Touch Screen Detection Using Current Mirrors and Pre-Charge Logic
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing touch screen technologies face challenges in detecting contact events efficiently due to the need for analog circuitry and analog-to-digital converters, which introduce delays and require specific design for each type of touch screen, and capacitive touch screens require pre-charging that can be misinterpreted as contact events.
Innovation Solution
The implementation of a touch detection system that uses current mirrors to detect contact events based on changes in current output from the touch screen, includes a pre-charge circuit to prevent false detection during the pre-charging process, and diagnostic logic to identify faults in the touch screen.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If analog circuitry and analog-to-digital converters are used to detect touch events, then touch detection capability is achieved, but detection delay increases and device complexity increases
Solution Approach 1:
The patent extracts the analog-to-digital conversion function by using a current mirror circuit that directly generates a digital output signal from the analog touch sensor output. This eliminates the need for separate analog-to-digital converters, reducing detection delay while maintaining touch detection capability.
Solution Approach 2:
The patent replaces the traditional mechanical/analog signal processing chain with an electronic current mirror circuit that directly produces digital signals. This substitution eliminates conversion delays and reduces the overall detection time while maintaining reliable touch event detection.
2Measurement precision
If analog circuitry is designed specifically for each touch screen type, then detection accuracy is optimized, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent creates a universal current mirror circuit design that can be applied across different touch screen types (resistive, capacitive, infrared) without requiring custom analog circuitry for each type. The circuit uses standard electronic components and principles that work universally, reducing design complexity while maintaining detection accuracy.
Solution Approach 2:
The patent allows for easy adaptation to different touch screen types by adjusting electrical parameters such as current levels, threshold voltages, and timing characteristics rather than redesigning the fundamental circuit architecture. This parameter-based adaptation maintains detection accuracy while significantly reducing device complexity.
3Reliability
If pre-charging is performed on capacitive touch screens, then proper operation is enabled, but false contact event detection occurs
Solution Approach 1:
The patent implements a preliminary action by performing pre-charging of the capacitive touch screen before normal operation begins. A separate pre-charge circuit charges the capacitive elements in advance, and the system enters a pre-charging state where touch detection is temporarily disabled. This preliminary charging action prevents false detection during the charging process while ensuring proper operation during actual use.
Solution Approach 2:
The patent uses feedback mechanisms to distinguish between pre-charging current and actual touch event current. The circuit monitors current characteristics and uses feedback to determine whether a signal corresponds to pre-charging or a real touch event, enabling accurate detection while maintaining proper pre-charging operation.
Data Source
AI summary
A method includes driving a current through a touch screen that is based on contact of the touch screen, generating a proportional second current, and detecting contact of the touch screen from the second current. Another method includes providing a touch screen with parallel plates, disabling contact detection when a plate voltage is lower than a threshold voltage, and enabling contact detection when the plate voltage is at least equal to the threshold voltage. A device includes a first node and a second node coupled to a touch screen, a third node, a first current mirror coupled to the second node and the third node configured to generate a current at the third node that is proportional to a second current at the second node, and a detection circuit that provides a signal based on the first current that indicates contact of the touch screen.