Capacitive Touch Sensor Channel Sensing With Parallel Discharge
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Solution Overview
Problem
Existing touch sensors require a significant amount of time to detect the presence of a body at multiple positions on a two-dimensional surface due to the need to drive and measure each channel individually, which increases the time and complexity of the detection process.
Innovation Solution
A touch sensor system that uses a controller to drive and measure channels in a sequence, with a parallel pre-discharge of charge measurement capacitors to reduce the time required for each measurement, allowing for simultaneous discharge and measurement across multiple channels, thereby reducing the overall detection time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If individual channel driving and measurement is performed sequentially, then measurement precision is maintained, but detection time increases significantly
Solution Approach 1:
The patent applies preliminary action by pre-charging all charge measurement capacitors to a known reference voltage level before the actual measurement phase. This preparation step allows subsequent parallel measurement of multiple channels without requiring sequential charging operations, thereby reducing total detection time while maintaining measurement accuracy through the established reference baseline
Solution Approach 2:
The patent implements continuity of useful action by enabling simultaneous charging of multiple charge measurement capacitors from their respective channel coupling capacitors during the same time interval. This parallel operation maintains continuous measurement activity across all channels rather than interrupting for sequential processing, thus reducing overall detection time while preserving the integrity of capacitance measurements
2Productivity
If parallel measurement of multiple channels is implemented, then detection time is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by designing a measurement architecture where multiple channel coupling capacitors can be simultaneously connected to respective charge measurement capacitors through a common control mechanism. This multi-functional setup allows the same basic measurement circuit topology to serve multiple channels in parallel, achieving faster detection without proportionally increasing overall system complexity
Solution Approach 2:
The patent uses segmentation by dividing the touch sensor into multiple independent channel pairs, each with its own coupling capacitor that can be measured in parallel. This segmentation allows the system to process multiple channels simultaneously through identical measurement circuits, improving detection speed while keeping each individual measurement unit simple and manageable
3Device complexity
If sequential discharge of charge measurement capacitors is used, then circuit simplicity is maintained, but measurement time increases
Solution Approach 1:
The patent applies preliminary action by pre-discharging all charge measurement capacitors to a standardized reference level before beginning the measurement sequence. This preparation ensures that subsequent parallel discharge operations can proceed simultaneously without requiring complex sequential coordination, reducing measurement cycle time while maintaining circuit simplicity through a uniform discharge protocol
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 the time needed to detect the presence of a body across multiple channels, improving the efficiency and sensitivity of the touch sensor system while minimizing the need for multiple comparators and analog-to-digital converters.
Implementation Method 1
a touch sensitive capacitive sensor... relies on measuring the capacitance of a sensing electrode... The capacitive sensing device... relies on measuring the capacitance of a sensing electrode to a system reference potential (earth)
Implementation Method 2
transferred the induced charge from the key to a charge measurement capacitor of a charge detection circuit... measure the charge present on the charge measurement capacitor
Implementation Method 3
discharging the charge measurement capacitors... by discharging the charge measurement capacitor of each of the charge sensing circuits contemporaneously by a predetermined amount, before an amount of charge remaining on each of the charge measurement capacitors is determined
Implementation Method 4
the presence of the body being determined as a result of a change in capacitance of the channel... detect the presence of an object near the key as a result of a change in an amount of the charge induced onto the key. Effectively, this provides a measure of a change in capacitance of the key
Data Source
AI summary
A touch sensor senses the presence of an object at one of a plurality of channels on a surface of the touch sensor, wherein proximity of the object to the touch sensor results in a change in capacitance at the position of the channel. The touch sensor includes a drive circuit and a charge sensing circuit, each coupled to each of the channels. The charge sensing circuit includes at least one charge measurement capacitor. A measurement cycle is applied to the touch sensor having a drive portion and a sense portion. During the drive portion a charge is applied to the channels and therefore the charge measurement capacitors of the touch sensor, and during a sense portion the charge measurement capacitors are discharged by a predetermined amount and the remaining charge on the charge measurement capacitors is measured.