Ground-shifted touch input sensor for capacitively driving an electrostatic plate
An input/output interface for an electronic device receives touch and/or force input and, additionally provides haptic output to a user. In particular the input/output interface is operated in conjunction with an input surface and includes at least one input sensor and at least one haptic output element. In typical embodiments, the input sensor is ground-shifted to prevent damage to the input sensor when the haptic output element is driven.
1. An apparatus comprising:
a system voltage domain;
a shifted voltage domain shifted from the system voltage domain, the shifted voltage domain comprising:
a display; and
a haptic output element capacitively coupled to the display; and
an isolator circuit configured to isolate the shifted voltage domain from the system voltage domain.
2. The apparatus of claim 1 , wherein the display is a capacitive touch sensing display.
3. The apparatus of claim 1 , further comprising:
a housing, wherein the display is positioned within at least a portion of the housing.
4. The apparatus of claim 1 , wherein the isolator circuit comprises:
a communications isolator configured to physically and conductively isolate communications of the shifted voltage domain from the system voltage domain; and
a power isolator configured to physically and conductively isolate a voltage of the shifted voltage domain from the system voltage domain.
5. The apparatus of claim 4 , wherein the communications isolator comprises at least one of:
an octocoupler;
a capacitive coupling;
a transformer; or
a galvanic isolator.
6. The apparatus of claim 4 , wherein the power isolator comprises at least one of:
a transformer;
a capacitive coupling; or
a galvanic isolator.
7. The apparatus of claim 1 , further comprising a controller, the controller communicatively coupled to the isolator circuit and configured to regulate a power output of the apparatus.
8. The apparatus of claim 1 , wherein the haptic output element comprises an electrically conductive sheet.
9. The apparatus of claim 8 , wherein the electrically conductive sheet is formed from a high-resistivity material.
10. The apparatus of claim 8 , wherein the electrically conductive sheet is disposed on a surface of the display.
11. The apparatus of claim 1 , wherein:
the shifted voltage domain comprises a power regulator; and
the power regulator is configured to maintain a constant direct current bias between a shifted source and a shifted ground of the shifted voltage domain.
12. The apparatus of claim 1 , wherein:
the system voltage domain comprises a power management system; and
the power management system is configured to cause a high voltage driver to output a high voltage signal that follows a particular waveform.
13. The apparatus of claim 1 , wherein the shifted voltage domain and the system voltage domain are configured to follow a waveform in a phase that corresponds to an instruction from the haptic output element.
14. An apparatus comprising:
a touch input surface;
a system voltage source;
a system ground;
a display below the touch input surface and conductively decoupled from the system voltage source and the system ground; and
a controller configured to provide an electrostatic haptic output through the touch input surface.
15. The apparatus of claim 14 , further comprising a conductive layer disposed above the display, wherein the conductive layer is:
conductively decoupled from the display; and
capacitively coupled to the display.
16. The apparatus of claim 15 , wherein the conductive layer is optically transparent.
17. The apparatus of claim 14 , further comprising an input sensor positioned below the display.
18. The apparatus of claim 17 , wherein the input sensor is a touch input sensor and comprises a piezoelectric body.
19. The apparatus of claim 18 , further comprising:
a first set of electrodes disposed on a first surface of the piezoelectric body; and
a second set of electrodes disposed on a second surface of the piezoelectric body, wherein the controller is configured to:
couple at least one first set electrode of the first set of electrodes to a local voltage source; and
couple at least one second set electrode of the second set of electrodes to a local ground.
20. The apparatus of claim 14 , further comprising:
a system voltage domain comprising the system voltage source and the system ground; and
a shifted voltage domain, shifted from the system voltage domain, wherein the controller facilitates a communication between the shifted voltage domain and the system voltage domain.