Signal processing circuit for processing sensing signal from touch panel

• US 10,503,319 B2
• Filed: 12/27/2017
• Issued: 12/10/2019
• Est. Priority Date: 12/27/2017
• Status: Active Grant

• Current Assignee: Novatek Microelectronics Corporation (Novatek Microelectronics Corp Limited)
• Original Assignee: Novatek Microelectronics Corporation (Novatek Microelectronics Corp Limited)
• Inventors: Chang, Tsen-Wei
• Primary Examiner(s): Eurice, Michael J
• Application Number:
  US15/856,034
• Publication Number:
  US 20190196652A1
• Time in Patent Office: 713 Days
• CPC Class Codes: G06F 21/32 using biometric data, e.g. fingerprints, iris scans or voiceprints
• CPC Class Codes: G06F 2203/04112 Electrode mesh in capacitive digitiser: electrode for touch sensing is formed of a mesh of very fine, normally metallic, interconnected lines that are almost invisible to see. This provides a quite large but transparent electrode surface, without need for ITO or similar transparent conductive material
• CPC Class Codes: G06F 3/03547 Touch pads, in which fingers can move on a surface
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0414 using force sensing means to determine a position
• CPC Class Codes: G06F 3/0416 Control or interface arrangements specially adapted for digitisers
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/047 using sets of wires, e.g. crossed wires
• CPC Class Codes: H03M 1/124 Sampling or signal conditioning arrangements specially adapted for A/D converters
• CPC Class Codes: H03M 3/396 among different frequency bands
• CPC Class Codes: H03M 3/422 having one quantiser only
• CPC Class Codes: H03M 3/438 the modulator having a higher order loop filter in the feedforward path
• CPC Class Codes: H03M 3/458 Analogue/digital converters using delta-sigma modulation as an intermediate step

Abstract

A signal processing circuit is provided. The signal processing circuit includes an analog-front-end circuit and a filter circuit. The analog-front-end circuit is configured to receive a sensing signal from a touch panel and perform a signal capture operation on the sensing signal to output a current signal. The filter circuit is coupled to the analog-front-end circuit. The filter circuit is configured to receive the current signal from the analog-front-end circuit and perform a signal filter operation on the current signal to output a first voltage signal. The filter circuit includes an anti-aliasing filter and a comb filter coupled in series.

Claims

1. A signal processing circuit comprising:

an analog-front-end circuit configured to receive a sensing signal from a touch panel, perform a signal capture operation on the sensing signal to output a current signal; and

a filter circuit coupled to the analog-front-end circuit and configured to receive the current signal from the analog-front-end circuit and perform a signal filter operation on the current signal to output a first voltage signal,

wherein the filter circuit comprises an anti-aliasing filter and a comb filter coupled in series.

2. The signal processing circuit according to claim 1, wherein the analog-front-end circuit comprises an operational amplifier circuit and a current mirror circuit, and the current mirror circuit mirrors an operational current of the operational amplifier circuit to generate the current signal.

3. The signal processing circuit according to claim 1, wherein the comb filter is selected from one of a first-order comb filter, a second-order comb filter and a fourth-order comb filter.

4. The signal processing circuit according to claim 1, wherein the touch panel is selected from one of a self-capacitance touch panel and a mutual-capacitance touch panel.

5. The signal processing circuit according to claim 1, wherein the anti-aliasing filter receives the current signal and provides a preset bandwidth, and the anti-aliasing filter filters the current signal based on the preset bandwidth to output a second voltage signal to the comb filter.

6. The signal processing circuit according to claim 5, wherein the comb filter is coupled to the anti-aliasing filter in series and receives the second voltage signal from the anti-aliasing filter, and the comb filter operates based on a first operation frequency and filters the second voltage signal to output the first voltage signal.

7. The signal processing circuit according to claim 6, further comprising:

an analog-to-digital converter coupled to the comb filter and configured to receive the first voltage signal and convert the first voltage signal of an analog format into the first voltage signal of a digital format based on the first operation frequency.

8. The signal processing circuit according to claim 6, further comprising:

a down-sampling circuit coupled to the comb filter and configured to receive the first voltage signal and perform a down-sampling operation on the first voltage signal to output a third voltage signal.

9. The signal processing circuit according to claim 8, further comprising:

an analog-to-digital converter coupled to the down-sampling circuit and configured to receive the third voltage signal and convert the third voltage signal of an analog format into the third voltage signal of a digital format based on a second operation frequency, wherein the second operation frequency is smaller than the first operation frequency.