Glass touch sensing circuit

• US 6,885,365 B1
• Filed: 11/03/2000
• Issued: 04/26/2005
• Est. Priority Date: 06/13/2000
• Status: Expired due to Fees

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Kang, Sang-Seog
• Primary Examiner(s): Wu, Xiao
• Assistant Examiner(s): ABDULSELAM, ABBAS I
• Application Number:
  US09/704,761
• Time in Patent Office: 1,635 Days
• Field of Search: 178/18.02, 178/18.06, 178/19.03, 307/116, 307/139, 361/179, 361/181, 382/124, 340/562, 345/174, 345/175, 345/176, 345/173, 345/177, 345/1.1, 345/208, 345/210
• US Class Current: 345/173
• CPC Class Codes: H03K 17/96 Touch switches specially adapted for electronic time-pieces with no moving parts G04G21/08

Abstract

A glass touch sensing circuit which is capable of accurately detecting a sense signal resulting from a user'"'"'s touch under no influence of variations in temperature. The glass touch sensing circuit is adapted to compare the level of an output signal from a switching device, which indicates whether the user touches a touch sensor, with that of a reference signal and convert the output signal from the switching device into a wave-shaped signal in accordance with the compared result. The present glass touch sensing circuit is further adapted to determine the level of the reference signal for compensation for a variation in the output signal from the switching device with temperature. Therefore, the glass touch sensing circuit can be employed in a human body touch-based key input sensing system to provide a constant performance irrespective of a variation in temperature so as to sense a key input based on a touching operation.

Claims

1. A glass touch sensing circuit, comprising:

a touch sensor which provides a signal in response to a user'"'"'s touch;

a switch having a switching period of time differently determined depending on a level of the touch sensor signal;

a compensator which produces an independent temperature reference signal corresponding to a variation in temperature of the glass touch sensing circuit, and compares an output signal from said switch proportional to the touch sensor signal with that of the independent temperature reference signal, said independent temperature reference signal and said output signal from said switch have substantially a same slope such that the compensator outputs a square wave-shaped signal in accordance with a compared result; and

a touch detector responsive to an output signal from said compensator for detecting whether the user touched said touch sensor.

2. A glass touch sensing circuit as set forth in claim 1, further comprising:

a charging/discharging unit which charges and discharges a voltage which is different in level according to whether the user touches said touch panel, said switching time period of said switch determined depending on a level of said voltage charged and discharged by said charging/discharging unit.

3. A glass touch sensing circuit as set forth in claim 1, wherein said touch detector includes:

a signal output unit which provides an output signal synchronously with said output signal from said compensator; and

a recognition unit which recognizes a touched key in response to the output signal from said signal output unit.

4. A glass touch sensing circuit as set forth in claim 3, wherein said recognition unit recognizes an input of said touched key and initializes said signal output unit.

5. A glass touch sensing circuit as set forth in claim 1, wherein said touch detector includes:

a flip-flop having a clock terminal connected to an output terminal of said compensator, said flip-flop being enabled in response to a clock signal applied to said clock terminal; and

a processor having an input terminal connected to an output terminal of said flip-flop, said processor recognizing the user'"'"'s touch with said touch sensor in response to an output signal from said flip-flop and initializing said flip-flop.

6. A glass touch sensing circuit as set forth in claim 1, wherein said compensator includes a thermistor which compensates for the level of said reference signal for the temperature variation.

7. A glass touch sensing circuit as set forth in claim 6, wherein said compensator further includes:

a comparator having a first input terminal connected to an output terminal of said switch, and a second input terminal for inputting a voltage determined in level by said thermistor and fixed resistors.

8. A glass touch sensing circuit as set forth in claim 1, wherein said switch includes a transistor which turns on in response to said output signal from said touch sensor.

9. A glass touch sensing circuit as set forth in claim 5, wherein said flip-flop is a D flip-flop.

10. A glass touch sensing circuit as set forth in claim 1, further comprising:

a pair of resistors connected in series to a supply input terminal and a ground source; and

a thermistor connected to an input terminal of a comparator included in the compensator and the ground source, and being in parallel to the pair of resistors.

11. A touch sensing system, comprising:

an input terminal for receiving a signal output from a touch sensor; and

a controller which processes the signal from the touch sensor based on an independent temperature reference signal corresponding to a variation in temperature to generate a touch detection signal,

wherein the controller includes;

a switch which outputs a switch signal based on the signal from the touch sensor;

a signal generator which generates a reference signal; and

a comparator which compares the switch signal to the reference signal,

wherein the signal generator includes a level-controller which controls a level of the reference signal based on temperature variation, and

wherein the level-controller varies the level of the reference signal to coincide with changes in the switch signal that result from variation in temperature such that the comparator outputs a square wave-shaped signal.

12. A touch sensing system as set forth in claim 11, wherein the controller processes the signal from the touch sensor in a manner which achieves a constant level of touch detection sensitivity in spite of temperature variation.

13. A touch sensing system as set forth in claim 11, wherein the controller includes:

a switch which outputs a switch signal based on the signal from the touch sensor, and

a compensator which compensates for variations in the switch signal based on temperature variation.

14. A touch sensing system as set forth in claim 11, wherein the controller generates the touch detection signal based on an output of the comparator.

15. A touch sensing system as set forth in claim 11, wherein the level-controller decreases the level of the reference signal to a first non-zero value as temperature increases, and increases the level of the reference signal to a second non-zero value as temperature decreases.

16. A touch sensing system as set forth in claim 11, wherein the level-controller includes a thermistor which outputs a voltage value that varies the level of the reference value based on temperature variation of the touch sensing system.

17. A touch sensing system as set forth in claim 11, further comprising:

a pair of resistors connected in series to a supply input terminal and a ground source; and

a thermistor connected to an input terminal of the comparator and the ground source, and being in parallel to the pair of resistors.

18. A touch sensing system, comprising:

a switch which outputs a switch signal based on a touch sensor signal; and

a controller which compensates for variations in a turning-on period of the switch to generate a touch detection signal by comparing an independent temperature reference signal corresponding to a variation in temperature with the switch signal output from the switch,

wherein the controller includes;

a comparator for comparing the switch signal to a reference signal having substantially a same slope as the switch signal to generate a square waved-shape compensated switch signal.

19. A touch sensing system as set forth in claim 18, wherein the controller compensates for variations in falling edge depth of the switch signal output from the switch.

20. A touch sensing system as set forth in claim 18, wherein the controller generates the touch detection signal based on the compensated switch signal.

21. A touch sensing system as set forth in claim 20, wherein the controller includes:

a compensator which varies the reference signal based on temperature variations.

22. A touch sensing system as set forth in claim 21, wherein the compensator includes a thermistor which outputs a value for varying the reference signal based on temperature variations.

23. A touch sensing system as set forth in claim 20, wherein the controller includes:

a flip-flop circuit having an input connected to the output of the comparator and an output for supplying the touch detection signal, wherein the compensated switch signal is input into a clock terminal of the flip-flop.

24. A glass touch sensing system as set forth in claim 18, further comprising:

a pair of resistors connected in series to a supply input terminal and a ground source; and

a thermistor connected to an input terminal of the comparator and the ground source, and being in parallel to the pair of resistors.