Charge transfer device and method, touch sensing device and method

• US 7,598,752 B2
• Filed: 12/29/2006
• Issued: 10/06/2009
• Est. Priority Date: 04/19/2006
• Status: Active Grant

• Current Assignee: Beijing Sigmachip Company Limited
• Original Assignee: Beijing Sigmachip Company Limited
• Inventors: Li, Zhiqian
• Primary Examiner(s): Nguyen; Vincent Q
• Application Number:
  US11/618,416
• Publication Number:
  US 20070247172A1
• Time in Patent Office: 1,012 Days
• Field of Search: 324/687, 341/33, 345/173, 178/18.06
• US Class Current: 324/657
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2017/9602 characterised by the type or shape of the sensing electrodes
• CPC Class Codes: H03K 2217/94031 Calibration involving digital processing
• CPC Class Codes: H03K 2217/960725 Charge-transfer

Abstract

The disclosure relates to a touch sensing device and method. An embodiment of the disclosed method includes starting to count with a counter while charging a sensing point which has distributed capacitance periodically, then transferring the charge on the sensing point to a second capacitor. Next, the voltage on the second capacitor is compared with a reference voltage, and if the former exceeds the latter, the counter stops counting and saving the value. If the voltage on the second capacitor is less than the reference voltage, the sensing point is judged to determine whether it is in touching state or in non-touching state according to the saved count value while discharging the second capacitor, clearing the counter after the discharge, then restarting the method. Using the device and method of this disclosure, the touching sensing action can be tested accurately.

Claims

1. A touch sensing device comprising:

a sensing point for producing a sensing capacitor;

a power supply connected to a first switch for charging the sensing capacitor produced at the sensing point periodically;

a second capacitor connected with the sensing capacitor via a second switch and the charge accumulated on the sensing capacitor is transferred to the second capacitor;

a comparator for comparing voltage on the second capacitor with a reference voltage;

a counter;

a processor;

wherein the processor performs the steps of

a) comparing whether the current count value exceeds the last count value, wherein if the current count value exceeds the last count value, the process proceeds to step b), wherein if the current count value does not exceed the last count value, the process proceeds to step c);

b) judging whether the sensing point was in a touching state the last time, wherein if the sensing point was in the touching state the last time, the process proceeds to step d), wherein if the sensing point was not in the touching state the last time, the non-touching count value is refreshed with half of the sum of the current count value and the process is ended;

c) judging whether the sensing point was in a touching state the last time, wherein if the sensing point was in the touching state the last time, the touching count value is refreshed with half of the sum of the current count value and the last count value and the process flow is ended, wherein if the sensing point was not in a touching state the last time, the process proceeds to step e);

d) calculating the difference between the current count value and the last count value, then comparing whether the difference exceeds a non-touching state standard difference set in advance, wherein if the difference exceeds the non-touching state standard difference, the sensing point is in the non-touching state and the non-touching count value is refreshed with half of the sum of the current count value and the last count value and the process is ended;

wherein if the difference does not exceed the non-touching state standard difference, the sensing point is in the touching state and the process is ended; and

e) calculating the difference between the current count value and the last touching count value, then comparing whether the difference exceeds the touching standard difference;

wherein if the difference exceeds the touching standard difference, the sensing point is in a touching state;

wherein if the difference is less than the touching standard difference, the sensing point is in a non-touching state;

a third switch;

wherein the comparator produces a turnover signal and sends it to the third switch and the counter;

wherein after receiving the turnover signal, the third switch is closed and the second capacitor discharges, the third switch opens after the discharge;

and the counter stops counting after receiving the turnover signal and sends a count value to the processor which judges whether the sensing point is in touch state according to the count value, then the processor returns a signal and clears the counter, the counter restarts the count.

2. The touch sensing device according to claim 1, wherein the opening and closing of the first switch and the second switch are controlled by a non-overlapping clock signal respectively.

3. The touch sensing device according to claim 1, wherein the sensing point is constructed of printed circuit board wire.

4. The touch sensing device according to claim 1, wherein the processor calculates a difference between the count value and the non-touching count value set in advance, wherein if the difference exceeds a standard difference, the processor determines that the sensing point is in a touching state, otherwise the sensing point is in a non-touching state.

5. The touch sensing device according to claim 1, wherein the reference voltage is less than half of the charging voltage.

6. The touch sensing device according to claim 1, wherein the first switch and the second switch are one of a metal-oxide semiconductor tube, triode, relay and optical coupler.

7. The touch sensing device according to claim 1, wherein the scale of the count value of the counter is 100-65500.

8. The touching sensing device of claim 1, wherein the scale of the touching standard difference and the non-touching standard difference is 10-500.