LED Backlight Driver Transient Mitigation via Staggered PWM
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Solution Overview
Problem
Display systems experience load fluctuations due to multiple LEDs turning on or off at the same time, leading to perceivable audible noise, reduced electrical performance, and decreased power efficiency, which existing technologies fail to adequately address.
Innovation Solution
A processor determines precise pulse start and end times for LEDs based on a gap clock, strategically delaying or advancing these times to prevent overlap, ensuring that LEDs do not turn on or off simultaneously, thereby reducing load fluctuations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LEDs are driven simultaneously to improve display brightness and coverage, then illumination intensity is improved, but load fluctuations increase causing audible noise and reduced power efficiency
Solution Approach 1:
The patent applies periodic action by implementing pulse-width modulation (PWM) to drive LEDs in sequential pulses rather than continuous operation. The controller generates pulse signals with specific widths and frequencies, where each LED is activated in periodic intervals. This periodic driving approach maintains average brightness while reducing instantaneous load fluctuations that cause audible noise, as the sequential pulsing prevents simultaneous switching of multiple LEDs.
Solution Approach 2:
The patent applies segmentation by dividing the backlight system into multiple independently controllable LED groups or zones. Instead of driving all LEDs simultaneously, the controller segments the driving sequence into discrete time slots, activating different LED segments at different times. This segmentation of the driving process allows brightness maintenance through cumulative illumination while eliminating the harmful load transients caused by simultaneous switching.
2Object-generated harmful factors
If LEDs are driven with precise timing control to eliminate load fluctuations, then audible noise is reduced, but device complexity increases due to additional timing coordination requirements
Solution Approach 1:
The patent applies self-service by implementing a decentralized timing control mechanism where each LED driver circuit incorporates local timing logic and automatic phase shifting capabilities. Rather than requiring a centralized complex controller to coordinate every LED individually, each driver unit autonomously manages its own timing based on simple reference signals from the main controller. This self-service approach reduces the overall system complexity while maintaining precise timing control to eliminate load fluctuations.
Solution Approach 2:
The patent introduces an intermediary timing synchronization signal that mediates between the main controller and individual LED drivers. This intermediary mechanism provides a standardized reference timing signal that automatically coordinates the switching of multiple LED groups without requiring complex point-to-point control wiring. The intermediary timing signal acts as a simple yet effective mediator that synchronizes all LED drivers, reducing control complexity while preventing simultaneous switching.
3Measurement precision
If pulse widths are extended to improve backlight brightness accuracy, then illumination precision is improved, but power consumption increases due to longer LED activation periods
Solution Approach 1:
The patent applies dynamics by implementing adaptive pulse width modulation where the LED pulse widths are dynamically adjusted based on real-time feedback regarding actual brightness requirements and power consumption levels. Rather than using fixed extended pulse widths, the system continuously optimizes the pulse duration for each LED group, extending pulses only when and where needed to achieve target brightness accuracy while minimizing overall power consumption through dynamic rather than static timing control.
Data Source
AI summary
A display device include a first light emitting diode (LED), a second LED, and at least one processor of a driver. The processor drives the first LED and the second LED. The processor determines a first pulse width associated with the first LED and a second pulse width associated with the second LED based on a level of brightness to be emitted by the first LED and the second LED. The processor also receives a gap clock and determines a first pulse start time and a first pulse end time for the first LED based on the first pulse width. Moreover, the processor determines a second pulse start time and a second pulse end time for the second LED based on the first pulse end time, the second pulse width, and/or the gap clock, in which the first pulse end time and the second pulse end time are different.