control of the output period by calculating the difference between the current input period and the previous output period. This dynamic adjustment allows the system to track frequency changes smoothly rather than making sudden changes, thereby maintaining stable brightness and preventing flickering while still adapting to frequency variations.
Solution Approach 2:
The patent changes the output period parameter gradually based on the calculated difference between current input period and previous output period. By adjusting the period parameter in a controlled manner rather than suddenly, the system maintains stable PWM signal generation and consistent backlight brightness while tracking frequency changes.
3Stability of the object's composition
If the output period is limited within a predefined range, then sudden changes are prevented and stability is improved, but the ability to respond to frequency changes is reduced
Solution Approach 1:
The patent implements a dynamic period limiting mechanism that allows the output period to change within a predefined range based on the calculated difference between current input period and previous output period. This dynamic approach maintains stability by constraining changes within acceptable limits while still allowing the system to respond to frequency changes when they fall within the predefined range.
Solution Approach 2:
The patent applies parameter changes to the output period by limiting it within a predefined range. The system adjusts the period parameter based on frequency changes but constrains it to remain within acceptable boundaries, thereby maintaining stability while preserving the ability to respond to legitimate frequency variations.
Data Source
AI summary
Disclosed are method and circuit for synchronizing input and output synchronization signals, which can synchronize an output synchronization signal based on frequency change of an input synchronization signal and limit input and output periods, thereby preventing flickering, a backlight driver of a liquid crystal display device using the same, and a method for driving the backlight driver. The method for synchronizing input and output synchronization signals, includes generating an output synchronization signal whose output period is set based on a comparison result between an input period of an input synchronization signal and a previous output period of the output synchronization signal, and limiting the output period of the output synchronization signal within a predefined limit range from the previous output period.