Touch sensor excitation using transformer
AssigneeApple Inc.
InventorsMichael NUSSBAUM, Blake R. MARSHALL, Jason P. MARINI, Li-Quan TAN
Life of this patent
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Abstract
Input device power consumption can be reduced with a magnetic drive system. In some examples, the input device can include a transformer configured to generate a desired high output voltage from logic-level input pulses. In some examples, the distributed capacitance and associated resonance of the transformer can act as a low-pass filter, and can create a relatively clean output waveform from input logic signal waveforms. In some examples, the transformer can be an autotransformer. In some examples, to stabilize an amplitude of the output by sampling the output of the transformer and adjusting the input to the transformer based on the sampled output.
Claims20
An active stylus, comprising:
- a first electrode at a distal end of the active stylus;
- a first transformer circuit coupled to the first electrode, the transformer configured as an autotransformer;
- and
- control circuitry coupled to the first transformer circuit capable of applying one or more first signals to the first transformer circuit to generate one or more second signals at the first electrode.
A method for operating an active stylus capable of stimulating a touch-sensitive device, the method comprising:
- generating, at control circuitry in the active stylus, one or more logic signals;
- applying the one or more logic signals to a primary side of an autotransformer circuit;
- generating, at an output of a secondary side of the autotransformer circuit, a stimulation signal;
- and
- applying the stimulation signal to an electrode at a distal end of the active stylus.
A non-transitory computer readable storage medium having stored therein instructions, which when executed by an active stylus capable of stimulating a touch sensitive device, cause the active stylus to:
- generate, at control circuitry in the active stylus, one or more logic signals;
- apply the one or more logic signals to a primary side of an autotransformer circuit;
- generate, at an output of a secondary side of the autotransformer circuit, a stimulation signal;
- and
- apply the stimulation signal to an electrode at a distal end of the active stylus.
Dependencies are inferred from the claim text.