Method and apparatus for sensing
First Claim
1. An apparatus for sensing a change in capacitance of a sensing electrode to a system ground, the apparatus comprisinga sample capacitor having two terminals, a first of the two terminals being coupled to the sensing electrode,a voltage measurement circuit being coupled to a second of the terminals of the sample capacitor, the voltage measurement circuit being arranged in operation to determine a voltage at the second terminal of the sample capacitor, anda voltage biasing arrangement which is arranged under the control of a controller to apply a biasing voltage or the system ground to the first terminal or the second terminal of the sample capacitor in accordance with a measurement cycle, the measurement cycle comprisinggrounding the first and second terminals of the sample capacitor during an initialisation part of the measurement cycle by connecting the first and second terminals to the system ground,charging the sensing electrode via the sample capacitor, during a charging part of the measurement cycle by applying a drive voltage to the second terminal of the sample capacitor, whilst floating the first terminal by not applying the system ground or a biasing voltage, and during a measurement part of the measurement cycle grounding the first terminal whilst floating the second terminal by not applying the system ground or a biasing voltage, and measuring the voltage at the second terminal, anddetermining whether there has been a change in capacitance of the sensing electrode in accordance with the measured voltage, wherein before or after the measurement cycle the controller is arranged to perform a sleep mode in which the sensing electrode is biased at a voltage which is greater than the system ground.
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Accused Products
Abstract
An apparatus for sensing a change in capacitance of a sensing electrode to a system ground, such as that which may be used to form a touch sensor, with the sensing electrode forming touch sensitive surface is arranged to include a sleep mode of operation. The apparatus includes a sample capacitor having a first terminal coupled to the sensing electrode, and a second terminal coupled to a voltage measurement circuit. The voltage measurement circuit is arranged in operation to determine a voltage at the second terminal of the sample capacitor. A voltage biasing arrangement is arranged under the control of a controller to apply a biasing voltage or the system ground to the first terminal or the second terminal of the sample capacitor in accordance with a measurement cycle.
29 Citations
18 Claims
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1. An apparatus for sensing a change in capacitance of a sensing electrode to a system ground, the apparatus comprising
a sample capacitor having two terminals, a first of the two terminals being coupled to the sensing electrode, a voltage measurement circuit being coupled to a second of the terminals of the sample capacitor, the voltage measurement circuit being arranged in operation to determine a voltage at the second terminal of the sample capacitor, and a voltage biasing arrangement which is arranged under the control of a controller to apply a biasing voltage or the system ground to the first terminal or the second terminal of the sample capacitor in accordance with a measurement cycle, the measurement cycle comprising grounding the first and second terminals of the sample capacitor during an initialisation part of the measurement cycle by connecting the first and second terminals to the system ground, charging the sensing electrode via the sample capacitor, during a charging part of the measurement cycle by applying a drive voltage to the second terminal of the sample capacitor, whilst floating the first terminal by not applying the system ground or a biasing voltage, and during a measurement part of the measurement cycle grounding the first terminal whilst floating the second terminal by not applying the system ground or a biasing voltage, and measuring the voltage at the second terminal, and determining whether there has been a change in capacitance of the sensing electrode in accordance with the measured voltage, wherein before or after the measurement cycle the controller is arranged to perform a sleep mode in which the sensing electrode is biased at a voltage which is greater than the system ground.
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9. A pair of audio reproducing devices comprising a first ear phone and a second ear phone, each of the first and the second ear phones including a touch sensing apparatus which is arranged to detect a body proximate a sensing electrode of the touch sensing apparatus from a change in capacitance of the sensing electrode to a system ground, the touch sensing apparatus comprising
a sample capacitor having two terminals, a first of the two terminals being connected to the sensing electrode, a voltage measurement circuit connected to a second of the terminals of the sample capacitor, the voltage measurement circuit being arranged in operation to determine a voltage at the second terminal of the measurement capacitor, and a voltage biasing arrangement which is arranged under the control of a controller to apply a biasing voltage or the system ground to the first terminal or the second terminal of the sample capacitor in accordance with a measurement cycle, the measurement cycle comprising grounding the first and second terminals of the sample capacitor during an initialisation part of the measurement cycle by connecting the first and second terminals to the system ground, charging the sensing electrode via the sample capacitor, during a charging part of the measurement cycle by applying a drive voltage to the second terminal of the sample capacitor for a predetermined period, whilst floating the first terminal by not applying the system ground or a biasing voltage, and during a measurement part of the measurement cycle grounding the first terminal whilst floating the second terminal by not applying a system ground or biasing voltage, and measuring the voltage at the second terminal, and determining whether there has been a change in capacitance of the sensing electrode in accordance with the measured voltage, wherein the measurement cycle includes a sleep mode in which the sensing electrode is biased at a voltage which is greater than the system ground.
