Coordinate input device and display device with the same
A capacitance detection device of a capacitance system includes: a capacitance sensor electrode for detecting a capacitance; a power source for supplying charges to be charged in the capacitance sensor electrode; an electric charge storage capacitor in which an amount of charges to be charged therein changes according to the electric charges charged in the capacitance sensor electrode; and a switch for changing a reference potential of the electric charge storage capacitor. The reference potential of the electric charge storage capacitor is changed in a period of measuring the capacitance.
1. A touch panel comprising:
a first coordinate electrode for detecting a touch coordinate;
a power source for supplying electric charges to the first electrode;
an electric charge storage capacitor electrically connecting the first coordinate electrode, and including a first capacitor electrode connecting the first coordinate electrode and a second capacitor electrode opposing to the first capacitor electrode;
a first switch electrically connecting between the second electrode of the electric charge storage capacitor and a reference voltage;
a second switch electrically connecting between the second electrode of the electric charge storage capacitor and a noise voltage; and
an amplifier for detecting electric charges which are transferred from the coordinate electrode to the electric charge storage capacitor via a third switch,
wherein the third switch directly connects between the first coordinate electrode and the amplifier in order to transfer the electric charges,
wherein the reference voltage is applied to the second electrode of the electric charge storage capacitor before the noise voltage is applied to the second electrode of the electric charge storage capacitor,
wherein the noise voltage is applied to the second electrode of the electric charge storage capacitor for detecting the touch coordinate, and
wherein the third switch is configured to be turned ON at the same time as the noise voltage is applied to the second electrode of the electric charge storage capacitor.
2. The touch panel according to claim 1 ,
wherein the reference voltage is applied to the amplifier.
3. The touch panel according to claim 1 ,
wherein the first switch and the second switch are turned ON and OFF alternately.
4. The touch panel according to claim 1 ,
further comprise a fourth switch connecting the power source and the first coordinate electrode,
wherein the third switch and the fourth switch are turned ON and OFF alternately.
5. The touch panel according to claim 1 ,
wherein electric charges of the electric charge storage capacitor are stepped increased by supplying electric charges to the first electrode.
6. The touch panel according to claim 4 ,
wherein output of the amplifier is stepped increased by alternately turned ON and OFF of the third switch and the fourth switch.
7. A touch panel comprising:
a first coordinate electrode for detecting a touch coordinate;
a power source for supplying electric charges to the first electrode;
a storage capacitor electrically connecting the first coordinate electrode, and including a first capacitor electrode connecting the first coordinate electrode and a second capacitor electrode opposing to the first capacitor electrode;
a first switch electrically connecting between the second electrode of the storage capacitor and a reference voltage;
a second switch electrically connecting between the second electrode of the storage capacitor and a noise voltage; and
an amplifier detecting electric charges of the storage capacitor,
wherein a third switch directly connects between the first coordinate electrode and the amplifier in order to transfer the electric charges,
wherein the reference voltage is applied to the second electrode,
wherein the noise voltage is applied to the second electrode after the reference voltage is applied to the second electrode for detecting the touch coordinate,
wherein the third switch is configured to be turned ON at the same period as the noise voltage is applied to the second electrode.
8. The touch panel according to claim 7 ,
wherein the reference voltage is applied to the amplifier.
9. The touch panel according to claim 7 ,
wherein the first switch and the second switch are turned ON and OFF alternately.
10. The touch panel according to claim 7 ,
further comprise a fourth switch connecting the power source and the first coordinate electrode,
wherein the third switch and the fourth switch are turned ON and OFF alternately.
11. The touch panel according to claim 7 ,
wherein electric charges of the storage capacitor are stepped increased by supplying electric charges to the first electrode.
12. The touch panel according to claim 10 ,
wherein output of the amplifier is stepped increased by alternately turned ON and OFF of the third switch and the fourth switch.