Touch sensing apparatus with differential signal source

• US 7,602,383 B2
• Filed: 01/23/2006
• Issued: 10/13/2009
• Est. Priority Date: 04/08/2005
• Status: Expired due to Fees

• Current Assignee: Gold Charm Limited (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, Li, Xiao-Guang, Wang, Han-Che, Lin, Shi-Quan
• Primary Examiner(s): Mengistu; Amare
• Assistant Examiner(s): PATEL, PREMAL R
• Application Number:
  US11/307,099
• Publication Number:
  US 20060227119A1
• Time in Patent Office: 1,359 Days
• Field of Search: 345173-178, 178 1803- 1811, 178/20.01, 735/141.6, 324/678, 250/215, 340/679
• US Class Current: 345/173
• CPC Class Codes: G06F 3/044 by capacitive means

Abstract

A preferred embodiment of the touch sensing apparatus includes one or more touch sensing units, a detector, and a signal processing unit. Each touch sensing unit comprises: a differential signal source for generating two signals which have a same frequency but reverse phases; and two sensors for receiving a touch signal of a user'"'"'s finger. One sensor is connected to an anode of the differential signal source, and the other sensor is connected to a cathode of the differential signal source. The detector is for converting the received signal into a digital signal. An input terminal of the detector is connected to the sensors of each touch sensing unit. The signal processing unit is for determining which sensor is touched according to the frequency and phase of the signal output from the detector. The signal processing unit is connected to an output terminal of the detector. The touch sensing unit may further include a reference signal circuit.

Claims

1. A touch sensing apparatus, comprising:

one or more touch sensing units, each touch sensing unit comprising;

a differential signal source for generating two signals which have a same frequency but reverse phases; and

two sensors for receiving a signal of a user'"'"'s touch, wherein one sensor is connected to an anode of the differential signal source and the other sensor is connected to a cathode of the differential signal source;

wherein, each differential signal source has an exclusive frequency;

a detector for converting the received signal into a digital signal, wherein the sensors of all the touch sensing units are connected to an input terminal of the detector; and

a signal processing unit for determining which sensor is touched according to a frequency and phase of the digital signal output from the detector, wherein the signal processing unit is connected to an output terminal of the detector.

2. The touch sensing apparatus as described in claim 1, wherein each touch sensing unit further comprises a first diode and a second diode, anodes of the two diodes are connected to the two sensors respectively, and cathodes of the diodes are both connected to the input terminal of the detector.

3. The touch sensing apparatus as described in claim 1, wherein the touch sensing unit further comprises a reference signal circuit for providing a reference signal for the signal processing unit to determine which sensor is touched, one end of the reference signal circuit is connected to the anode of each differential signal source, and the other end of the reference signal circuit connected to an input terminal of the signal processing unit.

4. The touch sensing apparatus as described in claim 2, further comprising a clamping circuit, the clamping circuit comprising:

a third diode for eliminating any input static from a user'"'"'s touch, wherein a cathode of the third diode connects to the cathodes of the first diode and the second diode, and an anode of the third diode is grounded; and

a capacitor for attenuating a touch signal from the diode, wherein one end of the capacitor connects to the input terminal of the detector, and the other end of the capacitor is grounded.

5. The touch sensing apparatus as described in claim 1, wherein the sensors are shunt capacitors.

6. The touch sensing apparatus as described in claim 1, wherein the detector is a high impedance input circuit.