TOUCH SENSING APPARATUS

• US 20070084645A1
• Filed: 10/09/2006
• Published: 04/19/2007
• Est. Priority Date: 10/14/2005
• Status: Abandoned Application

• Current Assignee: Hon Hai Precision Industry Co., Ltd.
• Original Assignee: Hon Hai Precision Industry Co., Ltd.
• Inventors: Hsieh, Kuan-Hong, Chung, Shin-Hong, Wang, Han-Che
• Application Number:
  US11/309,834
• Publication Number:
  US 20070084645A1
• Time in Patent Office: Days
• US Class Current: 178/18.60
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/96072 Phase comparison, i.e. where a phase comparator receives at one input the signal directly from the oscillator, at a second input the same signal but delayed, with a delay depending on a sensing capacitance

Abstract

A touch sensing apparatus includes a sensor (13), an AC signal source (14), a gate circuit (15) with two inputs, a first load circuit (18), a second load circuit (19) and a detector (16). The alternating current (AC) signal source is for outputting AC signals to the two input of the gate circuit. The sensor and the first and second load circuits are configured to enable the input signals to the two inputs of the gate circuit to be completely in phase and have same frequency and same duty cycle, and the gate circuit produces the first output type signal. The sensor receives electricity signals from the object and results in the gate circuit outputting a second output type signal. The detector detects the change of the output signal of the gate circuit from the first type to the second type and accordingly identifies a touch on the sensor.

Claims

1. A touch sensing apparatus comprising:

a gate circuit having a first input and a second input, the gate circuit producing a first output type signal when input signals applied to the first input and the second input are in phase, with a same frequency and a same duty cycle, and producing a second output type signal otherwise;

an alternating current (AC) signal source for outputting AC signals to the first input and the second input of the gate circuit;

a sensor connected to the first input of the gate circuit and configured for receiving electricity signals from an object that touches the sensor;

a first load circuit connected between the AC signal source and the first input of the gate circuit; and

a second load circuit connected between the AC signal source and the second input of the gate circuit;

a detector electrically connected to the gate circuit for receiving either the first output type signal or the second output type signal outputted from the gate circuit and identifying a touch on the sensor according to a change from the first output type signal to the second output type signal;

wherein the sensor and the first and second load circuits are configured to enable the input signals to the first and second inputs to be completely in phase and have frequency and same duty cycle, thereby enabling the gate circuit to produce the first output type signal;

the sensor receives electricity signals from the object and results in a phase difference between the input signals to the first and second inputs of the gate circuit, thereby enabling the gate circuit to output the second output type signal; and

the detector detects the change of the output signal of the gate circuit from the first type to the second type and accordingly identifies a touch on the sensor.

2. The touch sensing apparatus as described in claim 1, further comprising a microcontroller unit (MCU) electrically connected to the detector and configured for performing a procedure corresponding to the touch of the object on the sensor.

3. The touch sensing apparatus as described in claim 1, further comprising a differential signal source with a positive output and a negative output, the differential signal source providing an alternating magnetic field for the touch sensing apparatus.

4. The touch sensing apparatus as described in claim 3, further comprising two conductors respectively connected to the positive output and the negative output of the differential signal source.

5. The touch sensing apparatus as described in claim 4, wherein the sensor is located between the two conductors and forms two simulated capacitors respectively with the two conductors for offsetting environmental noise.

6. The touch sensing apparatus as described in claim 1, wherein the gate circuit is an exclusive OR gate (XOR).