Touch Panel Control Circuit Multi-Touch Detection
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Solution Overview
Problem
Resistive film touch panels are unable to distinguish between single-touch and multi-touch operations due to similar output voltage readings, leading to multi-touch operations being handled as input errors.
Innovation Solution
A control circuit for a touch panel that includes a voltage generating unit, a current detection unit, and a coordinate determination unit, which applies bias voltages, detects panel current, and determines coordinates based on panel voltage and current, allowing for the detection of multi-touch states and coordinates without affecting the panel voltage, even with large contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a resistive film touch panel determines position based on output voltage only, then the panel structure is simple, but it cannot distinguish between single-touch and multi-touch operations
Solution Approach 1:
The patent combines voltage detection and current detection into a unified control circuit system. The voltage detection unit monitors panel voltage while the current detection unit monitors panel current, and both signals are processed together by the coordinate determination unit to enable multi-touch detection without requiring separate independent systems.
Solution Approach 2:
The control circuit is designed to perform multiple functions: it detects both voltage and current signals, determines coordinates for both single-touch and multi-touch operations, and handles various touch scenarios through a single integrated system rather than requiring different circuits for different touch types.
2Measurement precision
If multi-touch operations are handled as input errors, then the voltage detection system remains simple, but the measurement precision for touch coordinates is degraded
Solution Approach 1:
The patent replaces the conventional voltage-only detection method with an enhanced detection system that incorporates current measurement. By using electrical current monitoring alongside voltage detection, the system achieves more precise multi-touch coordinate identification without mechanical modifications to the touch panel structure.
Solution Approach 2:
The coordinate determination unit uses feedback from both voltage detection and current detection to continuously refine touch coordinate calculations. The system processes both signal types together, allowing it to distinguish between single-touch and multi-touch scenarios and accurately determine coordinates for multiple contact points.
3Measurement precision
If the detection resistor is arranged on the same path as the first terminal, first resistive film, and second terminal, then the circuit configuration is simplified, but the panel voltage is affected and measurement precision is reduced
Solution Approach 1:
The patent segments the detection circuit into separate functional paths: the voltage detection path and the current detection path. The detection resistor is placed in the current detection path rather than the voltage measurement path, separating the two measurement functions to prevent mutual interference while maintaining accurate measurements for both parameters.
Solution Approach 2:
The detection transistor acts as an intermediary element that allows current measurement through the detection resistor without directly affecting the voltage measurement path. This intermediary component enables current detection while isolating the voltage measurement from the influence of the detection resistor.
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 accurate detection of multi-touch states and coordinates, supporting valid multi-touch operations by monitoring panel current and optimizing voltage settings, ensuring precise coordinate determination.
Implementation Method 1
a detection transistor connected to the output transistor such that they form a current mirror circuit
Implementation Method 2
an amplifier circuit configured to amplify a difference between a voltage drop across the detection resistor and a predetermined voltage, and to output the difference thus amplified as a value which represents the panel current
Implementation Method 3
a first resistive film having one edge connected to the first terminal and having another edge, which is opposite to the aforementioned edge, connected to the second terminal
Data Source
AI summary
A voltage generating unit includes an output transistor arranged as a first-terminal side extension of a path that includes a first terminal, a first resistive film, and a second terminal, and is configured to apply a first bias voltage to the first terminal. A current detection unit includes a detection transistor connected to the output transistor such that they form a current mirror circuit, a detection resistor arranged on a path of the detection transistor, and an amplifier circuit configured to amplify the difference between a voltage drop across a detection resistor and a predetermined voltage, and to output the difference thus amplified as a value which represents a panel current.