Calibration device and method for frequency point in touch screen, touch screen and display device

1. A calibration device for frequency point in a touch screen, configured for performing an automatic calibration on capacitances of a sensing capacitor in the touch screen at various frequency points, and comprising a calibration circuit and a comparison circuit, wherein

the calibration circuit is connected with the sensing capacitor and the comparison circuit, to transmit a calibration excitation signal to the touch screen to start calibration operations at the various frequency points, and calibrate the sensing capacitor in the touch screen according to a comparison result from the comparison circuit; and

the comparison circuit is configured for comparing a preset capacitance with a capacitance of the sensing capacitor in the touch screen at a current frequency point to obtain the comparison result, and feeding the comparison result back to the calibration circuit, so that the capacitance of the sensing capacitor is calibrated to a capacitance that matches with the current frequency point.

2. The calibration device according to claim 1 , wherein the comparison circuit comprises a plurality of comparison sub-circuits in parallel, each of which is connected to a corresponding sensing capacitor in the touch screen, each of the comparison sub-circuits returns a difference between the preset capacitance and the capacitance of the sensing capacitor in the touch screen at the current frequency point to the calibration circuit, and the calibration circuit calibrates the capacitance of the sensing capacitor at the current frequency point.

3. The calibration device according to claim 2 , wherein each of the plurality of comparison sub-circuits comprises a comparator, a feedback capacitor and a ground capacitor, the comparator is configured for comparing the preset capacitance with the capacitance of the sensing capacitor in the touch screen at the current frequency point to obtain the comparison result, and the feedback capacitor is configured for feeding the comparison result back to the calibration circuit.

4. A touch screen, comprising the sensing capacitor and the calibration device according to claim 2 .

5. A display device, comprising the touch screen according to claim 4 .

6. The calibration device according to claim 3 , wherein a preset value of the feedback capacitor in each of the plurality of comparison sub-circuits equals to an average value of initial values of all feedback capacitors of the plurality of comparison sub-circuits corresponding to the various frequency points.

7. The calibration device according to claim 3 , wherein the feedback capacitor is a variable capacitor.

8. A touch screen, comprising the sensing capacitor and the calibration device according to claim 3 .

9. A display device, comprising the touch screen according to claim 8 .

10. The calibration device according to claim 1 , wherein the various frequency points comprise two to six frequency points in different frequency bands.

11. The calibration device according to claim 10 , wherein the various frequency points comprise three frequency points, the three frequency points increase sequentially.

12. The calibration device according to claim 1 , wherein the calibration excitation signal transmitted to the touch screen by the calibration circuit comprises a plurality of square signals with different timings, and a pulse width of each of the square signals matches with a corresponding frequent point.

13. A touch screen, comprising the sensing capacitor and the calibration device according to claim 12 .

14. The calibration device according to claim 1 , wherein the calibration circuit is further configured for performing a preliminary calibration on the capacitances of the sensing capacitor in the touch screen at the various frequency points, and the comparison circuit is further configured for comparing the preset capacitance with the capacitance of the sensing capacitor at the current frequency point to obtain the comparison result after the preliminary calibration, and feeding the comparison result back to the calibration circuit.

15. A touch screen, comprising the sensing capacitor and the calibration device according to claim 1 .

16. A display device, comprising the touch screen according to claim 15 .

17. A calibration method for frequency point in a touch screen, comprising:

transmitting a calibration excitation signal to the touch screen to start calibration operations at various frequency points;

collecting a capacitance of a sensing capacitor in the touch screen at each of the various frequency points; and

calibrating a capacitance of the sensing capacitor at a current frequency point to a capacitance that matches with the current frequency point, by compensating the sensing capacitor according to a difference between a preset capacitance and the capacitance of the sensing capacitor at the current frequency point.

18. The calibration method according to claim 17 , wherein the calibration excitation signal transmitted to the touch screen comprises a plurality of square signals with different timings, and a pulse width of each of the square signals matches with a corresponding frequent point.

19. The calibration method according to claim 17 , further comprising establishing a corresponding relationship between the capacitance of the sensing capacitor and the preset capacitance at each of the frequency points.

20. The calibration method according to claim 19 , wherein before establishing a corresponding relationship between the capacitance of the sensing capacitor and the preset capacitance at each of the frequency points, the method further comprises: performing a preliminary calibration on the capacitances of the sensing capacitor in the touch screen at the various frequency points; and

establishing a corresponding relationship between the capacitance of the sensing capacitor and the preset capacitance at each of the frequency points further comprises:

establishing a corresponding relationship between the capacitance of the sensing capacitor at each of the frequency points after the preliminary calibration and the preset capacitance.