Driven shield for shaping an electric field of a touch sensor

• US 9,337,833 B2
• Filed: 06/14/2012
• Issued: 05/10/2016
• Est. Priority Date: 11/14/2011
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Siska, Andrew
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): Zheng, Xuemei
• Application Number:
  US13/523,372
• Publication Number:
  US 20130120310A1
• Time in Patent Office: 1,426 Days
• Field of Search: 345/173, 345/174
• US Class Current: 1/1
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/960765 Details of shielding arrangements
• CPC Class Codes: H03K 2217/96078 Sensor being a wire or a strip, e.g. used in automobile door handles or bumpers

Abstract

In one embodiment, a method comprises generating, by a control unit, a first drive signal and a second drive signal. The method further includes emitting, by a touch sensor, a first electric field that extends in a plurality of directions in response to reception of the first drive signal. The method also includes attenuating, by a conductive shield, a portion of the first electric field that extends from the touch sensor towards the conductive shield by generating a second electric field in response to reception of the second drive signal.

Claims

1. A device comprising:

a capacitive touch sensor configured to store an amount of charge indicative of whether an object is within a range of the capacitive touch sensor, the capacitive touch sensor configured to generate a first electric field that extends in a plurality of directions in response to receiving a first drive signal comprising a first plurality of electrical pulses;

a first conductive shield located in the same plane as the capacitive touch sensor, the first conductive shield configured to shape the first electric field by generating a second electric field in response to receiving a second drive signal comprising a second plurality of electrical pulses, the first conductive shield forming a loop around the capacitive touch sensor, the second drive signal having the same phase and polarity as the first drive signal such that the first conductive shield is configured to shape a first portion of the first electric field;

a second conductive shield located in a plane that is parallel to a plane that includes the capacitive touch sensor, the second conductive shield configured to further shape the first electric field by generating a third electric field in response to receiving a third drive signal comprising a third plurality of electrical pulses, the third drive signal having the same phase and polarity as the first drive signal such that the second conductive shield is configured to shape a second portion of the first electric field;

wherein the first conductive shield and the second conductive shield are configured to shape the first electric field such that the first electric field generally extends in a direction opposite of the second conductive shield;

a control unit coupled to the capacitive touch sensor and the first and second conductive shields, the control unit comprising a pulse driver configured to;

drive the capacitive touch sensor with the first drive signal;

drive the first conductive shield with the second drive signal;

drive the second conductive shield with the third drive signal;

adjust the second drive signal from a first amplitude to a second amplitude such that the second electric field of the first conductive shield further shapes the first portion of the first electric field; and

adjust the third drive signal from a third amplitude to a fourth amplitude such that the third electric field of the second conductive shield further shapes the second portion of the first electric field;

a transparent cover panel overlaying at least a portion of the capacitive touch sensor; and

a display overlaid by at least a portion of the capacitive touch sensor.

2. The device of claim 1, further comprising:

another capacitive touch sensor coupled to the control unit and configured to store an amount of charge indicative of whether an object is within a range of the another capacitive touch sensor, the another capacitive touch sensor configured to generate a fourth electric field that extends in a plurality of directions in response to receiving a fourth drive signal comprising a fourth plurality of electrical pulses; and

a third conductive shield coupled to the control unit and configured to shape the fourth electric field by generating a fifth electric field in response to receiving a fifth drive signal comprising a fifth plurality of electrical pulses, the fifth drive signal having the same phase and polarity as the fourth drive signal;

wherein the control unit comprising the pulse driver is further configured to drive the another capacitive touch sensor with the fourth drive signal and the third conductive shield with the fifth drive signal.

3. An apparatus comprising:

a touch sensor configured to store an amount of charge indicative of whether an object is within a range of the touch sensor, the touch sensor configured to generate a first electric field that extends in a plurality of directions;

a first conductive shield located in the same plane as the touch sensor, the first conductive shield configured to shape the first electric field by generating a second electric field, the first conductive shield forming a loop around the touch sensor, the first conductive shield configured to shape a first portion of the first electric field;

a second conductive shield located in a plane that is parallel to a plane that includes the touch sensor, the second conductive shield configured to further shape the first electric field by generating a third electric field, the second conductive shield configured to shape a second portion of the first electric field;

wherein the first conductive shield and the second conductive shield are configured to shape the first electric field such that the first electric field generally extends in a direction opposite of the second conductive shield; and

a control unit configured to;

drive the touch sensor with a first drive signal that causes the generation of the first electric field;

drive the first conductive shield with a second drive signal that causes the generation of the second electric field;

drive the second conductive shield with a third drive signal that causes the generation of the third electric field;

adjust the second drive signal from a first amplitude to a second amplitude such that the second electric field of the first conductive shield further shapes the first portion of the first electric field; and

adjust the third drive signal from a third amplitude to a fourth amplitude such that the third electric field of the second conductive shield further shapes the second portion of the first electric field.

4. The apparatus of claim 3, wherein the first drive signal and the second drive signal have substantially similar polarities and phases.

5. The apparatus of claim 3, further comprising a dielectric layer positioned between the touch sensor and the first conductive shield.

6. The apparatus of claim 3, wherein the touch sensor and the first conductive shield have substantially distinct geometries.

