Capacitive Touch Sensor Driver Using Hadamard Codes
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Solution Overview
Problem
Capacitive touch sensors face challenges in utilizing detection signals from initial periods due to values (V1 and −V1) that are not readily usable for touch event detection, often requiring additional circuits to process these signals.
Innovation Solution
The system employs a driver that supplies the same driving signal for a previous period when the driving code is set to 'A' and a different signal for the current period when set to '−A', using a Hadamard matrix code to maintain predetermined detection signal values across driving periods without the need for separate circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If orthogonal code driving signals are supplied to driving electrodes, then multi-touch detection accuracy is improved, but detection signals in initial periods have unusable values requiring additional circuits
Solution Approach 1:
The driver performs preliminary action by setting the driving signal for the initial period to be identical to the subsequent period, ensuring that detection signals from the initial period have usable values without requiring additional processing circuits. This preliminary configuration prevents the generation of unusable signal values in the first place.
Solution Approach 2:
The invention extracts and eliminates the problematic initial period signal issue by modifying the driving code assignment. Instead of using conventional orthogonal codes that produce unusable initial values, the system selectively assigns driving codes to ensure continuous usability of detection signals, removing the need for separate initial period processing circuits.
2Reliability
If additional circuits are provided to process initial period detection signals, then signal usability is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The driver circuit serves itself by internally managing the driving signal assignment to ensure all detection signals are usable. The driver automatically adjusts driving codes based on period information, making the system self-sufficient without requiring external or additional processing circuits for initial period signal correction.
Solution Approach 2:
The system performs preliminary action by pre-configuring driving signals for the initial period to match subsequent periods, ensuring signal usability from the start. This preliminary setup prevents the generation of unusable signals, eliminating the need for additional processing circuits.
3Measurement precision
If driving signals are changed for each driving period, then touch detection accuracy is improved, but signal consistency deteriorates causing unusable initial period values
Solution Approach 1:
The invention applies local quality by differentiating driving code assignment based on period characteristics. For the initial period, the system assigns driving codes that ensure signal consistency with subsequent periods, while for later periods, it uses conventional orthogonal coding schemes. This localized adaptation optimizes both signal consistency and detection accuracy.
Solution Approach 2:
The system dynamically adjusts driving code assignment based on the current driving period. The driver changes driving signals adaptively: maintaining consistency during the initial period and transitioning to conventional orthogonal codes in subsequent periods, thereby optimizing both signal stability and detection precision across different operational phases.
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 the use of detection signals without additional circuits, ensuring consistent and usable signal outputs for touch event detection across all driving periods.
Implementation Method 1
a capacitive touch sensor, capable of recognizing a touch position by detecting a point at which capacitance is changed by the contact of a hand of a person or an object
Data Source
AI summary
Disclosed is a touch sensor, including: a plurality of driving electrodes; a plurality of detection electrodes positioned to cross the driving electrodes; and a driver configured to supply driving signals corresponding to driving codes to the driving electrodes, in which the driver supplies the same driving signal as that of a previous driving period to a corresponding driving electrode for a current driving period when the driving code is set to a first value, and supplies a driving signal different from that of the previous driving period to the corresponding driving electrode for the current driving period when the driving code is set to a second value.