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10. A method of sensing a change in capacitance of a sensing electrode to a system ground, the sensing electrode being coupled to a first terminal of a sample capacitor with a second terminal of the sample capacitor being connected to a voltage measurement circuit for determining a voltage at the second terminal of the sample capacitor, the method comprising
applying the system ground to the first and second terminals of the sample capacitor during an initialisation part of the measurement cycle, charging the sensing electrode via the sample capacitor, during a charging part of the measurement cycle by applying a drive voltage to the second terminal of the sample capacitor, whilst floating the first terminal by not applying the system ground or a biasing voltage, during a measurement part of the measurement cycle applying the system ground to the first terminal whilst floating the second terminal by not applying the system ground or a biasing voltage, and measuring the voltage at the second terminal, and determining whether there has been a change in capacitance of the sensing electrode in accordance with the measured voltage, wherein the measurement cycle includes a sleep mode step, which includes biasing the sensing electrode at a voltage which is greater than the system ground.
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17. An apparatus for sensing a change in capacitance of a sensing electrode to a system ground, the sensing electrode being coupled to a first terminal of a sample capacitor with a second terminal of the sample capacitor being connected to a voltage measurement circuit for determining a voltage at the second terminal of the sample capacitor, the apparatus comprising
means for applying the system ground to the first and second terminals of the sample capacitor during an initialisation part of the measurement cycle, means for charging the sensing electrode via the sample capacitor, during a charging part of the measurement cycle by applying a drive voltage to the second terminal of the sample capacitor, whilst floating the first terminal by not applying the system ground or a biasing voltage, means for applying during a measurement part of the measurement cycle the system ground to the first terminal whilst floating the second terminal by not applying the system ground or a biasing voltage, and measuring the voltage at the second terminal, means for determining whether there has been a change in capacitance of the sensing electrode in accordance with the measured voltage, and means for biasing the first terminal of the sample capacitor at a voltage which is greater than the system ground, whilst the second terminal of the sample capacitor is floated by not applying the system ground or a biasing voltage, during a sleep mode, so that the sensing electrode is held at a voltage above the system ground during the sleep mode.
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18. A plurality of touch sensing devices, each of which is arranged to detect a body proximate a sensing electrode of the touch sensing device from a change in capacitance of the sensing electrode to a system ground, at least one of the plurality of touch sensing devices including
a sample capacitor having two terminals, a first of the two terminals being coupled to the sensing electrode, a voltage measurement circuit coupled to a second of the terminals of the sample capacitor, the voltage measurement circuit being arranged in operation to determine a voltage at the second terminal of the measurement capacitor, and a voltage biasing arrangement which is arranged under the control of a controller to apply a biasing voltage or the system ground to the first terminal or the second terminal of the sample capacitor in accordance with a measurement cycle, the measurement cycle comprising grounding the first and second terminals of the sample capacitor during an initialisation part of the measurement cycle by coupling the first and second terminals to ground, charging the sensing electrode via the sample capacitor, during a charging part of the measurement cycle by applying a drive voltage to the second terminal of the sample capacitor, whilst floating the first terminal by not applying the system ground or a biasing voltage, and during a measurement cycle of the measurement phase grounding the first terminal whilst floating the second terminal by not applying a system ground or biasing voltage, and measuring the voltage at the second terminal, and determining whether there has been a change in capacitance of the sensing electrode in accordance with the measured voltage, wherein the measurement cycle includes a sleep mode in which the first terminal of the sample capacitor is biased at a voltage which is greater than the system ground, whilst the second terminal of the sample capacitor is floated by not applying the system ground or a biasing voltage, so that the sensing electrode is held at a voltage above the system ground during the sleep mode.
Specification