Capacitive touch detection system and detection signal receiving and waveform shaping module

• US 8,436,831 B2
• Filed: 06/30/2010
• Issued: 05/07/2013
• Est. Priority Date: 09/14/2009
• Status: Active Grant

• Current Assignee: AU Optronics Corporation
• Original Assignee: AU Optronics Corporation
• Inventors: Wei, Fu-Cheng, Hsu, Yu-Min, Cheng, Yung-Tse
• Primary Examiner(s): Haley, Joseph
• Assistant Examiner(s): FRANK, EMILY J
• Application Number:
  US12/827,621
• Publication Number:
  US 20110063246A1
• Time in Patent Office: 1,042 Days
• Field of Search: None
• US Class Current: 345/174
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard

Abstract

An exemplary capacitive touch detection system includes a capacitive touch panel and a detection control circuit. The capacitive touch panel includes a plurality of input terminals and output terminals. The detection control circuit includes a scanning signal transmitting module electrically coupled to the input terminals and a detection signal receiving and waveform shaping module including a receiver and an impedance-matching network. The detection signal receiving and waveform shaping module is electrically coupled to the output terminals for receiving and processing a plurality of detection signals outputted from the respective output terminals and thereby producing a plurality of processed detection signals. The receiver is used for receiving the detection signals. The impedance-matching network is used for performing a waveform shaping operation applied to the detection signals to compensate an effect caused by uneven RC loading distribution in the capacitive touch panel and thereby producing the processed detection signals.

Claims

1. A capacitive touch detection system comprising:

a capacitive touch panel including a plurality of input terminals and a plurality of output terminals; and

a detection control circuit including a scanning signal transmitting module and a detection signal receiving and waveform shaping module, the scanning signal transmitting module being electrically coupled to the input terminals for providing a scanning voltage signal to the input terminals, the detection signal receiving and waveform shaping module being electrically coupled to the output terminals for receiving and processing a plurality of detection signals outputted from the respective output terminals to produce a plurality of processed detection signals;

wherein the detection signal receiving and waveform shaping module comprises a receiver for receiving the detection signals and an impedance-matching network for performing a waveform shaping operation applied to the detection signals thereby producing the plurality of processed detection signals, the impedance-matching network comprises a plurality of RC circuits independent from one another, a terminal of each of the RC circuits is electrically coupled to a predetermined potential, the other terminal of each of the RC circuits is electrically coupled to receive a corresponding one of the detection signals, each of the RC circuits comprises a resistor and a capacitor, and a resistance value and a capacitance value of each of the RC circuits are relevant with a ratio of a voltage amplitude of the corresponding one of the detection signals to a voltage amplitude of the corresponding one of the processed detection signals under the situation of the capacitive touch panel being untouched.

2. The capacitive touch detection system as claimed in claim 1, wherein the scanning signal transmitting module comprises a transmitter for generating an initial voltage signal and a level shifter for performing a level shift operation applied to the initial voltage signal thereby producing the scanning voltage signal.

3. The capacitive touch detection system as claimed in claim 1, wherein the detection control circuit further comprises a voltage amplifier, an analog-to-digital converter and a digital controller for controlling the scanning signal transmitting module, the detection signal receiving and waveform shaping module and the analog-to-digital converter, the processed detection signals are amplified by the voltage amplifier and then digitalized by the analog-to-digital converter and thereby a plurality of digital detection signals are obtained, the digital detection signals are processed by the digital controller to be a touch detection result for output.

4. The capacitive touch detection system as claimed in claim 3, wherein the detection control circuit further comprises a charging circuit electrically coupled between the detection signal receiving and waveform shaping module and the voltage amplifier and controlled by the digital controller.

5. The detection signal receiving and waveform shaping module as claimed in claim 1, wherein a transmission path of the scanning voltage signal is shorter, a compensation value for RC loading of a corresponding RC circuit is larger.

6. A detection signal receiving and waveform shaping module adapted to a detection control circuit for a capacitive touch panel, the detection signal receiving and waveform shaping module being electrically coupled to a plurality of output terminals of the capacitive touch panel, the detection signal receiving and waveform shaping module comprising:

a receiver for receiving a plurality of detection signals from the output terminals; and

an impedance-matching network for performing a waveform shaping operation applied to the detection signals to produce a plurality of processed detection signals and thereby voltage amplitudes of the processed detection signals under the situation of the capacitive touch panel being untouched are substantially identical with one another, the impedance-matching network comprises a plurality of RC circuits independent from one another, a terminal of each of the RC circuits is electrically coupled to a predetermined potential, another terminal of each of the RC circuits is electrically coupled to receive a corresponding one of the detection signals, each of the RC circuits comprises a resistor and a capacitor, and a resistance value and a capacitance value of each of the RC circuits are relevant with a ratio of a voltage amplitude of the corresponding one of the detection signals to a voltage amplitude of the corresponding one of the processed detection signals under the situation of the capacitive touch panel being untouched.

7. The detection signal receiving and waveform shaping module as claimed in claim 6, wherein a transmission path of a scanning voltage signal provided to the capacitive touch panel is shorter, a compensation value for RC loading of a corresponding RC circuit is larger.