Solid State Lighting Step-Wise Intensity Control
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Solution Overview
Problem
Solid state lighting systems using LEDs face challenges in controlling light output level without causing color shift or flicker, and the individual point source outputs can be undesirable, leading to non-uniform light distribution.
Innovation Solution
A lighting system with discrete ON/OFF control of multiple LEDs to achieve step-wise intensity levels, combined through an optical integrating cavity to produce a uniform virtual source of light, avoiding the need for continuous current adjustment or modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If continuous current adjustment is used to control light output level, then light intensity control range is improved, but color shift occurs
Solution Approach 1:
The patent segments the LED array into multiple independently controllable LED groups or individual LEDs, allowing discrete control of light output levels. Instead of continuously adjusting current for the entire array, the system selectively activates or deactivates specific segments, providing stepped dimming levels while maintaining color consistency across all active LEDs since they all operate at or near full current.
2Ease of manufacture
If pulse width modulation is used to control light output level, then color shift is avoided, but flicker becomes perceptible at low output levels
Solution Approach 1:
The patent divides the LED array into multiple controllable segments, enabling discrete ON/OFF control to achieve step-wise intensity levels. This segmentation approach allows the system to avoid PWM flicker by using simple on/off transitions of individual segments rather than modulating the drive signal, while still achieving smooth perceived dimming through the combination of multiple segments at different activation states.
Solution Approach 2:
The patent combines multiple LED segments or individual LEDs into a unified controllable array where the overall light output is determined by the number of active segments. By merging the output of multiple segments and controlling them in unison through discrete ON/OFF states, the system achieves smooth intensity control without the flicker associated with PWM modulation of individual LEDs.
3Measurement precision
If individual LEDs are directly observed, then control precision is improved, but non-uniform light distribution and visible point sources occur
Solution Approach 1:
The patent introduces an optical integrating cavity as an intermediary element between the LED array and the observer. This cavity receives light from the individual LEDs and redistributes it uniformly across its output surface, creating a virtual source that appears uniform to the observer. The integrating cavity thus mediates between the discrete point-source LEDs and the requirement for uniform light distribution, masking the individual LED positions while preserving the precision of discrete control.
4Ease of manufacture
If discrete ON/OFF control of multiple LEDs is used, then color shift and flicker are avoided, but maximum-to-minimum intensity ratio increases
Solution Approach 1:
The patent combines multiple LED segments into a unified array controlled through discrete ON/OFF states. By activating different numbers of segments, the system achieves multiple discrete intensity levels. The combining of outputs from multiple segments ensures that the overall light distribution remains uniform through the optical integrating cavity, while the discrete control of segment activation maintains color consistency and avoids flicker.
Solution Approach 2:
The optical integrating cavity serves as an intermediary that receives light from the discrete LED segments and redistributes it uniformly. This intermediary element equalizes the intensity distribution across the output surface, reducing the maximum-to-minimum intensity ratio even when discrete segments are activated in different combinations. The cavity ensures uniform light output regardless of which specific segments are active.
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 allows for precise control of light intensity without color shift or flicker, providing a uniform and consistent light output that masks individual LED activations, ensuring a low maximum-to-minimum intensity ratio across the output area.
Implementation Method 1
optical processing of the generated light, for example by diffuse reflection in an optical integrating cavity
Data Source
AI summary
A solid state lighting system controls overall light output level in a step-wise manner by discretely controlling the ON/OFF state of its light emitters. Solid state emitters that are ON at a given time are set and kept at a level intended to produce a desired output characteristic, e.g. at a level to produce a described color of light. The system utilizes optical processing of the generated light, for example by diffuse reflection in an optical integrating cavity, sufficient to convert the point source output(s) from the emitting elements into a uniform virtual source output. The virtual source output appears uniform regardless of how many emitters are ON or OFF, and only the perceptible intensity of the light output changes with the number of emitters that the system has ON.