Segmented LED Backlight Circuit Synchronization
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Solution Overview
Problem
Conventional segmented LED backlights experience intermodulation interference due to independent pulse-modulated signals, leading to visible stripe patterns on displays.
Innovation Solution
A circuit arrangement and method that synchronizes the modulated signal with the line and image frequencies of a display unit, using a generator to overlay synchronizing and data signals, thereby reducing or eliminating intermodulation interference by ensuring the modulated signal follows the clock rate of the synchronizing signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If segmented LED backlights are driven by independently generated pulse-modulated signals for each segment, then brightness control flexibility is improved, but intermodulation interference increases causing visible stripe patterns
Solution Approach 1:
The patent merges the generation of pulse-modulated signals for multiple LED segments into a single generator that produces all signals from one common synchronization reference. This ensures all segments are driven synchronously with the display's line and image frequencies, eliminating the intermodulation interference that arises from independently generated signals while preserving individual segment brightness control through digital processing of the synchronized signals.
Solution Approach 2:
The patent employs a synchronization mechanism where the generator receives and locks onto the display's synchronization signals (line frequency and image frequency). This feedback-based synchronization ensures that the pulse-modulated signals for all LED segments are precisely aligned with the display's scanning rates, preventing the formation of visible stripe patterns while maintaining flexible brightness control for each segment.
2Ease of operation
If multiple LED segments are driven with independently generated modulated signals, then individual brightness control is improved, but synchronization with display frequencies deteriorates
Solution Approach 1:
The patent combines the synchronization function for all LED segment drivers into a single reference source. The generator uses one common synchronization input to produce all pulse-modulated signals, ensuring that every segment operates in sync with the display's line and image frequencies. This merged approach maintains individual brightness control through digital signal processing while guaranteeing synchronization stability across all segments.
Solution Approach 2:
The single generator serves multiple functions: it generates synchronized clock signals, produces pulse-modulated control signals for each LED segment, and maintains synchronization with the display's scanning frequencies. This multi-functional design ensures that all segments are driven with signals that are both individually controllable and synchronously aligned with the display, eliminating the need for separate synchronization circuits for each segment.
3Speed
If LED backlight segments are controlled with high-frequency pulse modulation for fast response, then turn-on time is improved, but intermodulation noise increases
Solution Approach 1:
The patent uses feedback-based synchronization where the generator locks onto the display's line and image frequencies. This ensures that the high-frequency pulse-modulated signals are phased-coherent with the display's scanning rates, preventing the accumulation of phase errors that would manifest as intermodulation noise. The fast turn-on response is maintained through the inherent speed of LED response and pulse modulation, while the synchronization feedback eliminates the noise problem.
Solution Approach 2:
The patent structures the pulse-modulated signals to be periodic with periods that are integer multiples or submultiples of the display's line and image frequencies. This periodic alignment ensures that the high-frequency switching of LED segments occurs in a rhythm that is coherent with the display's scanning, preventing the generation of intermodulation noise while maintaining the fast response characteristics of pulse-modulated LED driving.
Data Source
AI summary
A circuit arrangement for controlling a segmented LED backlight in particular, comprises a generator (50) with a first input (10) to be supplied with a synchronizing signal (SYNC) that comprises image frequency information and/or line frequency information of a display unit, a second input (20) to be supplied with a data signal (DATA) that comprises image information of the display unit, and with an output (30) for providing a modulated signal (MOD).