Object sensing
First Claim
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1. An electric field object sensing system, comprising:
- a transmitter electrode;
a receiver electrode;
a charge pumping circuit coupled to the receiver electrode;
an alternating voltage source coupled to the transmitter electrode and the charge pumping circuit; and
an output connection coupled to the receiver electrode;
wherein the charge pumping circuit is arranged to perform charge pumping according to the common cycle of alternating voltages applied from the alternating voltage source to the transmitter electrode and the charge pumping circuit; and
the charge pumping circuit comprises a capacitor arranged such that a voltage developed across the capacitor saturates at a level dependent upon a capacitance between the transmitter electrode and the receiver electrode.
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Abstract
An electric field object sensing system uses a charge pumping circuit to provide a voltage over a capacitor that varies dependent upon the capacitive coupling between a transmitter electrode and a receiver electrode. The output of the charge pump is preferably fed to a high impedance read-out means, such as an analog-digital converter (ADC). The system is preferably implemented in CMOS and integrated in control circuits of electronic products.
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Citations
13 Claims
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1. An electric field object sensing system, comprising:
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a transmitter electrode; a receiver electrode; a charge pumping circuit coupled to the receiver electrode; an alternating voltage source coupled to the transmitter electrode and the charge pumping circuit; and an output connection coupled to the receiver electrode; wherein the charge pumping circuit is arranged to perform charge pumping according to the common cycle of alternating voltages applied from the alternating voltage source to the transmitter electrode and the charge pumping circuit; and
the charge pumping circuit comprises a capacitor arranged such that a voltage developed across the capacitor saturates at a level dependent upon a capacitance between the transmitter electrode and the receiver electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of providing an output from a receiver electrode of an electric field object sensing system, the method comprising:
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providing a first alternating voltage to a transmitter electrode; providing a second alternating voltage of the same phase as the first alternating voltage to a switching circuit coupled to the receiver electrode; performing charge pumping, using the switching circuit, according to the cycle of the alternating voltages, to provide a voltage over a capacitor of the switching circuit that increases dependent upon a capacitance coupling between the transmitter electrode and the receiver electrode; allowing the voltage over the capacitor of the switching circuit to saturate; and using the saturated voltage as an output that varies when an object is in the vicinity of the transmitter electrode and the receiver electrode. - View Dependent Claims (9, 10, 11, 12, 13)
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Specification