Reference Voltage Modulator for Low Power Capacitive Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing capacitive sensing technologies face challenges in efficiently detecting input objects in low power states and accurately determining object location without increasing power consumption or interfering with display operations.
Innovation Solution
The implementation of a reference voltage modulator that modulates reference voltage rails during capacitive sensing, allowing the input device to detect input objects by isolating these rails from the DC power supply and using them to acquire signals, thereby reducing power consumption and enabling precise location determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the device enters low power state to reduce power consumption, then power consumption is reduced, but capacitive sensing capability is lost
Solution Approach 1:
The system enters sleep mode periodically to conserve power while maintaining capacitive sensing capability through periodic wake-up cycles. The processor core is deactivated during sleep mode but can be quickly reactivated to perform sensing operations when needed, creating a periodic action pattern that balances power consumption with sensing reliability.
Solution Approach 2:
The system performs preliminary capacitive sensing operations before fully entering low power state to detect potential input objects. This preliminary action allows the system to maintain basic sensing awareness while preparing for power reduction, ensuring that sensing capability is not completely lost even when the processor is deactivated.
2Measurement precision
If separate sensing circuitry is activated for capacitive sensing, then sensing accuracy is improved, but power consumption increases
Solution Approach 1:
The processor core serves multiple functions by acting as both the main processing unit and the sensing circuitry. During active mode, it performs general processing tasks; during sleep mode, it can be selectively activated to perform capacitive sensing operations. This multi-functionality eliminates the need for separate dedicated sensing circuitry, maintaining sensing accuracy while reducing overall power consumption.
Solution Approach 2:
The patent merges the sensing circuitry functionality into the existing processor core structure. The sensor module interfaces directly with the processor core, combining what would traditionally be separate components into a unified architecture. This merging reduces the power overhead of having separate sensing circuitry while maintaining the required sensing accuracy through coordinated processor activation.
3Adaptability or versatility
If display operations continue during capacitive sensing, then user interface functionality is maintained, but interference with sensing signals occurs
Solution Approach 1:
The system segments the operational modes by separating display refresh operations from capacitive sensing operations in time. During vertical blanking intervals or specific time slots when display operations are minimized, the system performs capacitive sensing measurements. This temporal segmentation allows both display functionality and sensing accuracy to coexist by preventing simultaneous interference.
Solution Approach 2:
Capacitive sensing operations are performed periodically at specific intervals during the display refresh cycle. The system synchronizes sensing measurements with periods when display signal interference is minimal or absent, creating a periodic pattern that maintains both display functionality and sensing signal integrity through coordinated timing.
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 enables efficient capacitive sensing in low power states while maintaining accurate object detection and location determination, reducing power consumption and avoiding interference with display operations.
Implementation Method 1
a capacitive sensor device. The capacitive sensor comprises a first sensor electrode, a second sensor electrode, and a processing system coupled to the first sensor electrode and the second sensor electrode. In operation, the processing system acquires a first capacitive measurement by both emitting and receiving a first electrical signal with the first sensor electrode.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
This disclosure generally provides an input device that includes a reference voltage modulator that modulates reference voltage rails when performing capacitive sensing. In one embodiment, reference voltage rails are coupled to a DC power source which provides power to operate a panel that includes a display screen integrated with a touch sensing region. Before performing capacitive sensing, the input device may isolate the DC power source from the reference voltage rails and use the reference voltage rails to modulate the rails - e.g., VDD and VGND. The input device may include a receiver that simultaneously acquires resulting signals from a plurality of display and/or sensor electrodes when modulating the reference voltage rails. The resulting signals can then be processed to determine if an input object is interacting with the input device.