Capacitance detection circuit and electrostatic capacitance sensor device with a high-pass filter having first and second passive circuit elements for outputting an attenuated current signal
View Patent ↗A capacitance detection circuit includes an excitation signal source configured to supply an AC driving voltage to drive the detection electrode, a high-pass filter configured to cause a current signal input from the detecting electrode to be output after being attenuated in a prescribed frequency region that is lower than a frequency of the excitation signal source, and a current signal measurement circuit connected between the high-pass filter and the excitation signal source. The current signal measurement circuit is configured to measure a current signal from the high-pass filter. The high-pass filter includes a first passive circuit element connected in series between the detection electrode and the current signal measurement circuit, and a second passive circuit element connected in series between the excitation signal source and a node between the detection electrode and the first passive circuit element.
1. A capacitance detection circuit that measures a current from a detection electrode in order to measure a self-capacitance of the detection electrode, comprising:
an excitation signal source configured to supply an AC driving voltage to drive the detection electrode;
a high-pass filter configured to cause a current signal input from the detection electrode to be output after being attenuated in a prescribed frequency region that is lower than a frequency of the excitation signal source; and
a current signal measurement circuit connected between the high-pass filter and the excitation signal source, the current signal measurement circuit being configured to measure a current signal from the high-pass filter,
wherein the high-pass filter comprises:
a first passive circuit element connected in series between the detection electrode and the current signal measurement circuit; and
a second passive circuit element connected in series between the excitation signal source and a node between the detection electrode and the first passive circuit element.
2. The capacitance detection circuit according to claim 1 , wherein the first passive circuit element is a capacitance element, and
wherein the second passive circuit element is a resistance element.
3. The capacitance detection circuit according to claim 2 , wherein the current signal measurement circuit is a current voltage conversion circuit including an operation amplifier,
wherein an inverting input of the operation amplifier is connected to the capacitance element,
wherein the excitation signal source is connected to a non-inverting input of the operation amplifier, and
wherein a second resistance element is connected between an inverting input and an output of the operation amplifier.
4. The capacitance detection circuit according to claim 1 , wherein the first passive circuit element is a resistance element, and
wherein the second passive circuit element is an inductance element.
5. The capacitance detection circuit according to claim 1 , wherein the capacitance detection circuit is configured to measure the self-capacitance of the detection electrode of a touch panel,
wherein the touch panel includes a plurality of detection electrodes for identifying a touch position,
wherein the capacitance detection circuit measures a current from a detection circuit selected from the plurality of electrodes,
wherein an AC signal for presenting a tactile sense is input into a detection electrode that differs from said detection electrode selected by the capacitance detection circuit, and
wherein a frequency of the AC signal for presenting a tactile sense is within the prescribed frequency region.
6. An electrostatic capacitance sensor device, comprising:
a detection electrode; and
a controller configured to measure a current from the detection electrode in order to measure a self-capacitance of the detection electrode,
wherein the controller comprises:
an excitation signal source configured to supply an AC driving voltage to drive the detection electrode;
a high-pass filter configured to cause a current signal input from the detecting electrode to be output after being attenuated in a prescribed frequency region that is lower than a frequency of the excitation signal source; and
a current signal measurement circuit connected between the high-pass filter and the excitation signal source, the current signal measurement circuit being configured to measure a current signal from the high-pass filter, and
wherein the high-pass filter comprises:
a first passive circuit element connected in series between the detection electrode and the current signal measurement circuit; and
a second passive circuit element connected in series between the excitation signal source and a node between the detection electrode and the first passive circuit element.
7. The electrostatic capacitance sensor device according to claim 6 , wherein the first passive circuit element is a capacitance element, and
wherein the second passive circuit element is a resistance element.
8. The electrostatic capacitance sensor device according to claim 6 , wherein the first passive circuit element is a resistance element, and
wherein the second passive circuit element is an inductance element.
9. The electrostatic capacitance sensor device according to claim 6 ,
comprising a touch panel including a plurality of detection electrodes that include said detection electrode,
wherein the controller is configured to:
measure a current from a detection circuit sequentially selected from the plurality of electrodes; and
supply an AC signal for presenting a tactile sense to a detection electrode that differs from the detection electrode selected for the current measurement, and
wherein a frequency of the AC signal for presenting a tactile sense is within the prescribed frequency region.