LED Driver PWM Signal Modification for Linear Dimming
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Solution Overview
Problem
Existing methods for driving light sources using switching drivers result in non-linear luminosity control, leading to jerky transitions and chromatic deviations, especially at low intensities, due to the nature of PWM signals, which affects the fluidity and precision of dimming in LED circuits.
Innovation Solution
A method and device that modify the duration of the dimming signal pulse to ensure it never ends during inactive phases of the switching signal, making the luminosity control monotonic by 'skipping' off phases and mapping the on phase over the entire period, and adjusting the duty cycle to linearize the luminosity trend, using equations to calculate the modified duration and account for thermal deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If PWM dimming signal is used to control switching driver, then luminosity control is achieved, but luminosity increases in jerky steps instead of gradually
Solution Approach 1:
The patent dynamically adjusts the duty cycle of the PWM dimming signal based on the actual switching driver output characteristics. By continuously adapting the duty cycle to compensate for the non-linear luminosity response, the system achieves smooth and precise dimming control across the entire brightness range, eliminating the jerky steps observed in conventional fixed duty cycle approaches.
Solution Approach 2:
The patent implements a feedback mechanism where the actual luminosity output is monitored and used to adjust the PWM duty cycle. This closed-loop control ensures that the luminosity increases gradually and precisely by comparing the desired output with the actual output and making real-time corrections to the dimming signal.
2Illumination intensity
If duty cycle is increased to obtain higher luminosity, then luminosity increases, but the increase is not gradual due to switching signal inactive phases
Solution Approach 1:
The patent changes the parameter of duty cycle dynamically to achieve smooth luminosity transitions. By adjusting the duty cycle in a controlled manner that accounts for the switching driver's active and inactive phases, the system ensures that luminosity increases gradually without the jerky effects caused by discrete switching cycles.
3Adaptability or versatility
If multiple switching drivers are used in RGB system, then color control is achieved, but chromatic coordinates deviate at low intensities due to non-linear behavior
Solution Approach 1:
The patent applies local quality by independently optimizing the PWM duty cycle for each color channel (R, G, B) based on its specific switching driver characteristics. By tailoring the duty cycle adjustment to each channel's non-linear behavior, the system maintains accurate chromatic coordinates across all color channels, especially at low intensities where deviations typically occur.
Solution Approach 2:
The patent dynamically adjusts the duty cycle for each color channel to compensate for non-linear luminosity response. This dynamic adjustment ensures that the chromatic coordinates remain accurate during color mixing and dimming operations, preventing color shifts that would otherwise occur at low intensities.
4Ease of operation
If PWM frequency is kept low for dimming control, then dimming signal can be processed, but switching driver operates less efficiently
Solution Approach 1:
The patent uses periodic PWM dimming signals at optimized frequencies that balance dimming control capability with switching driver efficiency. By selecting appropriate PWM frequencies and duty cycles, the system achieves smooth dimming control while maintaining efficient switching driver operation, avoiding the power losses associated with excessively low frequencies.
Data Source
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AI summary
The present invention relates to a method for driving a light source by means of at least one switching driver, wherein said switching driver is driven by a pulse-type periodic dimming signal, e.g., a PWM signal. The method envisages calculating, on the basis of the switching signal, a modified duration (t'on) of the dimming signal pulse such that said pulse never ends in an instant of time in which the switching signal is equal to zero.