Display Driving Circuit for Touch Harmonic Prevention
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Solution Overview
Problem
The occurrence of harmonics between the frequency of the driving signal and the frequency of the touch signal in display devices can lead to increased jitter noise and a higher probability of ghost touches, which are exacerbated by temperature variations affecting the oscillators.
Innovation Solution
A driving circuit that utilizes a second clock signal to count cycles of synchronization signals and detects defects, controlling the frequencies of the oscillators to prevent harmonics by adjusting the frequency of the touch signal and the driving signal when the synchronization signal cycles fall out of a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frequency of the driving signal and the frequency of the touch signal are set to be different, then interference between the two signals is reduced, but temperature variations cause the frequencies to drift and harmonics to occur
Solution Approach 1:
The patent implements a feedback mechanism where the processor continuously monitors the frequencies of the driving signal and touch signal, and dynamically adjusts the touch signal frequency based on the detected driving signal frequency to prevent harmonic occurrence. This closed-loop control ensures the system adapts to temperature variations while maintaining signal stability.
Solution Approach 2:
The patent dynamically changes the frequency parameter of the touch signal based on the detected driving signal frequency. By continuously adjusting the touch signal frequency to maintain a non-harmonic relationship with the driving signal, the system adapts to environmental changes without causing interference.
2Reliability
If the frequency of the touch signal is adjusted to avoid harmonics with the driving signal, then jitter noise and ghost touches are reduced, but the system complexity increases due to frequency monitoring and adjustment mechanisms
Solution Approach 1:
The processor performs multiple functions: it generates control signals for the display, processes touch input signals, monitors signal frequencies, and adjusts the touch signal frequency to avoid harmonics. By consolidating these functions in a single processor, the patent reduces overall system complexity while maintaining touch detection accuracy.
Solution Approach 2:
The patent combines the frequency monitoring and adjustment functionality with the existing touch signal generation circuitry. The processor integrates the harmonic avoidance mechanism into the touch control system, eliminating the need for separate complex frequency control hardware and reducing overall device complexity.
Data Source
AI summary
A driving circuit includes: a display driver to generate a horizontal synchronization signal and a vertical synchronization signal according to a first clock signal of a first oscillator; a sensor driver to generate a touch signal according to a second clock signal of a second oscillator; and a determination circuit to detect a cycle of at least one of the horizontal synchronization signal or the vertical synchronization signal according to the second clock signal, and output a detection signal when the cycle is out of a range. The determination circuit is a part of the display driver or the sensor driver.