Acceleration sensor
First Claim
1. An acceleration sensor comprising:
- a driver circuit for outputting a biased alternating-current (AC) voltage having a variable bias voltage;
a detector element includinga fixed electrode having the biased AC voltage is applied thereto, anda first movable electrode facing the fixed electrode, wherein a capacitance provided between the fixed electrode and the first movable electrode changes depending on acceleration applied to the detector element;
a first current-voltage (CN) converter for converting a current output from the first movable electrode of the detector element into a voltage, and outputting the voltage;
a first operational amplifier includinga first input port having the voltage output from the first CN converter input thereto, andan output port for outputting a voltage depending on the input voltage;
a synchronous demodulator for synchronously detecting the voltage output from the first operational amplifier; and
a defect detector for outputting a defect detection signal when the defect detector determines that the voltage output from the first operational amplifier is out of a predetermined range while the biased AC voltage output from the driver circuit is a predetermined voltage, wherein the driver circuit includesan oscillator for generating an AC voltage, anda second operational amplifier includinga first input port having the AC voltage generated by the oscillator input thereto,a second input port having selectively a reference voltage and a variable voltage input thereto, andan output port connected to the fixed electrode of the detector element.
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Accused Products
Abstract
An acceleration sensor includes a driver circuit for outputting a biased alternating-current (AC) voltage having a variable bias voltage, a detector element having a capacitance provided between a fixed electrode and a movable electrode changing depending on acceleration applied to the detector element, a current-voltage (C/V) converter for converting a current output from the movable electrode of the detector element into a voltage and outputting the voltage, a first operational amplifier outputting a voltage depending on the input voltage, a synchronous demodulator for synchronously detecting the voltage output from the first operational amplifier, and a defect detector for outputting a defect detection signal when the defect detector determines that the voltage output from the first operational amplifier is out of a predetermined range while the biased AC voltage output from the driver circuit is a predetermined voltage. This acceleration sensor can have a small size.
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Citations
13 Claims
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1. An acceleration sensor comprising:
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a driver circuit for outputting a biased alternating-current (AC) voltage having a variable bias voltage; a detector element including a fixed electrode having the biased AC voltage is applied thereto, and a first movable electrode facing the fixed electrode, wherein a capacitance provided between the fixed electrode and the first movable electrode changes depending on acceleration applied to the detector element; a first current-voltage (CN) converter for converting a current output from the first movable electrode of the detector element into a voltage, and outputting the voltage; a first operational amplifier including a first input port having the voltage output from the first CN converter input thereto, and an output port for outputting a voltage depending on the input voltage; a synchronous demodulator for synchronously detecting the voltage output from the first operational amplifier; and a defect detector for outputting a defect detection signal when the defect detector determines that the voltage output from the first operational amplifier is out of a predetermined range while the biased AC voltage output from the driver circuit is a predetermined voltage, wherein the driver circuit includes an oscillator for generating an AC voltage, and a second operational amplifier including a first input port having the AC voltage generated by the oscillator input thereto, a second input port having selectively a reference voltage and a variable voltage input thereto, and an output port connected to the fixed electrode of the detector element. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An acceleration sensor comprising:
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a driver circuit for outputting a biased alternating-current (AC) voltage having a variable bias voltage; a detector element including a fixed electrode having the biased AC voltage applied thereto, a first movable electrode facing the fixed electrode, a second movable electrode facing the fixed electrode, a third movable electrode facing the fixed electrode, and a fourth movable electrode facing the fixed electrode, wherein a capacitance generated between the fixed electrode and each of the first movable electrode, the second movable electrode, the third movable electrode, and the fourth movable electrode changes depending on acceleration applied to the detector element; a first current-voltage (CN) converter for converting a current from the first movable electrode of the detector element to a voltage, and outputting the converted voltage; a second C/V converter for converting a current from the second movable electrode of the detector element to a voltage, and outputting the converted voltage; a third C/V converter for converting a current from the third movable electrode of the detector element to a voltage, and outputting the converted voltage; a fourth C/V converter for converting a current from the fourth movable electrode of the detector element to a voltage, and outputting the converted voltage; a first differential amplifier including a first input port having a voltage provided by summing the voltage output from the first C/V converter and the voltage output from the second C/V converter input thereto, a second input port having a voltage provided by summing the voltage output from the third C/V converter and the voltage output from the fourth C/V converter input thereto, and an output port for outputting a voltage which is a difference between the voltage input to the first input port and the voltage input to the second input port; a second differential amplifier including a first input port having a voltage provided by summing the voltage output from the first C/V converter and the voltage output from the fourth C/V converter input thereto, a second input port having a voltage provided by summing the voltage output from the second C/V converter and the voltage output from the third C/V converter input thereto, and an output port for outputting a voltage which is a difference between the voltage input to the first input port and the voltage input to the second input port; a first defect detector for outputting a defect detection signal when the first defect detector determines that the voltage output from the output port of the first differential amplifier is out of a predetermined range while the biased voltage output from the driver circuit is a predetermined voltage; and a second defect detector for outputting a defect detection signal when the second defect detector determines that the voltage output from the output port of the second differential amplifier is out of a predetermined range while the biased AC voltage output from the driver circuit is the predetermined voltage, wherein the driver circuit includes an oscillator for generating an AC voltage, and an operational amplifier including a first input port having the AC voltage generated by the oscillator input thereto, a second input port having a reference voltage and a variable voltage selectively input thereto, and an output port connected to the fixed electrode of the detector element. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification