US 2001/0011894 A1 · MICROPOWER CAP ACITANCE-BASED PROXIMITY SENSOR

Abstract

The present invention is a proximity detector for an electronic device. The proximity detector utilizes two capacitors which share a common electrode. The two capacitors are located on the housing of the electronic device. The capacitors are arranged so that when the electronic device is used in its normal orientation, a portion of the operator's body will occlude one of the capacitors, but not the other. The close proximity of the operator's body will change the electric field surrounding the capacitor. Thus, the capacitance of the occluded capacitor will be different than the unencumbered capacitor. A detection circuit is coupled to the capacitors and to the power supply of the device. The circuit uses very little power, and maintains the electronic device in a standby or powered down mode. Only when the circuit detects a difference in the capacitance generated by the two capacitors, will it allow full power to be delivered to the electronic device.

Claims18

Dependent claims

A capacitance based proximity detector for detecting the presence of an object proximate one of a plurality of capacitors, comprising:

a first capacitor;
a second capacitor coupled to the first capacitor;
and
a circuit, coupled to the first and second capacitor to detect a capacitance of the first and second capacitors, the circuit providing a first output when the capacitance of the first capacitor is equal to the capacitance of the second capacitor, and a second output when the capacitance of the first capacitor is not equal to the capacitance of the second capacitor.

1 more element

A proximity detector for an electronic device, comprising:

a housing, the housing containing the electronic device;
a power supply, the power supply providing power to the electronic device, and mounted within the housing;
a first electrode, a second electrode and a third electrode mounted in an outer wall of the housing;
a first capacitor, the first capacitor including the first electrode and the second electrode;
a second capacitor, the second capacitor including the second electrode and the third electrode;
a proximity detection circuit coupled to the electronic device and to the power supply, the proximity detection circuit including:
a logic gate driven by a clock, the logic gate coupled to the first capacitor and the second capacitor, and receiving power from the power supply, the logic gate and clock providing an input signal into the first capacitor and the second capacitor;
a first amplifier and filter coupled to the first capacitor for receiving a first signal from the first capacitor, and providing a first output;
a second amplifier and filter coupled to the second capacitor for receiving a second signal from the second capacitor, and providing a second output;
an inverter coupled to the second amplifier and filter, for inverting the second output;
and
a summing circuit, the summing circuit coupled to the inverter and the first amplifier and filter, wherein the summing circuit produces a first control signal when the first output is equal to the second output, and produces a second control signal when the first output is not equal to the second output;
wherein, the electronic device only receives full power from the power supply when the summing circuit generates the second output.

10 more elements

Dependencies are inferred from the claim text.

Micropower cap acitance-based proximity sensor

Life of this patent

Micropower cap acitance-based proximity sensor

Life of this patent

Abstract

Claims18