TOUCH SENSING APPARATUS

• US 20070074915A1
• Filed: 07/03/2006
• Published: 04/05/2007
• Est. Priority Date: 08/05/2005
• Status: Active Grant

• Current Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. (Hon Hai Precision Industry Co., Ltd.), Hon Hai Precision Industry Co., Ltd.
• Inventors: Hsieh, Kuan-Hong, Chung, Shin-Hong, Lin, Shi-Quan
• Granted Patent: US 7,714,848 B2
• Time in Patent Office: Days
• US Class Current: 178/18.60
• CPC Class Codes: H03K 17/962 Capacitive touch switches

Abstract

A touch sensing apparatus includes: a differential signal source for generating two alternating current signals with same frequency and reverse phase; two conductors connected to a cathode output end and an anode output end of the differential signal source; a sensor for receiving a noise generated by a contact of an object; wherein the sensor and the two conductors form two simulated capacitors that result in offsetting environmental noise; a detector having a first input end and a second input end, the detector upon receiving the noise transferred from the sensor resulting in voltage differences between the first and second input ends thereof, and outputting a signal; and a rectifying circuit for rectifying the alternating current signals generated by the differential signal source and simultaneously generating a noise.

Claims

1. A touch sensing apparatus comprising:

a differential signal source configured for generating two alternating current signals with same

frequency and reverse phase, wherein the differential signal source comprises a cathode output end and an anode output end;

two conductors respectively connected to the cathode output end and the anode output end of the differential signal source;

a sensor located between the two conductors for receiving a noise;

wherein the sensor and the two conductors form two simulated capacitors that offset environmental noise;

a detector having a first input end and a second input end, the detector upon receiving the noise transferred from the sensor resulting in voltage differences between the first and second input ends thereof, and outputting a signal; and

a rectifying circuit for rectifying the alternating current signals generated by the differential signal source, simultaneously generating a noise, wherein an end of the rectifier circuit is connected to the signal source and another end of the rectifier circuit is connected to the second input end of the detector.

2. The touch sensing apparatus as described in claim 1, further comprising a direct current power source, wherein the direct current power source is electrically connected to the second input end and a positive power input end of the detector, and provides a bias voltage for the detector.

3. The touch sensing apparatus as described in claim 2, further comprising a resistance element connected between the first input end and the second input end of the detector.

4. The touch sensing apparatus as described in claim 1, further comprising a microcontroller unit (MCU) for processing signals outputted by the detector.

5. The touch sensing apparatus as described in claim 1, wherein the detector comprises a relatively high input impedance.

6. The touch sensing apparatus as described in claim 1, wherein the differential signal source further provides an alternating magnetic field for the touch sensing apparatus.