Capacitance Sensing Circuit Using Voltage Sampling for Faster Response
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Solution Overview
Problem
Conventional methods for sensing capacitance are slow and not suitable for applications requiring faster response speeds, as they involve lengthy charge balance processes.
Innovation Solution
A circuit and method utilizing a switching circuit, transconductance amplifier mirror circuit, and charge calculation circuit to detect voltage variations and generate a sensed signal responsive to charge amount variations, allowing for faster capacitance sensing between electrodes or with reference to ground.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional charge balance method is used to sense capacitance, then measurement precision can be achieved, but response speed becomes slow due to lengthy charge balance process
Solution Approach 1:
The patent replaces the conventional charge balance method with a voltage sampling method. Instead of performing lengthy charge balance operations, the system samples the voltage at the second electrode during a voltage transition phase and calculates capacitance directly from the sampled voltage value, achieving both high precision and fast response
Solution Approach 2:
The patent performs preliminary voltage transition at the first electrode before the actual measurement is needed. By pre-charging or pre-discharging the first electrode and sampling the resulting voltage at the second electrode, the system prepares the measurement state in advance, enabling rapid capacitance determination without waiting for charge balance
2Measurement precision
If conventional charge balance method is used, then capacitance sensing can be performed, but time consumption increases due to waiting for charge balance to finish
Solution Approach 1:
The patent substitutes the time-consuming charge balance process with a voltage sampling operation. The system measures capacitance by sampling voltage during the transition phase and using the relationship Q=CV to calculate capacitance directly, eliminating the need to wait for charge balance completion
Solution Approach 2:
The patent skips the lengthy charge balance waiting period by performing voltage sampling during the voltage transition phase itself. Instead of waiting for the system to reach equilibrium, the method captures the voltage state during the dynamic transition, rushing through the measurement process to achieve rapid results
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
Enables faster capacitance sensing by maintaining voltage levels and generating sensed signals quickly, reducing the impact of parasitic capacitances and improving response speed in capacitive touch panels and other applications.
Implementation Method 1
a transconductance amplifier mirror circuit to detect the voltage variation at the second one of the two electrodes to cause a charge amount variation
Data Source
AI summary
A transconductance amplifier mirror circuit is connected to an electrode for sensing the capacitance of the electrode with reference to ground, or the capacitance between the electrode and another electrode. A voltage level change is produced on the electrode connected to the transconductance amplifier mirror circuit to cause the transconductance amplifier mirror circuit to supply charges to or drain charges from a charge calculation circuit. The charge amount variation is converted to a signal for calculating the sensed capacitance.