Capacitance sensing apparatus and touch screen apparatus
There is provided a capacitance sensing apparatus including a driving circuit unit applying a driving signal to a first capacitor at a predetermined interval; and a sensing circuit unit sensing a change in capacitance generated by the first capacitor based on the driving signal, in which a portion of a plurality of switches included in the sensing circuit unit operate at a first interval, the same as the interval of the driving signal, and remaining switches among the plurality of switches operate at a second interval, different from the first interval.
1. A capacitance sensing apparatus, comprising:
a driving circuit unit applying a driving signal having a predetermined cycle to a first capacitor; and
a sensing circuit unit sensing a change in capacitance generated in the first capacitor based on the driving signal, and comprising:
a first switch connected to an inverting terminal of a first operational amplifier,
a second switch connected to an inverting terminal of a second operational amplifier,
a third switch formed between an output terminal and the inverting terminal of the first operational amplifier,
a fourth switch formed between an output terminal and the inverting terminal of the second operational amplifier,
wherein the third switch and the fourth switch operate at a first cycle, the same as the cycle of the driving signal, and the first switch and second switch operate at a second cycle, different from the first cycle, and
wherein the third switch and the fourth switch operate at different turn-on timings.
2. The capacitance sensing apparatus of claim 1 , wherein
the first switch and the second switch operate at different turn-on timings.
3. A capacitance sensing apparatus, comprising:
a driving circuit unit applying a driving signal having a predetermined cycle to a first capacitor; and
a sensing circuit unit sensing a change in capacitance generated in the first capacitor based on the driving signal,
wherein a portion of a plurality of switches included in the sensing circuit unit operate at a first cycle, the same as the cycle of the driving signal, and remaining switches among the plurality of switches operate at a second cycle, different from the first cycle,
wherein the sensing circuit unit includes:
a first operational amplifier having an inverting terminal connected to a first switch; and
a second operational amplifier having an inverting terminal connected to a second switch, and
the first switch and the second switch operate at the second cycle and operate at different turn-on timings, and
wherein the sensing circuit unit includes a third operational amplifier having an inverting terminal connected to an output terminal of the first operational amplifier and a non-inverting terminal connected to an output terminal of the second operational amplifier.
4. The capacitance sensing apparatus of claim 3 , wherein the sensing circuit unit includes a fourth operational amplifier, and fifth and sixth switches formed between an output terminal of the third operational amplifier and an inverting terminal of the fourth operational amplifier, and
the fifth and sixth switches operate at the second cycle and operate at different turn-on timings.
5. The capacitance sensing apparatus of claim 4 , wherein the sensing circuit unit includes a second capacitor formed between the third operational amplifier and the fifth and sixth switches, and
the second capacitor is charged and discharged according to an output voltage of the third operational amplifier.
6. The capacitance sensing apparatus of claim 1 , wherein the second cycle is twice as long as the first cycle.
7. A touch screen apparatus, comprising:
a panel unit including a plurality of driving electrodes and a plurality of sensing electrodes;
a driving circuit unit applying driving signals to the plurality of driving electrodes, respectively;
a sensing circuit unit sensing changes in capacitance generated in intersections between the plurality of sensing electrodes and the driving electrodes to which the driving signals are applied and comprising:
a first switch connected to an inverting terminal of a first operational amplifier,
a second switch connected to an inverting terminal of a second operational amplifier,
a third switch formed between an output terminal and the inverting terminal of the first operational amplifier,
a fourth switch formed between an output terminal and the inverting terminal of the second operational amplifier; and
a controller controlling operations of the driving circuit unit and the sensing circuit unit,
wherein the third switch and the fourth switch operate at a first cycle, the same as the cycle of the driving signals, and the first switch and second switch operate at a second cycle, different from the first cycle, and
wherein the third switch and the fourth switch operate at different turn-on timings.
8. The touch screen apparatus of claim 7 , wherein the controller determines at least one of coordinates of a touch input applied to the panel unit, a gesture based on the touch input, and the number of touch inputs in which the touch input is provided, from an output signal of the sensing circuit unit.
9. The touch screen apparatus of claim 7 , wherein
the first switch and the second switch operate at different turn-on timings.
10. The touch screen apparatus of claim 7 , wherein the sensing circuit unit includes a third operational amplifier calculating and outputting a difference between an output voltage of the first operational amplifier and an output voltage of the second operational amplifier.
11. The touch screen apparatus of claim 10 , wherein the sensing circuit unit includes a fourth operational amplifier, and fifth and sixth switches formed between an output terminal of the third operational amplifier and an inverting terminal of the fourth operational amplifier, and
the fifth and sixth switches operate at the second cycle and operate at different turn-on timings.
12. The touch screen apparatus of claim 7 , wherein the first cycle is a cycle equal to a half of the second cycle.