CAPACITIVE TOUCH DEVICE WITH HIGH SENSITIVITY AND OPERATING METHOD THEREOF

• US 20160282991A1
• Filed: 03/25/2016
• Published: 09/29/2016
• Est. Priority Date: 03/26/2015
• Status: Abandoned Application

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: WU, Sung-Han
• Application Number:
  US15/080,718
• Publication Number:
  US 20160282991A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

There is provided a capacitive touch device including a touch panel and a control chip. The touch panel includes a detection electrode configured to form a self-capacitor. The control chip includes an emulation circuit and a subtraction circuit. The emulation circuit is configured to output a reference signal. The subtraction circuit is coupled to the emulation circuit and the detection electrode, subtracts the reference signal outputted by the emulation circuit from a detected signal outputted by the detection electrode to output a differential detected signal, and identifies a touch event according to an amplified differential detected signal so as to improve the touch sensitivity.

Claims

1. A capacitive touch device comprising:

a touch panel comprising a detection electrode configured to form a self-capacitor; and

a control chip comprising a detection capacitor, an input resistor, an amplifying circuit and an emulation circuit, wherein

the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit are configured to form a first filter circuit,

the emulation circuit is configured to form a second filter circuit, and

a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.

2. The capacitive touch device as claimed in claim 1, further comprising a subtraction circuit configured to perform a differential operation on a detection signal outputted by the first filter circuit and a reference signal outputted by the second filter circuit to output a differential detected signal.

3. The capacitive touch device as claimed in claim 2, further comprising a gain circuit configured to amplify the differential detected signal.

4. The capacitive touch device as claimed in claim 3, wherein the capacitive touch device is configured to identify a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.

5. The capacitive touch device as claimed in claim 1, wherein capacitance of the detection capacitor is smaller than 10 percent of capacitance of the self-capacitor.

6. The capacitive touch device as claimed in claim 1, wherein differences between pole frequencies of two poles of the first filter circuit and frequencies of poles, which correspond to the two poles of the first filter circuit, of the second filter circuit is lower than 35 percent of the pole frequencies of the first filter circuit.

7. The capacitive touch device as claimed in claim 1, wherein

the amplifying circuit comprises an operational amplifier, a feedback resistor and a compensation capacitor,

the feedback resistor and the compensation capacitor are connected between a negative input and an output of the operational amplifier,

the input resistor is coupled between a second end of the detection electrode and the negative input of the operational amplifier, and

a first end of the detection electrode is coupled to the detection capacitor.

8. The capacitive touch device as claimed in claim 7, wherein

the emulation circuit comprises an emulation detection capacitor, an emulation self-capacitor, an emulation input resistor and an emulation amplifying circuit, and

connections between the emulation detection capacitor, the emulation self-capacitor, the emulation input resistor and the emulation amplifying circuit are arranged based on connections between the detection capacitor, the self-capacitor, the input resistor and the amplifying circuit.

9. A capacitive touch device comprising:

a touch panel comprising a plurality of detection electrodes configured to respectively form a self-capacitor; and

a control chip comprising;

an emulation circuit configured to output a reference signal;

a plurality of programmable filters respectively coupled to the detection electrodes; and

a subtraction circuit, coupled to the emulation circuit, configured to be sequentially coupled to the programmable filters in a self-capacitive mode, and perform a differential operation on the reference signal outputted by the emulation circuit and a detection signal outputted by the coupled programmable filter to output a differential detected signal.

10. The capacitive touch device as claimed in claim 9, wherein the control chip further comprises a gain circuit configured to amplify the differential detected signal.

11. The capacitive touch device as claimed in claim 10, wherein the capacitive touch device is configured to identify a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.

12. The capacitive touch device as claimed in claim 9, further comprising a plurality of detection capacitors configured to be electrically coupled to signal inputs of the detection electrodes in the self-capacitive mode.

13. The capacitive touch device as claimed in claim 12, wherein the programmable filter, the self-capacitor and the detection capacitor are configured to form a first filter circuit.

14. The capacitive touch device as claimed in claim 13, wherein the emulation circuit is configured to form a second filter circuit, and a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.

15. The capacitive touch device as claimed in claim 12, wherein capacitance of the detection capacitors is smaller than 10 percent of capacitance of the self-capacitor.

16. The capacitive touch device as claimed in claim 12, wherein

the detection capacitors are respectively coupled to the detection electrodes via a plurality of switches, and

the subtraction circuit is coupled to the programmable filters respectively via a plurality of switches.

17. An operating method of a capacitive touch device, the capacitive touch device comprising a touch panel and a control chip, the touch panel comprising a plurality of drive electrodes and a plurality of receiving electrodes extending along different directions, and the control chip comprising a plurality of drive circuits, a plurality of detection capacitors, a subtraction circuit and an anti-aliasing filter, the operating method comprising:

respectively coupling, in a self-capacitive mode, the drive circuits to first ends of the drive electrodes via the detection capacitors, and respectively coupling the subtraction circuit to second ends of the drive electrodes; and

respectively coupling, in a mutual capacitive mode, the drive circuits to the first ends of the drive electrodes without passing the detection capacitors, and respectively coupling the anti-aliasing filter to second ends of the receiving electrodes without passing the subtraction circuit.

18. The operating method as claimed in claim 17, further comprising:

respectively coupling, in the self-capacitive mode, the drive circuits to first ends of the receiving electrodes via the detection capacitors, and

respectively coupling, in the self-capacitive mode, the subtraction circuit to the second ends of the receiving electrodes.

19. The operating method as claimed in claim 17, wherein the control chip further comprises an emulation circuit and a programmable filter, the subtraction circuit is electrically coupled to the second ends of the drive electrodes via the programmable filter, and the operating method further comprises:

performing a differential operation on a detection signal outputted by the programmable filter and a reference signal outputted by the emulation circuit to output a differential detected signal;

amplifying the differential detected signal; and

identifying a touch event according to a variation of peak-to-peak values of the amplified differential detected signal.

20. The operating method as claimed in claim 19, wherein

the programmable filter, the detection capacitors and self-capacitors of the drive electrodes form a first filter circuit,

the emulation circuit forms a second filter circuit, and

a frequency response of the second filter circuit is determined according to a frequency response of the first filter circuit.