Modulated Ground Voltage for Touch Display Parasitic Capacitance
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Solution Overview
Problem
As thin display devices become thinner, the increasing parasitic capacitance between the display panel electrode and the touch screen panel electrode leads to higher power consumption and decreased sensing sensitivity for touch events, due to the closer proximity of these electrodes.
Innovation Solution
A touch display system that employs a modulated ground (GND) voltage, oscillating between two predetermined voltage levels in a square wave, sine wave, or chopping wave shape, is supplied to both the display and touch systems, using a power management integrated circuit (PMIC) and a GND modulator to maintain a constant potential on parasitic capacitance, reducing the need for charging or discharging during touch sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If display devices are formed to be thinner, then weight is reduced and battery space is increased, but parasitic capacitance between display panel electrode and touch screen panel electrode increases
Solution Approach 1:
The patent applies dynamics by modulating the ground voltage level dynamically rather than keeping it static. The ground voltage is switched between first and second voltage levels according to a modulation signal, which actively compensates for the harmful effects of parasitic capacitance. This dynamic adjustment allows the system to maintain stable touch sensing performance despite the increased parasitic capacitance caused by thinner device design.
Solution Approach 2:
The patent changes the voltage level parameter of the ground connection dynamically. By switching the ground voltage between different levels (first voltage level and second voltage level) based on the modulation signal, the system alters the electrical parameters to counteract the increased parasitic capacitance. This parameter change approach enables the touch sensor to operate correctly despite the physical constraints of thinner device design.
2Use of energy by moving object
If parasitic capacitance increases, then power consumption for driving the touch sensor increases, but sensing sensitivity decreases
Solution Approach 1:
The patent uses dynamic ground voltage modulation to reduce the impact of parasitic capacitance on power consumption and sensing sensitivity. By actively switching the ground voltage level according to the modulation signal, the system minimizes the charge-discharge cycles caused by parasitic capacitance, thereby reducing power consumption while maintaining sensing sensitivity.
Solution Approach 2:
The patent applies preliminary anti-action by preemptively counteracting the harmful effects of parasitic capacitance through ground voltage modulation. Before the parasitic capacitance can cause excessive power consumption or sensitivity degradation, the modulated ground voltage compensates for these effects, preventing the deterioration of power efficiency and sensing performance.
3Use of energy by moving object
If ground voltage is modulated to reduce power consumption, then touch sensing capability is maintained, but interface signal levels are changed
Solution Approach 1:
The patent introduces an intermediary component (level shifter) to handle the interface signals. The level shifter acts as a mediator between the modulated ground voltage environment and the standard interface requirements, converting the interface signals to appropriate voltage levels while preserving the information content. This allows the system to benefit from ground voltage modulation for power reduction without losing interface signal integrity.
Data Source
AI summary
A touch display system includes a display system including a plurality of pixels, a touch system disposed on the display system and comprising a plurality of touch sensor electrodes, and a power management integrated circuit (PMIC) configured to supply power and a modulated ground (GND) voltage to the display system and the touch system.