LED Display Capacitive Sensing via Time-Multiplexed Voltage Modulation
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Solution Overview
Problem
Existing capacitive sensing technologies in LED displays face challenges in efficiently integrating capacitive sensing with light-emitting diode (LED) pixels, particularly in providing accurate and reliable input detection without interfering with the display functionality.
Innovation Solution
The integration of isolated supply domains, a multiplexer circuit, and control logic to modulate and supply anode and cathode voltages to LED pixels, enabling both display operation and capacitive sensing by using the same pixels, with the multiplexer circuit selectively providing voltages for sensing and display purposes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If capacitive sensing is integrated with LED pixels, then input detection capability is improved, but display functionality may be interfered with
Solution Approach 1:
The patent segments the operation into distinct time periods: display operation occurs during a first time period while capacitive sensing occurs during a second time period. This temporal segmentation allows both functions to operate without interfering with each other, as the LED pixels are used for display during their designated time and for sensing during the sensing time period.
Solution Approach 2:
The system employs periodic alternation between display mode and sensing mode. The controller selectively couples voltages to LED pixels during display periods and performs capacitive sensing during sensing periods. This periodic switching enables both functions to coexist by assigning them different time slots, thereby maintaining display reliability while adding input detection capability.
2Device complexity
If the same LED pixels are used for both display and sensing, then device complexity is reduced, but interference between functions increases
Solution Approach 1:
The patent implements periodic switching between display and sensing operations using the same LED pixels. By allocating specific time periods for each function, the system eliminates mutual interference while maintaining hardware simplicity. The controller manages the temporal multiplexing to ensure that display and sensing operations do not occur simultaneously, thus preventing functional interference.
Solution Approach 2:
The system dynamically reconfigures the function of LED pixels based on the operational phase. During display periods, pixels emit light; during sensing periods, pixels serve as capacitive sensors. This dynamic functional switching allows the same hardware to serve dual purposes without permanent interference, as the system adapts the pixel function according to temporal requirements.
3Measurement precision
If modulated voltages are supplied to LED pixels for sensing, then sensing accuracy is improved, but energy consumption increases
Solution Approach 1:
The patent applies modulated voltages to LED pixels only during the capacitive sensing time period, not continuously. The controller supplies isolated and modulated anode and cathode voltages during the second time period when sensing is performed, and uses standard display voltages during the first time period. This periodic application of modulated voltages improves sensing accuracy while limiting energy consumption to only when necessary for sensing operations.
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 solution allows for effective capacitive sensing while maintaining the display functionality, enhancing input detection accuracy and reducing interference, thereby improving the overall performance of LED-based input devices.
Implementation Method 1
a display including a plurality of light-emitting diode (LED) pixels
Implementation Method 2
perform capacitive sensing using the LED pixels
Data Source
AI summary
A processing system for an integrated display and capacitive sensing device, where the display includes light-emitting diode (LED) pixels. The processing system includes isolated supply domains having inputs that receive an anode voltage and a cathode voltage, first outputs that supply modulated anode voltages, and second outputs that modulated cathode voltages, where the modulated anode voltages and the modulated cathode voltages are constant with respect to each other and modulated with respect to an external reference voltage. The processing system additionally includes a multiplexer circuit having inputs coupled the isolated supply domains, the anode voltage, and the cathode voltage, and having outputs coupled to the LED pixels. Further, the processing system includes control logic configured to control the multiplexer circuit to selectively supply the anode voltage and the cathode voltage, or the modulated anode voltages and the modulated cathode voltages, to the LED pixels.