Capacitive Sensing Decoder Multiplexing for Fewer Signal Lines
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Solution Overview
Problem
Conventional capacitive detection devices face challenges in enhancing sensitivity and signal reliability due to noise interference and the need for reduced consumption current, particularly in mobile devices, where the detection of added capacitance is hindered by noise and requires complex signal line configurations.
Innovation Solution
The solution involves arranging Capacitor Detect Areas (CDAs) in a transverse and longitudinal direction with multiple signal lines, using detection and driving switch groups, and applying varying driving voltages to improve sensitivity and reliability by stabilizing the operational amplifier's operation point and shielding noise from the sensing signal line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple decoders are used to control multiple switch groups, then each switch group can be controlled independently, but the number of signal lines and device complexity increases
Solution Approach 1:
The patent combines multiple decoder functions into a single decoder by multiplexing its output. The decoder output is sequentially connected to multiple switch groups through time-division multiplexing, allowing one decoder to control multiple switch groups without requiring multiple separate decoders, thus reducing device complexity while maintaining control reliability
Solution Approach 2:
The patent implements periodic switching of the decoder output to different switch groups in a cyclic manner. The decoder output is periodically connected to different switch groups through sequential switching, enabling time-division multiplexed control where each switch group receives control signals in alternating time slots, achieving multi-group control with a single decoder
2Measurement precision
If multiple loaders output detection signals separately, then each detection signal can be processed independently, but the number of signal lines increases
Solution Approach 1:
The patent merges multiple detection signal lines into a single shared signal line by implementing time-division multiplexing. Different detection signals from multiple loaders are sequentially transmitted through the same signal line at different time slots, allowing independent processing of each detection signal while using a single shared transmission medium, thus reducing signal line quantity without compromising detection precision
Solution Approach 2:
The patent employs periodic switching to sequentially connect different loaders to the shared detection signal line. Each loader is periodically connected to the signal line in turn, enabling time-division multiplexed transmission where detection signals from multiple sources are alternately transmitted through the same line, achieving signal consolidation while maintaining independent processability
3Measurement precision
If driving voltage is increased to improve detection sensitivity, then capacitance detection sensitivity improves, but consumption current increases
Solution Approach 1:
The patent applies periodic driving voltages in alternating time slots rather than continuous high voltage. The driving voltage is applied periodically to different switch groups and detection areas in sequence, allowing the use of relatively high voltage for improved sensitivity during active measurement periods while maintaining lower average power consumption through time-division multiplexing and idle periods
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 detection sensitivity, improves the signal-to-noise ratio, and reduces the driving voltage, thereby minimizing consumption current and simplifying the configuration of display device modules by reducing the number of signal lines and control signals.
Implementation Method 1
a capacitive type of input device detects a change in capacitor that occurs when a finger or pen is adjacent to or in contact with the 'capacitor detect area'
Implementation Method 2
Cprs is 'internal parasitic capacitor' formed between the detection (or Sensing) signal line and the semiconductor substrate inside the Semiconductor IC
Data Source
AI summary
The present invention operates multiple capacitors to minimize the fluctuation of voltage detected on the CDA signal line 200, thereby enhancing the resolution of the ADC. The object capacitance (Cobj) generated between the CDA 100 and the object 20 due to the appearance of the object 20 is detected in the form of voltage. By analyzing with an ADC of improved resolution, it is possible to detect the presence of the object 20 more reliably.