LED Array Flickering Reduction via Synchronized PWM Dimming
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Solution Overview
Problem
Existing methods for controlling LED brightness through pulse width modulation often result in visible flickering, especially when LEDs in an array transition at different rates, leading to undesirable visual effects.
Innovation Solution
The method involves changing the PWM control signals for LEDs from initial values to a threshold value at a predetermined time, then simultaneously adjusting both signals to a final value at a uniform rate, minimizing flickering by synchronizing the dimming process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the frequency of PWM pulses is increased to reduce flickering, then the flickering effect is minimized, but the cost of the electronic controller increases
Solution Approach 1:
The patent changes the parameter of pulse frequency dynamically during the dimming process. Specifically, the pulse frequency is increased only when the duty cycle falls within the critical range (approximately 20-80%) where flickering is most noticeable to the human eye. When the duty cycle is outside this range (very low or very high), the normal lower frequency is maintained. This selective parameter change reduces flickering when necessary while avoiding the continuous high-frequency operation that would increase controller cost and power consumption.
2Ease of operation
If LEDs are dimmed at different rates to achieve smooth brightness transition, then the visual effect is improved, but visible flickering occurs due to different dimming rates of adjacent LEDs
Solution Approach 1:
The patent applies periodic action by using PWM (pulse width modulation) to control the dimming of LEDs. Instead of continuously varying the current, the system uses periodic pulses with varying duty cycles to achieve smooth brightness transitions. This periodic control method allows for precise brightness adjustment while maintaining uniform dimming rates across all LEDs, thereby avoiding the flickering that would result from different dimming rates.
Data Source
AI summary
A method of changing the brightness of light emitted by first and second light emitting diodes (LEDs) operated by respective first and second pulse width modulation (PWM) control signals includes the steps of (a) changing a first PWM control signal that operates a first LED from a first initial PWM value at a first rate of change to achieve a threshold PWM value at a predetermined point in time; (b) changing a second PWM control signal that operates a second LED from a second initial PWM value at a second rate of change to achieve the threshold PWM value at the predetermined point in time; and (c) subsequent to the predetermined time, changing both the first PWM control signal and the second PWM control signal from the threshold PWM value to achieve a final PWM value.