Capacitance Measurement Using Dual Voltage Divider Bridges
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Solution Overview
Problem
Existing methods for characterizing or measuring capacitance, particularly in touch screen displays, face challenges such as long acquisition times and complexity, which hinder rapid and precise detection of capacitance variations necessary for user interaction detection.
Innovation Solution
A method utilizing a first and second capacitive voltage divider bridge, where the capacitance is linked to a mid-point and a bias voltage applied, with a constant current discharging one mid-point to measure the time for the other to reach a determined voltage, allowing for the calculation of capacitance through time differences in various phases, including offset and calibration phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charge transfer methods are used to measure capacitance, then measurement precision is improved, but acquisition time increases significantly
Solution Approach 1:
The patent replaces traditional time-consuming charge transfer methods with a voltage comparison method using capacitive voltage divider bridges. Instead of physically transferring charges multiple times to determine capacitance, the invention uses electrical voltage relationships and time constant measurements to rapidly determine capacitance values, significantly reducing acquisition time while maintaining precision.
Solution Approach 2:
The patent changes the measurement parameter from charge quantity (requiring multiple transfer cycles) to voltage ratio and time constant. By measuring the time for voltage to reach a determined value during discharge and comparing it with a reference time constant, the system achieves rapid capacitance measurement without the iterative charge transfer process.
2Measurement precision
If traditional measurement circuits are used, then measurement capability is achieved, but device complexity increases
Solution Approach 1:
The patent creates a universal measurement circuit using capacitive voltage divider bridges that can measure both grounded and floating capacitances with the same hardware architecture. The dual-bridge configuration serves multiple functions: providing measurement references, enabling differential measurements, and accommodating different capacitance types without requiring separate dedicated circuits for each measurement mode.
Solution Approach 2:
The patent introduces capacitive voltage divider bridges as intermediary structures that simplify the measurement process. These bridges act as mediators between the capacitance under test and the measurement system, transforming complex capacitance measurements into simple voltage ratio comparisons and time constant measurements, thereby reducing overall system complexity.
3Productivity
If rapid scanning of capacitance matrix is required for touch screen control, then user interaction detection speed is improved, but measurement precision may deteriorate
Solution Approach 1:
The patent performs preliminary actions by pre-charging the capacitive voltage divider bridges to known voltage states before each measurement cycle. This preliminary charging establishes consistent initial conditions that enable rapid repeated measurements without requiring lengthy reset or stabilization periods, thus maintaining both high scan rates and measurement precision.
Solution Approach 2:
The patent employs periodic discharge and measurement cycles with the capacitive voltage divider bridges. By systematically charging the bridges to reference voltages, then periodically discharging them through the capacitance under test and measuring the time to reach determined voltage levels, the system achieves rapid repetitive measurements suitable for real-time touch screen scanning while maintaining precision through consistent periodic operation.
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 enables rapid and precise characterization of capacitances, reducing measurement time and complexity, and is applicable to both grounded and floating capacitances, enhancing the detection of user interactions in touch screen displays.
Implementation Method 1
discharging the second mid-point with a constant current; and measuring a first time for the second voltage to reach a determined value
Implementation Method 2
providing a first capacitive voltage divider bridge and a second capacitive voltage divider bridge in parallel with the first, the first divider bridge comprising a first mid-point having a first voltage and the second divider bridge comprising a second mid-point having a second voltage
Data Source
AI summary
A method for characterizing or measuring a capacitance includes linking the capacitance to a first mid-point of a first capacitive divider bridge, applying to the divider bridge a bias voltage, maintaining the voltage of the first mid-point near a reference voltage, discharging a second mid-point of a second divider bridge in parallel with the first using a constant current, and measuring the time for a voltage of the second mid-point to become equal to the voltage of the first mid-point. The method may be applied in particular to the control of a touch screen display.