Active Capacitive Pen Multi-Protocol Switching Circuit
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Solution Overview
Problem
Current active pens typically support only one protocol (MPP or USI) for capacitive touch screens, limiting their ability to perform touch operations under both Microsoft Pen Protocol and Universal Stylus Initiative protocols.
Innovation Solution
An active capacitive pen design featuring a barrel with three electrodes and a switching circuit, allowing the pen to switch between configurations for compatibility with both MPP and USI protocols by adjusting the signal transmission and reception electrodes, thereby accommodating different structural requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the active capacitive pen is designed to support only one protocol (MPP or USI), then the device complexity is reduced and ease of manufacture is improved, but the adaptability to different protocols deteriorates
Solution Approach 1:
The pen is divided into three separate electrodes (first, second, and third electrodes) that can be independently configured. The first electrode serves as the tip electrode, while the second and third electrodes can be selectively connected or disconnected to adapt to different protocols. This segmentation allows each electrode to have a specific function while collectively providing multi-protocol support.
Solution Approach 2:
The switching circuit dynamically changes the electrical connection state between the second and third electrodes based on the detected protocol. When operating in MPP mode, the switching circuit disconnects the third electrode from the second electrode. When operating in USI mode, the switching circuit connects them together. This dynamic reconfiguration enables the pen to adapt its electrode structure to match different protocol requirements.
2Measurement precision
If the second electrode is positioned far from the capacitive touch screen to ensure measurement precision, then the angle measurement accuracy is improved, but the amount of uplink signals received deteriorates
Solution Approach 1:
The second and third electrodes are electrically connected through the switching circuit in USI mode, merging their signal reception capabilities. This combination increases the total effective area for receiving uplink signals from the capacitive touch screen, compensating for the reduced signal strength caused by the second electrode's distance from the screen.
Solution Approach 2:
The third electrode acts as an additional signal reception element that copies the function of the second electrode. By placing the third electrode closer to the touch screen while maintaining electrical connection with the second electrode, the system creates a redundant signal path that enhances the overall signal reception capability without compromising the angular measurement function of the second electrode.
3Length of moving object
If the height of the signal transmitting and receiving electrode is reduced to minimize pen size, then the miniaturization is improved, but the amount of uplink signals received deteriorates
Solution Approach 1:
The switching circuit merges the second and third electrodes into a single electrical unit with combined effective area. Although each electrode individually has reduced height for miniaturization, their combined electrical connection creates a larger effective reception area, compensating for the reduced individual dimensions and maintaining adequate signal reception capability.
Data Source
AI summary
An active capacitive pen is disclosed, including: a barrel; a first electrode disposed at an end of the barrel, an end of the first electrode away from the barrel serving as a tip of the active capacitive pen; a second electrode disposed on the barrel and spaced apart from the first electrode in an axial direction of the barrel; a third electrode disposed on the barrel and located between the first electrode and the second electrode in the axial direction of the barrel; a switching circuit, connected with the second electrode and the third electrode and configured to electrically connect the third electrode with the first electrode, or disconnect the third electrode from the second electrode. Also disclosed is an electronic terminal with the active capacitive pen.