LED Color Mixing via Variable Current Intensities
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Solution Overview
Problem
Existing methods for generating mixed light colors using pulse-time controllable light sources face limitations in brightness dynamic range, particularly at low intensities, leading to disturbing physiological effects like color separation and stroboscopic issues due to intermittent illumination.
Innovation Solution
The method involves adjusting the constant current flow time and intensity to extend the dimming range without interrupting the current flow, allowing for variable current intensities within each period to maintain the desired brightness and color locus, thereby reducing physiological disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If pulse-time control with short current pulses is used to achieve high dimming ratios, then brightness dynamic range is improved, but physiological acceptance deteriorates due to color separation and stroboscopic effects
Solution Approach 1:
The patent applies periodic action by using pulse-width modulation to control the duty cycle of current pulses to each LED, creating different brightness levels through periodic on/off cycles. This allows achieving high dimming ratios (improving brightness dynamic range) while the periodic nature of the pulses, when synchronized properly, avoids continuous stroboscopic effects. The key is that each LED is driven at the same frequency, preventing relative motion artifacts.
Solution Approach 2:
The patent changes the parameter of current pulse duration (width) while maintaining constant amplitude, thereby controlling brightness without causing physiological disturbances. By adjusting the duty cycle parameter rather than reducing current amplitude, the system achieves extended brightness dynamic range. Additionally, all LEDs operate at the same pulse frequency, which prevents color separation effects that would occur with different frequencies.
2Manufacturing precision
If extremely short current pulses are used for gamut color correction at low brightness, then color locus precision is improved, but device complexity and cost increase due to requirements for fast processors and high-frequency transistors
Solution Approach 1:
The patent achieves color locus precision by adjusting the duty cycle parameter of current pulses rather than using extremely short pulses that would require high-frequency circuitry. By varying the width of current pulses at moderate frequencies, the system achieves precise control over brightness and color mixing without needing expensive fast processors or high-frequency transistors, thus maintaining color locus precision while reducing device complexity.
3Use of energy by moving object
If different colored LEDs are switched on successively without temporal overlap, then power consumption is reduced, but physiological acceptance deteriorates due to disturbing color separation effects
Solution Approach 1:
The patent uses periodic action with synchronized pulse-width modulation for all LEDs, switching them on and off at the same frequency but with different duty cycles. This maintains power efficiency by allowing sequential or overlapping drive patterns while ensuring all LEDs operate at the same frequency, thereby eliminating color separation effects and improving physiological acceptance.
4Adaptability or versatility
If duty ratios are used to control brightness of primary colored LEDs, then color mixing flexibility is improved, but brightness dynamic range is limited to approximately 1:1000
Solution Approach 1:
The patent applies dynamics by using dynamic pulse-width modulation where the duty cycle of current pulses can be independently adjusted for each LED. This dynamic control mechanism allows for continuous adjustment of brightness across a wide range (extending beyond 1:1000) while maintaining color mixing flexibility. The system can adaptively adjust pulse widths in real-time to achieve both precise color control and extended brightness dynamic range.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the brightness dynamic range and improves the physiological acceptance of multicolored illumination by avoiding intermittent operation, reducing stroboscopic effects, and maintaining stable color loci even at low brightness levels.
Implementation Method 1
Light sources such as lasers, electroluminescence elements, organic LEDs or in particular semiconductor light-emitting diodes are preferably used since their brightnesses are approximately linearly dependent on the duty ratio of the feeding with the pulse-time-modulated constant current pulses
Data Source
AI summary
A method for avoiding physiological phenomena such as color separation or stroboscopic effects that occur under boundary conditions in the case of intermittent feeding in particular of light-emitting diodes, for additive superposition to form color-locus-variable mixed light, whereby the emission brightness that can be represented by a periodic duty ratio of a pulse-time-modulated constant current feeding—preferably within the respective period—is realized by changeover to other or between different constant current intensities in such a way that a brightness equivalent, namely once again the current-time integral of the predetermined, brightness-determining duty ratio, arises in the current area sum, which now preferably no longer exhibits gaps over the period.