Touch sensing circuit and method thereof
A touch sensing circuit is applied to a touch panel to generate a sensing signal. The touch panel includes a sensing device. The touch sensing circuit includes: an interference signal detecting circuit, configured to detect an interference signal of the touch panel to generate an interference signal detection result; a control signal generating unit, configured to generate a control signal according to the interference signal detection result; and a sensed value analyzing circuit, configured to charge the sensing device in a first time interval and to discharge the sensing device in a second time interval, and to generate the sensing signal according to a sensed value of the sensing device. A length of one of the first time interval and the second time interval changes according to a control signal.
1. A touch sensing circuit, applied to a touch panel to generate a touch sensing result, the touch panel comprising a plurality of capacitors, the touch sensing circuit comprising:
a sensed value analyzing circuit, configured to charge the capacitors in a first time interval and to discharge the capacitor in a second time interval, and to generate a sensing signal according to capacitance information of the capacitors; and
a determining unit, configured to generate the touch sensing result according to the sensing signal;
wherein, a length of one of the first time interval and the second time interval changes according to a control signal,
an interference signal detecting circuit, coupled to the sensed value analyzing circuit, configured to detect an interference signal of the touch panel to generate an interference signal detection result;
a control signal generating unit, configured to generate the control signal according to the interference signal detection result; and
wherein the control signal generating unit determines the length of one of the first time interval and the second time interval according to a first predetermined period and the interference signal detection result: when the interference signal detection result after reaching the first predetermined period indicates a presence of interference, the control signal generating unit extends the length of the first time interval by a second predetermined period via the control signal, wherein a time point that the first predetermined period is reached is not later than an end of an unextended first time interval.
2. The touch sensing circuit according to claim 1 , wherein the sensed value analyzing circuit comprises:
a charging unit, configured to charge the capacitors via a charging path; and
a resistor, located on the charging path; and
the interference signal detecting circuit comprises:
a comparison unit, coupled to the resistor, configured to compare a cross-voltage of the resistor with a predetermined value to generate the interference signal detection result.
3. The touch sensing circuit according to claim 1 , wherein the sensed value analyzing circuit comprises:
a discharging unit, configured to discharge the capacitors via a discharging path; and
a resistor, located on the discharging path; and
the interference signal detecting circuit comprises:
a comparison unit, coupled to the resistor, configured to compare a cross-voltage of the resistor with a predetermined value to generate the interference signal detection result.
4. The touch sensing circuit according to claim 1 , wherein the sensed value analyzing circuit comprises:
a charging unit, configured to charge the capacitors via a charging path; and;
a discharging unit, configured to discharge the capacitors via a discharging path;
a first resistor, located on the charging path; and
a second resistor, located on the discharging path; and
the interference signal detecting circuit comprises:
a comparison unit, coupled to the first resistor and the second resistor, configured to compare a cross-voltage of the first resistor with a first predetermined value and a second cross-voltage of the second resistor with a second predetermined value to generate the interference signal detection result.
5. The touch sensing circuit according to claim 1 , wherein after reaching the second predetermined period, the control signal generating unit selectively extends the length of one of the first time interval and the second time interval by the second predetermined period via the control signal.
6. A touch sensing method, applied to a touch panel to generate a touch sensing result, the touch panel comprising a plurality of capacitors, the method comprising:
charging the capacitors according to a control signal in a first time interval;
discharging the capacitor according to the control signal in a second time interval;
generating a sensing signal according to a capacitance value of the capacitors;
and generating the touch sensing result according to the sensing signal;
wherein, a length of the one of the first time interval and the second time interval changes according to the control signal,
the method further comprising:
detecting an interference signal of the touch panel to generate an interference signal detection result;
generating the control signal according to the interference signal detection result, and
when the interference signal indicates a presence of interference after reaching a first predetermined period, extending the length of the first time interval by a second predetermined period, wherein a time period that the first predetermined period is reached is not later than an end of an unextended first time interval.
