Common Voltage Electrode Sensing to Reduce Display Buzzing
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Solution Overview
Problem
Existing input devices with proximity sensors face challenges in minimizing user-audible noise during input sensing periods due to voltage differences between display update and input sensing intervals, leading to annoying buzzing sounds.
Innovation Solution
The processing system drives common voltage electrodes with a fixed voltage during display update periods and a sensing signal with a duty cycle-adjusted waveform during input sensing periods, minimizing the mean voltage difference to reduce audible noise, while ensuring sufficient settling time for capacitive measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a sensing signal with high amplitude is driven on the common voltage electrode during input sensing period, then the sensing capability is improved, but the voltage difference between display update and input sensing periods increases causing user-audible noise
Solution Approach 1:
The patent adjusts the duty cycle parameter of the sensing signal to control its mean voltage level. By changing the duty cycle, the mean voltage of the sensing signal is matched to the fixed voltage used during display updates, thereby minimizing voltage differences and reducing audible noise while preserving sensing capability through adequate signal amplitude during the sensing period.
2Object-affected harmful factors
If the duty cycle of the sensing signal is adjusted to minimize voltage difference, then user-audible noise is reduced, but the settling time requirement may be compromised
Solution Approach 1:
The patent dynamically adjusts the duty cycle of the sensing signal to achieve an optimal balance between minimizing voltage difference (reducing noise) and ensuring adequate settling time for capacitive measurements. The duty cycle is tuned so that the sensing signal maintains sufficient amplitude duration to allow sensors to settle and complete measurements reliably, while keeping the mean voltage close to the fixed display update voltage.
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 effectively minimizes user-audible noise by adjusting the duty cycle of the sensing signal to match the fixed voltage used during display updates, maintaining signal quality and reducing electromagnetic emissions, thus enhancing user experience and device performance.
Implementation Method 1
reducing electromagnetic emissions
Implementation Method 2
complied with a minimum settling time of a sensor receiving the sensing signal
Data Source
AI summary
A processing system for an input device comprises drive circuitry configured to generate a fixed voltage for a common voltage electrode of the input device during a display update period, and generate a sensing signal for the common voltage electrode during an input sensing period, the sensing signal having a duty cycle and a mean value, wherein the duty cycle minimizes a difference between the fixed voltage and the mean value. An input device comprises one or more common voltage electrodes and a coupled processing system. The processing system is configured to drive the one or more common voltage electrodes with a fixed voltage during a display update period, and a sensing signal during an input sensing period. The sensing signal has a duty cycle and a mean value, the duty cycle configured to minimize a difference between the mean value and the fixed voltage.