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US 8,576,189 B1Granted
AC line synchronization for capacitive sensing
AssigneeCypress Semiconductor Corporation
InventorsAndriy Maharyta, Andriy Ryshtun, Victor Kremin
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Abstract
A method includes powering multiple touch sensors using DC power derived from an AC power signal; monitoring the AC power signal and producing from the AC power signal a trigger signal that occurs repeatedly at a predetermined point in a cycle of the AC power signal; and initiating a scan of the touch sensors when the trigger signal occurs during each cycle of the AC power signal.
Claims20
A touch sensing system, comprising:
- a plurality of touch sensors operated using direct current (DC) power;
- a digital controller;
- logic to monitor an alternating current (AC) signal from which the DC power is derived and to produce a trigger signal to the digital controller;
- and
- logic to cause the digital controller to wait for the trigger signal before scanning outputs of the touch sensors.
2 more elements
A device comprising:
- an AC-DC power converter;
- and
- a capacitive touch sensing system, comprising:
- a plurality of touch sensors operated using DC power from the power converter;
- a digital controller operated using DC power from the power converter;
- logic to monitor an AC signal from which the DC power is derived and to produce a trigger signal to the digital controller;
- and
- logic to cause the digital controller to respond to the trigger signal by initiating a scan of the touch sensors.
5 more elements
A method comprising:
- powering a plurality of touch sensors using DC power derived from an AC power signal;
- monitoring the AC power signal and producing from the AC power signal a trigger signal that occurs repeatedly at a same point in a cycle of the AC power signal;
- and
- delaying a scan of the touch sensors until the trigger signal occurs during each cycle of the AC power signal.
1 more element
A method comprising:
- introducing AC noise into at least one of a plurality of DC powered touch sensors;
- and
- mitigating effects of the AC noise by:
- monitoring an AC power signal that produces the DC power;
- producing from the AC power signal a trigger signal that occurs repeatedly at a same point in a cycle of the AC power signal;
- and
- initiating a scan of the touch sensors by a digital controller when the trigger signal occurs during each cycle of the AC power signal.
4 more elements
Dependencies are inferred from the claim text.