Touch Sensing Device With Shared Feedback Capacitors
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Solution Overview
Problem
Existing touch screen technologies face challenges in effectively canceling noise while maintaining a compact design, requiring larger capacitors to achieve a high dynamic range, which increases the size of the receiving unit.
Innovation Solution
A touch sensing device that connects two feedback capacitors to a single operational amplifier, utilizing switching units to short-circuit terminals at different phases of the electric signal to store charges and integrate noise-canceling signals, and incorporates an offset compensation circuit to minimize dynamic range impact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate operational amplifiers are used for each capacitor to accumulate charges, then noise cancellation capability is improved, but the size of the receiving unit increases
Solution Approach 1:
The patent combines multiple feedback capacitors (first feedback capacitor and second feedback capacitor) to share a single operational amplifier, rather than using separate operational amplifiers for each capacitor. This merging approach maintains the noise cancellation capability through charge accumulation while reducing the overall circuit area and component count, directly resolving the contradiction between noise cancellation performance and receiving unit size.
2Measurement precision
If larger capacitors are used to increase dynamic range, then signal sensitivity is improved, but the area required for internal capacitors increases
Solution Approach 1:
The patent employs periodic switching of the feedback capacitors between different operational phases (integration phase, reset phase, charge transfer phase) to accumulate charges over multiple signal cycles. This periodic action enables the use of smaller capacitors to achieve the same dynamic range and signal sensitivity that would otherwise require larger capacitors, thereby reducing the area occupied by internal capacitors while maintaining measurement precision.
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 allows for effective noise cancellation and high dynamic range implementation with a minimized receiving unit size, reducing the need for larger capacitors and minimizing the area required for internal capacitors, thereby enhancing signal quality and reducing noise interference.
Implementation Method 1
a first feedback capacitor and a second feedback capacitor. The first feedback capacitor and the second feedback capacitor store charges according to a positive signal and a negative signal input to the Rx circuit, respectively
Data Source
AI summary
A device for sensing a touch by measuring a variation in capacitance according to a contact of an object, and measuring a contact position of the object is provided. The device includes a touch screen panel comprising grid electrodes forming a plurality of electrode patterns, the grid electrodes serving as Tx antennas or Rx antennas, a Tx circuit unit connected with the grid electrode to apply an electric signal to the touch screen panel unit, an Rx circuit unit connected with the grid electrodes to sense variations in the capacitance in the plurality of electrode patterns, and a controller configured to control the touch screen panel unit, the Tx circuit unit, and the Rx circuit unit. The Rx circuit unit includes a first operational amplifier, a first feedback capacitor, and a second feedback capacitor. The first feedback capacitor and the second feedback capacitor are connected with the first operational amplifier. Both terminals of the first feedback capacitor and the first operational amplifier are connected through a first switching unit. The first switching unit includes a 1-1 switch and a 1-2 switch, which are controlled to be short-circuited at a first phase of the electric signal. Both terminals of the second feedback capacitor and the first operational amplifier are connected through a second switching unit. The second switching unit includes a 2-1 switch and a 2-2 switch, which are controlled to be short-circuited at a second phase of the electric signal. The controller is further configured to short-circuit the first switching unit and the second switching unit, at different times, to store charges in each of the first feedback capacitor and the second feedback capacitor.