Time interval measurement for capacitive detection

• US 20090046827A1
• Filed: 08/13/2007
• Published: 02/19/2009
• Est. Priority Date: 08/13/2007
• Status: Active Grant

• Current Assignee: Nuvoton Technology Corporation (Winbond Electronics Corporation)
• Original Assignee: Winbond Electronics Corporation
• Inventors: Tasher, Nir, Friedman, Yehezkel, Abramov, Vladimir
• Granted Patent: US 7,797,115 B2
• Time in Patent Office: Days
• US Class Current: 377/19
• CPC Class Codes: G01D 5/2405 by varying dielectric
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• CPC Class Codes: G06F 3/0443 using a single layer of sensing electrodes

Abstract

Capacitive detection systems, modules, and methods. In one embodiment, time interval measurement(s) are generated that are monotonic functions of the capacitance(s) of capacitive sensor(s) in a capacitive sensing area. In one embodiment, the generated time interval measurement(s), or any other monotonic function(s) of capacitance(s) of capacitive sensor(s) in a capacitive sensing area, may be analyzed to detect the presence of an object near the capacitive sensing area and/or to detect the position of an object near the capacitive sensing area.

Claims

1. A method of generating a time interval measurement which is a monotonic function of the capacitance of a capacitive sensor, comprising:

causing a voltage across a capacitive sensor to change at least one time; and

generating a time interval measurement which is a monotonic function of capacitance of said capacitive sensor by measuring at least one time interval during each of which said changing voltage across said sensor ranges between two predetermined values, wherein if said time interval measurement is generated by measuring at least two time intervals then said measuring is cumulative, and wherein said predetermined values corresponding to at least one of said at least one time interval are both non-zero.

2. The method of claim 1, wherein said causing includes:

charging said sensor so that said voltage increases during at least one of said at least one time interval.

3. The method of claim 1, wherein said causing includes:

discharging said sensor so that said voltage decreases during at least one of said at least one time interval.

4. The method of claim 1, wherein said measuring includes:

running a counter when said changing voltage ranges between said predetermined values.

5. The method of claim 1, wherein said causing is triggered independent of voltage value across said sensor.

6. The method of claim 1, further comprising:

analyzing said generated time interval measurement in order to detect or not detect presence of an object near said capacitive sensor.

7. The method of claim 1, further comprising:

causing each voltage across at least one other capacitive sensor in a same capacitive sensing area as said capacitive sensor to change at least one time; and

for each of said at least one other capacitive sensor, generating a time interval measurement which is a monotonic function of capacitance of said other capacitive sensor by measuring at least one time interval during each of which said changing voltage across said other sensor ranges between two predetermined values, wherein if said time interval measurement is generated by measuring at least two time intervals then said measuring is cumulative, and wherein said predetermined values corresponding to at least one of said at least one time interval are both non-zero.

8. The method of claim 7, wherein said measuring for said capacitive sensor and for at least one of said at least one other capacitive sensor are performed in parallel.

9. The method of claim 7, wherein said measuring of a time interval for said capacitive sensor and said measuring of a time interval for at least one of said at least one other capacitive sensor are performed sequentially.

10. The method of claim 7, further comprising:

analyzing said generated time interval measurement for said capacitive sensor and at least one generated time interval measurement corresponding to said at least one other capacitive sensor to detect a position of an object which is near said capacitive sensing area.

11. A module for generating a time interval measurement which is a monotonic function of the capacitance of a capacitive sensor, comprising:

means for causing a voltage across a capacitive sensor to change at least one time; and

means for generating a time interval measurement which is a monotonic function of capacitance of said capacitive sensor, including means for measuring a time interval during which said changing voltage across said sensor ranges between two predetermined values or means for cumulatively measuring at least two time intervals during each of which said changing voltage across said sensor ranges between two predetermined values, wherein said predetermined values corresponding to at least one measured time interval are both non-zero.

12. The module of claim 11, wherein said means for causing includes a charge/discharge circuit.

13. The module of claim 12, wherein said charge/discharge circuit is configured to charge and discharge said sensor independent of voltage value across said sensor.

14. The module of claim 12, further comprising:

a clock module configured to generate a charge/discharge control for controlling charging and discharging by said charge/discharge circuit.

15. The module of claim 11, further comprising:

a clock generator configured to generate a clock signal.

