Touch Detection Circuit Using Reference Voltage Noise Suppression
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Solution Overview
Problem
Conventional capacitive touch screens face challenges in accurately detecting touch events due to interference from noise and parasitic capacitance, leading to reduced sensitivity and reliability in determining touch location and operation.
Innovation Solution
A touch detection circuit incorporating charge/discharge circuits, a reference voltage generator, programmable gain amplifiers, and analog-to-digital converters to convert and amplify capacitance changes into quantifiable signals, using a reference voltage that suppresses common-mode noise and eliminates the need for charge integrators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional capacitive touch screens use traditional charge integrators for touch detection, then the circuit structure is simple, but noise interference and parasitic capacitance reduce detection sensitivity and reliability
Solution Approach 1:
The patent extracts and removes the charge integrator component from the traditional touch detection circuit. By eliminating this component, the circuit avoids the noise and parasitic capacitance issues associated with charge integration, thereby improving touch detection sensitivity and reliability without being affected by harmful factors
Solution Approach 2:
The patent introduces a reference voltage generator as an intermediary component that provides a stable reference voltage for comparison. This reference voltage acts as a mediator between the sense channel and the detection circuit, enabling accurate touch detection by comparing the sense voltage against the reference voltage, thereby improving measurement precision while filtering out noise interference
2Ease of manufacture
If conventional touch detection circuits use charge integrators, then the circuit implementation is straightforward, but chip area and cost increase due to additional components
Solution Approach 1:
The patent removes the charge integrator from the circuit, reducing the number of components required. This extraction simplifies the overall circuit structure while maintaining effective touch detection functionality, thereby reducing chip area without significantly compromising ease of manufacture
Solution Approach 2:
The reference voltage generator serves multiple functions: it provides a stable reference voltage for comparison, enables noise filtering through differential measurement, and simplifies the overall circuit architecture. This multi-functionality allows the circuit to achieve accurate touch detection with fewer components, reducing chip area while maintaining manufacturing simplicity
3Device complexity
If conventional touch detection circuits are used, then the structure is simple, but reliability is reduced due to noise and parasitic capacitance interference
Solution Approach 1:
The reference voltage generator acts as an intermediary that provides a stable reference for comparison with the sense voltage. This intermediary enables reliable touch detection by allowing the circuit to distinguish between actual touch signals and noise/parasitic capacitance effects, thereby improving reliability without significantly increasing circuit complexity
Solution Approach 2:
The patent replaces the charge integration mechanism with a voltage comparison mechanism. This substitution eliminates the reliability issues associated with charge integrators (noise susceptibility and parasitic capacitance effects) while maintaining a relatively simple circuit structure through direct voltage measurement and comparison
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
Improves touch detection sensitivity and reliability by reducing noise interference and optimizing chip area and cost, enabling precise determination of touch events and locations.
Implementation Method 1
charge/discharge circuits, which are coupled to respective sense channels of a touch screen and are configured to charge or discharge the sense channels during scanning periods to convert sense signals on the sense channels into sense voltages
Implementation Method 2
the operational amplifier configured to output an average of the voltages on the sense channels as the reference voltage
Implementation Method 3
the programmable gain amplifiers configured to amplify differences between the sense voltages and the reference voltage
Data Source
AI summary
A touch detection circuit, a touch sensing chip and an electronic device are disclosed. The touch detection circuit includes charge/discharge circuits, which are configured to charge or discharge the sense channels during scanning periods to convert sense signals on the sense channels into sense voltages; a reference voltage generator circuit, which is coupled to the sense channels of the touch screen and is configured to produce a reference voltage related to the voltages on the sense channels; programmable gain amplifiers including first input terminals coupled to output terminals of the charge/discharge circuits and second input terminals coupled to an output terminal of the reference voltage generator circuit, the programmable gain amplifiers configured to amplify differences between the sense voltages and the reference voltage; analog-to-digital converters, which are coupled to the programmable gain amplifiers and are configured for quantization of the differences that have been amplified by the programmable gain amplifiers.