Methods and systems for guarding a charge transfer capacitance sensor for proximity detection
First Claim
1. A system for determining a capacitance value associated with a sensor electrode, the system comprising:
- a guarding electrode proximate to the sensor electrode;
an integrating capacitance configured to store charge received from the sensor electrode;
a charge changing circuit coupled to the integrating capacitance; and
a controller configured to apply a guard signal to the guarding electrode, the guard signal comprising a waveform having at least two different voltages, the controller further configured to determine the capacitance value by repeatedly applying a voltage to the sensor electrode, repeatedly sharing charge between the sensor electrode and the integrating capacitance to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the integrating capacitance using a quantizer of the controller, generating quantized values responsive to the repeated measurings, repeatedly changing charge on the integrating capacitance based on the quantized values using the charge changing circuit, and determining the capacitance value of the measurable capacitance from the quantized values.
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Accused Products
Abstract
Methods, systems and devices are described for determining a measurable capacitance for proximity detection in a sensor having a plurality of sensing electrodes and at least one guarding electrode. A charge transfer process is executed for at least two executions. The charge transfer process includes applying a pre-determined voltage to at least one of the plurality of sensing electrodes using a first switch, applying a first guard voltage to the at least one guarding electrode using a second switch, sharing charge between the at least one of the plurality of sensing electrodes and a filter capacitance, and applying a second guard voltage different from the first guard voltage to the at least one guarding electrode. A voltage is measured on the filter capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection.
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Citations
23 Claims
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1. A system for determining a capacitance value associated with a sensor electrode, the system comprising:
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a guarding electrode proximate to the sensor electrode; an integrating capacitance configured to store charge received from the sensor electrode; a charge changing circuit coupled to the integrating capacitance; and a controller configured to apply a guard signal to the guarding electrode, the guard signal comprising a waveform having at least two different voltages, the controller further configured to determine the capacitance value by repeatedly applying a voltage to the sensor electrode, repeatedly sharing charge between the sensor electrode and the integrating capacitance to accumulate charge on the integrating capacitance, repeatedly measuring a voltage on the integrating capacitance using a quantizer of the controller, generating quantized values responsive to the repeated measurings, repeatedly changing charge on the integrating capacitance based on the quantized values using the charge changing circuit, and determining the capacitance value of the measurable capacitance from the quantized values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A method for determining a capacitance value associated with a sensor electrode, the method comprising the steps of:
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applying a guard signal to a guarding electrode proximate the sensor electrode, the guard signal comprising a waveform having at least two different voltages; providing a voltage to the sensor electrode using a first switch; allowing the first capacitance to share charge with an integrating capacitance; producing a quantized value with a quantizer, the quantized value reflective of whether the voltage on the integrating capacitance is past a threshold of the quantizer; changing a charge on the integrating capacitance by an amount of charge responsive to the voltage on the integrating capacitance being past the threshold of the quantizer, wherein the amount of charge is determined at least in part as a function of the quantized value produced with the quantizer; repeating each of the providing step, the allowing step, the outputting, and the changing step at least once to generate a plurality of quantized values; and determining the capacitance value using the plurality of quantized values generated by the repeating step. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A device for determining a measurable capacitance for proximity detection, the device comprising:
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a plurality of sensing electrodes, the measurable capacitance associated with at least one of the plurality of sensing electrodes; a guarding electrode proximate to the sensing electrode; a passive network that includes an integrating capacitance; and a controller coupled to the plurality of sensing electrodes, the guarding electrode, and the passive network, the controller configured to apply a guard signal to the guarding electrode, the guard signal comprising a waveform having at least two different voltages, the controller further configured to apply a voltage to at least one of the plurality of sensing electrodes, share charge between the at least one of the plurality of sensing electrodes and the passive network such that shared charge is accumulated on the integrating capacitance; and
measure a voltage on the integrating capacitance for a number of measurements equal to at least one to produce at least one result to determine the measurable capacitance for proximity detection. - View Dependent Claims (21, 22, 23)
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Specification