Solid-State Light Source Data Transmission via PWM
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Solution Overview
Problem
Lighting fixtures with solid-state light sources require communication of operational information such as color temperature and lifetime parameters, often necessitating expensive communication circuitry, which is not ideal for cost-effective solutions.
Innovation Solution
The use of pulse-width modulated (PWM) signals to control and modulate the light output of solid-state light sources, allowing for the transmission of data without additional communication circuitry, by varying the frequency and duty cycle of the PWM signals while maintaining constant duty cycle to avoid perceptible changes in light characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If communication circuitry is added to transmit operational information from lighting fixtures, then information transmission capability is improved, but device complexity and cost increase
Solution Approach 1:
The existing light output device is made to serve dual purposes: providing illumination and transmitting operational information. By modulating the light output with data while maintaining its primary lighting function, the patent eliminates the need for separate communication circuitry, thereby reducing device complexity and cost while preserving information transmission capability
Solution Approach 2:
The lighting fixture uses its own light output as the communication medium, making the system self-sufficient for information transmission without requiring external communication infrastructure or additional dedicated communication components. The light itself becomes both the service product and the communication channel
2Loss of information
If PWM frequency is varied to modulate light for data transmission, then data transmission capability is improved, but light characteristic stability deteriorates
Solution Approach 1:
Data is transmitted by periodically modulating the light output at frequencies imperceptible to human vision. The periodic modulation encodes information in the light signal while maintaining the overall stability of light characteristics, as the modulation occurs at frequencies above human perception thresholds
Solution Approach 2:
The patent modulates parameters of the light output (such as intensity or frequency) to encode data, while carefully controlling these changes to remain imperceptible to humans. By changing parameters within imperceptible ranges, the system achieves data transmission without noticeable degradation in light quality or characteristics
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
Enables the communication of operational information through the light output itself, reducing the need for additional circuitry and maintaining consistent light characteristics, thus providing a cost-effective solution for controlling and monitoring lighting fixtures.
Implementation Method 1
Solid-state lighting devices typically employ an array of light-emitting diodes (LEDs) as a light source
Implementation Method 2
The control output is configured to control the drive signal to modulate the light with data for transmission
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
The disclosure relates to a lighting fixture, which includes an array of solid-state light sources that are configured to generate light for general illumination lighting purposes and control circuitry. A drive signal is used to drive solid-state light sources. The control circuitry is configured to use a control output to control the drive signal to at least one of the solid-state light sources. The control output is configured to control the drive signal to 1) set at least one characteristic of the light generated by the array of the solid-state light sources, and 2) modulate the light with data for transmission. The light is modulated such that any change in the at least one characteristic based on the light being modulated is anthropically imperceptible. The characteristic of the light generated by the array of solid-state light sources may include the intensity, color, color temperature and the like.