Capacitance Sensing Circuit for Baseline Current Compensation
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Solution Overview
Problem
The baseline current between an electrode and a ground terminal in touch screens with ultra-thin protective layers interferes with accurate mutual-capacitance sensing, reducing the dynamic range and accuracy of touch determination.
Innovation Solution
A capacitance detection circuit with a driving circuit that keeps transmit electrodes floating and generates compensating driving signals to reduce the baseline current, utilizing a control unit to manage the conduction states of driving switches and signal generators to generate orthogonal signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mutual-capacitance sensing is used in touch screens with ultra-thin protective layers, then the coupling capacitance between electrode and finger increases, but the baseline current between receive electrode and ground terminal increases, reducing detection accuracy
Solution Approach 1:
The patent applies preliminary anti-action by generating a compensation signal before the baseline current interferes with the detection. The driving circuit pre-generates a compensation signal that is injected into the receive electrode to counteract the baseline current, preventing its harmful effect on the detection accuracy rather than merely reducing it after the fact.
Solution Approach 2:
The patent introduces a compensation signal as an intermediary element between the baseline current and the detection circuit. This compensation signal acts as a mediator that cancels out the baseline current's effect, allowing the detection circuit to operate accurately despite the presence of the baseline current in ultra-thin protective layer touch screens.
2Use of energy by moving object
If baseline current flows through receive electrode and ground terminal, then the dynamic range of ADC cannot be effectively utilized, but touch determination accuracy reduces
Solution Approach 1:
The driving circuit pre-generates a compensation signal that counteracts the baseline current before it degrades the ADC dynamic range utilization. By applying this preliminary anti-action, the system maintains effective use of the ADC's dynamic range while preserving touch determination accuracy.
Solution Approach 2:
The system employs feedback by continuously monitoring the baseline current and adjusting the compensation signal accordingly. The driving circuit uses the detected baseline current information to generate an appropriate compensation signal that optimizes ADC dynamic range utilization while maintaining detection accuracy.
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
The solution effectively compensates for baseline current, enhancing the dynamic range of the analog-to-digital converter and improving touch determination accuracy.
Implementation Method 1
capacitance detection circuit and an electronic device capable of reducing a baseline current between an electrode and a ground terminal... sense circuit, coupled to a plurality of receive electrodes and configured to generate a plurality of sense results, the plurality of sense results being associated with capacitance between a plurality of transmit electrodes and the plurality of receive electrodes
Data Source
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AI summary
The present disclosure provides a capacitance detection circuit, which includes a sense circuit coupled to a plurality of receive electrodes and configured to generate a plurality of sense results, the plurality of sense results being associated with capacitance between a plurality of transmit electrodes and the plurality of receive electrodes; and a first driving circuit coupled to the plurality of transmit electrodes; wherein when the first driving circuit keeps at least one first transmit electrode of the plurality of transmit electrodes floating, the first driving circuit generates at least one first driving signal and sends the least one first driving signal to at least one second transmit electrode of the plurality of transmit electrodes, to compensate a baseline current between the plurality of receive electrodes and a ground terminal.