Active stylus and control circuit thereof
First Claim
Patent Images
1. A control circuit for an active stylus comprising:
- a first electrode associated with the tip of an active stylus configured to receive an input signal from a touch-sensitive interface and support;
a capacitive bridge comprising at least three capacitors, including a first capacitor connecting the first electrode to a second capacitor and a reference capacitor connecting the second capacitor to a second electrode;
a transformer comprising a primary winding and a secondary winding, wherein the secondary winding connects a junction of the first capacitor and the second capacitor to the second electrode;
a first differential amplifier with a first input connected to the first electrode and a second input connected to a junction of the second capacitor and the reference capacitor;
a compensation amplifier configured to amplify a signal from the junction of the second capacitor and the reference capacitor; and
a second differential amplifier with a first input connected to an output of the first differential amplifier and a second input connected to an output of the compensation amplifier,wherein the primary winding of the transformer connects the output of the second differential amplifier to the second electrode, andwherein the gain of the compensation amplifier is dynamically adjusted based at least partially on a difference between a capacitance of the reference capacitor and a capacitance between the first electrode and the touch-sensitive interface.
2 Assignments
0 Petitions
Accused Products
Abstract
The present disclosure provides systems and methods for receiving an input signal from a touch-sensitive interface via a first electrode associated with a tip of an active stylus. An input signal may be amplified via a control circuit that adjusts the gain of one or more amplifiers to compensate for changes in tip capacitance between the tip of the active stylus and the touch-sensitive interface. Changes in tip capacitance may be indirectly detected and compensated for by comparing the tip capacitance with that of a reference capacitor via a differential amplification circuit that includes one or more differential amplifiers.
-
Citations
24 Claims
-
1. A control circuit for an active stylus comprising:
-
a first electrode associated with the tip of an active stylus configured to receive an input signal from a touch-sensitive interface and support; a capacitive bridge comprising at least three capacitors, including a first capacitor connecting the first electrode to a second capacitor and a reference capacitor connecting the second capacitor to a second electrode; a transformer comprising a primary winding and a secondary winding, wherein the secondary winding connects a junction of the first capacitor and the second capacitor to the second electrode; a first differential amplifier with a first input connected to the first electrode and a second input connected to a junction of the second capacitor and the reference capacitor; a compensation amplifier configured to amplify a signal from the junction of the second capacitor and the reference capacitor; and a second differential amplifier with a first input connected to an output of the first differential amplifier and a second input connected to an output of the compensation amplifier, wherein the primary winding of the transformer connects the output of the second differential amplifier to the second electrode, and wherein the gain of the compensation amplifier is dynamically adjusted based at least partially on a difference between a capacitance of the reference capacitor and a capacitance between the first electrode and the touch-sensitive interface. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
-
13. An active stylus comprising:
-
an elongated body comprising an outer housing; a tip for contacting a surface of a touch-sensitive device, wherein the tip is associated with a first electrode configured to receive an input signal from an electrode of the touch-sensitive device; a second electrode; and a control circuit configured to adjust a gain of at least one amplification stage based on a difference in (1) a capacitance of a fixed reference capacitor and (2) tip capacitance, the tip capacitance based at least in part on a capacitance of the first electrode relative to the touch-sensitive device, the control circuit further configured to amplify the input signal to produce a drive signal to be driven at the first electrode, the control circuit comprising; a capacitive bridge comprising at least three capacitors, including a first capacitor connecting the first electrode to a second capacitor and a reference capacitor connecting the second capacitor to the second electrode; a transformer comprising a primary winding and a secondary winding, wherein the secondary winding connects a junction of the first capacitor and the second capacitor to the second electrode; and a drive signal feedback circuit comprising at least one differential amplification stage with one input connected to an output of a gain compensation stage for the drive signal, a gain of the gain compensation stage adjusted based on a difference in the capacitance of a fixed reference capacitor and the tip capacitance such that the drive signal is substantially removed from the output of the differential amplification stage. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
-
Specification