LED Channel Lighting Control System With Time-Offset Synchronization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional pulse modulation techniques for LED backlights in displays, such as those used in 4K or UHD TV sets, often have an insufficient dynamic range for brightness control, particularly when trying to meet the high dynamic range (HDR) specifications.
Innovation Solution
The solution involves generating individual supply currents for LED channels based on both the width and magnitude of pulse-width modulated signals, with each channel having a unique time offset relative to a common synchronization signal, allowing for independent control of brightness without affecting neighboring channels. This is achieved through dedicated signal combiners and controlled current sources, which combine magnitude and pulse dimming signals with the synchronization signal to produce control signals that change only at specific time offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional pulse modulation techniques are used for LED backlight control, then the system is simple to implement, but the dynamic range of brightness control is insufficient
Solution Approach 1:
The backlight system is divided into multiple independently controllable LED channels, each with its own signal combiner and controlled current source. This segmentation allows each channel to be controlled with individual magnitude and pulse dimming signals, enabling extended dynamic range while maintaining manageable complexity through modular architecture
Solution Approach 2:
The invention transitions from conventional single-dimension pulse width modulation to two-dimensional control by introducing both magnitude dimming signals and pulse dimming signals for each LED channel. This dual-dimension approach (magnitude + pulse width) significantly expands the brightness control dynamic range beyond what traditional PWM can achieve
2Measurement precision
If individual brightness control is implemented for each LED channel, then brightness precision is improved, but interference between neighboring channels increases
Solution Approach 1:
Time offsets are predetermined and built into the synchronization mechanism for each LED channel. By pre-planning the timing sequence and applying time offsets before potential interference issues arise, the system ensures that brightness changes in one channel do not negatively affect neighboring channels, maintaining precision without cross-channel interference
Solution Approach 2:
The system uses periodic synchronization signals with defined time offsets for each LED channel. This periodic timing structure ensures that individual LED channel updates occur at staggered intervals, allowing one channel to complete its transition before the next channel begins, thereby preventing interference while maintaining precise individual control
3Speed
If changes in supply current are applied immediately, then responsiveness is improved, but negative effects on neighboring channels occur
Solution Approach 1:
Time offsets are predetermined and built into the synchronization mechanism for each LED channel. By pre-planning the timing sequence and applying time offsets before potential interference issues arise, the system ensures that brightness changes in one channel do not negatively affect neighboring channels, maintaining precision without cross-channel interference
Solution Approach 2:
The synchronization signal acts as an intermediary that coordinates changes across all LED channels. By mediating the timing of supply current changes through this central reference signal with defined time offsets, the system maintains responsiveness while preventing harmful interactions between channels
Data Source
Figure 1~2
Figure 3~4
AI summary
A lighting control system (LCS) for generating supply currents for at least two LED channels (CH1, CH2, CHn) comprises at least two controlled current sources for generating a supply current for a corresponding LED channel based on a corresponding control signal. The system further comprises at least two signal combiners for generating the corresponding control signals based on a synchronization signal (VSYNC) that comprises periodic starting pulses and on a combination of a magnitude dimming signal and a pulse dimming signal corresponding to one of the LED channels. The signal combiners are designed such that changes of the respective control signals come into effect only with a respective time offset with respect to one of the starting pulses of the synchronization signal.