Multi-Level Drive Scheme for Capacitive Touch Sensor Settling
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Solution Overview
Problem
Conventional methods for driving loads in capacitive sensing devices, such as touchpads and touch screens, face challenges with long settling times due to increased resistance and capacitance, which limit sensing frequency and degrade noise performance.
Innovation Solution
A method involving a multi-level drive scheme with boosted voltage levels is applied to capacitive pixels, where a first voltage greater than the ending voltage is applied for a specific duration followed by a second voltage, selected based on the settling responses of individual pixels, to reduce settling time and increase sensing frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional two-level voltage driving is used, then the device structure is simple, but the settling time increases
Solution Approach 1:
The patent changes the voltage parameter from conventional two-level (high/low) to multi-level (including boosted high level, standard high level, and low level). This parameter change allows faster charging of the capacitive load, reducing settling time while maintaining manageable circuit complexity through structured voltage level management.
Solution Approach 2:
The patent implements dynamic voltage selection where the driving circuit switches between different voltage levels (boosted, standard, low) based on real-time sensing requirements and pixel characteristics. This dynamic approach optimizes settling time for each specific sensing operation rather than using a fixed two-level scheme.
2Object-affected harmful factors
If the sensing frequency is increased, then the noise performance improves, but the settling time requirement becomes more difficult to meet
Solution Approach 1:
By introducing boosted voltage levels and multi-level driving schemes, the patent reduces the effective settling time required for each sensing cycle. This enables higher sensing frequencies to be achieved while maintaining adequate settling time, thereby improving noise performance through higher frequency operation.
Solution Approach 2:
The patent applies preliminary boosted voltage pulses before the actual sensing operation to pre-charge or pre-discharge the capacitive load. This preliminary action reduces the settling time required during the main sensing cycle, enabling faster overall operation and higher sensing frequencies with improved noise characteristics.
3Length of moving object
If thinner and longer electrical conductors are used, then the resistance increases, but the settling time increases as a result
Solution Approach 1:
The patent compensates for increased resistance in thin, long conductors by changing the voltage driving parameters to include boosted levels. The higher voltage levels provide stronger driving force that overcomes the increased resistive losses, maintaining acceptable settling times despite the conductor limitations.
4Area of stationary object
If physically larger load is driven, then the capacitance increases, but the settling time increases as a result
Solution Approach 1:
The patent addresses increased capacitance from physically larger loads by implementing multi-level voltage driving with boosted levels. The higher voltage steps provide increased driving capability that charges larger capacitive loads more quickly, reducing settling time despite the increased capacitance value.
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 significantly reduces settling time, enabling higher sensing frequencies and improved noise performance by driving capacitive sensors more efficiently, thus enhancing overall capacitive sensor performance.
Implementation Method 1
The time required to drive the load may be a function of a resistance and/or a capacitance (i.e., an RC time constant)
Data Source
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AI summary
A method and system for driving capacitive pixels in a touch sensor device using a multi-level drive scheme. The drive scheme includes driving a transmitter electrode with a boosted voltage for a first period, and driving the transmitter electrode with a second voltage for a second period. The multi-level transmitter signal is determined based on different settling responses associated with the capacitive pixels of the touch sensor device.