Aisin Seiki Kabushiki Kaisha

Kohei Kurachi

Hisashi Inaba

Rikuo Hatano

A capacitance detection apparatus includes a detection electrode for detecting approach of an object on the basis of a change of capacitance, a calculating circuit for calculating a value associated with the capacitance change, a judging circuit for judging whether the calculated value is a normal or initial value calculated after or before a predetermined period of time lapse from a start time of the capacitance detection apparatus, an initial reference value-determining circuit for determining an initial reference value, a difference calculating circuit for calculating a difference between the normal value and a value calculated earlier than a time when the normal value is calculated by the predetermined period of time or longer or between the initial value and the initial reference value, and a determining circuit for determining whether the object is approaching by comparing the difference with a predetermined threshold value.

Capacitance detection apparatus

A starter circuit includes a start detection circuit for detecting a change of an input signal and outputting a start digital signal, a digital OR circuit for outputting a determination digital signal based on the start digital signal, a power supply circuit being activated based on the determination digital signal, and a digital control circuit being operated based on a power from the power supply circuit. The digital control circuit inputs a retention signal to the digital OR circuit for maintaining an operation of the power supply circuit and a reset signal to the start detection circuit for resetting the start detection circuit.

Starter circuit

A capacitance change detection device includes a sensor electrode, and an electrode capacitance measurement device for measuring capacitance of the sensor electrode on the basis of a correlation value based on a reference capacitance at every first predetermined time. A detection signal is generated when a current measurement value of capacitance is changed by equal to or greater predetermined threshold value than a measurement value obtained a second predetermined time before the current measurement value is measured. The capacitance change detection device further includes a sensitivity compensation capacitance for generating capacitance variations equivalent to specific variations of capacitance of the sensor electrode, and being switched between a connected state and a disconnected state. The threshold value is determined as a difference between measurement values of capacitance of the sensor electrode measured at the connected state and at the disconnected state. The threshold value is renewed at every third predetermined time.

Capacitance change detection device

A capacitance detection apparatus includes a first open/close switch provided between both ends of a standard capacitor, one end of the standard capacitor being connected to a first voltage source, a second open/close switch provided between one end of a first capacitor to be measured and the other end of the standard capacitor, the other end of the first capacitor to be measured being connected to a second voltage source or free space, a third open/close switch provided between both ends of the first capacitor to be measured, a voltage measurement means for measuring voltage of the other end of the standard capacitor, a switch control means for performing a first switching control performing a first switching operation to open the first open/close switch after closing thereof, performing a second switching operation to open the second open/close switch after closing thereof, and a third switching operation to close the third open/close switch after closing thereof, wherein the second and third switching operations are repeatedly performed after the first switching operation, a counting means for counting the number of repetition of the second switching operation, and a judging means for judging a change of the capacitance of the first capacitor to be measured according to the number of repetition of the second switching operation, which is the number counted by the counting means during the voltage of the other end of the standard capacitor measured by the voltage measurement means being changed from an initial voltage after the first switching operation by a predetermined magnitude.

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Nishio, Japan

Kohei Kurachi