Active Stylus Control via Capacitive Coupling to Cut Battery Use
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Solution Overview
Problem
Conventional styluses with built-in power sources suffer from excessive battery consumption due to continuous one-way signal transmission, particularly when unique ID data transmission is required, which is inefficient and power-intensive.
Innovation Solution
A position detection device utilizing capacitive coupling between a tablet and a stylus, where the tablet transmits distinct control signals at different frequencies or modulation methods to control the stylus's operation modes, allowing it to reduce power consumption by minimizing unnecessary signal transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the stylus continuously transmits signals including unique ID from the position indicator to the tablet in a one-way communication system, then the tablet can recognize and track the position indicator, but the battery consumption of the stylus becomes excessive
Solution Approach 1:
The patent implements periodic bidirectional communication where the tablet sends inquiry signals at specific intervals and the stylus responds only when queried. This replaces continuous one-way transmission with periodic two-way communication, significantly reducing the stylus's battery consumption while maintaining reliable position tracking.
Solution Approach 2:
The patent inverts the communication direction by having the tablet actively send inquiry signals to the stylus, rather than the stylus continuously transmitting to the tablet. This role reversal allows the power-consuming transmission function to be performed by the tablet (which has larger power capacity) while the stylus only performs low-power reception and response.
2Reliability
If the stylus transmits unique ID data repeatedly to the tablet, then the tablet can maintain recognition of the position indicator, but the signal transmission time becomes excessively long
Solution Approach 1:
The patent establishes unique ID transmission as a preliminary action that occurs only during initial pairing or when the tablet needs to re-recognize the stylus. After the unique ID is transmitted once and stored by the tablet, subsequent communications use only position data, eliminating repeated transmission of the same ID information and reducing transmission time.
Solution Approach 2:
The patent extracts the unique ID transmission from the continuous communication stream, separating it as a distinct preliminary operation. The unique ID is transmitted only when necessary (during initial pairing or re-pairing), while normal operation uses a streamlined protocol that transmits only position information, thereby reducing overall transmission time.
3Reliability
If the stylus operates in continuous transmission mode without receiving control signals, then it can maintain position tracking capability, but it cannot optimize power consumption based on operational context
Solution Approach 1:
The patent implements a feedback mechanism where the tablet sends control signals to the stylus based on the current operational context (such as whether the stylus is in contact with the tablet surface, writing state, or idle state). The stylus receives these feedback signals and adjusts its transmission behavior accordingly, enabling dynamic power optimization while maintaining position tracking capability when needed.
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 device significantly reduces battery consumption by optimizing stylus operation modes based on received control signals, eliminating the need for continuous unique ID transmission and reducing signal transmission time.
Implementation Method 1
a position detection device that obtains a position pointed to by a position indicator on a tablet through capacitive coupling between the tablet and the position indicator
Data Source
AI summary
An active stylus is provided, which can reduce battery power consumption and reduce the time required for its signal transmission. A position detection device includes a tablet and the stylus having a built-in power source, which are capable of bi-directional transmission and reception of signals through capacitive coupling therebetween. The tablet is configured to transmit a trigger signal US_trg and then transmit a command signal US_cmd to the stylus. The trigger signal US_trg causes the stylus to start its command information receiver to receive the command signal US_cmd including information for controlling the stylus.