7. The touch sensing method according to claim 6 , wherein the step of charging the capacitors charges the capacitors via a charging path, the charging path comprises a resistor, and the step of detecting the interference signal of the touch panel to generate the interference signal detection result comprises:
comparing a cross-voltage of the resistor with a predetermined value to generate the interference signal detection result.
8. The touch sensing method according to claim 6 , wherein the step of discharging the capacitors discharges the capacitors via a discharging path, the discharging path comprises a resistor, and the step of detecting the interference signal of the touch panel to generate the interference signal detection result comprises:
comparing a cross-voltage of the resistor with a predetermined value to generate the interference signal detection result.
9. The touch sensing method according to claim 6 , wherein the step of charging the capacitors charges the capacitors via a charging path, the charging path comprises a first resistor, the step of discharging the capacitors discharges the capacitors via a discharging path, the discharging path comprises a second resistor, and the step of detecting the interference signal of the touch panel to generate the interference signal detection result comprises:
comparing a cross-voltage of the first resistor with a first predetermined value and comparing a cross-voltage of the second resistor with a second predetermined value to generate the interference signal detection result.
10. The touch sensing method according to claim 6 , further comprising:
after reaching the second predetermined period, selectively extending the length of the one of the first time interval and the second time interval by the second predetermined period according to the interference signal detection result.
11. A touch sensing circuit, applied to a touch panel to generate a sensing signal, the touch panel comprising a sensing device, the touch sensing circuit comprising:
an interference signal detecting circuit, configured to detect an interference signal of the touch panel to generate an interference signal detection result;
a control signal generating unit, configured to generate a control signal according to the interference signal detection result; and
a sensed value analyzing circuit, configured to charge the sensing device in a first time interval and to discharge the sensing device in a second time interval, and to generate the sensing signal according to a sensed value of the sensing device, wherein a length of one of the first time interval and the second time interval changes according to a control signal,
wherein the control signal generating unit determines the length of one of the first time interval and the second time interval according to a first predetermined period and the interference signal detection result; when the interference signal detection result after reaching a predetermined period indicates a presence of interference, the control signal generating unit extends the length of the first time interval by a second predetermined period via the control signal, wherein a time point that the first predetermined period is reached is not later than an end of an unextended first time interval.
12. The touch sensing circuit according to claim 11 , wherein the sensing device comprises a plurality of capacitors, the sensed value analyzing circuit comprises:
a charging unit, configured to charge the capacitors via a charging path according to the control signal; and
a resistor, located on the charging path; and
the interference signal detecting circuit comprises:
a comparison unit, coupled to the resistor, configured to compare a cross-voltage of the resistor with a predetermined value to generate the interference signal detection result.
13. The touch sensing circuit according to claim 11 , wherein the sensing device comprises a plurality of capacitors, the sensed value analyzing circuit comprises:
a discharging unit, configured to discharge the capacitors via a discharging path according to the control signal; and
a resistor, located on the discharging path; and
the interference signal detecting circuit comprises:
a comparison unit, coupled to the resistor, configured to compare a cross-voltage of the resistor with a predetermined value to generate the interference signal detection result.
14. The touch sensing circuit according to claim 11 , wherein the sensing device comprises a plurality of capacitors, the sensed value analyzing circuit comprises:
a charging unit, configured to charge the capacitors via a charging path according to the control signal;
a discharging unit, configured to discharge the capacitors via a discharging path according to the control signal;
a first resistor, located on the charging path; and
a second resistor, located on the discharging path; and
the interference signal detecting circuit comprises:
a comparison unit, coupled to the first resistor and the second resistor, configured to compare a cross-voltage of the first resistor with a first predetermined value and a second cross-voltage of the second resistor with a second predetermined value to generate the interference signal detection result.
15. The touch sensing circuit according to claim 11 , wherein after reaching the second predetermined period, the control signal generating unit selectively extends the length of one of the first time interval and the second time interval by the second predetermined period via the control signal according to the interference signal detection result.