7. The apparatus of claim 3, wherein the second conductive shield and the touch sensor have the same geometries and the geometries of the second conductive shield and the touch sensor are distinct from the geometry of the first conductive shield.

8. The apparatus of claim 3, wherein the first drive signal and the second drive signal have equal amplitudes.

9. The apparatus of claim 3, further comprising a buffer operable to amplify or attenuate the first drive signal to generate the second drive signal.

10. The apparatus of claim 3, further comprising:

a ground layer comprising a conductive material operable to absorb one or more of a third portion of the first electric field and a portion of the second electric field; and

a dielectric layer disposed between the ground layer and the first conductive shield.

11. The apparatus of claim 3, wherein the first electric field is generated by a first electrode of the touch sensor, and the apparatus further comprises:

a second electrode configured to store an amount of charge indicative of whether an object is within a range of the second electrode, the second electrode configured to generate a fourth electric field that extends in a plurality of directions; and

a third conductive shield configured to shape the fourth electric field by generating a fifth electric field.

12. The apparatus of claim 3, further comprising:

a first buffer operable to amplify or attenuate the first drive signal to generate the second drive signal, the first buffer configured to adjust the amplitude of the first drive signal based at least in part on one or more of a portion of the first electric field and a portion of the second electric field; and

a second buffer operable to amplify or attenuate the first drive signal to generate the third drive signal, the second buffer configured to adjust the amplitude of the first drive signal based at least in part on one or more of a portion of the first electric field and a portion of the third electric field.

13. The apparatus of claim 3, further comprising:

a first substrate located in the same plane as the touch sensor, the first substrate configured to electrically insulate the touch sensor from the first conductive shield; and

a second substrate located in a plane that is between the plane that includes the touch sensor and a plane that includes the second conductive shield, the second substrate configured to electrically insulate the touch sensor from the second conductive shield.

14. A method comprising:

generating, by a control unit, a first drive signal, a second drive signal, and a third drive signal;

emitting, by a touch sensor, a first electric field that extends in a plurality of directions in response to reception of the first drive signal;

shaping, by a first conductive shield located in the same plane as the touch sensor, a first portion of the first electric field that extends from the touch sensor towards the first conductive shield by generating a second electric field in response to reception of the second drive signal, the first conductive shield forming a loop around the touch sensor;

shaping, by a second conductive shield located in a plane that is parallel to a plane that includes the touch sensor, a second portion of the first electric field that extends from the touch sensor towards the second conductive shield by generating a third electric field in response to reception of the third drive signal,

wherein the first conductive shield and the second conductive shield shape the first electric field such that the first electric field generally extends in a direction opposite of the second conductive shield;

adjusting, by the control unit, the second drive signal from a first amplitude to a second amplitude such that the second electric field of the first conductive shield further shapes the first portion of the first electric field; and

adjusting, by the control unit, the third drive signal from a third amplitude to a fourth amplitude such that the third electric field of the second conductive shield further shapes the second portion of the first electric field.

15. The method of claim 14, wherein the first drive signal and the second drive signal have equal phases and polarities.

16. The method of claim 14, further comprising detecting whether an object is within a range of the touch sensor based on a change in capacitance of the touch sensor in response to the first drive signal.

17. The method of claim 14, wherein the first drive signal and the second drive signal have the same amplitudes.

18. A device comprising:

a touch sensor configured to store an amount of charge indicative of whether an object is within a range of the touch sensor, the touch sensor configured to generate a first electric field that extends in a plurality of directions;

a first conductive shield located in the same plane as the touch sensor, the first conductive shield configured to shape the first electric field by generating a second electric field, the first conductive shield configured to shape a first portion of the first electric field, the first conductive shield forming a loop around the touch sensor;

a second conductive shield located in a plane that is parallel to a plane that includes the touch sensor, the second conductive shield configured to further shape the first electric field by generating a third electric field, the second conductive shield configured to repel shape a second portion of the first electric field;

wherein the first conductive shield and the second conductive shield are configured to shape the first electric field such that the first electric field generally extends in a direction opposite of the second conductive shield;

a control unit configured to;

drive the touch sensor with a first drive signal that causes the generation of the first electric field;

drive the first conductive shield with a second drive signal that causes the generation of the second electric field;

drive the second conductive shield with a third drive signal that causes the generation of the third electric field;

adjust the second drive signal from a first amplitude to a second amplitude such that the second electric field of the first conductive shield further shapes the first portion of the first electric field; and

adjust the third drive signal from a third amplitude to a fourth amplitude such that the third electric field of the second conductive shield further shapes the second portion of the first electric field;

a sensing unit configured to sense when an object is within the range of the touch sensor based on a change of capacitance of the touch sensor in response to the first drive signal; and

a logic circuit in communication with the sensing unit and configured to initiate an action of the device upon sensing that the object is within the proximity of the touch sensor.

19. The device of claim 18, wherein the action comprises turning on a display of the device.

20. The device of claim 18, wherein the action comprises reducing the magnitude of at least one radio frequency transmission of the device.

21. The device of claim 18, wherein the action comprises powering on the device, powering off the device, or awakening the device from a sleep mode.