Managing power consumption of force sensors
A force-responsive sensor incorporating a force-sensitive element is in communication with a power controller. The power controller changes one or more performance characteristics associated with the force-responsive sensor. A performance characteristic can include a bias voltage or current, a duty cycle, a sampling rate, and so on. The performance characteristic(s) can be changed in response to a touch event or based on an operational setting of the force-responsive sensor (or an electronic device incorporating the force-responsive sensor). Regulation of the performance characteristic(s) reduces power consumption of the force-responsive sensor.
1. An electronic device comprising:
an input surface;
a force-responsive sensor coupled to the input surface and comprising an array of strain-sensitive elements, each associated with a different portion of the input surface;
a circuit coupled to each of the strain-sensitive elements; and
a power controller coupled to the circuit and configured to selectively enable a subset of the strain-sensitive elements in response to a touch event detected on the input surface, the subset of the strain-sensitive elements selected based on a location of the touch event; wherein
the power controller is configured to change a duty cycle of the circuit to a first duty cycle if the location is near an edge of the input surface or to a second duty cycle if the location is near a center of the input surface.
2. The electronic device of claim 1 , wherein the touch event is detected by a touch sensor positioned below the input surface.
3. The electronic device of claim 1 , wherein the circuit is a readout circuit.
4. The electronic device of claim 1 , wherein the power controller is further configured to change the duty cycle in response to the detected touch event.
5. The electronic device of claim 4 , wherein:
the circuit comprises a drive circuit; and
the duty cycle is associated with an amplifier of the drive circuit.
6. The electronic device of claim 4 , wherein the power controller is further configured to change the duty cycle based, at least in part, on the location.
7. The electronic device of claim 1 , wherein the first duty cycle is greater than the second duty cycle.
8. A method of operating a force-responsive sensor comprising:
detecting a touch event on an input surface of an electronic device;
determining a subset of force-sensitive elements associated with a force-responsive sensor and proximate to the touch event;
activating each force-sensitive element of the subset of force-sensitive elements;
changing a performance characteristic of a drive circuit configured to apply a drive signal to each force-sensitive element of the subset of force-sensitive elements, the performance characteristic based on the proximity of the touch event to an edge of the input surface.
9. The method of claim 8 , wherein the performance characteristic of the drive circuit is a duty cycle associated with an amplifier of the drive circuit.
10. The method of claim 8 , wherein the operation of changing the performance characteristic of the drive circuit comprises increasing a duty cycle of the drive circuit.
11. The method of claim 8 , wherein at least one force-sensitive element of the subset of force-sensitive elements is a strain-sensitive element.
12. The method of claim 8 , wherein the performance characteristic is based, at least in part, on an operational setting of the electronic device.
13. An electronic device comprising:
an input surface;
a touch sensor positioned below the input surface;
a force-responsive sensor positioned below the input surface and comprising an array of strain-sensitive elements arranged in a pattern below the input surface; and
a power controller coupled to the force-responsive sensor and the touch sensor, the power controller configured to:
set a first performance characteristic of the force-responsive sensor in response to a touch detected at an edge of the input surface; and
set a second performance characteristic of the force-responsive sensor in response to a touch detected at a center of the input surface.
14. The electronic device of claim 13 , further comprising an amplifier coupled to the force-responsive sensor and configured to amplify a sense signal output by the force-responsive sensor.
15. The electronic device of claim 13 , wherein:
the power controller is configured to disable the force-responsive sensor in response to the touch sensor determining that a touch event has ended.
16. The electronic device of claim 13 , further comprising:
a drive circuit comprising a signal source coupled to the force-responsive sensor.
17. The electronic device of claim 16 , wherein:
the first performance characteristic is an amplifier duty cycle; and
the power controller is configured to change a signal source duty cycle of the signal source in response a touch detected at an edge of the input surface.
18. The electronic device of claim 13 , wherein the first performance characteristic is an increased duty cycle.
19. The electronic device of claim 13 , wherein at least one strain-sensitive element of the array of strain-sensitive elements is a resistive sensor.