In-Cell Touch Controller Switching to Eliminate Spanning Voltage
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Solution Overview
Problem
Conventional in-cell touch screens face an increase in circuit area due to the spanning voltage problem, which arises from the difference in voltage levels between the display mode and touch sensing mode, requiring additional circuits or high-voltage MOS transistors to address this issue.
Innovation Solution
A controller for in-cell touch screens is designed with a common voltage (VCOM) circuit, display-mode switch, and touch-sensing-mode switch, where the display-mode switch is closed in display mode and open in touch sensing mode, and vice versa, utilizing MOS transistors to manage voltage levels without additional circuits, ensuring full-swing power compatibility between the VCOM circuit and detecting circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional circuits or high-voltage MOS transistors are used to address the spanning voltage problem, then the voltage level difference between display mode and touch sensing mode is resolved, but the circuit area increases
Solution Approach 1:
The patent merges the VCOM circuit and detecting circuit into a single integrated controller chip. The VCOM circuit generates the common voltage for display mode, while the detecting circuit processes sensing signals in touch sensing mode. By combining these circuits and using a single MOS transistor for switching between modes, the patent eliminates the need for separate additional circuits or high-voltage MOS transistors, thereby resolving the spanning voltage problem without increasing circuit area
Solution Approach 2:
The MOS transistor in the patent serves multiple functions: it acts as a switch to alternate between display mode and touch sensing mode, and it handles voltage switching between positive and negative levels. This multi-functional design eliminates the need for dedicated additional circuits or specialized high-voltage transistors, achieving voltage level compatibility while maintaining compact circuit area
2Length of stationary object
If conventional in-cell touch screen design is used, then the touch screen can be made thinner, but the spanning voltage problem requires additional circuits that increase chip area
Solution Approach 1:
The patent combines the VCOM circuit and detecting circuit into a single integrated controller, eliminating the need for separate additional circuits that would increase chip area. This integration maintains the thin profile benefits of in-cell technology while avoiding the area penalty of separate voltage management circuits
Solution Approach 2:
The patent changes the voltage parameter management by using a single MOS transistor that can handle both positive and negative voltage levels. The transistor switches between connecting the VCOM electrode to positive voltage (display mode) and negative voltage (touch sensing mode), thereby managing the spanning voltage problem through parameter control rather than additional hardware
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 solution inhibits the spanning voltage problem without increasing chip area, maintaining efficient operation in both display and touch sensing modes by ensuring full-swing power compatibility within the existing circuitry.
Implementation Method 1
a common voltage (VCOM) circuit generates a common voltage at an output node of the VCOM circuit
Implementation Method 2
The display-mode switch has a first end connected with the output node of the VCOM circuit, and has a second end connected with a VCOM electrode via an associated connecting line
Implementation Method 3
The touch-sensing-mode switch has a first end connected with the input/output node of the detecting circuit, and has a second end connected with the VCOM electrode via the associated connecting line
Implementation Method 4
A capacitor-based touch panel is a commonly used touch panel that utilizes capacitive coupling effect to detect touch position
Data Source
AI summary
A controller adapted to an in-cell touch screen includes a common voltage (VCOM) circuit generating a common voltage at an output node of the VCOM circuit, and a detecting circuit receiving a sensing signal at an input/output node of the detecting circuit. A display-mode switch is closed in a display mode such that a VCOM electrode is set at the common voltage, and a touch-sensing-mode switch is closed in a touch sensing mode such that the sensing signal from the VCOM electrode is received and processed by the detecting circuit. The detecting circuit has full-swing power that contains full-swing power of the VCOM circuit.