Touch Driving Circuit Phase Control for Low-PAPR Display Panels
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Solution Overview
Problem
Display devices with integrated touch sensing capabilities experience high peak-to-average ratio (PAPR) values in touch driving signals, leading to noise interference and electromagnetic interference (EMI), which affect the display performance.
Innovation Solution
A touch driving circuit that assigns frequencies to touch driving signals in ascending order, varies phases to minimize cumulative PAPR, includes guard periods, and applies roll-off factors to smoothing signals, using orthogonal codes and cyclic suffix/prefix signals to reduce noise influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If touch driving signals are supplied to drive the touch sensing device, then touch sensing functionality is enabled, but peak-to-average ratio (PAPR) increases causing noise interference and electromagnetic interference on the display unit
Solution Approach 1:
The patent applies phase shifting to touch driving signals to minimize cumulative PAPR values. By adjusting the phase parameter of each touch driving signal individually, the system reduces peak power while maintaining average power, thereby decreasing noise interference and electromagnetic interference on the display unit while preserving touch sensing functionality
Solution Approach 2:
The patent employs iterative optimization where the touch driving circuit repeatedly adjusts phases of touch driving signals over multiple periods. Through periodic refinement of phase parameters, the system converges to optimal phase values that minimize cumulative PAPR, effectively reducing harmful interference while maintaining reliable touch sensing operation
2Area of stationary object
If multiple touch driving signals are supplied simultaneously to multiple electrodes, then comprehensive touch sensing coverage is achieved, but cumulative PAPR values increase leading to increased noise influence
Solution Approach 1:
The patent individually adjusts the phase parameter of each touch driving signal supplied to different electrodes. By optimizing each signal's phase independently, the system minimizes the cumulative PAPR of all signals combined, thereby reducing overall noise influence while maintaining comprehensive touch sensing coverage across the display area
Solution Approach 2:
The touch driving circuit calculates cumulative PAPR values based on the superposition of all touch driving signals and uses this feedback to iteratively adjust individual signal phases. This feedback mechanism enables the system to achieve optimal phase configuration that minimizes cumulative noise influence while maintaining full touch sensing coverage
Data Source
AI summary
A display device includes: a display panel including a display layer and a touch layer; and a touch driving circuit connected to first electrodes and second electrodes of the touch layer. The touch driving circuit is to: determine frequencies of touch driving signals to be supplied to the first electrodes; assign the frequencies to the touch driving signals in an ascending order; determine a first phase of each of the touch driving signals that minimizes a cumulative value of PAPRs while sequentially varying phases of the touch driving signals; update the phases of the touch driving signals from the first phase to a second phase that minimizes the cumulative value of the PAPRs by sequentially varying the first phase of each of the touch driving signals; and output the touch driving signals based on the frequencies assigned to the touch driving signals, respectively, and the second phase.