Electrostatic capacitance detection circuit and input device
First Claim
1. An electrostatic capacitance detection circuit comprising;
- a drive electrode and a detection electrode that constitute a sensor;
an electric charge integral circuit into which a signal including detection electric charge of an inter-electrode capacitance formed between the drive electrode and the detection electrode, and electric charge due to an external noise flows, wherein the electric charge integral circuit includes a capacitor that accumulates the electric charge transferred from the inter-electrode capacitance, and continuously integrates the electric charge transferred due to a drive signal applied to the drive electrode, in the capacitor;
wherein the electric charge integral circuit includes;
a charge amplifier that has an operational amplifier in which the capacitor is provided on a feedback path, anda plurality of selection switches, each switching a direction of the drive signal applied to the capacitor, and wherein a voltage selection switch that switches rising or falling of the drive signal applied to the drive electrode and a feedback path selection switch that switches a path capacitor provided in the feedback path are controlled at the same time according to the rising falling of the drive signal; and
an A/D converter that converts an output of the electric charge integral circuit from an analog into a digital signal.
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Accused Products
Abstract
An electrostatic capacitance detection circuit includes a charge amplifier that has an operational amplifier in which a capacitor is provided on a feedback path, and into which a signal including detection of electric charge of an inter-electrode capacitor of a sensor electrode and electric charge due to an external noise, and a selection switch that can switch a direction of a capacitor that is connected to input and output terminals of the charge amplifier through a feedback path that switches the direction of the capacitor depending on a direction of electric charge flowing in from a detection-side electrode of the sensor electrode, due to a drive signal applied to the sensor electrode.
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Citations
13 Claims
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1. An electrostatic capacitance detection circuit comprising;
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a drive electrode and a detection electrode that constitute a sensor; an electric charge integral circuit into which a signal including detection electric charge of an inter-electrode capacitance formed between the drive electrode and the detection electrode, and electric charge due to an external noise flows, wherein the electric charge integral circuit includes a capacitor that accumulates the electric charge transferred from the inter-electrode capacitance, and continuously integrates the electric charge transferred due to a drive signal applied to the drive electrode, in the capacitor; wherein the electric charge integral circuit includes; a charge amplifier that has an operational amplifier in which the capacitor is provided on a feedback path, and a plurality of selection switches, each switching a direction of the drive signal applied to the capacitor, and wherein a voltage selection switch that switches rising or falling of the drive signal applied to the drive electrode and a feedback path selection switch that switches a path capacitor provided in the feedback path are controlled at the same time according to the rising falling of the drive signal; and an A/D converter that converts an output of the electric charge integral circuit from an analog into a digital signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An input device comprising:
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A sensor comprising a drive electrode and a detection electrode; and an electrostatic capacitance detection circuit connected to the sensor, the electrostatic capacitance detection circuit comprising; an electric charge integral circuit into which a signal including detection electric charge of an inter-electrode capacitance of both the drive electrode and the detection electrode, and electric charge due to an external noise flows, wherein the electric charge integral circuit includes a capacitor that accumulates the electric charge transferred from the inter-electrode capacitance, and continuously integrates the electric charge transferred due to a drive signal applied to the drive electrode in the capacitor; wherein the electric charge integral circuit includes; a charge amplifier that has an operational amplifier in which the capacitor is provided on a feedback path, and a plurality of selection switches, each switching a direction of the drive signal applied to the capacitor, and wherein a voltage selection switch that switches rising or falling of the drive signal applied to the drive electrode and a feedback path selection switch that switches a path of the capacitor provided in the feedback path are controlled at the same time according to the rising and falling of the drive signal; and an A/D converter that converts an output of the electric charge integral circuit from an analog signal into a digital signal.
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Specification