16. The module of claim 15, wherein said clock generator is configured to selectively provide a jitter in said generated clock signal.

17. The method of claim 16, wherein said means for generating includes a counter, and wherein said generated clock signal or a function thereof is provided to said counter.

18. The module of claim 11, wherein said means for generating includes a counter.

19. The module of claim 18, further comprising:

a comparator configured to compare said changing voltage with each of said two predetermined values and cause said counter to run when said changing voltage ranges between said two predetermined values.

20. The module of claim 19, wherein said comparator is configured to cause said counter to run in a mode selected from a group comprising:

running allowed while said sensor is charging, running allowed while said sensor is discharging and running allowed while said sensor is charging or discharging.

21. The module of claim 11, further comprising:

a controller configured to configure at least one operational parameter affecting operation of said module.

22. The module of claim 11, wherein operation of said module is affected by at least one operational parameter selected from a group comprising:

jitter enable/disable, jitter value, clock divider value, high voltage level, low voltage level, counter clock frequency, charge/discharge frequency, counter enable mode, number of charge/discharge cycles in accumulation cycle, charging and discharging enabling/disabling, auto mode, manual mode, new set ready, halt state, predefined interval between reads, and begin accumulation cycle.

23. The module of claim 11, further comprising:

a controller configured to receive said generated time interval measurement and to analyze said generated time interval measurement to detect or not detect presence of an object near said sensor.

24. The module of claim 11, further comprising:

means for causing each voltage across at least one other capacitive sensor in a same capacitive sensing area as said capacitive sensor to change at least one time; and

means for generating, for each of said at least one other capacitive sensor, a time interval measurement which is a monotonic function of the capacitance of said other capacitive sensor, including for each of said at least one other capacitive sensor, means for measuring a time interval during which said changing voltage across said other sensor ranges between two predetermined values or means for cumulatively measuring at least two time intervals during each of which said changing voltage across said other sensor ranges between two predetermined values, wherein said predetermined values corresponding to at least one measured time interval are both non-zero.

25. The module of claim 24, further comprising:

a controller configured to receive said generated time interval measurements corresponding to said sensor and said at least one other sensor and to analyze said generated time interval measurements to detect a position of an object near said capacitive sensing area.

26. The module of claim 24, further comprising:

means for configuring which among said sensor and said at least one other sensor have charging and discharging enabled.

27. The module of claim 24, further comprising:

means for configuring which among said sensor and said at least one other sensor measure time intervals in parallel and which among said sensor and said at least one other sensor measure time intervals sequentially.

28. A capacitive detection method comprising:

causing each voltage across at least one capacitive sensor in a capacitive sensing area to change at least one time;

for each of said at least one capacitive sensor, generating a time interval measurement which is a monotonic function of capacitance of said capacitive sensor by measuring at least one time interval during each of which said changing voltage across said sensor ranges between two non-zero predetermined values, wherein if said time interval measurement is generated by measuring at least two time intervals then said measuring is cumulative; and

analyzing said at least one generated time interval measurement corresponding to said at least one capacitive sensor in order to detect or not detect presence of an object near said capacitive sensing area.

29. The method of claim 28, wherein said at least one capacitive sensor includes at least two capacitive sensors, further comprising:

if presence was detected, analyzing generated time interval measurements for said at least two capacitive sensors in order to detect position of said object.

30. A capacitive detection system, comprising:

a capacitive sensing area comprising at least one capacitive sensor,

a capacitive gauging module configured to cause each voltage across at least one sensor in said capacitive sensing area to change at least one time and configured to generate for each of said at least one sensor whose voltage was caused to change, a time interval measurement which is a monotonic function of capacitance of said capacitive sensor, said gauging module including at least one counter, wherein each counter corresponds to one sensor and is configured to measure a time interval during which said changing voltage across said corresponding sensor ranges between two non-zero predetermined values or configured to cumulatively measure at least two time intervals during each of which said changing voltage across said corresponding sensor ranges between two non-zero predetermined values; and

a controller module configured to analyze said at least one generated time interval measurement corresponding to said at least one sensor whose at least one voltage was caused to change in order to detect or not detect presence of an object near said capacitive sensing area.

31. The system of claim 30, wherein said at least one capacitive sensor includes at least two capacitive sensors, said controller is further configured to analyze generated time interval measurements for said at least two capacitive sensors in order to detect position of an object whose presence was detected.