Capacitive Touch Sensor Circuit Using Current-Controlled Oscillation
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Solution Overview
Problem
The existing capacitive touch sensor circuits require a pair of power-supply voltage drop circuits and tank capacitors for each touch electrode pair, leading to a significant increase in circuit size, especially when sensing multiple touch electrode pairs in parallel.
Innovation Solution
A semiconductor device configuration that includes a pulse signal output circuit, a current converter, a current-controlled oscillator, and a counter, which detects capacitance changes without using a power-supply voltage drop circuit or tank capacitor, utilizing a current converter with transistors to convert currents and output oscillation signals based on capacitance changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pair of power-supply voltage drop circuit and tank capacitor is used for each touch electrode pair, then the touch sensor can generate constant voltage and suppress voltage variation, but the circuit scale increases significantly
Solution Approach 1:
The patent merges the power-supply voltage drop circuit and tank capacitor from individual per-electrode-pair components into shared resources. Multiple touch electrode pairs share common voltage drop circuits (first and second power supply voltage drop circuits) and common tank capacitors, eliminating the need for separate pairs for each electrode. This combining approach maintains voltage stability while dramatically reducing the overall circuit scale.
Solution Approach 2:
The voltage drop circuits and tank capacitors are designed to serve multiple touch electrode pairs simultaneously. The first power supply voltage drop circuit provides voltage to both first and second touch electrode pairs, while the second power supply voltage drop circuit serves similar multiple pairs. This multi-functional design allows single components to perform what previously required multiple dedicated components.
2Adaptability or versatility
If multiple sets of power-supply voltage drop circuits and tank capacitors are used for parallel sensing of multiple touch electrode pairs, then parallel sensing capability is achieved, but the circuit size increases remarkably
Solution Approach 1:
The patent combines power supply resources across multiple touch electrode pairs by implementing shared voltage drop circuits and tank capacitors. Instead of dedicating separate power supply chains to each electrode pair for parallel sensing, the system merges these resources so that first and second touch electrode pairs share common voltage drop circuits and tank capacitors, enabling parallel sensing with significantly reduced circuit footprint.
3Manufacturing precision
If power-supply voltage drop circuit and tank capacitor are used for each touch electrode pair, then constant voltage is generated, but the number of components increases
Solution Approach 1:
The patent merges previously separate power supply components into shared resources. Multiple touch electrode pairs share common voltage drop circuits and tank capacitors, reducing the total component count. The first power supply voltage drop circuit and first tank capacitor serve multiple electrode pairs, eliminating redundant components while maintaining constant voltage generation capability through shared regulatory circuits.
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 configuration effectively suppresses the increase in circuit size, allowing for efficient detection of capacitance changes in multiple touch electrode pairs without the need for additional power-supply voltage drop circuits or tank capacitors, thereby maintaining circuit size efficiency.
Implementation Method 1
a second transistor being current mirror connected to the first transistor
Implementation Method 2
a third transistor being coupled in series to the second transistor and outputting the second current by switching ON/OFF in response to the pulse signal
Implementation Method 3
a current-controlled oscillator outputting an oscillation signal having a frequency depending on the second current
Implementation Method 4
a counter counting a number of oscillating times of the oscillation signal per a predetermined period
Data Source
AI summary
A semiconductor device comprises a pulse signal output circuit providing a pulse signal for a transmission electrode of an electrode pair, a current converter converting a first current generated on the reception electrode to a second current, a current-controlled oscillator outputting an oscillation signal having a frequency depending on the second current, and a counter counting a number of oscillating times of the oscillation signal per a predetermined period; wherein the current converter comprises a first constant current source and output a combined current of the first constant current of the first constant current source and the first current as the second current in response to the pulse signal, so that the semiconductor device suppresses an increase circuit size.