Backlight Driver Synchronization Circuit for LCD Flicker Reduction
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Solution Overview
Problem
Existing backlight drivers in liquid crystal display devices fail to synchronize output periods with sudden changes in input vertical synchronizing signal frequencies, leading to inner clock generation errors and poor picture quality, such as flicker, due to mismatched duty ratios in PWM signals.
Innovation Solution
A method and circuit that detect and adjust input periods to match prior output periods, generating a stable output period by calculating differences and setting the adjusted input period as the new output period, ensuring synchronization and inner clock stability even with frequency changes, thereby maintaining a desired duty ratio for PWM signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the input period is adjusted to match sudden frequency changes, then synchronization speed is improved, but calculation complexity increases
Solution Approach 1:
The patent pre-calculates and stores multiple candidate output periods corresponding to different input period ratios (0.95-1.05) in a lookup table. When synchronization is needed, the system directly retrieves the appropriate candidate period based on the detected input period, avoiding real-time complex calculations and achieving fast synchronization.
Solution Approach 2:
The patent changes the parameter representation from continuous calculation to discrete predefined values. By storing candidate periods as discrete values in a lookup table corresponding to different input period ratios, the system transforms the continuous parameter adjustment into discrete selection, simplifying the synchronization process.
2Adaptability or versatility
If the output period is calculated at every frame, then adaptability to frequency changes is improved, but processing time increases
Solution Approach 1:
The patent pre-calculates candidate output periods for various input period ratios (0.95-1.05) and stores them in a lookup table before runtime. During operation, the system only needs to detect the input period and retrieve the corresponding candidate period from the table, significantly reducing processing time while maintaining adaptability to frequency changes.
Solution Approach 2:
The patent implements dynamic adaptation by detecting the actual input period and selecting the appropriate candidate output period from the lookup table based on the detected ratio. This dynamic selection allows the system to adapt to different frequency changes while using pre-computed values to minimize processing time.
3Reliability
If the duty ratio is adjusted to maintain brightness, then picture quality is improved, but control complexity increases
Solution Approach 1:
The patent incorporates feedback by detecting the actual input period, comparing it with the stored candidate periods, and selecting the appropriate candidate period that maintains the correct duty ratio. This feedback mechanism ensures that the output period is automatically adjusted to maintain picture quality while avoiding complex real-time duty ratio calculations.
Data Source
AI summary
A method and a circuit for synchronizing input and output synchronizing signals are disclosed. The method for synchronizing input and output synchronizing signals includes detecting an Nth (N is a positive integer) input period of the input synchronizing signal, determining whether the detected Nth input period is the same with a prior (N−1) the output period of the output synchronizing signal, detecting a difference between an end time of the (N−1)the output period and an end time of the Nth input period, if the detected Nth input period is not the same with the (N−1)the output period, operating the detected difference with the Nth input period, and setting the operated value as an Nth output period, and generating and outputting the output synchronizing signal having the set Nth output period.