In-Cell Touch Screen Test Circuit for Short-Circuit Detection
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Solution Overview
Problem
Conventional test circuits for in-cell touch screens fail to detect short-circuits between even-numbered or odd-numbered touch electrodes, leading to increased probability of touch defects in the screen.
Innovation Solution
A test circuit with cascaded scanning circuits connected to touch electrodes, featuring a test signal input terminal, a test signal output terminal, and a short-circuit feedback terminal, which forms a loop to lower the voltage on short-circuited touch electrodes, causing the corresponding display area to darken and facilitating defect detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional test circuits apply different voltages to odd and even touch electrodes, then display brightness difference can detect normal touch electrode operation, but short-circuits between even-numbered or odd-numbered touch electrodes cannot be detected
Solution Approach 1:
The touch electrodes are divided into different groups (odd-numbered and even-numbered) with different connection configurations. Odd-numbered touch electrodes are connected to one signal line while even-numbered touch electrodes are connected to another signal line, allowing independent voltage application and detection for each group to identify short-circuits within specific groups
Solution Approach 2:
Different voltage levels are applied to different groups of touch electrodes based on their positional characteristics (odd vs even numbering). This local differentiation in electrical properties enables the test circuit to identify short-circuits by comparing brightness differences in specific display regions corresponding to different electrode groups
2Ease of operation
If voltage is applied to touch electrodes through signal lines, then touch electrode operation can be tested, but short-circuited touch electrodes cannot be distinguished from normal ones
Solution Approach 1:
The test circuit incorporates a feedback mechanism where the display brightness is monitored in real-time. When a short-circuit is detected through abnormal brightness patterns in specific regions, the system can identify the defective area by correlating the brightness feedback with the known electrode-to-display-region mappings
Solution Approach 2:
The test method utilizes display brightness (optical property) changes as an indicator of electrical circuit status. By applying voltages to touch electrodes and observing the corresponding brightness changes in the display array, the system can detect short-circuits through abnormal optical responses in specific display regions
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
The proposed test circuit effectively detects short-circuited touch electrodes by reducing the brightness of the affected display area, improving the accuracy of touch circuit testing and reducing the likelihood of undetected defects in the touch screen.
Implementation Method 1
the TP1 signal line and the TP2 signal line are given different amounts of voltage... the brightness of the display area which the even-numbered touch electrode 103 corresponds to may be different from the brightness of the display area which the odd-numbered touch electrode 102 corresponds to
Data Source
AI summary
A test circuit which is configured to test an in-cell touch screen includes a plurality of cascaded scanning circuits. The scanning circuit includes a test signal input terminal, a test signal output terminal connected to the touch electrode correspondingly through a first signal line and configured to input a test signal to the corresponding touch electrode, and a short-circuit feedback terminal connected to the touch electrode which the test signal output terminal of the scanning circuit at a previous stage is connected to.