LED Driving Method for Brightness and Data Communication
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Solution Overview
Problem
Existing LED driving methods struggle to combine duty cycle switching for brightness control with coded switching for data communication without interfering with each other, especially in systems where multiple LEDs contribute to the illumination, making it difficult to distinguish individual signals and achieve high data rates.
Innovation Solution
A method that combines duty cycle control with coded switching, ensuring the signal spectrum has minimal low-frequency contributions to avoid flicker and allows for high data rates by varying the duty cycle independently from digital data, using matched filters to decode signals and adapt to different duty cycles, and employing bi-phase modulation with multiple cell segments to increase data capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If duty cycle control is used for brightness control, then brightness control is achieved, but data communication capability is lost or interfered with
Solution Approach 1:
The patent segments the light output into distinct time slots: illumination periods where duty cycle control adjusts brightness, and communication periods where coded switching transmits data. This temporal segmentation allows both functions to operate independently without interference, resolving the contradiction between brightness control and data communication capability
Solution Approach 2:
The patent employs periodic switching between illumination mode and communication mode. During illumination periods, duty cycle varies for brightness control; during communication periods, fixed-duty-cycle coded switching transmits data. This periodic alternation enables both brightness control and data communication to coexist without mutual interference
2Loss of information
If coded switching is used for data communication, then data transmission is achieved, but brightness control capability is lost or interfered with
Solution Approach 1:
The patent segments the operational timeline into dedicated illumination intervals and communication intervals. During communication intervals, coded switching operates at fixed duty cycle to ensure reliable data transmission, while brightness control is suspended. During illumination intervals, duty cycle control operates freely for brightness adjustment. This segmentation resolves the contradiction by providing dedicated time for each function
Solution Approach 2:
The system periodically switches between communication mode and illumination mode. In communication mode, coded switching with fixed duty cycle ensures data integrity. In illumination mode, duty cycle control enables brightness adjustment. This periodic alternation resolves the contradiction by preventing simultaneous operation that would cause interference
3Illumination intensity
If multiple LEDs are used to increase light output, then illumination intensity is improved, but individual LED signal distinction becomes difficult
Solution Approach 1:
The patent assigns unique coded switching patterns to individual LEDs or LED groups, creating distinct local characteristics for each light source. This allows a detector to distinguish which specific LED(s) are active even when multiple LEDs contribute to the overall illumination, resolving the contradiction between increased light output and maintainable signal distinction
Solution Approach 2:
The patent segments the control of multiple LEDs into independently controllable units, each with its own coded pattern. This allows the system to activate specific combinations of LEDs for both illumination and identification purposes, enabling signal distinction even when multiple LEDs operate simultaneously
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 reliable distinction of individual LED signals and achieves high data rates while maintaining control over brightness, reducing spectral energy at low frequencies to prevent flicker, and increasing data capacity by varying the duty cycle and using multiple cell segments for data encoding.
Implementation Method 1
an LED is driven by causing an electric current to flow through the LED... light output is proportional to current
Implementation Method 2
a detector receiving light from said plurality of LEDs can recognize the contribution of each individual LED
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
A method for driving a light source (11, 12, 13) is described, wherein the light source is alternately switched ON and OFF in an ON/OFF pattern, wherein the duty cycle of the ON/OFF pattern is varied to vary the average light intensity of the light source, and wherein the shape of the ON/OFF pattern is varied to transmit data. Thus, a control signal for the light source comprises data information as well as duty cycle information. The duty cycle is varied within a range from almost zero to almost 100%, and data is varied and transmitted without affecting the duty cycle.