Projected Capacitive Touch Panel Trace Scanning Optimization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional touch control devices for projected capacitive touch panels face inefficiencies in detecting touch events due to high current consumption and reduced sensitivity, especially when the number of traces increases, as they require scanning all traces to determine event location, which prolongs detection time and diminishes data report rates.
Innovation Solution
Implementing a pre-wakeup mode where a charge control signal is outputted to only one trace, keeping others floating, allowing the touch control device to determine touch events by comparing voltage signals with a threshold, reducing the need to scan all traces and optimizing operation modes between drive and sleep modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If all traces are scanned to determine touch event location, then measurement precision is improved, but loss of time increases and productivity decreases
Solution Approach 1:
The touch panel traces are segmented into multiple groups, with only one group scanned at a time. The scanning process is divided into multiple scanning periods, where each period scans a specific group of traces. This segmentation allows the system to reduce detection time by not scanning all traces simultaneously, while still maintaining location detection accuracy through systematic group-by-group scanning.
Solution Approach 2:
The system performs preliminary scanning of trace groups in a systematic sequence before determining the final touch location. By pre-organizing traces into groups and scanning them in predetermined scanning periods, the system prepares detection data efficiently, reducing overall detection time while maintaining measurement precision through the structured approach.
2Measurement precision
If all traces are scanned to determine touch event location, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The scanning process is segmented into multiple scanning periods, each handling a specific group of traces. This segmentation enables parallel processing of different trace groups, increasing the overall data report rate. The system can report detected touch events from scanned groups without waiting to complete scanning of all traces, thereby improving productivity while maintaining location detection accuracy.
Solution Approach 2:
The system implements periodic scanning of trace groups, where each scanning period is dedicated to scanning a specific group of traces. This periodic action allows the system to maintain a high data report rate by continuously cycling through different trace groups, ensuring that touch events are detected and reported promptly without the bottleneck of scanning all traces in a single continuous process.
3Reliability
If traces not being scanned are kept at fixed voltage level, then reliability is improved, but use of energy increases
Solution Approach 1:
The voltage level of non-scanned traces is dynamically adjusted based on the current scanning phase. During active scanning of a trace group, non-scanned traces are maintained at a fixed voltage level to ensure detection reliability. When scanning is complete or in between scanning periods, the system releases these traces to floating state, reducing energy consumption. This dynamic voltage management maintains reliability during critical detection phases while minimizing energy use during transitional periods.
Solution Approach 2:
The system temporarily discards the fixed voltage level maintenance for non-scanned traces when they are not currently being scanned or when scanning is complete. By releasing these traces to floating state and only re-establishing fixed voltage levels when needed for scanning, the system reduces energy consumption while maintaining detection reliability during active scanning 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 reduces current consumption while enhancing touch event detection sensitivity and data report rates by selectively scanning only one trace, allowing for more efficient operation and improved performance in detecting touch events.
Implementation Method 1
a capacitor is formed between the coupling node and a ground. When a user touches or approaches the coupling node, a body capacitance may be coupled to the capacitor at the coupling node. Therefore, a location of this touch event is determined by detecting which trace capacitance change occurs on.
Implementation Method 2
the A/D converter 100 sequentially outputs a charge control signal, e.g. a square wave signal, to each trace for charging/discharging a capacitor on each trace, and converts a voltage signal on each trace, which shows a charging/discharging curve, into a digital signal
Data Source
AI summary
A method of detecting a touch event for a touch panel which comprises a plurality of intersecting traces. The method includes outputting a charge control signal to a trace of the plurality of traces, and keeping other traces except for the trace floating and determining whether the touch event happens according to a voltage signal on the trace.